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Hopkins SR, Stickland MK. The Pulmonary Vasculature. Semin Respir Crit Care Med 2023; 44:538-554. [PMID: 37816344 PMCID: PMC11192587 DOI: 10.1055/s-0043-1770059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/12/2023]
Abstract
The pulmonary circulation is a low-pressure, low-resistance circuit whose primary function is to deliver deoxygenated blood to, and oxygenated blood from, the pulmonary capillary bed enabling gas exchange. The distribution of pulmonary blood flow is regulated by several factors including effects of vascular branching structure, large-scale forces related to gravity, and finer scale factors related to local control. Hypoxic pulmonary vasoconstriction is one such important regulatory mechanism. In the face of local hypoxia, vascular smooth muscle constriction of precapillary arterioles increases local resistance by up to 250%. This has the effect of diverting blood toward better oxygenated regions of the lung and optimizing ventilation-perfusion matching. However, in the face of global hypoxia, the net effect is an increase in pulmonary arterial pressure and vascular resistance. Pulmonary vascular resistance describes the flow-resistive properties of the pulmonary circulation and arises from both precapillary and postcapillary resistances. The pulmonary circulation is also distensible in response to an increase in transmural pressure and this distention, in addition to recruitment, moderates pulmonary arterial pressure and vascular resistance. This article reviews the physiology of the pulmonary vasculature and briefly discusses how this physiology is altered by common circumstances.
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Affiliation(s)
- Susan R. Hopkins
- Department of Radiology, University of California, San Diego, California
| | - Michael K. Stickland
- Department of Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta
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Lukic A, Cmelak L, Draženović D, Kojundzic H, Lukic IK, Gluncic V. Pulmonary Arteriovenous Malformation Unmasked by Pregnancy: A Review of Pulmonary Arteriovenous Malformations and Cardiovascular and Respiratory Changes in Pregnancy. Case Rep Pulmonol 2023; 2023:5469592. [PMID: 37026089 PMCID: PMC10072959 DOI: 10.1155/2023/5469592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 03/05/2023] [Accepted: 03/15/2023] [Indexed: 03/30/2023] Open
Abstract
Pulmonary arteriovenous malformations are abnormal, direct communications between the branches of the pulmonary artery and pulmonary veins, but without pulmonary capillaries between them. During pregnancy, PAVMs can enlarge and become symptomatic, causing even serious complications like haematothorax. To recognize the PAVM that becomes symptomatic in pregnancy, one must be able to distinguish the patient’s symptoms caused by developing complications of PAVM, as in the case we present, from physiological changes accompanying a healthy pregnancy, including their degree in relation to the stage of pregnancy. The modified early obstetric warning score charts are a very helpful tool in the assessment of (ab)normal signs and symptoms in pregnant women, especially for physicians who rarely manage pregnant women.
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Alakhfash A, Alqwaiee A, Almesned A, Al-Hassnan ZN. Pulmonary arteriovenous malformation with unexplained cyanosis as the first presentation of hereditary haemorrhagic telangiectasia, case report, and literature review. EUROPEAN HEART JOURNAL-CASE REPORTS 2021; 5:ytab261. [PMID: 34377910 PMCID: PMC8343466 DOI: 10.1093/ehjcr/ytab261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 01/22/2021] [Accepted: 06/08/2021] [Indexed: 11/29/2022]
Abstract
Background Pulmonary arteriovenous malformations (PAVMs) are rare pulmonary vascular anomalies. They can result in right-to-left shunt and, if significant, low systemic saturation, cyanosis, polycythaemia, and paradoxical systemic embolization. Case summary Eighteen months old female child was referred to our centre due to unexplained central and peripheral cyanosis. Based on the agitated saline contrast echocardiography study, computed tomography scan confirmed the presence of abnormal vasculature at the left lower lobe. Percutaneous closure of the PAVM was performed using Amplatzer Duct Occluder type 1 device. The genetic study revealed a pathogenic mutation in the endoglin gene, which is a known cause of hereditary haemorrhagic telangiectasia (HHT) inhered in an autosomal dominance pattern. Discussion PAVM could be the first manifestation of HHT. Closing the malformation percutaneously is feasible, which can eliminate the right to left shunt and improves the saturation. Genetic study is warranted in these cases, as well as long-term follow-up.
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Affiliation(s)
- Ali Alakhfash
- Pediatric Cardiology Department, Prince Sultan cardiac Center-Qassim (PSCC-Qassim), MOH, Qassim, Saudi Arabia.,PhD researcher, Cardiovascular sciences, Sapienza Università di Roma - La Sapienza
| | - Abdullah Alqwaiee
- Pediatric Cardiology Department, Prince Sultan cardiac Center-Qassim (PSCC-Qassim), MOH, Qassim, Saudi Arabia
| | - Abdulrahman Almesned
- Pediatric Cardiology Department, Prince Sultan cardiac Center-Qassim (PSCC-Qassim), MOH, Qassim, Saudi Arabia
| | - Zuhair N Al-Hassnan
- Department of Genetics, Cardiovascular Genetics Program, King Faisal Specialist Hospital & Research Centre (KFSH&RC), Riyadh, Saudi Arabia
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Rock NM, Beghetti M, Tissot C, Willi JP, Bouhabib M, McLin VA, Maggio ABR. Reliable Detection of Intrapulmonary Shunts Using Contrast-Enhanced Echocardiography in Children With Portal Hypertension or Portosystemic Shunt. J Pediatr Gastroenterol Nutr 2021; 73:73-79. [PMID: 33605662 DOI: 10.1097/mpg.0000000000003079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
OBJECTIVES The aim of this study was to analyze if contrast-enhanced echocardiography (CEE) is as reliable as lung perfusion scintigraphy (LPS) to detect intrapulmonary shunting (IPS) in children with portal hypertension (PHTN) or congenital/surgical portosystemic shunts (PSS) and to define the number of cardiac cycles required to exclude intrapulmonary shunting. METHODS Inclusion criteria for this cross-sectional study were: (1) presence of PHTN or PSS diagnosed on abdominal ultrasound, (2) technically valid saline contrast echocardiography, (3) lung perfusion scintigraphy within 6 months of CEE. The number of cardiac cycles between right atrial opacification and the arrival of contrast in the left atrium were counted. We analyzed our CEE data at three and five cardiac cycles and compared them with LPS results. RESULTS The study population was composed of 78 children (38 girls, 49%) ages 2.1-18.8 years (mean 9.8). Sixty-nine patients had PHTN (88%), and nine had a PSS (11%). Eleven subjects (14%) presented evidence of IPS on LPS. Peripheral oxygen saturation was lower in the subjects with IPS detected on LPS (95.3 ± 1.7% vs 99.0 ± 1.4%; P < 0.01). Comparison of LPS with CEE before three and five cardiac cycles showed that CEE is highly specific (95.7%) as early as three cardiac cycles with markedly better sensitivity (72.7%) when using five cardiac cycles. Furthermore, a negative study using five cardiac cycles ruled out IPS with a 95% negative predictive value. The cardiac cycle at which the bubbles appeared in the left atrium was inversely correlated to the shunt index measured using LPS (r = -0.563; P = 0.001). CONCLUSION CEE is sufficient for the screening of IPS in children with PHTN or congenital/surgical PSS, obviating the need for LPS.
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Affiliation(s)
- Nathalie M Rock
- Pediatric Gastroenterology, Hepatology and Nutrition Unit, Division of Pediatric Specialties, Department of Pediatrics, Gynecology and Obstetrics
| | - Maurice Beghetti
- Pediatric Cardiology Unit, Division of Pediatric Specialties, Department of Pediatrics, Gynecology and Obstetrics
| | - Cécile Tissot
- Pediatric Cardiology Unit, Division of Pediatric Specialties, Department of Pediatrics, Gynecology and Obstetrics
| | | | - Maya Bouhabib
- Pediatric Cardiology Unit, Division of Pediatric Specialties, Department of Pediatrics, Gynecology and Obstetrics
| | - Valérie A McLin
- Pediatric Gastroenterology, Hepatology and Nutrition Unit, Division of Pediatric Specialties, Department of Pediatrics, Gynecology and Obstetrics
| | - Albane B R Maggio
- Pediatric Sport Medicine and Obesity Care Program, Division of Pediatric Specialties, Department of Pediatrics, Gynecology and Obstetrics, University Hospitals of Geneva, Switzerland
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Gühne F, Drescher R, Ndum F, Seifert P, Freesmeyer M. Complete Right-to-Left Shunt in Lung Perfusion Scintigraphy. Clin Nucl Med 2021; 46:e162-e164. [PMID: 32956119 DOI: 10.1097/rlu.0000000000003286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
ABSTRACT Lung scintigraphy was performed to rule out pulmonary embolism in a 37-year-old woman suffering from dyspnea and hypoxemia after routine diagnostics failed to find the underlying disease. Perfusion scans did not show tracer uptake within the lungs despite ventilation scans being unremarkable. Instead, the result suggested a complete right-to-left shunt, which was a conundrum. With the assistance of CT an uncommon congenital vessel aberration turned out to be the cause of this exceptional scintigraphy finding, as well as the yet unexplained hypoxemia.
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Affiliation(s)
- Falk Gühne
- From the Clinic of Nuclear Medicine, Jena University Hospital, Jena, Germany
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Nikolaou I, Rafailidis V, Kartas A, Kouskouras K, Giannakoulas G. A case of pulmonary arteriovenous malformation in the setting of Rendu Osler Weber syndrome. Radiol Case Rep 2020; 16:483-486. [PMID: 33363687 PMCID: PMC7753088 DOI: 10.1016/j.radcr.2020.12.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 12/07/2020] [Accepted: 12/07/2020] [Indexed: 12/30/2022] Open
Abstract
Rendu Osler Weber syndrome is a rare disorder, in which arteriovenous malformations are a hallmark feature. We describe the case of a 77-year-old female patient who presented with dyspnea, recurrent epistaxis, and signs of right ventricular heart failure, along with hypoxia and severe anemia. Several imaging modalities facilitated diagnostic workup. The computed tomography revealed an area of pulmonary arteriovenous malformation. Visceral involvement, along with clinical criteria and medical history, established the diagnosis of Rendu Osler Weber syndrome. The patient was scheduled for embolization of the PAVM soon after the diagnosis. Proper imaging, guided by clinical suspicion can be extremely helpful in diagnosing and treating this rare entity.
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Affiliation(s)
- Irini Nikolaou
- Department of Radiology, AHEPA University Hospital of Thessaloniki, 54621, Thessaloniki, Greece
- Corresponding author.
| | - Vasileios Rafailidis
- Department of Radiology, AHEPA University Hospital of Thessaloniki, 54621, Thessaloniki, Greece
| | - Anastasios Kartas
- Department of Cardiology, AHEPA University Hospital of Thessaloniki, Greece
| | - Konstantinos Kouskouras
- Department of Radiology, AHEPA University Hospital of Thessaloniki, 54621, Thessaloniki, Greece
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Stickland MK, Tedjasaputra V, Seaman C, Fuhr DP, Collins SÉ, Wagner H, van Diepen S, Byers BW, Wagner PD, Hopkins SR. Intra-pulmonary arteriovenous anastomoses and pulmonary gas exchange: evaluation by microspheres, contrast echocardiography and inert gas elimination. J Physiol 2019; 597:5365-5384. [PMID: 31429918 PMCID: PMC6858494 DOI: 10.1113/jp277695] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 08/12/2019] [Indexed: 01/23/2023] Open
Abstract
KEY POINTS Imaging techniques such as contrast echocardiography suggest that anatomical intra-pulmonary arteriovenous anastomoses (IPAVAs) are present at rest and are recruited to a greater extent in conditions such as exercise. IPAVAs have the potential to act as a shunt, although gas exchange methods have not demonstrated significant shunt in the normal lung. To evaluate this discrepancy, we compared anatomical shunt with 25-µm microspheres to contrast echocardiography, and gas exchange shunt measured by the multiple inert gas elimination technique (MIGET). Intra-pulmonary shunt measured by 25-µm microspheres was not significantly different from gas exchange shunt determined by MIGET, suggesting that MIGET does not underestimate the gas exchange consequences of anatomical shunt. A positive agitated saline contrast echocardiography score was associated with anatomical shunt measured by microspheres. Agitated saline contrast echocardiography had high sensitivity but low specificity to detect a ≥1% anatomical shunt, frequently detecting small shunts inconsequential for gas exchange. ABSTRACT The echocardiographic visualization of transpulmonary agitated saline microbubbles suggests that anatomical intra-pulmonary arteriovenous anastomoses are recruited during exercise, in hypoxia, and when cardiac output is increased pharmacologically. However, the multiple inert gas elimination technique (MIGET) shows insignificant right-to-left gas exchange shunt in normal humans and canines. To evaluate this discrepancy, we measured anatomical shunt with 25-µm microspheres and compared the results to contrast echocardiography and MIGET-determined gas exchange shunt in nine anaesthetized, ventilated canines. Data were acquired under the following conditions: (1) at baseline, (2) 2 µg kg-1 min-1 i.v. dopamine, (3) 10 µg kg-1 min-1 i.v. dobutamine, and (4) following creation of an intra-atrial shunt (in four animals). Right to left anatomical shunt was quantified by the number of 25-µm microspheres recovered in systemic arterial blood. Ventilation-perfusion mismatch and gas exchange shunt were quantified by MIGET and cardiac output by direct Fick. Left ventricular contrast scores were assessed by agitated saline bubble counts, and separately by appearance of 25-µm microspheres. Across all conditions, anatomical shunt measured by 25-µm microspheres was not different from gas exchange shunt measured by MIGET (microspheres: 2.3 ± 7.4%; MIGET: 2.6 ± 6.1%, P = 0.64). Saline contrast bubble score was associated with microsphere shunt (ρ = 0.60, P < 0.001). Agitated saline contrast score had high sensitivity (100%) to detect a ≥1% shunt, but low specificity (22-48%). Gas exchange shunt by MIGET does not underestimate anatomical shunt measured using 25-µm microspheres. Contrast echocardiography is extremely sensitive, but not specific, often detecting small anatomical shunts which are inconsequential for gas exchange.
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Affiliation(s)
- Michael K Stickland
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Canada
- G.F. MacDonald Centre for Lung Health, Covenant Health, Edmonton, Alberta, Canada
| | - Vincent Tedjasaputra
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Canada
- Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Cameron Seaman
- Division of Pediatric Cardiology, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Canada
| | - Desi P Fuhr
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Canada
| | - Sophie É Collins
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Alberta, Canada
| | - Harrieth Wagner
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, University of California San Diego, San Diego, USA
| | - Sean van Diepen
- Department of Critical Care and Division of Cardiology, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Canada
| | - Bradley W Byers
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Canada
- Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Peter D Wagner
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, University of California San Diego, San Diego, USA
| | - Susan R Hopkins
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, University of California San Diego, San Diego, USA
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Meier NM, Foster ML, Battaile JT. Hereditary hemorrhagic telangiectasia and pulmonary arteriovenous malformations: clinical aspects. Cardiovasc Diagn Ther 2018; 8:316-324. [PMID: 30057878 DOI: 10.21037/cdt.2017.12.07] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Hereditary hemorrhagic telangiectasia (HHT) is a genetic disorder of blood vessel formation resulting in mucocutaneous telangiectasias and visceral arteriovenous malformations. Nearly half of patients with HHT will have pulmonary arteriovenous malformations (PAVM) that place them at risk for potentially fatal complications that can occur when blood bypasses the pulmonary capillary circulation or as a result of PAVM rupture. Other manifestations of HHT outside the lung may increase the rate and severity of PAVM complications, creating unique clinical challenges. Management hinges on timely screening and diagnosis, followed by treatment of amenable PAVMs with transcatheter embolization in conjunction with medical management and prophylactic measures to treat and prevent complications. The purpose of this review is to highlight the clinical manifestations of PAVMs specific to patients with HHT and to detail screening and treatment strategies that can reduce the risk of developing life-threatening complications.
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Affiliation(s)
- Nathaniel M Meier
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Michael L Foster
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - John T Battaile
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
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Hemoglobin Is a Vital Determinant of Arterial Oxygen Content in Hypoxemic Patients with Pulmonary Arteriovenous Malformations. Ann Am Thorac Soc 2018; 14:903-911. [PMID: 28267932 DOI: 10.1513/annalsats.201611-872oc] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
RATIONALE PaO2 and SaO2 are commonly measured in respiratory practice, but arterial oxygen content (CaO2) refers to the volume of oxygen delivered to the tissues per unit blood volume. CaO2 is calculated from SaO2 and the hemoglobin concentration in blood, recognizing that each gram of hemoglobin can transport approximately 1.34 ml of oxygen when fully saturated. OBJECTIVES To prospectively evaluate serial changes in CaO2 in humans, incorporating and excluding dynamic changes to oxygenation and hemoglobin parameters that may occur during life. METHODS A cohort of 497 consecutive patients at risk of both hypoxemia and anemia were recruited. The patients had radiologically proven pulmonary arteriovenous malformations (PAVMs), which result in hypoxemia due to right-to-left shunting, and concurrent hereditary hemorrhagic telangiectasia, which placed them at risk of iron deficiency anemia due to recurrent hemorrhagic iron losses. Presentation SaO2 (breathing room air, by pulse oximetry), hemoglobin, red cell and iron indices were measured, and CaO2 calculated as SaO2 × hemoglobin × 1.34 ml/g. Serial measurements were evaluated in 100 cases spanning up to 32.1 (median, 10.5) years. RESULTS Presentation CaO2 ranged from 7.6 to 27.5 (median, 17.6) ml/dl. CaO2 did not change appreciably across the SaO2 quartiles. In contrast, hemoglobin ranged from 5.9 to 21.8 g/dl (median, 14.1 g/dl), with a linear increase in CaO2 across hemoglobin quartiles. After PAVM embolization and an immediate increase in SaO2, hemoglobin fell and CaO2 was unchanged 1.6-12 (median, 4) months later. When hemoglobin fell because of iron deficiency, there was no change in SaO2. Similarly, when hemoglobin rose after iron treatment, there was no change in SaO2, and the expected CaO2 increment was observed. These relationships were not evident during pregnancy when hemoglobin fell, and PAVMs usually deteriorated: in pregnancy SaO2 commonly increased, and serial CaO2 values (incorporating hemodilution/anemia) more accurately reflected deteriorating PAVM status. An apparent fall in CaO2 with age in females was attributable to the development of iron deficiency. There was an unexplained increase in CaO2 with age in follow-up of males after embolization. CONCLUSIONS Hemoglobin/CaO2 should be further incorporated into oxygenation considerations. More attention should be given to modest changes in hemoglobin that substantially modify CaO2.
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Duke JW, Elliott JE, Laurie SS, Voelkel T, Gladstone IM, Fish MB, Lovering AT. Bubble and macroaggregate methods differ in detection of blood flow through intrapulmonary arteriovenous anastomoses in upright and supine hypoxia in humans. J Appl Physiol (1985) 2017; 123:1592-1598. [PMID: 28970204 DOI: 10.1152/japplphysiol.00673.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Blood flow through intrapulmonary arteriovenous anastomoses (Q̇IPAVA) increases in healthy humans breathing hypoxic gas and is potentially dependent on body position. Previous work in subjects breathing room air has shown an effect of body position when Q̇IPAVA is detected with transthoracic saline contrast echocardiography (TTSCE). However, the potential effect of body position on Q̇IPAVA has not been investigated when subjects are breathing hypoxic gas or with a technique capable of quantifying Q̇IPAVA. Thus the purpose of this study was to quantify the effect of body position on Q̇IPAVA when breathing normoxic and hypoxic gas at rest. We studied Q̇IPAVA with TTSCE and quantified Q̇IPAVA with filtered technetium-99m-labeled macroaggregates of albumin (99mTc-MAA) in seven healthy men breathing normoxic and hypoxic (12% O2) gas at rest while supine and upright. On the basis of previous work using TTSCE, we hypothesized that the quantified Q̇IPAVA would be greatest with hypoxia in the supine position. We found that Q̇IPAVA quantified with 99mTc-MAA significantly increased while subjects breathed hypoxic gas in both supine and upright body positions (ΔQ̇IPAVA = 0.7 ± 0.4 vs. 2.5 ± 1.1% of cardiac output, respectively). Q̇IPAVA detected with TTSCE increased from normoxia in supine hypoxia but not in upright hypoxia (median hypoxia bubble score of 2 vs. 0, respectively). Surprisingly, Q̇IPAVA magnitude was greatest in upright hypoxia, when Q̇IPAVA was undetectable with TTSCE. These findings suggest that the relationship between TTSCE and 99mTc-MAA is more complex than previously appreciated, perhaps because of the different physical properties of bubbles and MAA in solution. NEW & NOTEWORTHY Using saline contrast bubbles and radiolabeled macroaggregrates (MAA), we detected and quantified, respectively, hypoxia-induced blood flow through intrapulmonary arteriovenous anastomoses (Q̇IPAVA) in supine and upright body positions in healthy men. Upright hypoxia resulted in the largest magnitude of Q̇IPAVA quantified with MAA but the lowest Q̇IPAVA detected with saline contrast bubbles. These surprising results suggest that the differences in physical properties between saline contrast bubbles and MAA in blood may affect their behavior in vivo.
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Affiliation(s)
- Joseph W Duke
- Department of Biological Sciences, Northern Arizona University , Flagstaff, Arizona
| | | | | | - Thomas Voelkel
- Department of Nuclear Medicine, Sacred Heart Medical Center , Springfield, Oregon
| | - Igor M Gladstone
- Department of Pediatrics, Oregon Health and Sciences University , Portland, Oregon
| | - Mathews B Fish
- Department of Nuclear Medicine, Sacred Heart Medical Center , Springfield, Oregon
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon , Eugene, Oregon
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Duke JW, Elliott JE, Laurie SS, Voelkel T, Gladstone IM, Fish MB, Lovering AT. Relationship between quantitative and descriptive methods of studying blood flow through intrapulmonary arteriovenous anastomoses during exercise. Respir Physiol Neurobiol 2017; 243:47-54. [PMID: 28536067 DOI: 10.1016/j.resp.2017.05.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 05/09/2017] [Accepted: 05/15/2017] [Indexed: 10/19/2022]
Abstract
Several methods exist to study intrapulmonary arteriovenous anastomoses (IPAVA) in humans. Transthoracic saline contrast echocardiography (TTSCE), i.e., bubble scores, is minimally-invasive, but cannot be used to quantify the magnitude of blood flow through IPAVA (QIPAVA). Radiolabeled macroaggregates of albumin (99mTc-MAA) have been used to quantify QIPAVA in humans, but this requires injection of radioactive particles. Previous work has shown agreement between 99mTc-MAA and TTSCE, but this has not been tested simultaneously in the same group of subjects. Thus, the purpose of this study was to determine if there was a relationship between QIPAVA quantified with 99mTc-MAA and bubble scores obtained with TTSCE. To test this, we used 99mTc-MAA and TTSCE to quantify and detect QIPAVA at rest and during exercise in humans. QIPAVA significantly increased from rest to exercise using 99mTc-MAA and TTSCE and there was a moderately-strong, but significant relationship between methods. Our data suggest that high bubble scores generally correspond with large QIPAVA quantified with 99mTc-MAA during exercise.
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Affiliation(s)
- Joseph W Duke
- Northern Arizona University, Department of Biological Sciences, Flagstaff, AZ, USA.
| | | | | | - Thomas Voelkel
- Sacred Heart Medical Center, Department of Nuclear Medicine, Springfield, OR, USA
| | - Igor M Gladstone
- Oregon Health and Sciences University, Department of Pediatrics, Portland, OR, USA
| | - Mathews B Fish
- Sacred Heart Medical Center, Department of Nuclear Medicine, Springfield, OR, USA
| | - Andrew T Lovering
- University of Oregon, Department of Human Physiology, Eugene, OR, USA
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Duke JW, Davis JT, Ryan BJ, Elliott JE, Beasley KM, Hawn JA, Byrnes WC, Lovering AT. Decreased arterial PO2, not O2 content, increases blood flow through intrapulmonary arteriovenous anastomoses at rest. J Physiol 2016; 594:4981-96. [PMID: 27062157 DOI: 10.1113/jp272211] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 03/23/2016] [Indexed: 12/25/2022] Open
Abstract
KEY POINTS The mechanism(s) that regulate hypoxia-induced blood flow through intrapulmonary arteriovenous anastomoses (QIPAVA ) are currently unknown. Our previous work has demonstrated that the mechanism of hypoxia-induced QIPAVA is not simply increased cardiac output, pulmonary artery systolic pressure or sympathetic nervous system activity and, instead, it may be a result of hypoxaemia directly. To determine whether it is reduced arterial PO2 (PaO2) or O2 content (CaO2) that causes hypoxia-induced QIPAVA , individuals were instructed to breathe room air and three levels of hypoxic gas at rest before (control) and after CaO2 was reduced by 10% by lowering the haemoglobin concentration (isovolaemic haemodilution; Low [Hb]). QIPAVA , assessed by transthoracic saline contrast echocardiography, significantly increased as PaO2 decreased and, despite reduced CaO2 (via isovolaemic haemodilution), was similar at iso-PaO2. These data suggest that, with alveolar hypoxia, low PaO2 causes the hypoxia-induced increase in QIPAVA , although where and how this is detected remains unknown. ABSTRACT Alveolar hypoxia causes increased blood flow through intrapulmonary arteriovenous anastomoses (QIPAVA ) in healthy humans at rest. However, it is unknown whether the stimulus regulating hypoxia-induced QIPAVA is decreased arterial PO2 (PaO2) or O2 content (CaO2). CaO2 is known to regulate blood flow in the systemic circulation and it is suggested that IPAVA may be regulated similar to the systemic vasculature. Thus, we hypothesized that reduced CaO2 would be the stimulus for hypoxia-induced QIPAVA . Blood volume (BV) was measured using the optimized carbon monoxide rebreathing method in 10 individuals. Less than 5 days later, subjects breathed room air, as well as 18%, 14% and 12.5% O2 , for 30 min each, in a randomized order, before (CON) and after isovolaemic haemodilution (10% of BV withdrawn and replaced with an equal volume of 5% human serum albumin-saline mixture) to reduce [Hb] (Low [Hb]). PaO2 was measured at the end of each condition and QIPAVA was assessed using transthoracic saline contrast echocardiography. [Hb] was reduced from 14.2 ± 0.8 to 12.8 ± 0.7 g dl(-1) (10 ± 2% reduction) from CON to Low [Hb] conditions. PaO2 was no different between CON and Low [Hb], although CaO2 was 10.4%, 9.2% and 9.8% lower at 18%, 14% and 12.5% O2 , respectively. QIPAVA significantly increased as PaO2 decreased and, despite reduced CaO2, was similar at iso-PaO2. These data suggest that, with alveolar hypoxia, low PaO2 causes the hypoxia-induced increase in QIPAVA . Whether the low PO2 is detected at the carotid body, airway and/or the vasculature remains unknown.
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Affiliation(s)
- Joseph W Duke
- Ohio University, Division of Exercise Physiology, Athens, OH, USA
| | - James T Davis
- University of Oregon, Department of Human Physiology, Eugene, OR, USA
| | - Benjamin J Ryan
- University of Colorado at Boulder, Department of Integrative Physiology, Boulder, CO, USA
| | | | - Kara M Beasley
- University of Oregon, Department of Human Physiology, Eugene, OR, USA
| | - Jerold A Hawn
- Oregon Heart and Vascular Institute, Springfield, OR, USA
| | - William C Byrnes
- University of Colorado at Boulder, Department of Integrative Physiology, Boulder, CO, USA
| | - Andrew T Lovering
- University of Oregon, Department of Human Physiology, Eugene, OR, USA
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Hanley M, Ahmed O, Chandra A, Gage KL, Gerhard-Herman MD, Ginsburg M, Gornik HL, Johnson PT, Oliva IB, Ptak T, Steigner ML, Strax R, Rybicki FJ, Dill KE. ACR Appropriateness Criteria Clinically Suspected Pulmonary Arteriovenous Malformation. J Am Coll Radiol 2016; 13:796-800. [PMID: 27209598 DOI: 10.1016/j.jacr.2016.03.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 03/23/2016] [Indexed: 11/17/2022]
Abstract
Pulmonary arteriovenous malformations are often included in the differential diagnosis of common clinical presentations, including hypoxemia, hemoptysis, brain abscesses, and paradoxical stroke, as well as affecting 30% to 50% of patients with hereditary hemorrhagic telangiectasia (HHT). Various imaging studies are used in the diagnostic and screening settings, which have been reviewed by the ACR Appropriateness Criteria Vascular Imaging Panel. Pulmonary arteriovenous malformation screening in patients with HHT is commonly performed with transthoracic echocardiographic bubble study, followed by CT for positive cases. Although transthoracic echocardiographic bubble studies and radionuclide perfusion detect right-to-left shunts, they do not provide all of the information needed for treatment planning and may remain positive after embolization. Pulmonary angiography is appropriate for preintervention planning but not as an initial test. MR angiography has a potential role in younger patients with HHT who may require lifelong surveillance, despite lower spatial resolution compared with CT. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every three years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.
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Affiliation(s)
- Michael Hanley
- University of Virginia Health System, Charlottesville, Virginia.
| | | | - Ankur Chandra
- Scripps Green Hospital, La Jolla, California, Society for Vascular Surgery
| | | | | | | | - Heather L Gornik
- Cleveland Clinic Heart and Vascular Institute, Cleveland, Ohio, American College of Cardiology
| | | | - Isabel B Oliva
- University of Arizona College of Medicine, Tucson, Arizona
| | - Thomas Ptak
- Massachusetts General Hospital, Boston, Massachusetts
| | - Michael L Steigner
- Brigham and Women's Hospital, Boston, Massachusetts, American College of Cardiology
| | | | - Frank J Rybicki
- Ottawa Hospital Research Institute and the Department of Radiology, University of Ottawa, Ottawa, Ontario, Canada
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Duke JW, Elliott JE, Lovering AT. Clinical consideration for techniques to detect and quantify blood flow through intrapulmonary arteriovenous anastomoses: lessons from physiological studies. Echocardiography 2015; 32 Suppl 3:S195-204. [PMID: 25693624 DOI: 10.1111/echo.12839] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Intrapulmonary arteriovenous anastomoses (IPAVA) are large diameter (>50 μm) vascular conduits, present in >95% of healthy humans. Because IPAVA are large diameter pathways that allow blood flow to bypass the pulmonary capillary network, blood flow through IPAVA (QIPAVA) can permit the transpulmonary passage of particles larger than pulmonary capillaries. IPAVA have been known to exist for over 50 years, but their physiological and clinical significance are still being established; although, currently suggested roles for QIPAVA include allowing emboli to reach the systemic circulation and providing a source of shunt. Studying QIPAVA is an important area of research and as the suggested roles become better established, detecting and quantifying QIPAVA may become significantly more important in the clinic. Several techniques that can be used to quantify and/or detect QIPAVA in animals, ex vivo human/animal lungs, and intact healthy humans; microspheres, radiolabeled macroaggregated albumin particles, and saline contrast echocardiography, are reviewed with limitations and advantages to each. The current body of literature using these techniques to study QIPAVA in animals, ex vivo lungs, and healthy humans has established conditions when QIPAVA is present, such as during exercise or with arterial hypoxemia and conditions when QIPAVA is absent, such as at rest or during exercise breathing 100% O2 . Many of these physiological studies have direct application to patient populations and we discuss each of these findings in the context of their potential to influence the clinical utility, and interpretation, of the results from these techniques highlighted in this review.
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Affiliation(s)
- Joseph W Duke
- Division of Exercise Physiology, Ohio University, Athens, Ohio
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15
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Chawla A, Babu SB, Kannivelu A, Shikhare SS, Chung R. Imaging features and transcatheter treatment of a giant pulmonary arteriovenous malformation in an elderly patient. BJR Case Rep 2015; 2:20150005. [PMID: 30364486 PMCID: PMC6195913 DOI: 10.1259/bjrcr.20150005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 07/21/2015] [Accepted: 09/02/2015] [Indexed: 11/15/2022] Open
Abstract
Pulmonary arteriovenous malformations (PAVMs) comprise an anomalous communication between the pulmonary arterial and systemic circulation. The drainage is usually into one of the pulmonary veins, although rare instances of direct drainage into the left atrium or inferior vena cava have been reported. The result is a high-flow, low-resistance, right-toleft shunt. Although considered uncommon, PAVMs are being diagnosed with increasing frequency in this era of enhanced cross-sectional imaging with CT for lung screening. There is a strong association between PAVMs and hereditary haemorrhagic telangiectasia (HHT); PAVMs are more commonly found in females, with a female to male ratio of 8:1. These have varying clinical presentation, with most symptomatic PAVMs being diagnosed in the first three decades of life. The most common mode of presentation is dyspnoea on exertion. Other reported symptoms are epistaxis, chest pain, cough and, in the event of rupture, haemoptysis. Endocarditis, stroke and brain abscess formation occur frequently in patients with undiagnosed HHT with PAVMs. A 76-year-old female, with a presumed clinical diagnosis of asthma, presented to the emergency department with worsening shortness of breath. The imaging studies revealed a giant PAVM and a radionuclide scan demonstrated a large right-to-left shunt, likely accounting for her symptoms. She underwent successful transcatheter embolization (TCE) with a vascular plug performed by the interventional radiology team. The aim of this case report is to describe the imaging findings and TCE treatment of a giant PAVM.
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Affiliation(s)
- Ashish Chawla
- Department of Diagnostic Radiology, Khoo Teck Puat Hospital, Yishun Central, Singapore
| | | | - Anbalagan Kannivelu
- Department of Diagnostic Radiology, Khoo Teck Puat Hospital, Yishun Central, Singapore
| | - Sumer S Shikhare
- Department of Diagnostic Radiology, Khoo Teck Puat Hospital, Yishun Central, Singapore
| | - Raymond Chung
- Department of Diagnostic Radiology, Khoo Teck Puat Hospital, Yishun Central, Singapore
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What radiologists need to know about the pulmonary–systemic flow ratio (Qp/Qs): What it is, how to calculate it, and what it is for. RADIOLOGIA 2015. [DOI: 10.1016/j.rxeng.2015.07.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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17
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What radiologists need to know about the pulmonary-systemic flow ratio (Qp/Qs): what it is, how to calculate it, and what it is for. RADIOLOGIA 2015; 57:369-79. [PMID: 26070521 DOI: 10.1016/j.rx.2015.04.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Revised: 04/26/2015] [Accepted: 04/28/2015] [Indexed: 11/22/2022]
Abstract
Cardiac magnetic resonance imaging (cMRI) provides abundant morphological and functional information in the study of congenital heart disease. The functional information includes pulmonary output and systemic output; the ratio between these two (Qp/Qs) is the shunt fraction. After birth, in normal conditions the pulmonary output is practically identical to the systemic output, so Qp/Qs = 1. In patients with « shunts » between the systemic and pulmonary circulations, the ratio changes, and the interpretation of these findings varies in function of the location of the shunt (intracardiac or extracardiac) and of the associated structural or postsurgical changes. We review the concept of Qp/Qs; the methods to calculate it, with special emphasis on cMRI; and the meaning of the results obtained. We place special emphasis on the relevance of these findings depending on the underlying disease and the treatment the patient has undergone.
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Howard LSGE, Santhirapala V, Murphy K, Mukherjee B, Busbridge M, Tighe HC, Jackson JE, Hughes JMB, Shovlin CL. Cardiopulmonary exercise testing demonstrates maintenance of exercise capacity in patients with hypoxemia and pulmonary arteriovenous malformations. Chest 2015; 146:709-718. [PMID: 24676541 DOI: 10.1378/chest.13-2988] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
BACKGROUND Patients with pulmonary arteriovenous malformations (PAVMs) are unusual because hypoxemia results from right-to-left shunting and not airway or alveolar disease. Their surprisingly well-preserved exercise capacity is not generally appreciated. METHODS To examine why exercise tolerance is preserved, cardiopulmonary exercise tests were performed while breathing room air in 21 patients with radiologically proven PAVMs, including five restudied 3 to 12 months after embolization when their PAVMs had regressed. Where physiologic matching was demonstrable, comparisons were made with 12 healthy control subjects. RESULTS The majority of patients achieved their predicted work rate despite a resting arterial oxygen saturation (SaO₂) of 80% to 96%. Peak work rate and oxygen consumption (VO₂) were no lower in patients with more hypoxemia. Despite higher SaO₂ following embolization (median, 96% and 90%; P = .009), patients achieved similar work rates and similar peak VO₂. Strikingly, treated patients reset to virtually identical peak oxygen pulses (ie, VO₂ per heart beat) and in many cases to the same point on the peak oxygen pulse/work rate plot. The 21 patients had increased minute ventilation (VE) for given increases in CO₂ production (VE/VCO₂ slope), but perceived dyspnea was no greater than in the 12 control subjects or in the same patients before compared to after embolization comparison. Overall, work rate and peak VO₂ were associated not with oxygenation parameters but with VE/VCO₂ slope, BMI, and anaerobic threshold. CONCLUSIONS Patients with hypoxemia and PAVMs can maintain normal oxygen delivery/VO₂ during peak exercise. Following improvement of SaO₂ by embolization, patients appeared to reset compensatory mechanisms and, as a result, achieved similar peak VO₂ per heart beat and peak work rates.
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Affiliation(s)
- Luke S G E Howard
- Divisions of Cardiovascular Medicine, Imperial College Healthcare NHS Trust
| | - Vatshalan Santhirapala
- National Heart and Lung Institute Cardiovascular Sciences, Imperial College London, London, England; Respiratory Sciences, Imperial College London, London, England; Imperial College School of Medicine, Imperial College London, London, England
| | - Kevin Murphy
- Respiratory Medicine, Imperial College Healthcare NHS Trust
| | - Bhashkar Mukherjee
- Divisions of Cardiovascular Medicine, Imperial College Healthcare NHS Trust
| | - Mark Busbridge
- Clinical Chemistry, Imperial College Healthcare NHS Trust
| | - Hannah C Tighe
- Respiratory Medicine, Imperial College Healthcare NHS Trust
| | | | - J Michael B Hughes
- Respiratory Medicine, Imperial College Healthcare NHS Trust; National Heart and Lung Institute Cardiovascular Sciences, Imperial College London, London, England; Respiratory Sciences, Imperial College London, London, England
| | - Claire L Shovlin
- Respiratory Medicine, Imperial College Healthcare NHS Trust; National Heart and Lung Institute Cardiovascular Sciences, Imperial College London, London, England.
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Lovering AT, Duke JW, Elliott JE. Intrapulmonary arteriovenous anastomoses in humans--response to exercise and the environment. J Physiol 2015; 593:507-20. [PMID: 25565568 DOI: 10.1113/jphysiol.2014.275495] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 12/05/2014] [Indexed: 12/17/2022] Open
Abstract
Intrapulmonary arteriovenous anastomoses (IPAVA) have been known to exist in human lungs for over 60 years. The majority of the work in this area has largely focused on characterizing the conditions in which IPAVA blood flow (Q̇IPAVA ) is either increased, e.g. during exercise, acute normobaric hypoxia, and the intravenous infusion of catecholamines, or absent/decreased, e.g. at rest and in all conditions with alveolar hyperoxia (FIO2 = 1.0). Additionally, Q̇IPAVA is present in utero and shortly after birth, but is reduced in older (>50 years) adults during exercise and with alveolar hypoxia, suggesting potential developmental origins and an effect of age. The physiological and pathophysiological roles of Q̇IPAVA are only beginning to be understood and therefore these data remain controversial. Although evidence is accumulating in support of important roles in both health and disease, including associations with pulmonary arterial pressure, and adverse neurological sequelae, there is much work that remains to be done to fully understand the physiological and pathophysiological roles of IPAVA. The development of novel approaches to studying these pathways that can overcome the limitations of the currently employed techniques will greatly help to better quantify Q̇IPAVA and identify the consequences of Q̇IPAVA on physiological and pathophysiological processes. Nevertheless, based on currently published data, our proposed working model is that Q̇IPAVA occurs due to passive recruitment under conditions of exercise and supine body posture, but can be further modified by active redistribution of pulmonary blood flow under hypoxic and hyperoxic conditions.
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Affiliation(s)
- Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, OR, USA
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20
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Merkus D. Pulmonary arteriovenous malformations: haemodynamics and shunt closure. Neth Heart J 2014; 22:326-7. [PMID: 24668220 PMCID: PMC4099439 DOI: 10.1007/s12471-014-0546-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- D. Merkus
- Department of Cardiology, Erasmus MC, PO Box 2040, 3000 CA Rotterdam, the Netherlands
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21
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Santhirapala V, Williams LC, Tighe HC, Jackson JE, Shovlin CL. Arterial oxygen content is precisely maintained by graded erythrocytotic responses in settings of high/normal serum iron levels, and predicts exercise capacity: an observational study of hypoxaemic patients with pulmonary arteriovenous malformations. PLoS One 2014; 9:e90777. [PMID: 24637882 PMCID: PMC3956463 DOI: 10.1371/journal.pone.0090777] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 02/04/2014] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Oxygen, haemoglobin and cardiac output are integrated components of oxygen transport: each gram of haemoglobin transports 1.34 mls of oxygen in the blood. Low arterial partial pressure of oxygen (PaO2), and haemoglobin saturation (SaO2), are the indices used in clinical assessments, and usually result from low inspired oxygen concentrations, or alveolar/airways disease. Our objective was to examine low blood oxygen/haemoglobin relationships in chronically compensated states without concurrent hypoxic pulmonary vasoreactivity. METHODOLOGY 165 consecutive unselected patients with pulmonary arteriovenous malformations were studied, in 98 cases, pre/post embolisation treatment. 159 (96%) had hereditary haemorrhagic telangiectasia. Arterial oxygen content was calculated by SaO2 x haemoglobin x 1.34/100. PRINCIPAL FINDINGS There was wide variation in SaO2 on air (78.5-99, median 95)% but due to secondary erythrocytosis and resultant polycythaemia, SaO2 explained only 0.1% of the variance in arterial oxygen content per unit blood volume. Secondary erythrocytosis was achievable with low iron stores, but only if serum iron was high-normal: Low serum iron levels were associated with reduced haemoglobin per erythrocyte, and overall arterial oxygen content was lower in iron deficient patients (median 16.0 [IQR 14.9, 17.4]mls/dL compared to 18.8 [IQR 17.4, 20.1]mls/dL, p<0.0001). Exercise tolerance appeared unrelated to SaO2 but was significantly worse in patients with lower oxygen content (p<0.0001). A pre-defined athletic group had higher Hb:SaO2 and serum iron:ferritin ratios than non-athletes with normal exercise capacity. PAVM embolisation increased SaO2, but arterial oxygen content was precisely restored by a subsequent fall in haemoglobin: 86 (87.8%) patients reported no change in exercise tolerance at post-embolisation follow-up. SIGNIFICANCE Haemoglobin and oxygen measurements in isolation do not indicate the more physiologically relevant oxygen content per unit blood volume. This can be maintained for SaO2 ≥78.5%, and resets to the same arterial oxygen content after correction of hypoxaemia. Serum iron concentrations, not ferritin, seem to predict more successful polycythaemic responses.
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Affiliation(s)
- Vatshalan Santhirapala
- Imperial College School of Medicine, Imperial College, London, United Kingdom
- National Heart and Lung Institute (NHLI) Cardiovascular Science, Imperial College, London, United Kingdom
- Respiratory Medicine, Hammersmith Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
| | - Louisa C. Williams
- Respiratory Medicine, Hammersmith Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
| | - Hannah C. Tighe
- Respiratory Medicine, Hammersmith Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
| | - James E. Jackson
- Department of Imaging, Hammersmith Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
| | - Claire L. Shovlin
- National Heart and Lung Institute (NHLI) Cardiovascular Science, Imperial College, London, United Kingdom
- Respiratory Medicine, Hammersmith Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
- * E-mail:
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22
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Claessen G, Claus P, Delcroix M, Bogaert J, Gerche AL, Heidbuchel H. Interaction between respiration and right versus left ventricular volumes at rest and during exercise: a real-time cardiac magnetic resonance study. Am J Physiol Heart Circ Physiol 2014; 306:H816-24. [DOI: 10.1152/ajpheart.00752.2013] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Breathing-induced changes in intrathoracic pressures influence left ventricular (LV) and right ventricular (RV) volumes, the exact nature and extent of which have not previously been evaluated in humans. We sought to examine this “respiratory pump” using novel real-time cardiac magnetic resonance (CMR) imaging. Eight healthy subjects underwent serial multislice real-time CMR during normal breathing, breath holding, and the Valsalva maneuver. Subsequently, a separate cohort of nine subjects underwent real-time CMR at rest and during incremental exercise. LV and RV end-diastolic volume (EDV) and end-systolic volume (ESV) and diastolic and systolic eccentricity indexes were determined at peak inspiration and expiration. During normal breathing, inspiration resulted in an increase in RV volumes [RVEDV: +18 ± 8%, RVESV: +14 ± 12%, and RV stroke volume (SV): +21 ± 10%, P < 0.01] and an opposing decrease in LV volumes ( P < 0.0001 for interaction). During end-inspiratory breath holding, RV SV decreased by 9 ± 10% ( P = 0.046), whereas LV SV did not change. During the Valsalva maneuver, volumes decreased in both ventricles (RVEDV: −29 ± 11%, RVESV: −16 ± 14%, RV SV: −36 ± 14%, LVEDV: −22 ± 17%, and LV SV: −25 ± 17%, P < 0.01). The reciprocal effect of respiration on LV and RV volumes was maintained throughout exercise. The diastolic and systolic eccentricity indexes were greater during inspiration than during expiration, both at rest and during exercise ( P < 0.0001 for both). In conclusion, ventricular volumes oscillate with respiratory phase such that RV and LV volumes are maximal at peak inspiration and expiration, respectively. Thus, interpretation of RV versus LV volumes requires careful definition of the exact respiratory time point for proper interpretation, both at rest and during exercise.
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Affiliation(s)
- Guido Claessen
- Department of Cardiovascular Medicine, University Hospitals Leuven, Leuven, Belgium
| | - Piet Claus
- Department of Cardiovascular Imaging and Dynamics, University of Leuven, Leuven, Belgium
| | - Marion Delcroix
- Department of Pneumology, University Hospitals Leuven, Leuven, Belgium
| | - Jan Bogaert
- Department of Radiology, University Hospitals Leuven, Leuven, Belgium; and
| | - Andre La Gerche
- Department of Cardiovascular Medicine, University Hospitals Leuven, Leuven, Belgium
- St Vincent's Hospital Department of Medicine, University of Melbourne, Fitzroy, South Australia, Australia
| | - Hein Heidbuchel
- Department of Cardiovascular Medicine, University Hospitals Leuven, Leuven, Belgium
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Ischaemic strokes in patients with pulmonary arteriovenous malformations and hereditary hemorrhagic telangiectasia: associations with iron deficiency and platelets. PLoS One 2014; 9:e88812. [PMID: 24586400 PMCID: PMC3929507 DOI: 10.1371/journal.pone.0088812] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2013] [Accepted: 01/13/2014] [Indexed: 01/24/2023] Open
Abstract
Background Pulmonary first pass filtration of particles marginally exceeding ∼7 µm (the size of a red blood cell) is used routinely in diagnostics, and allows cellular aggregates forming or entering the circulation in the preceding cardiac cycle to lodge safely in pulmonary capillaries/arterioles. Pulmonary arteriovenous malformations compromise capillary bed filtration, and are commonly associated with ischaemic stroke. Cohorts with CT-scan evident malformations associated with the highest contrast echocardiographic shunt grades are known to be at higher stroke risk. Our goal was to identify within this broad grouping, which patients were at higher risk of stroke. Methodology 497 consecutive patients with CT-proven pulmonary arteriovenous malformations due to hereditary haemorrhagic telangiectasia were studied. Relationships with radiologically-confirmed clinical ischaemic stroke were examined using logistic regression, receiver operating characteristic analyses, and platelet studies. Principal Findings Sixty-one individuals (12.3%) had acute, non-iatrogenic ischaemic clinical strokes at a median age of 52 (IQR 41–63) years. In crude and age-adjusted logistic regression, stroke risk was associated not with venous thromboemboli or conventional neurovascular risk factors, but with low serum iron (adjusted odds ratio 0.96 [95% confidence intervals 0.92, 1.00]), and more weakly with low oxygen saturations reflecting a larger right-to-left shunt (adjusted OR 0.96 [0.92, 1.01]). For the same pulmonary arteriovenous malformations, the stroke risk would approximately double with serum iron 6 µmol/L compared to mid-normal range (7–27 µmol/L). Platelet studies confirmed overlooked data that iron deficiency is associated with exuberant platelet aggregation to serotonin (5HT), correcting following iron treatment. By MANOVA, adjusting for participant and 5HT, iron or ferritin explained 14% of the variance in log-transformed aggregation-rate (p = 0.039/p = 0.021). Significance These data suggest that patients with compromised pulmonary capillary filtration due to pulmonary arteriovenous malformations are at increased risk of ischaemic stroke if they are iron deficient, and that mechanisms are likely to include enhanced aggregation of circulating platelets.
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Abstract
Pulmonary arteriovenous malformations (PAVMs) are abnormal vascular structures that most often connect a pulmonary artery to a pulmonary vein, bypassing the normal pulmonary capillary bed and resulting in an intrapulmonary right-to-left shunt. As a consequence, patients with PAVM can have hypoxemia and paradoxical embolization complications, including stroke and brain abscess. PAVMs may be single or multiple, unilateral or bilateral, and simple or complex. Most PAVMs are hereditary and occur in hereditary hemorrhagic telangiectasia, an autosomal dominant vascular disorder, and screening for PAVM is indicated in this subgroup. PAVMs may also be idiopathic, occur as a result of trauma and infection, or be secondary to hepatopulmonary syndrome and bidirectional cavopulmonary shunting. Diagnostic testing involves identifying an intrapulmonary shunt, with the most sensitive test being transthoracic contrast echocardiography. Chest CT scan is useful in characterizing PAVM in patients with positive intrapulmonary shunting. Transcatheter embolotherapy is the treatment of choice for PAVM. Lifelong follow-up is important because recanalization and collateralization may occur after embolization therapy. Surgical resection is rarely necessary and reserved for patients who are not candidates for embolization. Antibiotic prophylaxis for procedures with a risk of bacteremia (eg, dental procedures) is recommended in all patients with PAVM because of the risk of cerebral abscess.
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Affiliation(s)
- Rodrigo Cartin-Ceba
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, MN.
| | - Karen L Swanson
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, MN
| | - Michael J Krowka
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, MN
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Abstract
Diseases of the pulmonary vasculature are a cause of increased pulmonary vascular resistance (PVR) in pulmonary embolism, chronic thromboembolic pulmonary hypertension (CTEPH), and pulmonary arterial hypertension or decreased PVR in pulmonary arteriovenous malformations on hereditary hemorrhagic telangiectasia, portal hypertension, or cavopulmonary anastomosis. All these conditions are associated with a decrease in both arterial PO2 and PCO2. Gas exchange in pulmonary vascular diseases with increased PVR is characterized by a shift of ventilation and perfusion to high ventilation-perfusion ratios, a mild to moderate increase in perfusion to low ventilation-perfusion ratios, and an increased physiologic dead space. Hypoxemia in these patients is essentially explained by altered ventilation-perfusion matching amplified by a decreased mixed venous PO2 caused by a low cardiac output. Hypocapnia is accounted for by hyperventilation, which is essentially related to an increased chemosensitivity. A cardiac shunt on a patent foramen ovale may be a cause of severe hypoxemia in a proportion of patients with pulmonary hypertension and an increase in right atrial pressure. Gas exchange in pulmonary arteriovenous malformations is characterized by variable degree of pulmonary shunting and/or diffusion-perfusion imbalance. Hypocapnia is caused by an increased ventilation in relation to an increased pulmonary blood flow with direct peripheral chemoreceptor stimulation by shunted mixed venous blood flow.
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Affiliation(s)
- C Mélot
- Department of Emergency Medicine, Erasme University Hospital, Brussels, Belgium.
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26
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Abstract
Severe cyanosis due to pulmonary arteriovenous fistulas occurs often after a bidirectional superior cavopulmonary anastomosis (Glenn operation) and also in some congenital anomalies in which hepatic venous blood bypasses the lungs in the first passage. Relocation of hepatic flow into the lungs usually causes these fistulas to disappear. Similar pulmonary arteriovenous fistulas are observed in hereditary haemorrhagic telangiectasia, and in liver disease (hepatopulmonary syndrome). There is no convincing identification yet of a responsible hepatic factor that produces these lesions. Candidates for such a factor are reviewed, and the possibility of angiotensin or bradykinin contributing to the fistulas is discussed.
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Stickland MK, Lindinger MI, Olfert IM, Heigenhauser GJF, Hopkins SR. Pulmonary gas exchange and acid-base balance during exercise. Compr Physiol 2013; 3:693-739. [PMID: 23720327 PMCID: PMC8315793 DOI: 10.1002/cphy.c110048] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
As the first step in the oxygen-transport chain, the lung has a critical task: optimizing the exchange of respiratory gases to maintain delivery of oxygen and the elimination of carbon dioxide. In healthy subjects, gas exchange, as evaluated by the alveolar-to-arterial PO2 difference (A-aDO2), worsens with incremental exercise, and typically reaches an A-aDO2 of approximately 25 mmHg at peak exercise. While there is great individual variability, A-aDO2 is generally largest at peak exercise in subjects with the highest peak oxygen consumption. Inert gas data has shown that the increase in A-aDO2 is explained by decreased ventilation-perfusion matching, and the development of a diffusion limitation for oxygen. Gas exchange data does not indicate the presence of right-to-left intrapulmonary shunt developing with exercise, despite recent data suggesting that large-diameter arteriovenous shunt vessels may be recruited with exercise. At the same time, multisystem mechanisms regulate systemic acid-base balance in integrative processes that involve gas exchange between tissues and the environment and simultaneous net changes in the concentrations of strong and weak ions within, and transfer between, extracellular and intracellular fluids. The physicochemical approach to acid-base balance is used to understand the contributions from independent acid-base variables to measured acid-base disturbances within contracting skeletal muscle, erythrocytes and noncontracting tissues. In muscle, the magnitude of the disturbance is proportional to the concentrations of dissociated weak acids, the rate at which acid equivalents (strong acid) accumulate and the rate at which strong base cations are added to or removed from muscle.
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Affiliation(s)
- Michael K. Stickland
- Division of Pulmonary Medicine, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
| | - Michael I. Lindinger
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - I. Mark Olfert
- Robert C. Byrd Health Sciences Center, Center for Cardiovascular and Respiratory Sciences, Division of Exercise Physiology, West Virginia University School of Medicine, Morgantown, West Virginia
| | | | - Susan R. Hopkins
- Departments of Medicine and Radiology, University of California, San Diego, San Diego, California
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Kennedy JM, Foster GE, Koehle MS, Potts JE, Sandor GG, Potts MT, Houghton KM, Henderson WR, Sheel AW. Exercise-induced intrapulmonary arteriovenous shunt in healthy women. Respir Physiol Neurobiol 2012; 181:8-13. [DOI: 10.1016/j.resp.2012.01.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 12/15/2011] [Accepted: 01/10/2012] [Indexed: 12/18/2022]
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Ando K, Mochizuki A, Kurimoto N, Yokote K, Nakajima Y, Osada H, Nakamura H. Coil embolization for pulmonary arteriovenous malformation as an organ-sparing therapy: outcome of long-term follow-up. Ann Thorac Cardiovasc Surg 2011; 17:118-23. [PMID: 21597407 DOI: 10.5761/atcs.oa.10.01536] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Accepted: 02/23/2010] [Indexed: 11/16/2022] Open
Abstract
PURPOSE Pulmonary artery coil embolization (PACE) is increasingly utilized to treat pulmonary arteriovenous malformations (PAVMs), but the long-term outcome of this treatment modality remains unclear. By evaluating the long-term outcome of patients at St. Marianna University Hospital treated with PACE, we wanted to see if PACE could effectively replace the surgical resection of PAVMs. PATIENTS AND METHODS We retrospectively evaluated 9 consecutive patients (4 males, 5 females; age range, 16-67 years; mean ± SD, 43.6 ± 18.7 years) who underwent PACE for PAVMs. Selective pulmonary artery angiography using Seldinger's method was initially performed to identify the feeding arteries. This was followed by embolization using interlocking detachable coils and microcoils. RESULTS The procedure resulted in no severe complications. All treated patients were free from PAVM symptoms. A recurrence did not occur after PACE in 8 of 9 (88%) patients for 31 to 173 months (86 ± 51). Recanalization of the embolized malformation occurred after 3 months in one patient. This patient underwent an additional successful PACE without any further recurrences for 73 months. CONCLUSIONS PACE is an organ-sparing therapy with satisfactory long-term results. It can safely replace the surgical resection of PAVMs.
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Affiliation(s)
- Koji Ando
- Chest Surgery, St. Marianna University School of Medicine, Kawasaki, Kanagawa, Japan.
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Elliott JE, Choi Y, Laurie SS, Yang X, Gladstone IM, Lovering AT. Reply to Van Liew and Vann. J Appl Physiol (1985) 2011. [DOI: 10.1152/japplphysiol.01229.2010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
| | - Yujung Choi
- University of Puget Sound, Tacoma, Washington; and
| | - Steven S. Laurie
- Department of Human Physiology, University of Oregon, Eugene, Oregon
| | - Ximeng Yang
- Department of Human Physiology, University of Oregon, Eugene, Oregon
| | - Igor M. Gladstone
- Department of Human Physiology, University of Oregon, Eugene, Oregon
- Department of Pediatrics, Oregon Health and Science University, Portland, Oregon
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Arena R, Myers J, Lavie CJ, Forman DE, Guazzi M. Ordering a cardiopulmonary exercise test for your patient: key considerations for the physician. Future Cardiol 2011; 7:55-60. [DOI: 10.2217/fca.10.112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cardiopulmonary exercise testing (CPX) is a specialized exercise assessment that provides valuable information in a number of patient populations. Physicians are often familiar with standard exercise testing procedures (i.e., the cardiac stress test) and, therefore, appropriately refer patients with signs/symptoms suggestive of myocardial ischemia. However, the procedures surrounding referral for CPX, and the relevance of the data obtained, may not be as widely understood in the medical community. The purpose of the current special report is to provide physicians referring patients for CPX with information on the appropriateness of CPX referral and testing logistics, the identification of an appropriate CPX laboratory for referral, and definitions on key CPX variables that should be included in the final report.
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Affiliation(s)
- Ross Arena
- Departments of Physical Therapy, Internal Medicine & Physiology, Virginia Commonwealth University, Richmond, VA, USA
| | - Jonathan Myers
- VA Palo Alto Health Care System, Cardiology Division, Palo Alto, CA, USA
| | - Carl J Lavie
- Department of Cardiovascular Diseases, John Ochsner Heart & Vascular Institute, Ochsner Clinical School, The University of Queensland School of Medicine, New Orleans, LA, USA
| | - Daniel E Forman
- Brigham & Women’s Hospital, Cardiovascular Division, Boston, MA, USA
- VA Boston Healthcare System, Geriatric Research, Education & Clinical Center, Boston, MA, USA
| | - Marco Guazzi
- University of Milano, San Paolo Hospital, Cardiopulmonary Laboratory, Cardiology Division, Milano, Italy
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La Gerche A, MacIsaac AI, Burns AT, Mooney DJ, Inder WJ, Voigt JU, Heidbüchel H, Prior DL. Pulmonary transit of agitated contrast is associated with enhanced pulmonary vascular reserve and right ventricular function during exercise. J Appl Physiol (1985) 2010; 109:1307-17. [DOI: 10.1152/japplphysiol.00457.2010] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pulmonary transit of agitated contrast (PTAC) occurs to variable extents during exercise. We tested the hypothesis that the onset of PTAC signifies flow through larger-caliber vessels, resulting in improved pulmonary vascular reserve during exercise. Forty athletes and fifteen nonathletes performed maximal exercise with continuous echocardiographic Doppler measures [cardiac output (CO), pulmonary artery systolic pressure (PASP), and myocardial velocities] and invasive blood pressure (BP). Arterial gases and B-type natriuretic peptide (BNP) were measured at baseline and peak exercise. Pulmonary vascular resistance (PVR) was determined as the regression of PASP/CO and was compared according to athletic and PTAC status. At peak exercise, athletes had greater CO (16.0 ± 2.9 vs. 12.4 ± 3.2 l/min, P < 0.001) and higher PASP (60.8 ± 12.6 vs. 47.0 ± 6.5 mmHg, P < 0.001), but PVR was similar to nonathletes ( P = 0.71). High PTAC (defined by contrast filling of the left ventricle) occurred in a similar proportion of athletes and nonathletes (18/40 vs. 10/15, P = 0.35) and was associated with higher peak-exercise CO (16.1 ± 3.4 vs. 13.9 ± 2.9 l/min, P = 0.010), lower PASP (52.3 ± 9.8 vs. 62.6 ± 13.7 mmHg, P = 0.003), and 37% lower PVR ( P < 0.0001) relative to low PTAC. Right ventricular (RV) myocardial velocities increased more and BNP increased less in high vs. low PTAC subjects. On multivariate analysis, maximal oxygen consumption (V̇o2max) ( P = 0.009) and maximal exercise output ( P = 0.049) were greater in high PTAC subjects. An exercise-induced decrease in arterial oxygen saturation (98.0 ± 0.4 vs. 96.7 ± 1.4%, P < 0.0001) was not influenced by PTAC status ( P = 0.96). Increased PTAC during exercise is a marker of pulmonary vascular reserve reflected by greater flow, reduced PVR, and enhanced RV function.
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Affiliation(s)
- André La Gerche
- Departments of 1Medicine and of
- Department of Cardiovascular Medicine, University Hospital, University of Leuven, Leuven, Belgium
| | - Andrew I. MacIsaac
- Cardiology, St. Vincent's Hospital, University of Melbourne, Melbourne, Australia; and
| | - Andrew T. Burns
- Cardiology, St. Vincent's Hospital, University of Melbourne, Melbourne, Australia; and
| | - Don J. Mooney
- Cardiology, St. Vincent's Hospital, University of Melbourne, Melbourne, Australia; and
| | | | - Jens-Uwe Voigt
- Department of Cardiovascular Medicine, University Hospital, University of Leuven, Leuven, Belgium
| | - Hein Heidbüchel
- Department of Cardiovascular Medicine, University Hospital, University of Leuven, Leuven, Belgium
| | - David L. Prior
- Departments of 1Medicine and of
- Cardiology, St. Vincent's Hospital, University of Melbourne, Melbourne, Australia; and
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Lovering AT, Elliott JE, Beasley KM, Laurie SS. Pulmonary pathways and mechanisms regulating transpulmonary shunting into the general circulation: an update. Injury 2010; 41 Suppl 2:S16-23. [PMID: 21144922 PMCID: PMC4385739 DOI: 10.1016/s0020-1383(10)70004-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Embolic insults account for a significant number of neurologic sequelae following many routine surgical procedures. Clearly, these post-intervention embolic events are a serious public health issue as they are potentially life altering. However, the pathway these emboli utilize to bypass the pulmonary microcirculatory sieve in patients without an intracardiac shunt such as an atrial septal defect or patent foramen ovale, remains unclear. In the absence of intracardiac routes and large diameter pulmonary arteriovenous malformations, inducible large diameter intrapulmonary arteriovenous anastomoses in otherwise healthy adult humans may prove to be the best explanation. Our group and others have demonstrated that inducible large diameter intrapulmonary arteriovenous anastomoses are closed at rest but can open during hyperdynamic conditions such as exercise in more than 90% of healthy humans. Furthermore, the patency of these intrapulmonary anastomoses can be modulated through the fraction of inspired oxygen and by body positioning. Of particular clinical interest, there appears to be a strong association between arterial hypoxemia and neurologic insults, suggesting a breach in the filtering ability of the pulmonary microvasculature under these conditions. In this review, we present evidence demonstrating the existence of inducible intrapulmonary arteriovenous anastomoses in healthy humans that are modulated by exercise, oxygen tension and body positioning. Additionally, we identify several clinical conditions associated with both arterial hypoxemia and an increased risk for embolic insults. Finally, we suggest some precautionary measures that should be taken during interventions to keep intrapulmonary arteriovenous anastomoses closed in order to prevent or reduce the incidence of paradoxical embolism.
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Affiliation(s)
- Andrew T Lovering
- Department of Human Physiology, University of Oregon, Cardiopulmonary & Respiratory Physiology Laboratory, Eugene, OR 97401, USA.
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Abstract
An idea of arteriovenous shunts (AVS) was proposed for explanation of dynamic regulation of oxygenation and venous hyperoxia. A formula enabling calculation of AVS and real CO 2 production has recently been derived by comparing data of arterial and venous blood gases. Regarding venous hyperoxia, there is a need to differentiate capillary to tissue transport defect (low oxygen utilisation-LOU) from AVS, which may exist simultaneously. The AVS may be associated with normal or relatively high oxygen utilization from the capillary vessels and increased CO2 production. AVS is proposed to carry protective and ‘stealing’ properties including renal, cardiac, and pulmonary hemodynamic. Calculations of the AVS may be important for dynamic assessment of vascular and metabolic status and in emergency medicine.
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Affiliation(s)
- Alexander P Rozin
- B. Shine Department of Rheumatology, Rambam Health Care Campus and Technion, Haifa, Israel,
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35
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Bates ML. A potential role for intrapulmonary shunt pathways in pathology. J Appl Physiol (1985) 2009; 107:1000-1; discussion 997-8, 998. [PMID: 19774713 DOI: 10.1152/japplphysiol.00660.2009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Melissa L Bates
- Department of Pediatrics, Division of Critical Care, The University of Wisconsin, USA
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36
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Lovering AT, Haverkamp HC, Romer LM, Hokanson JS, Eldridge MW. Transpulmonary passage of 99mTc macroaggregated albumin in healthy humans at rest and during maximal exercise. J Appl Physiol (1985) 2009; 106:1986-92. [PMID: 19372301 PMCID: PMC2692773 DOI: 10.1152/japplphysiol.01357.2007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 04/10/2009] [Indexed: 11/22/2022] Open
Abstract
We have demonstrated that 50-mum-diameter arteriovenous pathways exist in isolated, healthy human and baboon lungs, ventilated and perfused under physiological pressures. These findings have been confirmed and extended by demonstrating the passage of 25-microm microspheres through the lungs of exercising dogs, but not at rest. Determination of blood flow through these large-diameter intrapulmonary arteriovenous pathways would be an important first step to establish a physiological role for these vessels. Currently, we sought to estimate blood flow through these arteriovenous pathways using technetium-99m ((99m)Tc)-labeled macroaggregated albumin (MAA) in healthy humans at rest and during maximal treadmill exercise. We hypothesized that the percentage of (99m)Tc MAA able to traverse the pulmonary circulation (%transpulmonary passage) would increase during exercise. Seven male subjects without patent foramen ovale were injected with (99m)Tc MAA at rest on 1 day and during maximal treadmill exercise on a separate day (>6 days). Within 5 min after injection, subjects began whole body imaging in the supine position. Six of the seven subjects showed an increase in transpulmonary passage of MAA with maximal exercise. Using two separate analysis methods, percent transpulmonary passage significantly increased with exercise from baseline to absolute values of 1.2 +/- 0.8% (P = 0.008) and 1.3 +/- 1.0% (P = 0.016), respectively (means +/- SD; paired t-test). We conclude that MAA may be traversing the pulmonary circulation via large-diameter intrapulmonary arteriovenous conduits in healthy humans during exercise. Recruitment of these pathways may divert blood flow away from pulmonary capillaries during exercise and compromise the lung's function as a biological filter.
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Affiliation(s)
- Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, OR 97403-1240, USA.
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37
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MR Angiography for Detection of Pulmonary Arteriovenous Malformations in Patients with Hereditary Hemorrhagic Telangiectasia. AJR Am J Roentgenol 2008; 190:892-901. [DOI: 10.2214/ajr.07.2966] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Lovering AT, Stickland MK, Eldridge MW. Intrapulmonary shunt during normoxic and hypoxic exercise in healthy humans. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 588:31-45. [PMID: 17089877 DOI: 10.1007/978-0-387-34817-9_4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This review presents evidence for the recruitment of intrapulmonary arteriovenous shunts (IPAVS) during exercise in normal healthy humans. Support for pre-capillary connections between the arterial and venous circulation in lungs of humans and animals have existed for over one-hundred years. Right-to-left physiological shunt has not been detected during exercise with gas exchange-dependent techniques. However, fundamental assumptions of these techniques may not allow for measurement of a small (1-3%) anatomical shunt, the magnitude of which would explain the entire A-aDO2 typically observed during normoxic exercise. Data from contrast echocardiograph studies are presented demonstrating the development of IPAVS with exercise in 90% of subjects tested. Technetium-99m labeled macroaggregated albumin studies also found exercise IPAVS and calculated shunt to be approximately 2% at max exercise. These exercise IPAVS appear strongly related to the alveolar to arterial PO2 difference, pulmonary blood flow and mean pulmonary artery pressure. Hypoxic exercise was found to induce IPAVS at lower workloads than during normoxic exercise in 50% of subjects, while all subjects continued to shunt during recovery from hypoxic exercise, but only three subjects demonstrated intrapulmonary shunt during recovery from normoxic exercise. We suggest that these previously under-appreciated intrapulmonary arteriovenous shunts develop during exercise, contributing to the impairment in gas exchange typically observed with exercise. Future work will better define the conditions for shunt recruitment as well as their physiologic consequence.
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Affiliation(s)
- Andrew T Lovering
- The John Rankin Laboratory of Pulmonary Medicine, Department of Population Health Sciences, University of Wisconsin-Madison, Wisconsin, USA.
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39
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Stickland MK, Lovering AT. Exercise-induced intrapulmonary arteriovenous shunting and pulmonary gas exchange. Exerc Sport Sci Rev 2006; 34:99-106. [PMID: 16829736 DOI: 10.1249/00003677-200607000-00003] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Recent research suggests the recruitment of intrapulmonary shunt vessels during exercise, which may contribute to the exercise-induced impairment in pulmonary gas exchange. These findings are consistent with substantial anatomical data demonstrating large-diameter (> 25 microm) anatomical shunts in the lung, but are contrary to the considerable functional gas exchange-dependent research that has not detected right-to-left physiological shunt during exercise.
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Affiliation(s)
- Michael K Stickland
- The John Rankin Laboratory of Pulmonary Medicine, Department of Population Health Sciences, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706-1532, USA.
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40
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Stickland MK, Welsh RC, Haykowsky MJ, Petersen SR, Anderson WD, Taylor DA, Bouffard M, Jones RL. Effect of acute increases in pulmonary vascular pressures on exercise pulmonary gas exchange. J Appl Physiol (1985) 2006; 100:1910-7. [PMID: 16514002 DOI: 10.1152/japplphysiol.01484.2005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to determine the effect of acute increases in pulmonary vascular pressures, caused by the application of lower-body positive pressure (LBPP), on exercise alveolar-to-arterial Po2 difference (A-aDo2), anatomical intrapulmonary (IP) shunt recruitment, and ventilation. Eight healthy men performed graded upright cycling to 90% maximal oxygen uptake under normal conditions and with 52 Torr (1 psi) of LBPP. Pulmonary arterial (PAP) and pulmonary artery wedge pressures (PAWP) were measured with a Swan-Ganz catheter. Arterial blood samples were obtained from a radial artery catheter, cardiac output was calculated by the direct Fick method, and anatomical IP shunt was determined by administering agitated saline during continuous two-dimensional echocardiography. LBPP increased both PAP and PAWP while upright at rest, and at all points during exercise (mean increase in PAP and PAWP 3.7 and 4.0 mmHg, respectively, P < 0.05). There were no differences in exercise oxygen uptake or cardiac output between control and LBPP. Despite the increased PAP and PAWP with LBPP, A-aDo2 was not affected. In the upright resting position, there was no evidence of shunt in the control condition, whereas LBPP caused shunt in one subject. At the lowest exercise workload (75 W), shunt occurred in three subjects during control and in four subjects with LBPP. LBPP did not affect IP shunt recruitment during subsequent higher workloads. Minute ventilation and arterial Pco2 were not consistently affected by LBPP. Therefore, small acute increases in pulmonary vascular pressures do not widen exercise A-aDo2 or consistently affect IP shunt recruitment or ventilation.
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Affiliation(s)
- Michael K Stickland
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Canada.
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41
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Kinane TB, Westra SJ. Case records of the Massachusetts General Hospital. Weekly clinicopathological exercises. Case 31-2004. A four-year-old boy with hypoxemia. N Engl J Med 2004; 351:1667-75. [PMID: 15483286 DOI: 10.1056/nejmcpc049023] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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42
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Stickland MK, Welsh RC, Haykowsky MJ, Petersen SR, Anderson WD, Taylor DA, Bouffard M, Jones RL. Intra-pulmonary shunt and pulmonary gas exchange during exercise in humans. J Physiol 2004; 561:321-9. [PMID: 15388775 PMCID: PMC1665323 DOI: 10.1113/jphysiol.2004.069302] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
In young, healthy people the alveolar-arterial P(O(2)) difference (A-aDO(2)) is small at rest, but frequently increases during exercise. Previously, investigators have focused on ventilation/perfusion mismatch and diffusion abnormalities to explain the impairment in gas exchange, as significant physiological intra-pulmonary shunt has not been found. The aim of this study was to use a non-gas exchange method to determine if anatomical intra-pulmonary (I-P) shunts develop during exercise, and, if so, whether there is a relationship between shunt and increased A-aDO(2). Healthy male participants performed graded upright cycling to 90% while pulmonary arterial (PAP) and pulmonary artery wedge pressures were measured. Blood samples were obtained from the radial artery, cardiac output was calculated by the direct Fick method and I-P shunt was determined by administering agitated saline during continuous 2-D echocardiography. A-aDO(2) progressively increased with exercise and was related to (r = 0.86) and PAP (r = 0.75). No evidence of I-P shunt was found at rest in the upright position; however, 7 of 8 subjects developed I-P shunts during exercise. In these subjects, point bi-serial correlations indicated that I-P shunts were related to the increased A-aDO(2) (r = 0.68), (r = 0.76) and PAP (r = 0.73). During exercise, intra-pulmonary shunt always occurred when A-aDO(2) exceeded 12 mmHg and was greater than 24 l min(-1). These results indicate that anatomical I-P shunts develop during exercise and we suggest that shunt recruitment may contribute to the widened A-aDO(2) during exercise.
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Affiliation(s)
- Michael K Stickland
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada.
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43
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Gossage JR. The role of echocardiography in screening for pulmonary arteriovenous malformations. Chest 2003; 123:320-2. [PMID: 12576340 DOI: 10.1378/chest.123.2.320] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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Gupta P, Mordin C, Curtis J, Hughes JMB, Shovlin CL, Jackson JE. Pulmonary arteriovenous malformations: effect of embolization on right-to-left shunt, hypoxemia, and exercise tolerance in 66 patients. AJR Am J Roentgenol 2002; 179:347-55. [PMID: 12130431 DOI: 10.2214/ajr.179.2.1790347] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE This study assessed the effect and safety of percutaneous transcatheter coil embolization of pulmonary arteriovenous malformations. MATERIALS AND METHODS In 58 (88%) of 66 patients, all malformations with feeding vessels greater than or equal to 3 mm in diameter were embolized with steel coils. Arterial oxygen saturation at rest and exercise, intrapulmonary right-to-left anatomic shunt fraction ((99m)Tc-macroaggregate injection), maximum exercise capacity (incremental work rate test), and pulmonary function were measured before and after embolization. Complications were analyzed. RESULTS Three categories of patients were identified. Patients in group 1 (27%) had complete occlusion of all angiographically visible pulmonary arteriovenous malformations; patients in group 2 (61%) had complete occlusion of all malformations with feeding vessels greater than or equal to 3 mm in diameter, but with smaller lesions persisting; and patients in group 3 (12%) had incomplete embolization, with feeding vessels greater than or equal to 3 mm in diameter remaining. The mean right-to-left shunt after embolization was least in group 1 (7%), intermediate in group 2 (10%), and greatest in group 3 (19%). Arterial oxygen saturation and right-to-left shunt fraction returned to normal levels (>96% and <3.5%, respectively) in 33% of patients. A significant improvement occurred after embolization in carbon monoxide diffusing capacity per unit of alveolar volume and in exercise capacity in 16 and 10 patients, respectively. In 93 procedures, 12 complications (13%) occurred. CONCLUSION Coil embolization of pulmonary arteriovenous malformations is effective in reducing right-to-left anatomic shunt fraction and in improving arterial oxygenation. Coil embolization of pulmonary arteriovenous malformations is well tolerated and has a low complication rate.
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Affiliation(s)
- P Gupta
- Department of Imaging, Imperial College Faculty of Medicine, Hammersmith Hospital, Du Cane Rd., London W12 0NN, England
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45
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Puvaneswary M. Three-dimensional gadolinium-enhanced magnetic resonance angiography of pulmonary arteriovenous malformation. AUSTRALASIAN RADIOLOGY 2002; 46:189-93. [PMID: 12060161 DOI: 10.1046/j.1440-1673.2001.01035.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Pulmonary arteriovenous malformations (AVMs) are rare vascular malformations of the lung. Although most patients are asymptomatic, AVMs can bleed and result in haemoptysis and haemothorax. We describes a case of pulmonary AVMs in a patient with Osler-Weber-Rendu syndrome with 3-D contrast-enhanced MR angiography. Magnetic resonance angiography provided accurately and non-invasively the number and size of the feeding arteries and draining veins.
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Affiliation(s)
- M Puvaneswary
- Department of Medical Imaging, John Hunter Hospital, New South Wales, Australia
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46
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Abstract
Pulmonary arteriovenous malformations (PAVM) are rare pulmonary vascular anomalies. Although most patients are asymptomatic, PAVMs can cause dyspnoea from right-to-left shunt. Because of paradoxical emboli, various central nervous system complications have been described including stroke and brain abscess. There is a strong association between PAVM and hereditary haemorrhagic telangiectasia. Chest radiography and contrast enhanced computed tomography are essential initial diagnostic tools but pulmonary angiography is the gold standard. Contrast echocardiography is useful for diagnosis and monitoring after treatment. Most patients should be treated. Therapeutic options include angiographic embolisation with metal coil or balloon occlusion and surgical excision.
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Affiliation(s)
- I Khurshid
- Department of Pulmonary and Critical Care Medicine, Brody School of Medicine, East Carolina University, Greenville, North Carolina 27834, USA.
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47
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Abstract
Ventilation and perfusion scintigraphy (VQ scans) provide a relatively non-invasive evaluation of lung function. They indicate the relative blood flow to each lung and allow a quantitative assessment of the perfusion of each lung segment. They can detect areas of abnormal aeration and demonstrate air trapping. However, VQ scanning gives relatively poor anatomical detail of the lungs and so is commonly used in conjunction with other radiological modalities, most notably the chest X-ray. VQ scans have been utilized for a large range of pathological conditions including congenital cardiac and lung abnormalities, suspected pulmonary emboli, the assessment of childhood diseases, including cystic fibrosis, bronchopulmonary dysplasia and asthma.
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Affiliation(s)
- K Johnson
- Birmingham Children's Hospital, Steelhouse Lane, Birmingham B4 6NH, UK
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48
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Iqbal M, Rossoff LJ, Steinberg HN, Marzouk KA, Siegel DN. Pulmonary arteriovenous malformations: a clinical review. Postgrad Med J 2000; 76:390-4. [PMID: 10878194 PMCID: PMC1741661 DOI: 10.1136/pmj.76.897.390] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Pulmonary arteriovenous malformations (PAVMs) are a rare clinical entity. Most of them are associated with hereditary haemorrhagic telangiectasia. The usual clinical presentation is exertional dyspnoea and hypoxaemia. The initial test of choice for screening is the 100% oxygen method. A pulmonary angiogram is needed to define the anatomy and guide transcatheter embolisation (TCE). TCE has been shown to be effective and safe with a very low recanalisation rate and has largely replaced surgery for PAVMs. Computed tomography of the chest can be used for the follow up of asymptomatic PAVMs and TCE.
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Affiliation(s)
- M Iqbal
- Division of Pulmonary and Critical Care Medicine, Long Island Jewish Medical Centre, Long Island Campus of the Albert Einstein College of Medicine, Room C-20, 270-05 76th Avenue, New Hyde Park, NY 11042, USA
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Vettukattil JJ, Slavik Z, Lamb RK, Monro JL, Keeton BR, Tsang VT, Aldous AJ, Zivanovic A, Johns S, Lewington V, Salmon AP. Intrapulmonary arteriovenous shunting may be a universal phenomenon in patients with the superior cavopulmonary anastomosis: a radionuclide study. Heart 2000; 83:425-8. [PMID: 10722543 PMCID: PMC1729376 DOI: 10.1136/heart.83.4.425] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
OBJECTIVE To evaluate the extent of intrapulmonary right to left shunting in children after bidirectional cavopulmonary anastomosis (BCPA). DESIGN Prospective study of patients who underwent BCPA in a single centre. PATIENTS 17 patients with complex cyanotic congenital cardiac malformations who underwent BCPA at 1-45 months of age (median 21 months) were evaluated 15-64 months postoperatively (median 32 months). Five children between 1 and 10 years (median 5 years) with normal or surgically corrected intracardiac anatomy and peripheral pulmonary circulation who required V/Q scanning for other reasons were used as controls. INTERVENTIONS All patients underwent cardiac catheterisation to exclude angiographically demonstrable venovenous collaterals followed by pulmonary perfusion scanning using (99m)technetium ((99m)Tc) labelled albumen microspheres to quantify the intrapulmonary right to left shunt. MAIN OUTCOME MEASURE Percentage of intrapulmonary right to left shunt. RESULTS The mean (SD) level of physiological right to left shunting found in the control group was 5.4 (2.3)%. All patients with BCPA showed the presence of a significantly higher level of intrapulmonary shunting (26.8 (16.9)%, p < 0.001). The degree of shunting was significantly increased in the subgroup of 11 patients with BCPA as the only source of pulmonary blood flow (34.9 (15.8)%), when compared to the six remaining patients with an additional source of pulmonary blood supply (12.0 (2.6)%, p < 0.001). There was a negative correlation between age at BCPA and the shunt percentage found in the patients with a competitive source of pulmonary blood flow (r = -0.63, p < 0. 01). CONCLUSIONS Intrapulmonary right to left shunting develops in all patients following BCPA. This may be caused by a sustained and inappropriate vasodilatation resulting from absence or decreased levels of a substance that inhibits pulmonary vasodilatation. Augmenting BCPA with an additional source of blood flow containing hepatic factor limits the degree of intrapulmonary arteriovenous shunting and may help provide successful longer term palliation.
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Affiliation(s)
- J J Vettukattil
- Wessex Cardiothoracic Unit and Department of Nuclear Medicine, Southampton University Hospital NHS Trust, Southampton, UK
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Saluja S, Henderson KJ, White RI. Embolotherapy in the bronchial and pulmonary circulations. Radiol Clin North Am 2000; 38:425-48, ix. [PMID: 10765399 DOI: 10.1016/s0033-8389(05)70172-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This two-part article first discusses the role of bronchial artery transcatheter embolotherapy in the management of patients with hemoptysis. Following this discussion, the authors review pulmonary arteriovenous malformations, their embolization, follow-up protocols, and outcome criteria as currently practiced at the authors' Vascular Malformation Center.
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Affiliation(s)
- S Saluja
- Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
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