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Jang JH, Park JH, Ko KY, Baek YS, Kwon SW, Park SD, Shin SH, Woo SI, Kwan J, Kim DH. An analysis of vascular properties using pulse wave analysis in patients with vasovagal syncope. Clin Cardiol 2020; 43:781-788. [PMID: 32557670 PMCID: PMC7368349 DOI: 10.1002/clc.23380] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 04/08/2020] [Accepted: 04/22/2020] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND Vasovagal syncope (VVS) is a common cause of recurrent syncope. Nevertheless, the exact hemodynamic mechanism has not been elucidated. Pulse wave analysis (PWA) is widely used to evaluate vascular properties, as it reflects the condition of the entire arterial system. HYPOTHESIS Cardiovascular autonomic modulation may influence the hemodynamic mechanism and result in different vascular properties between VVS patients and healthy individuals. METHODS We enrolled consecutive patients diagnosed with VVS on head-up tilt testing from January 2014 to August 2019. Healthy subjects were enrolled as the control group. We performed PWA on all participants. Using propensity score matching, we assembled a study population with similar baseline characteristics and compared hemodynamic parameters. RESULTS A total of 111 VVS patients (43 ± 18 years, 72 females) and 475 healthy control subjects (48 ± 13 years, 192 females) were enrolled. Compared to the healthy control subjects, the VVS patients had a higher augmentation index (AIx) adjusted to a heart rate of 75 beats per minute (AIx@HR75, 20.5 ± 13.1% vs 16.7 ± 11.9%, P = .003). After 1:1 matched comparison (111 matched control), VVS patients consistently showed higher AIx@HR75 (20.5 ± 13.1% vs 16.7 ± 12.9%, P = .02) than the matched control group. According to age distribution, VVS patients showed significantly higher AIx@HR75 (10.6 ± 11.7% vs 2.5 ± 11.1%, P = .01) in a young age (15-33 years) group. CONCLUSIONS VVS patients had greater arterial stiffness than healthy subjects. This is one of the plausible mechanisms of the pathophysiology of VVS.
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Affiliation(s)
- Ji-Hun Jang
- Department of Cardiology, Inha University Hospital Cardiovascular Center, Incheon, Republic of Korea
| | - Jin-Hee Park
- Department of Cardiology, Inha University Hospital Cardiovascular Center, Incheon, Republic of Korea
| | - Kyu-Yong Ko
- Department of Cardiology, Inha University Hospital Cardiovascular Center, Incheon, Republic of Korea
| | - Yong-Soo Baek
- Department of Cardiology, Inha University Hospital Cardiovascular Center, Incheon, Republic of Korea
| | - Sung-Woo Kwon
- Department of Cardiology, Inha University Hospital Cardiovascular Center, Incheon, Republic of Korea
| | - Sang-Don Park
- Department of Cardiology, Inha University Hospital Cardiovascular Center, Incheon, Republic of Korea
| | - Sung-Hee Shin
- Department of Cardiology, Inha University Hospital Cardiovascular Center, Incheon, Republic of Korea
| | - Seong-Ill Woo
- Department of Cardiology, Inha University Hospital Cardiovascular Center, Incheon, Republic of Korea
| | - Jun Kwan
- Department of Cardiology, Inha University Hospital Cardiovascular Center, Incheon, Republic of Korea
| | - Dae-Hyeok Kim
- Department of Cardiology, Inha University Hospital Cardiovascular Center, Incheon, Republic of Korea
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Sled JG, Stortz G, Cahill LS, Milligan N, Ayyathurai V, Serghides L, Morgen E, Seravalli V, Delp C, McShane C, Baschat A, Kingdom J, Macgowan CK. Reflected hemodynamic waves influence the pattern of Doppler ultrasound waveforms along the umbilical arteries. Am J Physiol Heart Circ Physiol 2019; 316:H1105-H1112. [PMID: 30794433 DOI: 10.1152/ajpheart.00704.2018] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The pulsatile pattern of blood motion measured by Doppler ultrasound within the umbilical artery is known to contain useful diagnostic information and is widely used to monitor pregnancies at risk of fetal growth restriction or stillbirth. Animal studies have identified reflected pressure waves traveling counter to the direction of blood flow as an important factor in the shape of these waveforms. In the present study, we establish a method to measure reflected waves in the human umbilical artery and assess their influence on blood velocity pulsation. Ninety-five pregnant women were recruited from a general obstetrics clinic between 26 and 37 wk of gestation and examined by Doppler ultrasound. Blood velocity waveforms were recorded for each umbilical artery at three locations along the umbilical cord. With the use of a computational procedure, a pair of forward and reverse propagating waves was identified to explain the variation in observed Doppler ultrasound waveforms along the cord. Among the data sets that met data quality requirements, waveforms in 93 of the 130 arteries examined agreed with the wave reflection model to within 1.5% and showed reflections ranging in magnitude from 3 to 52% of the forward wave amplitude. Strong reflections were associated with large differences in pulsatility between the fetal and placental ends of the cord. As reflections arise from transitions in the biomechanical properties of blood vessels, these observations provide a plausible mechanism for the link between abnormal waveforms and clinically significant placental pathology and could lead to more precise screening methods for detecting pregnancies complicated by placental disease. NEW & NOTEWORTHY The pulsatile pattern of blood motion measured by Doppler ultrasound within the umbilical artery is known to contain useful diagnostic information and is widely used to monitor pregnancies at risk of fetal growth restriction. We demonstrate based on a study of 95 pregnant women that the shape of these umbilical artery waveforms is explained by the presence of a reflected pressure wave traveling counter to the direction of blood flow.
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Affiliation(s)
- John G Sled
- Hospital for Sick Children , Toronto, Ontario , Canada.,Department of Medical Biophysics, University of Toronto , Toronto, Ontario , Canada.,Department of Obstetrics and Gynecology, University of Toronto , Toronto, Ontario , Canada
| | - Greg Stortz
- Hospital for Sick Children , Toronto, Ontario , Canada
| | | | | | | | - Lena Serghides
- Toronto General Hospital Research Institute, University Health Network , Toronto, Ontario , Canada.,Department of Immunology, University of Toronto , Toronto, Ontario , Canada
| | - Eric Morgen
- Mount Sinai Hospital , Toronto, Ontario , Canada.,Department of Laboratory Medicine and Pathobiology, University of Toronto , Toronto, Ontario , Canada
| | - Viola Seravalli
- Center for Fetal Therapy, Johns Hopkins Medicine, Baltimore, Maryland.,Department of Health Sciences, University of Florence , Florence , Italy
| | - Cassandra Delp
- Center for Fetal Therapy, Johns Hopkins Medicine, Baltimore, Maryland
| | - Cyrethia McShane
- Center for Fetal Therapy, Johns Hopkins Medicine, Baltimore, Maryland
| | - Ahmet Baschat
- Center for Fetal Therapy, Johns Hopkins Medicine, Baltimore, Maryland
| | - John Kingdom
- Department of Obstetrics and Gynecology, University of Toronto , Toronto, Ontario , Canada.,Mount Sinai Hospital , Toronto, Ontario , Canada
| | - Christopher K Macgowan
- Hospital for Sick Children , Toronto, Ontario , Canada.,Department of Medical Biophysics, University of Toronto , Toronto, Ontario , Canada
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Rahman A, Zhou YQ, Yee Y, Dazai J, Cahill LS, Kingdom J, Macgowan CK, Sled JG. Ultrasound detection of altered placental vascular morphology based on hemodynamic pulse wave reflection. Am J Physiol Heart Circ Physiol 2017; 312:H1021-H1029. [PMID: 28364018 DOI: 10.1152/ajpheart.00791.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 03/16/2017] [Accepted: 03/28/2017] [Indexed: 11/22/2022]
Abstract
Abnormally pulsatile umbilical artery (UA) Doppler ultrasound velocity waveforms are a hallmark of severe or early onset placental-mediated intrauterine growth restriction (IUGR), whereas milder late onset IUGR pregnancies typically have normal UA pulsatility. The diagnostic utility of these waveforms to detect placental pathology is thus limited and hampered by factors outside of the placental circulation, including fetal cardiac output. In view of these limitations, we hypothesized that these Doppler waveforms could be more clearly understood as a reflection phenomenon and that a reflected pulse pressure wave is present in the UA that originates from the placenta and propagates backward along the UA. To investigate this, we developed a new ultrasound approach to isolate that portion of the UA Doppler waveform that arises from a pulse pressure wave propagating backward along the UA. Ultrasound measurements of UA lumen diameter and flow waveforms were used to decompose the observed flow waveform into its forward and reflected components. Evaluation of CD1 and C57BL/6 mice at embryonic day (E)15.5 and E17.5 demonstrated that the reflected waveforms diverged between the strains at E17.5, mirroring known changes in the fractal geometry of fetoplacental arteries at these ages. These experiments demonstrate the feasibility of noninvasively measuring wave reflections that originate from the fetoplacental circulation. The observed reflections were consistent with theoretical predictions based on the area ratio of parent to daughters at bifurcations in fetoplacental arteries suggesting that this approach could be used in the diagnosis of fetoplacental vascular pathology that is prevalent in human IUGR. Given that the proposed measurements represent a subset of those currently used in human fetal surveillance, the adaptation of this technology could extend the diagnostic utility of Doppler ultrasound in the detection of placental vascular pathologies that cause IUGR.NEW & NOTEWORTHY Here, we describe a novel approach to noninvasively detect microvascular changes in the fetoplacental circulation using ultrasound. The technique is based on detecting reflection pulse pressure waves that travel along the umbilical artery. Using a proof-of-principle study, we demonstrate the feasibility of the technique in two strains of experimental mice.
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Affiliation(s)
- Anum Rahman
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - Yu-Qing Zhou
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Yohan Yee
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - Jun Dazai
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Lindsay S Cahill
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, Ontario, Canada
| | - John Kingdom
- Department of Obstetrics and Gynecology, University of Toronto, Toronto, Ontario, Canada.,Mount Sinai Hospital, Toronto, Ontario, Canada; and
| | - Christopher K Macgowan
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.,Physiology and Experimental Medicine, Hospital for Sick Children, Toronto, Ontario, Canada
| | - John G Sled
- Mouse Imaging Centre, Hospital for Sick Children, Toronto, Ontario, Canada; .,Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.,Department of Obstetrics and Gynecology, University of Toronto, Toronto, Ontario, Canada.,Physiology and Experimental Medicine, Hospital for Sick Children, Toronto, Ontario, Canada
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Evaluation of cerebrovascular impedance and wave reflection in mouse by ultrasound. J Cereb Blood Flow Metab 2015; 35:521-6. [PMID: 25515209 PMCID: PMC4348395 DOI: 10.1038/jcbfm.2014.229] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 11/14/2014] [Accepted: 11/25/2014] [Indexed: 11/13/2022]
Abstract
Genetic and surgical mouse models are commonly used to study cerebrovascular disease, but their size makes invasive hemodynamic testing technically challenging. The purpose of this study was to demonstrate a noninvasive measurement of cerebrovascular impedance and wave reflection in mice using high-frequency ultrasound in the left common carotid artery (LCCA), and to examine whether microvascular changes associated with hypercapnia could be detected with such an approach. Ten mice (C57BL/6J) were studied using a high-frequency ultrasound system (40 MHz). Lumen area and blood flow waveforms were obtained from the LCCA and used to calculate pulse-wave velocity, input impedance, and reflection amplitude and transit time under both normocapnic and hypercapnic (5% CO2) ventilation. With hypercapnia, vascular resistance was observed to decrease by 87%±12%. Although the modulus of input impedance was unchanged with hypercapnia, a phase decrease indicative of increased total arterial compliance was observed at low harmonics together with an increased reflection coefficient in both the time (0.57±0.08 versus 0.68±0.08, P=0.04) and frequency domains (0.62±0.08 versus 0.73±0.06, P=0.02). Interestingly, the majority of LCCA blood flow was found to pass into the internal carotid artery (range=76% to 90%, N=3), suggesting that hemodynamic measurements in this vessel are a good metric for intracerebral reactivity in mouse.
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Sung SH, Chen ZY, Tseng TW, Lu DY, Yu WC, Cheng HM, Chen CH. Wave reflections, arterial stiffness, and orthostatic hypotension. Am J Hypertens 2014; 27:1446-55. [PMID: 24815677 DOI: 10.1093/ajh/hpu063] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND The effect of wave reflections on blood pressure change associated with posture remains unclear. We therefore applied a wave separation technique to investigate the relations of the backward pressure wave amplitude with orthostatic pressure changes and orthostatic hypotension (OH). METHODS We analyzed data from 613 subjects who had participated in our hemodynamic studies. Measurements of brachial systolic (SBP) and diastolic blood pressures (DBP), carotid-femoral pulse wave velocity (cf-PWV), and backward pressure wave amplitude from a decomposed carotid pressure wave (Pb) were obtained at supine position. SBP and DBP were measured again 3 minutes after standing. OH was defined as a fall of ≥20 mm Hg in SBP and/or ≥10 mm Hg in DBP. RESULTS Subjects with OH (n = 100) were characterized with significantly higher supine SBP and DBP and significantly lower standing SBP and DBP when compared with subjects without OH. Subjects with OH were also characterized with significantly higher cf-PWV and Pb. cf-PWV and Pb separately were significantly associated with the orthostatic SBP change in univariable and multivariable analyses. Also, cf-PWV and Pb separately were significant predictors of OH in univariable and multivariable analyses. cf-PWV predicted OH in the younger but less so in the older subgroup, whereas Pb demonstrated similar prediction in both subgroups. In a final multivariable model, both cf-PWV and Pb were significant independent predictors of OH. CONCLUSIONS Wave reflections are an independent determinant of orthostatic SBP change and OH in both younger and older subjects.
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Affiliation(s)
| | - Zu-Yin Chen
- Department of Medicine, National Yang-Ming University, Taipei, Taiwan; Department of Medicine, National Yang-Ming University Hospital, Yilan, Taiwan
| | - Tzu-Wei Tseng
- Department of Medicine, National Yang-Ming University, Taipei, Taiwan; Division of Cardiology, Taipei City Hospital, Yang-Ming Branch, Taipei, Taiwan
| | - Dai-Yin Lu
- Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Publich Health, National Yang-Ming University, Taipei, Taiwan
| | - Wen-Chung Yu
- Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Hao-Min Cheng
- Department of Medical Education, Taipei Veterans General Hospital, Taipei, Taiwan. Department of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Chen-Huan Chen
- Department of Medical Education, Taipei Veterans General Hospital, Taipei, Taiwan.
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Lu DY, Sung SH, Yu WC, Cheng HM, Chuang SY, Chen CH. Wave reflections, arterial stiffness, heart rate variability and orthostatic hypotension. Hypertens Res 2014; 37:1056-61. [DOI: 10.1038/hr.2014.127] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 06/16/2014] [Accepted: 07/03/2014] [Indexed: 11/09/2022]
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Parry SW, Norton M, Pairman J, Baptist M, Wilton K, Reeve P, Sutcliffe K, Newton JL. Impedance cardiography: a role in vasovagal syncope diagnosis? Age Ageing 2009; 38:718-23. [PMID: 19749201 DOI: 10.1093/ageing/afp167] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND vasovagal syncope is the most common cause of syncope in all age groups, with diagnosis usually based on history, examination and basic investigations to exclude alternative causes of syncope. Where doubt exists, the head-up tilt (HUT) test is used for diagnosis but is time consuming and lacks a gold standard to accurately assess sensitivity and specificity. Alternative methods of diagnosing vasovagal syncope would thus be useful. OBJECTIVE to investigate the potential for impedance cardiography (ICG)-derived haemodynamic measures to predict HUT test outcome in unexplained syncope. DESIGN prospective controlled study. SUBJECTS eighty-six patients with unexplained syncope and 43 non-syncopal controls. METHODS all subjects underwent continuous heart rate, blood pressure and ICG measurements during 10 min supine rest and during HUT. Vasovagal syncope was diagnosed when patients experienced symptom reproduction with concomitant haemodynamic derangements. RESULTS during rest prior to HUT, the syncopal group had higher mean heart rate (P = 0.0008) and lower baroreceptor effectiveness index (P < 0.0001) compared to non-syncopal controls. On comparing patients who presented with unexplained syncope who subsequently had a positive HUT (therefore a diagnosis of vasovagal syncope 55 [64%]; mean age 47 years, range 17-85) to those having a negative tilt test (n = 31; mean age 47 years, range 17-88), there were no significant differences found in cardiovascular or autonomic parameters prior to HUT. A predictive ROC curve model at a 85% threshold allowed using cardiac index (CI), end-diastolic index (EDI) and left ventricular work index (LVWI) would identify those who would have a positive HUT from baseline cardiovascular measurements (CI >3.5, EDI > 77, LVWI >4.7) with 93% sensitivity and 17% specificity. CONCLUSION supine haemodynamic measures derived from transthoracic ICG can simply, non-invasively and sensitively differentiate HUT-positive patients from those with negative tilt tests. Further work is needed, particularly in older patients, before this technique can be used in clinical practice.
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Affiliation(s)
- Steve W Parry
- Institute for Ageing and Health, Newcastle University, Newcastle upon Tyne, NE4 5PL, UK
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Simek J, Wichterle D, Melenovsky V, Malik J, Svobodova J, Svacina S. Pulse wave analysis during supine rest may identify subjects with recurrent vasovagal syncope. Clin Sci (Lond) 2005; 109:165-70. [PMID: 15740456 DOI: 10.1042/cs20040304] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In the present study, we studied whether analysis of the FAP (finger arterial pressure) waveform during supine rest discriminates subjects with recurrent VVS (vasovagal syncope) from healthy controls. Signal-averaged FAP waveforms (Finapres) were obtained in 32 head-up tilt-test-positive subjects with recurrent VVS (35±13 years) and in 32 sex- and age-matched healthy controls. The DT (time delay) between the systolic and diastolic peaks of the FAP waveform was measured and large artery SI (stiffness index) was calculated as a ratio of body height and DT. VVS patients had significantly shorter DT compared with controls (303±31 compared with 329±18 ms; P<0.001) and higher SI (5.79±0.70 compared with 5.20±0.36 m/s; P<0.001). The differences were independent of heart rate and blood pressure. SI >5.45 m/s identified subjects with syncope with a sensitivity of 72% and a specificity of 84%. Age-corrected DT (cDT=DT+age−350) identified subjects with syncope with a sensitivity of 75% and a specificity of 84%. Combined use of cDT <0 ms and SI >5.45 m/s increased sensitivity and specificity to 81% and 96% respectively. The discriminative power of FAP descriptors improved further when younger subjects were excluded. In subjects aged >30 years (median age), the combination of cDT and SI identified subjects with syncope with a sensitivity of 93% and a specificity of 100%. These results suggest that FAP descriptors during supine rest might be useful in the diagnosis of VVS in middle-aged subjects.
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Affiliation(s)
- Jan Simek
- Third Department of Internal Medicine, General University Hospital, Prague, Czech Republic.
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Hsu HY, Chao AC, Chen YT, Wong WJ, Chern CM, Hsu LC, Kuo JS, Hu HH. Comparison of Critical Closing Pressures Extracted from Carotid Tonometry and Finger Plethysmography. Cerebrovasc Dis 2005; 19:369-75. [PMID: 15838164 DOI: 10.1159/000085204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2004] [Accepted: 01/27/2005] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND The reliability of critical closing pressure (CrCP) estimates derived from peripheral blood pressure (BP) measurements is unclear. We attempted to evaluate the influences of peripheral circulation on determining CrCP. METHODS Twenty-five young healthy volunteers were studied. BP waves were obtained with plethysmography (Portapres) and carotid applanatory tonometry, respectively, for analysis. Transcranial Doppler was used to monitor cerebral flow velocity. Using linear regression analysis, beat-to-beat CrCP was calculated at rest, during voluntary hyperventilation and during 5% CO2 inhalation. RESULTS Twenty of 25 participants demonstrating satisfactory tonometric tracings for both tests were included in the analysis. The systolic BP measured using plethysmography was higher than that derived from tonometry (139.4 +/- 24.7 vs. 105.5 +/- 29.6, p < 0.001). CrCP values derived from tonometry were all positive and higher than CrCP values derived from plethysmography (62.9 +/- 19.9 vs. 11.1 +/- 17.8, p < 0.001). The changes in CrCP induced by 5% CO2 inhalation and hyperventilation had a correlation between two BP monitoring methods (r = 0.52, p = 0.001). CONCLUSIONS Pressure waveform is an important determinant in calculating CrCP by linear regression analysis. The relative changes in CrCP induced by hemodynamic challenges remained a relevant indicator of cerebrovascular regulation regardless of the methods used for non-invasive BP recording.
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Affiliation(s)
- Hung-Yi Hsu
- Department of Internal Medicine, Veterans General Hospital-Taichung, Taiwan
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Abstract
Pulse pressure, especially in central arteries, is an independent predictor of adverse cardiovascular events in patients with increased elastic artery stiffness (or elastance). The central arterial pressure wave is composed of a forward traveling wave generated by left ventricular ejection and a later arriving reflected wave from the periphery. Increased stiffness of elastic arteries is the primary cause of increased pulse pressure in subjects with degeneration and hyperplasia of the arterial wall. As stiffness increases, transmission velocity of both forward and reflected waves increase, which causes the reflected wave to arrive earlier in the central aorta and augments pressure in late systole [ie, augmentation index = (augmented pressure/pulse pressure) increases]. These changes in wave reflection properties are associated with vascular disease and aging and cause an increase in left ventricular afterload, myocardial mass, and oxygen consumption. Vasoactive drugs have little direct effect on large elastic arteries but can markedly change wave reflection amplitude and augmentation index by altering stiffness of the muscular arteries and modifying transmission velocity of the reflected wave from the periphery to the heart. This change in amplitude and timing of the reflected wave causes a generalized change in central arterial systolic and pulse pressure that is not detected by cuff pressure measurements in the brachial artery.
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Affiliation(s)
- Wilmer W Nichols
- Department of Medicine/Cardiology, University of Florida College of Medicine, Gainesville, 32610, USA.
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