Aortic Pressure Levels and Waveform Indexes in People Living With Human Immunodeficiency Virus: Impact of Calibration Method on the Differences With Respect to Non-HIV Subjects and Optimal Values

Background: There are scarce and controversial data on whether human immunodeficiency virus (HIV) infection is associated with changes in aortic pressure (aoBP) and waveform-derived indexes. Moreover, it remains unknown whether potential differences in aoBP and waveform indexes between people living with HIV (PLWHIV) and subjects without HIV (HIV-) would be affected by the calibration method of the pressure waveform.Aims: To determine: (i) whether PLWHIV present differences in aoBP and waveform-derived indexes compared to HIV- subjects; (ii) the relative impact of both HIV infection and cardiovascular risk factors (CRFs) on aoBP and waveform-derived indexes; (iii) whether the results of the first and second aims are affected by the calibration method.Methods: Three groups were included: (i) PLWHIV (n = 86), (ii) HIV- subjects (general population; n = 1,000) and (iii) a Reference Group (healthy, non-exposed to CRFs; n = 398). Haemodynamic parameters, brachial pressure (baBP; systolic: baSBP; diastolic: baDBP; mean oscillometric: baMBPosc) and aoBP and waveform-derived indexes were obtained. Brachial mean calculated (baMBPcalc=baDBP+[baSBP-baDBP]/3) pressure was quantified. Three waveform calibration schemes were used: systolic-diastolic, calculated (baMBPcalc/baDBP) and oscillometric mean (baMBPosc/baDBP).Results: Regardless of CRFs and baBP, PLWHIV presented a tendency of having lower aoBP and waveform-derived indexes which clearly reached statistical significance when using the baMBPosc/baDBP or baMBPcalc/baDBP calibration. HIV status exceeded the relative weight of other CRFs as explanatory variables, being the main explanatory variable for variations in central hemodynamics when using the baMBPosc/baDBP, followed by the baMBPcalc/baDBP calibration.Conclusions: The peripheral waveform calibration approach is an important determinant to reveal differences in central hemodynamics in PLWHIV.

New Method to Estimate Central Systolic Blood Pressure From Peripheral Pressure: A Proof of Concept and Validation Study

Objective: The non-invasive estimation of central systolic blood pressure (cSBP) is increasingly performed using new devices based on various pulse acquisition techniques and mathematical analyses. These devices are most often calibrated assuming that mean (MBP) and diastolic (DBP) BP are essentially unchanged when pressure wave travels from aorta to peripheral artery, an assumption which is evidence-based. We tested a new empirical formula for the direct central blood pressure estimation of cSBP using MBP and DBP only (DCBP = MBP2/DBP).Methods and Results: First, we performed a post-hoc analysis of our prospective invasive high-fidelity aortic pressure database (n = 139, age 49 ± 12 years, 78% men). The cSBP was 146.0 ± 31.1 mmHg. The error between aortic DCBP and cSBP was −0.9 ± 7.4 mmHg, and there was no bias across the cSBP range (82.5–204.0 mmHg). Second, we analyzed 64 patients from two studies of the literature in whom invasive high-fidelity pressures were simultaneously obtained in the aorta and brachial artery. The weighed mean error between brachial DCBP and cSBP was 1.1 mmHg. Finally, 30 intensive care unit patients equipped with fluid-filled catheter in the radial artery were prospectively studied. The cSBP (115.7 ± 18.2 mmHg) was estimated by carotid tonometry. The error between radial DCBP and cSBP was −0.4 ± 5.8 mmHg, and there was no bias across the range.Conclusion: Our study shows that cSBP could be reliably estimated from MBP and DBP only, provided BP measurement errors are minimized. DCBP may have implications for assessing cardiovascular risk associated with cSBP on large BP databases, a point that deserves further studies.

Exercise in Water Provides Better Cardiac Energy Efficiency Than on Land

Although water-based exercise is one of the most recommended forms of physical activity, little information is available regarding its influence on cardiac workload and myocardial oxygen supply-to-demand. To address this question, we compared subendocardial viability ratio (SEVR, the ratio of myocardial oxygen supply-to-demand), cardiac inotropy (via the maximum rate of aortic pressure rise [dP/dTmax]), and stroke volume (SV, via a Modelflow method) responses between water- and land-based exercise. Eleven healthy men aged 24 ± 1 years underwent mild- to moderate-intensity cycling exercise in water (WC) and on land (LC) consecutively on separate days. In WC, cardiorespiratory variables were monitored during leg cycling exercise (30, 45, and 60 rpm of cadence for 5 min each) using an immersible stationary bicycle. In LC, each participant performed a cycling exercise at the oxygen consumption (VO2) matched to the WC. SEVR and dP/dTmax were obtained by using the pulse wave analysis from peripheral arterial pressure waveforms. With increasing exercise intensity, SEVR exhibited similar progressive reductions in WC (from 211 ± 44 to 75 ± 11%) and LC (from 215 ± 34 to 78 ± 9%) (intensity effect: P < 0.001) without their conditional differences. WC showed higher SV at rest and a smaller increase in SV than LC (environment-intensity interaction: P = 0.009). The main effect of environment on SV was significant (P = 0.002), but that of dP/dTmax was not (P = 0.155). SV was correlated with dP/dTmax (r = 0.717, P < 0.001). When analysis of covariance (ANCOVA) was performed with dP/dTmax as a covariate, the environment effect on SV was still significant (P < 0.001), although environment-intensity interaction was abolished (P = 0.543). These results suggest that water-based exercise does not elicit unfavorable myocardial oxygen supply-to-demand balance at mild-to-moderate intensity compared with land-based exercise. Rather, water-based exercise may achieve higher SV and better myocardial energy efficiency than land-based exercise, even at the same inotropic force.

Central Blood Pressure and Subclinical Atherosclerotic Risk in Young Hispanic American Women

Background: The incidence of younger women being hospitalized from cardiovas­cular disease (CVD) events is on the rise. Hispanic women are generally thought to have higher CVD risk factor burden than non-Hispanic White (NHW) women yet Hispanic Americans have lower mortality from CVD. Traditional measures of CVD may not accurately capture CVD risk in His­panic Americans. Hence, the purpose of this study was to assess the impact of ethnicity on vascular reactivity and central hemody­namic load to gain insight into subclinical CVD risk in young women.Methods: Brachial flow-mediated dilation (FMD), low-flow mediated constriction (L-FMC), carotid-femoral pulse wave velocity (cfPWV), and pulse wave analysis (from synthesized aortic pressure waveforms) were measured in 25 Hispanic women and 31 NHW women aged between 18-35 years. FMD and L-FMC were combined to provide an index of total vessel reactivity.Results: NHW and Hispanic women did not differ in age or traditional CVD risk factors (P>.05 for all). Compared with NHW women, Hispanic women had greater vascular reactivity (8.7±4.1 vs 11.7±4.1 %, P=.011), lower central pulse pressure (28±5 vs 24±3 mm Hg, P=.001) and lower pressure from wave reflections (12±2 vs 10±1 mm Hg, P=.001). There were no differences in cfPWV between NHW women and Hispanic women (5.4±0.7 vs 5.3±0.7 m/s, P=.73).Conclusion: Young Hispanic women have greater vascular reactivity and lower central pulsatile hemodynamic load compared with NHW women, suggesting lower subclinical CVD risk.Ethn Dis. 2021;31(4):489-500; doi:10.18865/ed.31.4.489

Damage control approach to refractory neurogenic shock: a new proposal to a well-established algorithm

Resuscitative endovascular balloon occlusion of the aorta (REBOA) is commonly used as an adjunct to resuscitation and bridge to definitive control of non-compressible torso hemorrhage in patients with hemorrhagic shock. It has also been performed for patients with neurogenic shock to support the central aortic pressure necessary for cerebral, coronary and spinal cord perfusion. Although volume replacement and vasopressors are the cornerstones of the management of neurogenic shock, we believe that a REBOA can be used as an adjunct in carefully selected cases to prevent prolonged hypotension and the risk of further anoxic spinal cord injury. This manuscript aims to propose a new damage control algorithmic approach to refractory neurogenic shock that includes the use of a REBOA in Zone 3. There are still unanswered questions on spinal cord perfusion and functional outcomes using a REBOA in Zone 3 in trauma patients with refractory neurogenic shock. However, we believe that its use in these case scenarios can be beneficial to the overall outcome of these patients.

A Novel Technique for Invasive Aortic Valve Pressure Gradient Measurement Using a 6Fr Swan-Ganz Catheter - Case Series

Background Simultaneous left ventricular and aortic pressure gradient assessment has been rendered challenging since the recall of the Langston catheter. Here we describe a simple method for simultaneous left ventricular and aortic pressure gradient assessment using a Swan-Ganz catheter. Case Summary We describe 2 cases where assessment of simultaneous left ventricle and aortic valve gradients was done using a Swan-Ganz Catheter to assess the degree of aortic stenosis and dynamic left ventricular outflow obstruction. Discussion Using Swan-Ganz catheter assessment of simultaneous left ventricle and aortic valve gradients can simplify the procedure with reduced cost and increased patient safety.

Fractional-order Approach to Modeling and Characterizing the Complex and Frequency-dependent Apparent Arterial Compliance: In Human and Animal Validation

Recently, experimental and theoretical studies have revealed the potential of fractional calculus to represent viscoelastic blood vessel and arterial biomechanical properties. This paper presents five fractional-order models to describe the dynamic relationship between aortic blood pressure and volume, representing the apparent vascular compliance. The proposed model employs fractional-order capacitor element (FOC) to lump the complex and frequency dependence characteristics of arterial compliance. FOC combines both resistive and capacitive properties, which the fractional differentiation order, alpha, can control. The proposed representations have been compared with generalized integer-order models of arterial compliance. All structures have been validated using different aortic pressure and flow rate waveforms collected from various human and animal species such as pigs and dogs. The results demonstrate that the fractional-order scheme can reconstruct the overall dynamic of the complex and frequency-dependent apparent compliance dynamic and reduce the complexity. The physiological relevance of the proposed models' parameters was assessed by evaluating the variance-based global sensitivity analysis. Moreover, the simplest fractional-order representation has been embed in a global arterial lumped parameter representation to develop a novel fractional-order modified arterial Windkessel. The introduced arterial model has been validated by applying real human and animal hemodynamic data and shows an accurate reconstruction of the proximal blood pressure. The novel proposed paradigm confers a potential to be adopted in clinical practice and basic cardiovascular mechanics research.