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Guensch DP, Utz CD, Jung B, Dozio S, Huettenmoser SP, Friess JO, Terbeck S, Erdoes G, Huber AT, Eberle B, Fischer K. Introducing a free-breathing MRI method to assess peri-operative myocardial oxygenation and function: A volunteer cohort study. Eur J Anaesthesiol 2024; 41:480-489. [PMID: 38323332 PMCID: PMC11155273 DOI: 10.1097/eja.0000000000001964] [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: 02/08/2024]
Abstract
BACKGROUND Induction of general anaesthesia has many potential triggers for peri-operative myocardial ischaemia including the acute disturbance of blood gases that frequently follows alterations in breathing and ventilation patterns. Free-breathing oxygenation-sensitive cardiovascular magnetic resonance (OS-CMR) imaging may provide the opportunity to continuously quantify the impact of such triggers on myocardial oxygenation. OBJECTIVE To investigate the impact of breathing patterns that simulate induction of general anaesthesia on myocardial oxygenation in awake healthy adults using continuous OS-CMR imaging. DESIGN Prospective observational study. SETTING Single-centre university hospital. Recruitment from August 2020 to January 2022. PARTICIPANTS Thirty-two healthy volunteers younger than 45 years old were recruited. Data were analysed from n = 29 (69% male individuals). INTERVENTION Participants performed a simulated induction breathing manoeuvre consisting of 2.5 min paced breathing with a respiration rate of 14 breaths per minute, followed by 5 deep breaths, then apnoea for up to 60s inside a magnetic resonance imaging scanner (MRI). Cardiac images were acquired with the traditional OS-CMR sequence (OS bh-cine ), which requires apnoea for acquisition and with two free-breathing OS-CMR sequences: a high-resolution single-shot sequence (OS fb-ss ) and a real-time cine sequence (OS fb-rtcine ). MAIN OUTCOME MEASURES Myocardial oxygenation response at the end of the paced breathing period and at the 30 s timepoint during the subsequent apnoea, reflecting the time of successful intubation in a clinical setting. RESULTS The paced breathing followed by five deep breaths significantly reduced myocardial oxygenation, which was observed with all three techniques (OS bh-cine -6.0 ± 2.6%, OS fb-ss -12.0 ± 5.9%, OS fb-rtcine -5.4 ± 7.0%, all P < 0.05). The subsequent vasodilating stimulus of apnoea then significantly increased myocardial oxygenation (OS bh-cine 6.8 ± 3.1%, OS fb-ss 8.4 ± 5.6%, OS fb-rtcine 15.7 ± 10.0%, all P < 0.01). The free-breathing sequences were reproducible and were not inferior to the original sequence for any stage. CONCLUSION Breathing manoeuvres simulating induction of general anaesthesia cause dynamic alterations of myocardial oxygenation in young volunteers, which can be quantified continuously with free-breathing OS-CMR. Introducing these new imaging techniques into peri-operative studies may throw new light into the mechanisms of peri-operative perturbations of myocardial tissue oxygenation and ischaemia. VISUAL ABSTRACT http://links.lww.com/EJA/A922.
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Affiliation(s)
- Dominik P Guensch
- From the Department of Anaesthesiology and Pain Medicine (DPG, CDU, JOF, ST, GE, BE, KF) and Department of Diagnostic, Interventional and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland (DPG, BJ, SD, SPH, ATH)
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Loai S, Qiang B, Laflamme MA, Cheng HLM. Blood-pool MRI assessment of myocardial microvascular reactivity. Front Cardiovasc Med 2023; 10:1216587. [PMID: 38028477 PMCID: PMC10646425 DOI: 10.3389/fcvm.2023.1216587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 10/20/2023] [Indexed: 12/01/2023] Open
Abstract
Purpose The ability to non-invasively image myocardial microvascular dilation and constriction is essential to assessing intact function and dysfunction. Yet, conventional measurements based on blood oxygenation are not specific to changes in blood volume. The purpose of this study was to extend to the heart a blood-pool MRI approach for assessing vasomodulation in the presence of blood gas changes and investigate if sex-related differences exist. Methods Animals [five male and five female healthy Sprague Dawley rats (200-500 g)] were intubated, ventilated, and cycled through room air (normoxia) and hypercapnia (10% CO2) in 10-minute cycles after i.v. injection of blood-pool agent Ablavar (0.3 mmol/kg). Pre-contrast T1 maps and T1-weighted 3D CINE were acquired on a 3 Tesla preclinical MRI scanner, followed by repeated 3D CINE every 5 min until the end of the gas regime. Invasive laser Doppler flowmetry of myocardial perfusion was performed to corroborate MRI results. Results Myocardial microvascular dilation to hypercapnia and constriction to normoxia were readily visualized on T1 maps. Over 10 min of hypercapnia, female myocardial T1 reduced by 20% (vasodilation), while no significant change was observed in the male myocardium. After return to normoxia, myocardial T1 increased (vasoconstriction) in both sexes (18% in females and 16% in males). Laser Doppler perfusion measurements confirmed vasomodulatory responses observed on MRI. Conclusion Blood-pool MRI is sensitive and specific to vasomodulation in the myocardial microcirculation. Sex-related differences exist in the healthy myocardium in response to mild hypercapnic stimuli.
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Affiliation(s)
- Sadi Loai
- Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada
- Translational Biology & Engineering Program, Ted Rogers Centre for Heart Research, Toronto, ON, Canada
| | - Beiping Qiang
- McEwen Stem Cell Institute, University Health Network, Toronto, ON, Canada
| | - Michael A. Laflamme
- McEwen Stem Cell Institute, University Health Network, Toronto, ON, Canada
- Peter Munk Cardiac Centre, University Health Network, Toronto, ON, Canada
- Laboratory of Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - Hai-Ling Margaret Cheng
- Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada
- Translational Biology & Engineering Program, Ted Rogers Centre for Heart Research, Toronto, ON, Canada
- The Edward S. Rogers Sr. Department of Electrical and Computer Engineering, University of Toronto, Toronto, ON, Canada
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Hopman LH, Hillier E, Liu Y, Hamilton J, Fischer K, Seiberlich N, Friedrich MG. Dynamic Cardiac Magnetic Resonance Fingerprinting During Vasoactive Breathing Maneuvers: First Results. J Cardiovasc Imaging 2023; 31:71-82. [PMID: 37096671 PMCID: PMC10133810 DOI: 10.4250/jcvi.2022.0080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 08/22/2022] [Accepted: 10/10/2022] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Cardiac magnetic resonance fingerprinting (cMRF) enables simultaneous mapping of myocardial T1 and T2 with very short acquisition times. Breathing maneuvers have been utilized as a vasoactive stress test to dynamically characterize myocardial tissue in vivo. We tested the feasibility of sequential, rapid cMRF acquisitions during breathing maneuvers to quantify myocardial T1 and T2 changes. METHODS We measured T1 and T2 values using conventional T1 and T2-mapping techniques (modified look locker inversion [MOLLI] and T2-prepared balanced-steady state free precession), and a 15 heartbeat (15-hb) and rapid 5-hb cMRF sequence in a phantom and in 9 healthy volunteers. The cMRF5-hb sequence was also used to dynamically assess T1 and T2 changes over the course of a vasoactive combined breathing maneuver. RESULTS In healthy volunteers, the mean myocardial T1 of the different mapping methodologies were: MOLLI 1,224 ± 81 ms, cMRF15-hb 1,359 ± 97 ms, and cMRF5-hb 1,357 ± 76 ms. The mean myocardial T2 measured with the conventional mapping technique was 41.7 ± 6.7 ms, while for cMRF15-hb 29.6 ± 5.8 ms and cMRF5-hb 30.5 ± 5.8 ms. T2 was reduced with vasoconstriction (post-hyperventilation compared to a baseline resting state) (30.15 ± 1.53 ms vs. 27.99 ± 2.07 ms, p = 0.02), while T1 did not change with hyperventilation. During the vasodilatory breath-hold, no significant change of myocardial T1 and T2 was observed. CONCLUSIONS cMRF5-hb enables simultaneous mapping of myocardial T1 and T2, and may be used to track dynamic changes of myocardial T1 and T2 during vasoactive combined breathing maneuvers.
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Affiliation(s)
- Luuk H.G.A. Hopman
- Research Institute of the McGill University Health Center, Montreal, QC, Canada
- Department of Cardiology, Amsterdam UMC, Amsterdam, The Netherlands
| | - Elizabeth Hillier
- Research Institute of the McGill University Health Center, Montreal, QC, Canada
- Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Yuchi Liu
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
| | - Jesse Hamilton
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
| | - Kady Fischer
- Department of Anaesthesiology and Pain Medicine, Bern University Hospital, Inselspital, University of Bern, Bern, Switzerland
| | - Nicole Seiberlich
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
- Department of Radiology, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
| | - Matthias G. Friedrich
- Research Institute of the McGill University Health Center, Montreal, QC, Canada
- Departments of Cardiology and Diagnostic Radiology, McGill University Health Centre, Montreal, QC, Canada
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Spicher B, Fischer K, Zimmerli ZA, Yamaji K, Ueki Y, Bertschinger CN, Jung B, Otsuka T, Bigler MR, Gräni C, von Tengg-Kobligk H, Räber L, Eberle B, Guensch DP. Combined Analysis of Myocardial Deformation and Oxygenation Detects Inducible Ischemia Unmasked by Breathing Maneuvers in Chronic Coronary Syndrome. Front Cardiovasc Med 2022; 9:800720. [PMID: 35282374 PMCID: PMC8907543 DOI: 10.3389/fcvm.2022.800720] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Accepted: 01/31/2022] [Indexed: 12/20/2022] Open
Abstract
Introduction In patients with chronic coronary syndromes, hyperventilation followed by apnea has been shown to unmask myocardium susceptible to inducible deoxygenation. The aim of this study was to assess whether such a provoked response is co-localized with myocardial dysfunction. Methods A group of twenty-six CAD patients with a defined stenosis (quantitative coronary angiography > 50%) underwent a cardiovascular magnetic resonance (CMR) exam prior to revascularization. Healthy volunteers older than 50 years served as controls (n = 12). Participants hyperventilated for 60s followed by brief apnea. Oxygenation-sensitive images were analyzed for changes in myocardial oxygenation and strain. Results In healthy subjects, hyperventilation resulted in global myocardial deoxygenation (-10.2 ± 8.2%, p < 0.001) and augmented peak circumferential systolic strain (-3.3 ± 1.6%, p < 0.001). At the end of apnea, myocardial signal intensity had increased (+9.1 ± 5.3%, p < 0.001) and strain had normalized to baseline. CAD patients had a similar global oxygenation response to hyperventilation (−5.8 ± 9.6%, p = 0.085) but showed no change in peak strain from their resting state (-1.3 ± 1.6%), which was significantly attenuated in comparison the strain response observed in controls (p = 0.008). With apnea, the CAD patients showed an attenuated global oxygenation response to apnea compared to controls (+2.7 ± 6.2%, p < 0.001). This was accompanied by a significant depression of peak strain (3.0 ± 1.7%, p < 0.001), which also differed from the control response (p = 0.025). Regional analysis demonstrated that post-stenotic myocardium was most susceptible to de-oxygenation and systolic strain abnormalities during respiratory maneuvers. CMR measures at rest were unable to discriminate post-stenotic territory (p > 0.05), yet this was significant for both myocardial oxygenation [area under the curve (AUC): 0.88, p > 0.001] and peak strain (AUC: 0.73, p = 0.023) measured with apnea. A combined analysis of myocardial oxygenation and peak strain resulted in an incrementally higher AUC of 0.91, p < 0.001 than strain alone. Conclusion In myocardium of patients with chronic coronary syndromes and primarily intermediate coronary stenoses, cine oxygenation-sensitive CMR can identify an impaired vascular and functional response to a vasoactive breathing maneuver stimulus indicative of inducible ischemia.
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Affiliation(s)
- Barbara Spicher
- Department of Anaesthesiology and Pain Medicine, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Kady Fischer
- Department of Anaesthesiology and Pain Medicine, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Zoe A. Zimmerli
- Department of Anaesthesiology and Pain Medicine, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Kyohei Yamaji
- Department of Cardiology, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Yasushi Ueki
- Department of Cardiology, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Carina N. Bertschinger
- Department of Diagnostic, Interventional and Paediatric Radiology, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Bernd Jung
- Department of Diagnostic, Interventional and Paediatric Radiology, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Tatsuhiko Otsuka
- Department of Cardiology, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Marius R. Bigler
- Department of Cardiology, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Christoph Gräni
- Department of Cardiology, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Hendrik von Tengg-Kobligk
- Department of Diagnostic, Interventional and Paediatric Radiology, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Lorenz Räber
- Department of Cardiology, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Balthasar Eberle
- Department of Anaesthesiology and Pain Medicine, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Dominik P. Guensch
- Department of Anaesthesiology and Pain Medicine, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
- Department of Diagnostic, Interventional and Paediatric Radiology, Inselspital, University Hospital Bern, University of Bern, Bern, Switzerland
- *Correspondence: Dominik P. Guensch
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Kwiatkowski G, Kozerke S. Quantitative myocardial first-pass perfusion imaging of CO 2 -induced vasodilation in rats. NMR IN BIOMEDICINE 2021; 34:e4593. [PMID: 34337796 DOI: 10.1002/nbm.4593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 07/02/2021] [Accepted: 07/08/2021] [Indexed: 06/13/2023]
Abstract
Inducible hypercapnia is an alternative for increasing the coronary blood flow necessary to facilitate the quantification of myocardial blood flow during hyperemia. The current study aimed to quantify the pharmacokinetic effect of a CO2 gas challenge on myocardial perfusion in rats using high-resolution, first-pass perfusion CMR and compared it with pharmacologically induced hyperemia using regadenoson. A dual-contrast, saturation-recovery, gradient-echo sequence with a Cartesian readout was used on a small-animal 9.4-T scanner; additional cine images during hyperemia/rest were recorded with an ultrashort echo time sequence. The mean myocardial blood flow value at rest was 6.1 ± 1.4 versus 13.9 ± 3.7 and 14.3 ± 4 mL/g/min during vasodilation with hypercapnia and regadenoson, respectively. Accordingly, the myocardial flow reserve value was 2.6 ± 1.1 for the gas challenge and 2.5 ± 1.4 for regadenoson. During hyperemia with both protocols, a significantly increased cardiac output was found. It was concluded that hypercapnia leads to significantly increased coronary flow and yields similar myocardial flow reserves in healthy rats as compared with pharmacological stimulation. Accordingly, inducible hypercapnia can be selected as an alternative stressor in CMR studies of myocardial blood flow in small animals.
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Affiliation(s)
- Grzegorz Kwiatkowski
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Sebastian Kozerke
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
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6
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Hillier E, Friedrich MG. The Potential of Oxygenation-Sensitive CMR in Heart Failure. Curr Heart Fail Rep 2021; 18:304-314. [PMID: 34378154 DOI: 10.1007/s11897-021-00525-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/05/2021] [Indexed: 12/24/2022]
Abstract
PURPOSE OF REVIEW Cardiac magnetic resonance imaging (CMR) use in the context of heart failure (HF) has increased over the last decade as it is able to provide detailed, quantitative information on function, morphology, and myocardial tissue composition. Furthermore, oxygenation-sensitive CMR (OS-CMR) has emerged as a CMR imaging method capable of monitoring changes of myocardial oxygenation without the use of exogenous contrast agents. RECENT FINDINGS The contributions of OS-CMR to the investigation of patients with HF includes not only a fully quantitative assessment of cardiac morphology, function, and tissue characteristics, but also high-resolution information on both endothelium-dependent and endothelium-independent vascular function as assessed through changes of myocardial oxygenation. In patients with heart failure, OS-CMR can provide deep phenotyping on the status and important associated pathophysiology as a one-stop, needle-free diagnostic imaging test.
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Affiliation(s)
- Elizabeth Hillier
- Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada.,Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Matthias G Friedrich
- Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada. .,Departments of Medicine and Diagnostic Radiology, McGill University, 1001 Decarie Blvd, Montreal, QC, H4A 3J1, Canada.
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7
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Troy AM, Cheng HM. Human microvascular reactivity: a review of vasomodulating stimuli and non-invasive imaging assessment. Physiol Meas 2021; 42. [PMID: 34325417 DOI: 10.1088/1361-6579/ac18fd] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 07/29/2021] [Indexed: 11/11/2022]
Abstract
The microvasculature serves an imperative function in regulating perfusion and nutrient exchange throughout the body, adaptively altering blood flow to preserve hemodynamic and metabolic homeostasis. Its normal functioning is vital to tissue health, whereas its dysfunction is present in many chronic conditions, including diabetes, heart disease, and cognitive decline. As microvascular dysfunction often appears early in disease progression, its detection can offer early diagnostic information. To detect microvascular dysfunction, one uses imaging to probe the microvasculature's ability to react to a stimulus, also known as microvascular reactivity (MVR). An assessment of MVR requires an integrated understanding of vascular physiology, techniques for stimulating reactivity, and available imaging methods to capture the dynamic response. Practical considerations, including compatibility between the selected stimulus and imaging approach, likewise require attention. In this review, we provide a comprehensive foundation necessary for informed imaging of MVR, with a particular focus on the challenging endeavor of assessing microvascular function in deep tissues.
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Affiliation(s)
- Aaron M Troy
- Institute of Biomedical Engineering, University of Toronto, Toronto, CANADA
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8
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Shi K, Yang MX, Xia CC, Peng WL, Zhang K, Li ZL, Guo YK, Yang ZG. Noninvasive oxygenation assessment after acute myocardial infarction with breathing maneuvers-induced oxygenation-sensitive magnetic resonance imaging. J Magn Reson Imaging 2021; 54:284-289. [PMID: 33433045 DOI: 10.1002/jmri.27509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 12/29/2020] [Accepted: 12/30/2020] [Indexed: 02/05/2023] Open
Abstract
The safety profiles when performing stress oxygenation-sensitive magnetic resonance imaging (OS-MRI) have raised concerns in clinical practice. Adenosine infusion can cause side effects such as chest pain, dyspnea, arrhythmia, and even cardiac death. The aim of this study was to investigate the feasibility of breathing maneuvers-induced OS-MRI in acute myocardial infarction (MI). This was a prospective study, which included 14 healthy rabbits and nine MI rabbit models. This study used 3 T MRI/modified Look-Locker inversion recovery sequence for native T1 mapping, balanced steady-state free precession sequence for OS imaging, and phase-sensitive inversion recovery sequence for late gadolinium enhancement. The changes in myocardial oxygenation (ΔSI) were assessed under two breathing maneuvers protocols in healthy rabbits: a series of extended breath-holding (BH), and a combined maneuver of hyperventilation followed by the extended BH (HVBH). Subsequently, OS-MRI with HVBH in acute MI rabbits was performed, and the ΔSI was compared with that of adenosine stress protocol. Student's t-test, Wilcoxon rank test, and Friedman test were used to compare ΔSI in different subgroups. Pearson and Spearman correlation was used to obtain the association of ΔSI between breathing maneuvers and adenosine stress. Bland-Altman analysis was used to assess the bias of ΔSI between HVBH and adenosine stress. In healthy rabbits, BH maneuvers from 30 to 50 s induced significant increase in SI compared with the baseline (all p < 0.05). By contrast, hyperventilation for 60 s followed by 10 s-BH (HVBH 10 s) exhibited a comparable ΔSI to that of stress test (p = 0.07). In acute MI rabbits, HVBH 10 s-induced ΔSIs among infarcted, salvaged, and the remote myocardial area were no less effectiveness than adenosine stress when performing OS-MRI (r = 0.84; p < 0.05). Combined breathing maneuvers with OS-MRI have the potential to be used as a nonpharmacological alternative for assessing myocardial oxygenation in patients with acute MI. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY STAGE: 2.
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Affiliation(s)
- Ke Shi
- Department of Radiology, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Meng-Xi Yang
- Department of Radiology, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, China.,Department of Radiology, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Chun-Chao Xia
- Department of Radiology, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Wan-Lin Peng
- Department of Radiology, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Kun Zhang
- Department of Radiology, Key Laboratory of Obstetric and Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Zhen-Lin Li
- Department of Radiology, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Ying-Kun Guo
- Department of Radiology, Key Laboratory of Obstetric and Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Zhi-Gang Yang
- Department of Radiology, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, China
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Yang HJ, Oksuz I, Dey D, Sykes J, Klein M, Butler J, Kovacs MS, Sobczyk O, Cokic I, Slomka PJ, Bi X, Li D, Tighiouart M, Tsaftaris SA, Prato FS, Fisher JA, Dharmakumar R. Accurate needle-free assessment of myocardial oxygenation for ischemic heart disease in canines using magnetic resonance imaging. Sci Transl Med 2020; 11:11/494/eaat4407. [PMID: 31142677 DOI: 10.1126/scitranslmed.aat4407] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 05/08/2019] [Indexed: 12/24/2022]
Abstract
Myocardial oxygenation-the ability of blood vessels to supply the heart muscle (myocardium) with oxygen-is a critical determinant of cardiac function. Impairment of myocardial oxygenation is a defining feature of ischemic heart disease (IHD), which is caused by pathological conditions that affect the blood vessels supplying oxygen to the heart muscle. Detecting altered myocardial oxygenation can help guide interventions and prevent acute life-threatening events such as heart attacks (myocardial infarction); however, current diagnosis of IHD relies on surrogate metrics and exogenous contrast agents for which many patients are contraindicated. An oxygenation-sensitive cardiac magnetic resonance imaging (CMR) approach used previously to demonstrate that CMR signals can be sensitized to changes in myocardial oxygenation showed limited ability to detect small changes in signals in the heart because of physiologic and imaging noise during data acquisition. Here, we demonstrate a CMR-based approach termed cfMRI [cardiac functional magnetic resonance imaging (MRI)] that detects myocardial oxygenation. cfMRI uses carbon dioxide for repeat interrogation of the functional capacity of the heart's blood vessels via a fast MRI approach suitable for clinical adoption without limitations of key confounders (cardiac/respiratory motion and heart rate changes). This method integrates multiple whole-heart images within a computational framework to reduce noise, producing confidence maps of alterations in myocardial oxygenation. cfMRI permits noninvasive monitoring of myocardial oxygenation without requiring ionizing radiation, contrast agents, or needles. This has the potential to broaden our ability to noninvasively identify IHD and a diverse spectrum of heart diseases related to myocardial ischemia.
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Affiliation(s)
- Hsin-Jung Yang
- Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.,University of California, Los Angeles CA 90095, USA
| | | | - Damini Dey
- Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.,University of California, Los Angeles CA 90095, USA
| | - Jane Sykes
- Lawson Health Research Institute, University of Western Ontario, London, ON N6C 2R5, Canada
| | - Michael Klein
- University of Toronto and University Health Network, Toronto, ON M5G 2C4, Canada
| | - John Butler
- Lawson Health Research Institute, University of Western Ontario, London, ON N6C 2R5, Canada
| | - Michael S Kovacs
- Lawson Health Research Institute, University of Western Ontario, London, ON N6C 2R5, Canada
| | - Olivia Sobczyk
- University of Toronto and University Health Network, Toronto, ON M5G 2C4, Canada
| | - Ivan Cokic
- Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Piotr J Slomka
- Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.,University of California, Los Angeles CA 90095, USA
| | - Xiaoming Bi
- MR R&D Collaborations, Siemens Healthineers, Los Angeles, CA 90048, USA
| | - Debiao Li
- Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.,University of California, Los Angeles CA 90095, USA
| | | | | | - Frank S Prato
- Lawson Health Research Institute, University of Western Ontario, London, ON N6C 2R5, Canada
| | - Joseph A Fisher
- University of Toronto and University Health Network, Toronto, ON M5G 2C4, Canada
| | - Rohan Dharmakumar
- Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA. .,University of California, Los Angeles CA 90095, USA
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10
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Yang HJ, Dey D, Sykes J, Butler J, Biernaski H, Kovacs M, Bi X, Sharif B, Cokic I, Tang R, Slomka P, Prato FS, Dharmakumar R. Heart Rate-Independent 3D Myocardial Blood Oxygen Level-Dependent MRI at 3.0 T with Simultaneous 13N-Ammonia PET Validation. Radiology 2020; 295:82-93. [PMID: 32096705 PMCID: PMC7106942 DOI: 10.1148/radiol.2020191456] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 12/20/2019] [Accepted: 01/03/2020] [Indexed: 11/11/2022]
Abstract
Background Despite advances, blood oxygen level-dependent (BOLD) cardiac MRI for myocardial perfusion is limited by inadequate spatial coverage, imaging speed, multiple breath holds, and imaging artifacts, particularly at 3.0 T. Purpose To develop and validate a robust, contrast agent-unenhanced, free-breathing three-dimensional (3D) cardiac MRI approach for reliably examining changes in myocardial perfusion between rest and adenosine stress. Materials and Methods A heart rate-independent, free-breathing 3D T2 mapping technique at 3.0 T that can be completed within the period of adenosine stress (≤4 minutes) was developed by using computer simulations, ex vivo heart preparations, and dogs. Studies in dogs were performed with and without coronary stenosis and validated with simultaneously acquired nitrogen 13 (13N) ammonia PET perfusion in a clinical PET/MRI system. The MRI approach was also prospectively evaluated in healthy human volunteers (from January 2017 to September 2017). Myocardial BOLD responses (MBRs) between normal and ischemic myocardium were compared with mixed model analysis. Results Dogs (n = 10; weight range, 20-25 kg; mongrel dogs) and healthy human volunteers (n = 10; age range, 22-53 years; seven men) were evaluated. In healthy dogs, T2 MRI at adenosine stress was greater than at rest (mean rest vs stress, 38.7 msec ± 2.5 [standard deviation] vs 45.4 msec ± 3.3, respectively; MBR, 1.19 ± 0.08; both, P < .001). At the same conditions, mean rest versus stress PET perfusion was 1.1 mL/mg/min ± 0.11 versus 2.3 mL/mg/min ± 0.82, respectively (P < .001); myocardial perfusion reserve (MPR) was 2.4 ± 0.82 (P < .001). The BOLD response and PET MPR were positively correlated (R = 0.67; P < .001). In dogs with coronary stenosis, perfusion anomalies were detected on the basis of MBR (normal vs ischemic, 1.09 ± 0.05 vs 1.00 ± 0.04, respectively; P < .001) and MPR (normal vs ischemic, 2.7 ± 0.08 vs 1.7 ± 1.1, respectively; P < .001). Human volunteers showed increased myocardial T2 at stress (rest vs stress, 44.5 msec ± 2.6 vs 49.0 msec ± 5.5, respectively; P = .004; MBR, 1.1 msec ± 8.08). Conclusion This three-dimensional cardiac blood oxygen level-dependent (BOLD) MRI approach overcame key limitations associated with conventional cardiac BOLD MRI by enabling whole-heart coverage within the standard duration of adenosine infusion, and increased the magnitude and reliability of BOLD contrast, which may be performed without requiring breath holds. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Almeida in this issue.
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Affiliation(s)
- Hsin-Jung Yang
- From the Department of Biomedical Sciences, Cedars-Sinai Medical
Center, Biomedical Imaging Research Institute, PACT Bldg–Suite 400, 8700
Beverly Blvd, Los Angeles, CA 90048 (H.J.Y., D.D., B.S., I.C., R.T., P.S.,
R.D.); Department of Bioengineering (H.J.Y., R.D.) and David Geffen School of
Medicine (D.D., P.S.), University of California, Los Angeles Calif; Lawson
Health Research Institute, London, Canada (J.S., J.B., H.B., M.K., F.S.P.); and
MR R&D, Siemens Healthcare, Los Angeles, Calif (X.B.)
| | - Damini Dey
- From the Department of Biomedical Sciences, Cedars-Sinai Medical
Center, Biomedical Imaging Research Institute, PACT Bldg–Suite 400, 8700
Beverly Blvd, Los Angeles, CA 90048 (H.J.Y., D.D., B.S., I.C., R.T., P.S.,
R.D.); Department of Bioengineering (H.J.Y., R.D.) and David Geffen School of
Medicine (D.D., P.S.), University of California, Los Angeles Calif; Lawson
Health Research Institute, London, Canada (J.S., J.B., H.B., M.K., F.S.P.); and
MR R&D, Siemens Healthcare, Los Angeles, Calif (X.B.)
| | - Jane Sykes
- From the Department of Biomedical Sciences, Cedars-Sinai Medical
Center, Biomedical Imaging Research Institute, PACT Bldg–Suite 400, 8700
Beverly Blvd, Los Angeles, CA 90048 (H.J.Y., D.D., B.S., I.C., R.T., P.S.,
R.D.); Department of Bioengineering (H.J.Y., R.D.) and David Geffen School of
Medicine (D.D., P.S.), University of California, Los Angeles Calif; Lawson
Health Research Institute, London, Canada (J.S., J.B., H.B., M.K., F.S.P.); and
MR R&D, Siemens Healthcare, Los Angeles, Calif (X.B.)
| | - John Butler
- From the Department of Biomedical Sciences, Cedars-Sinai Medical
Center, Biomedical Imaging Research Institute, PACT Bldg–Suite 400, 8700
Beverly Blvd, Los Angeles, CA 90048 (H.J.Y., D.D., B.S., I.C., R.T., P.S.,
R.D.); Department of Bioengineering (H.J.Y., R.D.) and David Geffen School of
Medicine (D.D., P.S.), University of California, Los Angeles Calif; Lawson
Health Research Institute, London, Canada (J.S., J.B., H.B., M.K., F.S.P.); and
MR R&D, Siemens Healthcare, Los Angeles, Calif (X.B.)
| | - Heather Biernaski
- From the Department of Biomedical Sciences, Cedars-Sinai Medical
Center, Biomedical Imaging Research Institute, PACT Bldg–Suite 400, 8700
Beverly Blvd, Los Angeles, CA 90048 (H.J.Y., D.D., B.S., I.C., R.T., P.S.,
R.D.); Department of Bioengineering (H.J.Y., R.D.) and David Geffen School of
Medicine (D.D., P.S.), University of California, Los Angeles Calif; Lawson
Health Research Institute, London, Canada (J.S., J.B., H.B., M.K., F.S.P.); and
MR R&D, Siemens Healthcare, Los Angeles, Calif (X.B.)
| | - Michael Kovacs
- From the Department of Biomedical Sciences, Cedars-Sinai Medical
Center, Biomedical Imaging Research Institute, PACT Bldg–Suite 400, 8700
Beverly Blvd, Los Angeles, CA 90048 (H.J.Y., D.D., B.S., I.C., R.T., P.S.,
R.D.); Department of Bioengineering (H.J.Y., R.D.) and David Geffen School of
Medicine (D.D., P.S.), University of California, Los Angeles Calif; Lawson
Health Research Institute, London, Canada (J.S., J.B., H.B., M.K., F.S.P.); and
MR R&D, Siemens Healthcare, Los Angeles, Calif (X.B.)
| | - Xiaoming Bi
- From the Department of Biomedical Sciences, Cedars-Sinai Medical
Center, Biomedical Imaging Research Institute, PACT Bldg–Suite 400, 8700
Beverly Blvd, Los Angeles, CA 90048 (H.J.Y., D.D., B.S., I.C., R.T., P.S.,
R.D.); Department of Bioengineering (H.J.Y., R.D.) and David Geffen School of
Medicine (D.D., P.S.), University of California, Los Angeles Calif; Lawson
Health Research Institute, London, Canada (J.S., J.B., H.B., M.K., F.S.P.); and
MR R&D, Siemens Healthcare, Los Angeles, Calif (X.B.)
| | - Behzad Sharif
- From the Department of Biomedical Sciences, Cedars-Sinai Medical
Center, Biomedical Imaging Research Institute, PACT Bldg–Suite 400, 8700
Beverly Blvd, Los Angeles, CA 90048 (H.J.Y., D.D., B.S., I.C., R.T., P.S.,
R.D.); Department of Bioengineering (H.J.Y., R.D.) and David Geffen School of
Medicine (D.D., P.S.), University of California, Los Angeles Calif; Lawson
Health Research Institute, London, Canada (J.S., J.B., H.B., M.K., F.S.P.); and
MR R&D, Siemens Healthcare, Los Angeles, Calif (X.B.)
| | - Ivan Cokic
- From the Department of Biomedical Sciences, Cedars-Sinai Medical
Center, Biomedical Imaging Research Institute, PACT Bldg–Suite 400, 8700
Beverly Blvd, Los Angeles, CA 90048 (H.J.Y., D.D., B.S., I.C., R.T., P.S.,
R.D.); Department of Bioengineering (H.J.Y., R.D.) and David Geffen School of
Medicine (D.D., P.S.), University of California, Los Angeles Calif; Lawson
Health Research Institute, London, Canada (J.S., J.B., H.B., M.K., F.S.P.); and
MR R&D, Siemens Healthcare, Los Angeles, Calif (X.B.)
| | - Richard Tang
- From the Department of Biomedical Sciences, Cedars-Sinai Medical
Center, Biomedical Imaging Research Institute, PACT Bldg–Suite 400, 8700
Beverly Blvd, Los Angeles, CA 90048 (H.J.Y., D.D., B.S., I.C., R.T., P.S.,
R.D.); Department of Bioengineering (H.J.Y., R.D.) and David Geffen School of
Medicine (D.D., P.S.), University of California, Los Angeles Calif; Lawson
Health Research Institute, London, Canada (J.S., J.B., H.B., M.K., F.S.P.); and
MR R&D, Siemens Healthcare, Los Angeles, Calif (X.B.)
| | - Piotr Slomka
- From the Department of Biomedical Sciences, Cedars-Sinai Medical
Center, Biomedical Imaging Research Institute, PACT Bldg–Suite 400, 8700
Beverly Blvd, Los Angeles, CA 90048 (H.J.Y., D.D., B.S., I.C., R.T., P.S.,
R.D.); Department of Bioengineering (H.J.Y., R.D.) and David Geffen School of
Medicine (D.D., P.S.), University of California, Los Angeles Calif; Lawson
Health Research Institute, London, Canada (J.S., J.B., H.B., M.K., F.S.P.); and
MR R&D, Siemens Healthcare, Los Angeles, Calif (X.B.)
| | - Frank S. Prato
- From the Department of Biomedical Sciences, Cedars-Sinai Medical
Center, Biomedical Imaging Research Institute, PACT Bldg–Suite 400, 8700
Beverly Blvd, Los Angeles, CA 90048 (H.J.Y., D.D., B.S., I.C., R.T., P.S.,
R.D.); Department of Bioengineering (H.J.Y., R.D.) and David Geffen School of
Medicine (D.D., P.S.), University of California, Los Angeles Calif; Lawson
Health Research Institute, London, Canada (J.S., J.B., H.B., M.K., F.S.P.); and
MR R&D, Siemens Healthcare, Los Angeles, Calif (X.B.)
| | - Rohan Dharmakumar
- From the Department of Biomedical Sciences, Cedars-Sinai Medical
Center, Biomedical Imaging Research Institute, PACT Bldg–Suite 400, 8700
Beverly Blvd, Los Angeles, CA 90048 (H.J.Y., D.D., B.S., I.C., R.T., P.S.,
R.D.); Department of Bioengineering (H.J.Y., R.D.) and David Geffen School of
Medicine (D.D., P.S.), University of California, Los Angeles Calif; Lawson
Health Research Institute, London, Canada (J.S., J.B., H.B., M.K., F.S.P.); and
MR R&D, Siemens Healthcare, Los Angeles, Calif (X.B.)
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11
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Guensch DP, Fischer K, Jung C, Hurni S, Winkler BM, Jung B, Vogt AP, Eberle B. Relationship between myocardial oxygenation and blood pressure: Experimental validation using oxygenation-sensitive cardiovascular magnetic resonance. PLoS One 2019; 14:e0210098. [PMID: 30650118 PMCID: PMC6334913 DOI: 10.1371/journal.pone.0210098] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Accepted: 12/16/2018] [Indexed: 12/14/2022] Open
Abstract
Background The relationship between mean arterial pressure (MAP) and coronary blood flow is well described. There is autoregulation within a MAP range of 60 to 140 mmHg providing near constant coronary blood flow. Outside these limits flow becomes pressure-dependent. So far, response of myocardial oxygenation to changes in pressure and flow has been more difficult to assess. While established techniques mostly require invasive approaches, Oxygenation-Sensitive (OS) Cardiovascular Magnetic Resonance (CMR) is a technique that can non-invasively assess changes in myocardial tissue oxygenation. The purpose of this study was to follow myocardial oxygenation over a wide range of blood pressure variation within and outside known coronary autoregulatory limits using OS-CMR, and to relate these data to coronary hemodynamics. Methods Ten anaesthetized swine (German Large White) underwent left-sided thoracotomy and attachment of a perivascular flow probe to the proximal left anterior descending (LAD) coronary artery for continuous measurement of blood flow (QLAD). Thereafter, animals were transferred into a 3T MRI scanner. Mean arterial pressure (MAP) was varied in 10–15 mmHg steps by administering alpha1-receptor agents phenylephrine or urapidil. For each MAP level, OS-CMR images as well as arterial and coronary sinus blood gas samples were obtained simultaneously during brief periods of apnea. Relative changes (Δ) of coronary sinus oxygen saturation (ScsO2), oxygen delivery (DO2) and demand (MVO2), extraction ratio (O2ER) and excess (Ω) from respective reference levels at a MAP of 70 mmHg were determined and were compared to %change in OS-signal intensity (OS-SI) in simultaneously acquired OS-CMR images. Results QLAD response indicated autoregulation between MAP levels of 52 mmHg (lower limit) and127 mmHg (upper limit). OS-CMR revealed a global myocardial oxygenation deficit occurring below the lower autoregulation limit, with the nadir of OS-SI at -9.0%. With MAP values surpassing 70 mmHg, relative OS-SI increased to a maximum of +10.6%. Consistent with this, ΔScsO2, ΔDO2, ΔMVO2, ΔO2ER and ΔΩ responses indicated increasing mismatch of oxygenation balance outside the autoregulated zone. Changes in global OS-CMR were significantly correlated with all of these parameters (p≤0.02) except with ΔMVO2. Conclusion OS-CMR offers a novel and non-invasive route to evaluate the effects of blood pressure variations, as well as of cardiovascular drugs and interventions, on global and regional myocardial oxygenation, as demonstrated in a porcine model. OS-CMR identified mismatch of O2 supply and demand below the lower limit of coronary autoregulation. Vasopressor induced acute hypertension did not compromise myocardial oxygenation in healthy hearts despite increased cardiac workload and O2 demand. The clinical usefulness of OS-CMR remains to be established.
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Affiliation(s)
- Dominik P. Guensch
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Institute for Diagnostic, Interventional and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- * E-mail:
| | - Kady Fischer
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Institute for Diagnostic, Interventional and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- McGill University Health Centre, Montreal, QC, Canada
| | - Christof Jung
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Samuel Hurni
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Bernhard M. Winkler
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Bernd Jung
- Institute for Diagnostic, Interventional and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Andreas P. Vogt
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Balthasar Eberle
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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12
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Vermeulen TD, Boulet LM, Stembridge M, Williams AM, Anholm JD, Subedi P, Gasho C, Ainslie PN, Feigl EO, Foster GE. Influence of myocardial oxygen demand on the coronary vascular response to arterial blood gas changes in humans. Am J Physiol Heart Circ Physiol 2018; 315:H132-H140. [PMID: 29600897 DOI: 10.1152/ajpheart.00689.2017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It remains unclear if the human coronary vasculature is inherently sensitive to changes in arterial Po2 and Pco2 or if coronary vascular responses are the result of concomitant increases in myocardial O2 consumption/demand ([Formula: see text]). We hypothesized that the coronary vascular response to Po2 and Pco2 would be attenuated in healthy men when [Formula: see text] was attenuated with β1-adrenergic receptor blockade. Healthy men (age: 25 ± 1 yr, n = 11) received intravenous esmolol (β1-adrenergic receptor antagonist) or volume-matched saline in a double-blind, randomized crossover study and were exposed to poikilocapnic hypoxia, isocapnic hypoxia, and hypercapnic hypoxia. Measurements made at baseline and after 5 min of steady state at each gas manipulation included left anterior descending coronary blood velocity (LADV; Doppler echocardiography), heart rate, and arterial blood pressure. LADV values at the end of each hypoxic condition were compared between esmolol and placebo. The rate-pressure product (RPP) and left ventricular mechanical energy (MELV) were calculated as indexes of [Formula: see text]. All gas manipulations augmented RPP, MELV, and LADV, but only RPP and MELV were attenuated (4-18%) after β1-adrenergic receptor blockade ( P < 0.05). Despite attenuated RPP and MELV responses, β1-adrenergic receptor blockade did not attenuate the mean LADV vasodilatory response compared with placebo during poikilocapnic hypoxia (29.4 ± 2.2 vs. 27.3 ± 1.6 cm/s) and isocapnic hypoxia (29.5 ± 1.5 vs. 30.3 ± 2.2 cm/s). Hypercapnic hypoxia elicited a feedforward coronary dilation that was blocked by β1-adrenergic receptor blockade. These results indicate a direct influence of arterial Po2 on coronary vascular regulation that is independent of [Formula: see text]. NEW & NOTEWORTHY In humans, arterial hypoxemia led to an increase in epicardial coronary artery blood velocity. β1-Adrenergic receptor blockade did not diminish the hypoxemic coronary response despite reduced myocardial O2 demand. These data indicate hypoxemia can regulate coronary blood flow independent of myocardial O2 consumption. A plateau in the mean left anterior descending coronary artery blood velocity-rate-pressure product relationship suggested β1-adrenergic receptor-mediated, feedforward epicardial coronary artery dilation. In addition, we observed a synergistic effect of Po2 and Pco2 during hypercapnic hypoxia.
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Affiliation(s)
- Tyler D Vermeulen
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna, British Columbia , Canada
| | - Lindsey M Boulet
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna, British Columbia , Canada
| | - Mike Stembridge
- Cardiff School of Sport, Cardiff Metropolitan University , Cardiff , United Kingdom
| | - Alexandra M Williams
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna, British Columbia , Canada
| | | | | | - Chris Gasho
- Loma Linda University , Loma Linda, California
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna, British Columbia , Canada
| | - Eric O Feigl
- Department of Physiology and Biophysics, University of Washington , Seattle, Washington
| | - Glen E Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna, British Columbia , Canada
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13
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Pelletier-Galarneau M, deKemp RA, Hunter CR, Klein R, Klein M, Ironstone J, Fisher JA, Ruddy TD. Effects of Hypercapnia on Myocardial Blood Flow in Healthy Human Subjects. J Nucl Med 2017; 59:100-106. [DOI: 10.2967/jnumed.117.194308] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 06/08/2017] [Indexed: 11/16/2022] Open
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14
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Mou A, Zhang C, Li M, Jin F, Song Q, Liu A, Li Z. Evaluation of myocardial microcirculation using intravoxel incoherent motion imaging. J Magn Reson Imaging 2017; 46:1818-1828. [PMID: 28306208 DOI: 10.1002/jmri.25706] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 03/02/2017] [Indexed: 11/07/2022] Open
Affiliation(s)
- Anna Mou
- Department of Radiology; First Affiliated Hospital of Dalian Medical University; Dalian P.R. China
| | - Chen Zhang
- Department of Radiology; First Affiliated Hospital of Dalian Medical University; Dalian P.R. China
| | - Mengying Li
- Department of Radiology; First Affiliated Hospital of Dalian Medical University; Dalian P.R. China
| | - Fengqiang Jin
- Department of Radiology; First Affiliated Hospital of Dalian Medical University; Dalian P.R. China
| | - Qingwei Song
- Department of Radiology; First Affiliated Hospital of Dalian Medical University; Dalian P.R. China
| | - Ailian Liu
- Department of Radiology; First Affiliated Hospital of Dalian Medical University; Dalian P.R. China
| | - Zhiyong Li
- Department of Radiology; First Affiliated Hospital of Dalian Medical University; Dalian P.R. China
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15
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Yang HJ, Dey D, Sykes J, Klein M, Butler J, Kovacs MS, Sobczyk O, Sharif B, Bi X, Kali A, Cokic I, Tang R, Yumul R, Conte AH, Tsaftaris SA, Tighiouart M, Li D, Slomka PJ, Berman DS, Prato FS, Fisher JA, Dharmakumar R. Arterial CO 2 as a Potent Coronary Vasodilator: A Preclinical PET/MR Validation Study with Implications for Cardiac Stress Testing. J Nucl Med 2017; 58:953-960. [PMID: 28254864 DOI: 10.2967/jnumed.116.185991] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 01/31/2017] [Indexed: 11/16/2022] Open
Abstract
Myocardial blood flow (MBF) is the critical determinant of cardiac function. However, its response to increases in partial pressure of arterial CO2 (PaCO2), particularly with respect to adenosine, is not well characterized because of challenges in blood gas control and limited availability of validated approaches to ascertain MBF in vivo. Methods: By prospectively and independently controlling PaCO2 and combining it with 13N-ammonia PET measurements, we investigated whether a physiologically tolerable hypercapnic stimulus (∼25 mm Hg increase in PaCO2) can increase MBF to that observed with adenosine in 3 groups of canines: without coronary stenosis, subjected to non-flow-limiting coronary stenosis, and after preadministration of caffeine. The extent of effect on MBF due to hypercapnia was compared with adenosine. Results: In the absence of stenosis, mean MBF under hypercapnia was 2.1 ± 0.9 mL/min/g and adenosine was 2.2 ± 1.1 mL/min/g; these were significantly higher than at rest (0.9 ± 0.5 mL/min/g, P < 0.05) and were not different from each other (P = 0.30). Under left-anterior descending coronary stenosis, MBF increased in response to hypercapnia and adenosine (P < 0.05, all territories), but the effect was significantly lower than in the left-anterior descending coronary territory (with hypercapnia and adenosine; both P < 0.05). Mean perfusion defect volumes measured with adenosine and hypercapnia were significantly correlated (R = 0.85) and were not different (P = 0.12). After preadministration of caffeine, a known inhibitor of adenosine, resting MBF decreased; and hypercapnia increased MBF but not adenosine (P < 0.05). Conclusion: Arterial blood CO2 tension when increased by 25 mm Hg can induce MBF to the same level as a standard dose of adenosine. Prospectively targeted arterial CO2 has the capability to evolve as an alternative to current pharmacologic vasodilators used for cardiac stress testing.
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Affiliation(s)
- Hsin-Jung Yang
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California.,Department of Bioengineering, University of California, Los Angeles, California
| | - Damini Dey
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California.,Department of Bioengineering, University of California, Los Angeles, California
| | - Jane Sykes
- University of Western Ontario, Lawson Health Research Institute, London, Ontario, Canada
| | - Michael Klein
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - John Butler
- University of Western Ontario, Lawson Health Research Institute, London, Ontario, Canada
| | - Michael S Kovacs
- University of Western Ontario, Lawson Health Research Institute, London, Ontario, Canada
| | - Olivia Sobczyk
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Behzad Sharif
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - Xiaoming Bi
- MR R&D, Siemens Healthcare, Los Angeles, California
| | - Avinash Kali
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California.,Department of Bioengineering, University of California, Los Angeles, California
| | - Ivan Cokic
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - Richard Tang
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - Roya Yumul
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California.,Department of Medicine, University of California, Los Angeles, California
| | - Antonio H Conte
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - Sotirios A Tsaftaris
- School of Engineering, Institute of Digital Communications, University of Edinburgh, Edinburgh, United Kingdom; and
| | - Mourad Tighiouart
- Biostatistics and Bioinformatics Research Center, Cedars-Sinai Medical Center, Los Angeles, California
| | - Debiao Li
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California.,Department of Bioengineering, University of California, Los Angeles, California
| | - Piotr J Slomka
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California.,Department of Medicine, University of California, Los Angeles, California
| | - Daniel S Berman
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California.,Department of Medicine, University of California, Los Angeles, California
| | - Frank S Prato
- University of Western Ontario, Lawson Health Research Institute, London, Ontario, Canada
| | - Joseph A Fisher
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Rohan Dharmakumar
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California .,Department of Bioengineering, University of California, Los Angeles, California.,Department of Medicine, University of California, Los Angeles, California
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16
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Fischer K, Guensch DP, Shie N, Lebel J, Friedrich MG. Breathing Maneuvers as a Vasoactive Stimulus for Detecting Inducible Myocardial Ischemia - An Experimental Cardiovascular Magnetic Resonance Study. PLoS One 2016; 11:e0164524. [PMID: 27741282 PMCID: PMC5065132 DOI: 10.1371/journal.pone.0164524] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 09/27/2016] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Breathing maneuvers can elicit a similar vascular response as vasodilatory agents like adenosine; yet, their potential diagnostic utility in the presence of coronary artery stenosis is unknown. The objective of the study is to investigate if breathing maneuvers can non-invasively detect inducible ischemia in an experimental animal model when the myocardium is imaged with oxygenation-sensitive cardiovascular magnetic resonance (OS-CMR). METHODS AND FINDINGS In 11 anesthetised swine with experimentally induced significant stenosis (fractional flow reserve <0.75) of the left anterior descending coronary artery (LAD) and 9 control animals, OS-CMR at 3T was performed during two different breathing maneuvers, a long breath-hold; and a combined maneuver of 60s of hyperventilation followed by a long breath-hold. The resulting change of myocardial oxygenation was compared to the invasive measurements of coronary blood flow, blood gases, and oxygen extraction. In control animals, all breathing maneuvers could significantly alter coronary blood flow as hyperventilation decreased coronary blood flow by 34±23%. A long breath-hold alone led to an increase of 97±88%, while the increase was 346±327% (p<0.001), when the long breath-hold was performed after hyperventilation. In stenosis animals, the coronary blood flow response was attenuated after both hyperventilation and the following breath-hold. This was matched by the observed oxygenation response as breath-holds following hyperventilation consistently yielded a significant difference in the signal of the MRI images between the perfusion territory of the stenosis LAD and remote myocardium. There was no difference between the coronary territories during the other breathing maneuvers or in the control group at any point. CONCLUSION In an experimental animal model, the response to a combined breathing maneuver of hyperventilation with subsequent breath-holding is blunted in myocardium subject to significant coronary artery stenosis. This maneuver may allow for detecting severe coronary artery stenosis and have a significant clinical potential as a non-pharmacological method for diagnostic testing in patients with suspected coronary artery disease.
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Affiliation(s)
- Kady Fischer
- Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Université de Montréal, Montreal, QC, Canada
- University Hospital Bern, Department Anaesthesiology and Pain Therapy, Inselspital, University of Bern, Bern, Switzerland
- University Hospital Bern, Institute for Diagnostic, Interventional and Paediatric Radiology, Inselspital, University of Bern, Bern, Switzerland
| | - Dominik P Guensch
- Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Université de Montréal, Montreal, QC, Canada
- University Hospital Bern, Department Anaesthesiology and Pain Therapy, Inselspital, University of Bern, Bern, Switzerland
- University Hospital Bern, Institute for Diagnostic, Interventional and Paediatric Radiology, Inselspital, University of Bern, Bern, Switzerland
| | - Nancy Shie
- Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Université de Montréal, Montreal, QC, Canada
| | - Julie Lebel
- Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Université de Montréal, Montreal, QC, Canada
- Research Institute of the McGill University Health Centre, Montreal, QC, Canada
| | - Matthias G Friedrich
- Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Université de Montréal, Montreal, QC, Canada
- Department of Radiology, Université de Montréal, Montreal, QC, Canada
- Departments of Medicine and Diagnostic Radiology, McGill University, Montreal, QC, Canada
- Department of Cardiology, Heidelberg University Hospital, Heidelberg, Germany
- Departments of Cardiac Sciences and Radiology, University of Calgary, Calgary, Canada
- * E-mail:
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17
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Boulet LM, Stembridge M, Tymko MM, Tremblay JC, Foster GE. The effects of graded changes in oxygen and carbon dioxide tension on coronary blood velocity independent of myocardial energy demand. Am J Physiol Heart Circ Physiol 2016; 311:H326-36. [PMID: 27233761 DOI: 10.1152/ajpheart.00107.2016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 05/19/2016] [Indexed: 11/22/2022]
Abstract
In humans, coronary blood flow is tightly regulated by microvessels within the myocardium to match myocardial energy demand. However, evidence regarding inherent sensitivity of the microvessels to changes in arterial partial pressure of carbon dioxide and oxygen is conflicting because of the accompanied changes in myocardial energy requirements. This study aimed to investigate the changes in coronary blood velocity while manipulating partial pressures of end-tidal CO2 (Petco2) and O2 (Peto2). It was hypothesized that an increase in Petco2 (hypercapnia) or decrease in Peto2 (hypoxia) would result in a significant increase in mean blood velocity in the left anterior descending artery (LADVmean) due to an increase in both blood gases and energy demand associated with the concomitant cardiovascular response. Cardiac energy demand was assessed through noninvasive measurement of the total left ventricular mechanical energy. Healthy subjects (n = 13) underwent a euoxic CO2 test (Petco2 = -8, -4, 0, +4, and +8 mmHg from baseline) and an isocapnic hypoxia test (Peto2 = 64, 52, and 45 mmHg). LADVmean was assessed using transthoracic Doppler echocardiography. Hypercapnia evoked a 34.6 ± 8.5% (mean ± SE; P < 0.01) increase in mean LADVmean, whereas hypoxia increased LADVmean by 51.4 ± 8.8% (P < 0.05). Multiple stepwise regressions revealed that both mechanical energy and changes in arterial blood gases are important contributors to the observed changes in LADVmean (P < 0.01). In summary, regulation of the coronary vasculature in humans is mediated by metabolic changes within the heart and an inherent sensitivity to arterial blood gases.
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Affiliation(s)
- Lindsey M Boulet
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada; and
| | - Mike Stembridge
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Michael M Tymko
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada; and
| | - Joshua C Tremblay
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada; and
| | - Glen E Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada; and
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18
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Guensch DP, Nadeshalingam G, Fischer K, Stalder AF, Friedrich MG. The impact of hematocrit on oxygenation-sensitive cardiovascular magnetic resonance. J Cardiovasc Magn Reson 2016; 18:42. [PMID: 27435406 PMCID: PMC4952059 DOI: 10.1186/s12968-016-0262-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 06/28/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Oxygenation-sensitive (OS) Cardiovascular Magnetic Resonance (CMR) is a promising utility in the diagnosis of heart disease. Contrast in OS-CMR images is generated through deoxyhemoglobin in the tissue, which is negatively correlated with the signal intensity (SI). Thus, changing hematocrit levels may be a confounder in the interpretation of OS-CMR results. We hypothesized that hemodilution confounds the observed signal intensity in OS-CMR images. METHODS Venous and arterial blood from five pigs was diluted with lactated Ringer solution in 10 % increments to 50 %. The changes in signal intensity (SI) were compared to changes in blood gases and hemoglobin concentration. We performed an OS-CMR scan in 21 healthy volunteers using vasoactive breathing stimuli at baseline, which was then repeated after rapid infusion of 1 L of lactated Ringer's solution within 5-8 min. Changes of SI were measured and compared between the hydration states. RESULTS The % change in SI from baseline for arterial (r = -0.67, p < 0.0001) and venous blood (r = -0.55, p = 0.002) were negatively correlated with the changes in hemoglobin (Hb). SI changes in venous blood were also associated with SO2 (r = 0.68, p < 0.0001) and deoxyHb concentration (-0.65, p < 0.0001). In healthy volunteers, rapid infusion resulted in a significant drop in the hemoglobin concentration (142.5 ± 15.2 g/L vs. 128.8 ± 15.2 g/L; p < 0.0001). Baseline myocardial SI increased by 3.0 ± 5.7 % (p = 0.026) following rapid infusion, and in males there was a strong association between the change in hemoglobin concentration and % changes in SI (r = 0.82, p = 0.002). After hyperhydration, the SI response after hyperventilation was attenuated (HV, p = 0.037), as was the maximum SI increase during apnea (p = 0.012). The extent of SI attenuation was correlated with the reduction in hemoglobin concentration at the end of apnea (r = 0.55, p = 0.012) for all subjects and at maximal SI (r = 0.63, p = 0.037) and the end of breath-hold (r = 0.68, p = 0.016) for males only. CONCLUSION In dynamic studies using oxygenation-sensitive CMR, the hematocrit level affects baseline signal intensity and the observed signal intensity response. Thus, the hydration status of the patient may be a confounder for OS-CMR image analysis.
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Affiliation(s)
- Dominik P. Guensch
- />Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Montreal, QC Canada
- />Department of Anesthesiology and Pain Therapy, Inselspital, Bern University Hospital, University of Bern, Freiburgstrasse, 3010 Bern, Switzerland
- />Instutite of Diagnostic, Interventional and Pediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Gobinath Nadeshalingam
- />Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Montreal, QC Canada
| | - Kady Fischer
- />Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Montreal, QC Canada
- />Department of Anesthesiology and Pain Therapy, Inselspital, Bern University Hospital, University of Bern, Freiburgstrasse, 3010 Bern, Switzerland
| | | | - Matthias G. Friedrich
- />Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Montreal, QC Canada
- />Department of Medicine, Heidelberg University, Heidelberg, Germany
- />Departments of Cardiac Sciences and Radiology, University of Calgary, Calgary, AB Canada
- />Department of Radiology, Université de Montréal, Montreal, QC Canada
- />Departments of Medicine and Radiology, McGill University Health Centre, Montreal, QC Canada
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19
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Teixeira T, Nadeshalingam G, Fischer K, Marcotte F, Friedrich MG. Breathing maneuvers as a coronary vasodilator for myocardial perfusion imaging. J Magn Reson Imaging 2016; 44:947-55. [DOI: 10.1002/jmri.25224] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2015] [Accepted: 02/22/2016] [Indexed: 11/10/2022] Open
Affiliation(s)
- Tiago Teixeira
- Montreal Heart Institute; Departments of Cardiology and Radiology; Université de Montréal; Montréal Canada
- Lenitudes Medical Center and Research; Sta Maria da Feira Portugal
| | - Gobinath Nadeshalingam
- Montreal Heart Institute; Departments of Cardiology and Radiology; Université de Montréal; Montréal Canada
| | - Kady Fischer
- Montreal Heart Institute; Departments of Cardiology and Radiology; Université de Montréal; Montréal Canada
| | - François Marcotte
- Montreal Heart Institute; Departments of Cardiology and Radiology; Université de Montréal; Montréal Canada
| | - Matthias G. Friedrich
- Montreal Heart Institute; Departments of Cardiology and Radiology; Université de Montréal; Montréal Canada
- McGill University Health Centre; Departments of Cardiology and Diagnostic Radiology; McGill University; Montreal Canada
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20
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Ganesh T, Estrada M, Duffin J, Cheng HL. T2* and T1 assessment of abdominal tissue response to graded hypoxia and hypercapnia using a controlled gas mixing circuit for small animals. J Magn Reson Imaging 2016; 44:305-16. [PMID: 26872559 DOI: 10.1002/jmri.25169] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 01/12/2016] [Indexed: 01/13/2023] Open
Abstract
PURPOSE To characterize T2* and T1 relaxation time response to a wide spectrum of gas challenges in extracranial tissues of healthy rats. MATERIALS AND METHODS A range of graded gas mixtures (hyperoxia, hypercapnia, hypoxia, and hypercapnic hypoxia) were delivered through a controlled gas-mixing circuit to mechanically ventilated and intubated rats. Quantitative magnetic resonance imaging (MRI) was performed on a 3T clinical scanner; T2* and T1 maps were computed to determine tissue response in the liver, kidney cortex, and paraspinal muscles. Heart rate and blood oxygen saturation (SaO2 ) were measured through a rodent oximeter and physiological monitor. RESULTS T2* decreases consistent with lowered SaO2 measurements were observed for hypercapnia and hypoxia, but decreases were significant only in liver and kidney cortex (P < 0.05) for >10% CO2 and <15% O2 , with the new gas stimulus, hypercapnic hypoxia, producing the greatest T2* decrease. Hyperoxia-related T2* increases were accompanied by negligible increases in SaO2 . T1 generally increased, if at all, in the liver and decreased in the kidney. Significance was observed (P < 0.05) only in kidney for >90% O2 and >5% CO2 . CONCLUSION T2* and T1 provide complementary roles for evaluating extracranial tissue response to a broad range of gas challenges. Based on both measured and known physiological responses, our results are consistent with T2* as a sensitive marker of blood oxygen saturation and T1 as a weak marker of blood volume changes. J. Magn. Reson. Imaging 2016;44:305-316.
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Affiliation(s)
- Tameshwar Ganesh
- Translational Biology & Engineering Program, Ted Rogers Centre for Heart Research, Toronto, Canada.,Leslie Dan Faculty of Pharmacy, University of Toronto, Canada.,Physiology & Experimental Medicine, Hospital for Sick Children Research Institute, Toronto, Canada
| | - Marvin Estrada
- Lab Animal Services, Hospital for Sick Children, Toronto, Canada
| | - James Duffin
- Department of Anesthesia, University of Toronto, Canada
| | - Hai Ling Cheng
- Translational Biology & Engineering Program, Ted Rogers Centre for Heart Research, Toronto, Canada.,Leslie Dan Faculty of Pharmacy, University of Toronto, Canada.,Physiology & Experimental Medicine, Hospital for Sick Children Research Institute, Toronto, Canada.,The Edward S. Rogers Sr. Department of Electrical & Computer Engineering, University of Toronto, Canada.,Institute of Biomaterials & Biomedical Engineering, University of Toronto, Canada
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