Predictive Models for Pulmonary Artery Size in Fontan Patients

We developed models of pulmonary artery (PA) size in Fontan patients as a function of age and body surface area (BSA) using linear regression and breakpoint analyses based on data from 43 Fontan patients divided into two groups: the extracardiac conduit (ECC) group (n = 24) and the non-ECC group (n = 19). Model predictions were compared against those of a non-Fontan control group (n = 18) and published literature. We observed strong positive correlations of the mean PA diameter with BSA (r = 0.9, p \u3c 0.05) and age (r = 0.88, p \u3c 0.05) in the ECC group. The absolute percentage differences between our BSA and age model predictions against published literature were less than 16% and 20%, respectively. Predicted PA size for Fontan patients was consistently smaller than the control group. These models may serve as useful references for clinicians and be utilized to construct 3D anatomic models that correspond to patient body size or age

Arterial pulse wave modelling and analysis for vascular age studies: a review from VascAgeNet

Arterial pulse waves (PWs) such as blood pressure and photoplethysmogram (PPG) signals contain a wealth of information on the cardiovascular (CV) system that can be exploited to assess vascular age and identify individuals at elevated CV risk. We review the possibilities, limitations, complementarity, and differences of reduced-order, biophysical models of arterial PW propagation, as well as theoretical and empirical methods for analyzing PW signals and extracting clinically relevant information for vascular age assessment. We provide detailed mathematical derivations of these models and theoretical methods, showing how they are related to each other. Finally, we outline directions for future research to realize the potential of modeling and analysis of PW signals for accurate assessment of vascular age in both the clinic and in daily life

Brachial-cuff excess pressure is associated with carotid intima-media thickness among Australian children: a cross-sectional population study

Reservoir pressure parameters (i.e., reservoir pressure [RP] and excess pressure [XSP]) independently predict cardiovascular events in adults, but this has not been investigated in children. This study aimed to determine (1) the association of reservoir pressure parameters with carotid intima-media thickness (carotid IMT), a preclinical vascular phenotype, and (2) whether a multivariable regression model with or without reservoir pressure parameters fits better for estimating carotid IMT in children. Study participants were 11–12-year-old children (n = 1231, 50% male) from the Child Health CheckPoint study, a cross-sectional substudy of the population-based Longitudinal Study of Australian Children. RP and XSP were obtained using brachial-cuff oscillometry (SphygmoCor XCEL, AtCor, Sydney). Carotid IMT was quantified by vascular ultrasonography. XSP was associated with carotid IMT after adjusting for confounders including age, sex, BMI z-score, heart rate, pubertal stage, moderate-to-vigorous physical activity, and mean arterial pressure (β = 0.93 µm, 95% CI 0.30–1.56 for XSP peak and β = 0.04 µm, 95% CI 0.01–0.08 for XSP integral). The results of the likelihood ratio test indicated a trend that the model with XSP and the above confounders fit better than a similar model without XSP for estimating carotid IMT. Our findings indicate that brachial-cuff device-measured XSP is associated with carotid IMT independent of conventional cardiovascular risk factors, including standard BP. This implies that a clinically convenient cuff approach could provide meaningful information for the early assessment of cardiovascular risk among children. </p

Association of brachial-cuff excess pressure with carotid intima-media thickness in Australian adults: a cross-sectional study

Objective: Reservoir pressure parameters [e.g. reservoir pressure (RP) and excess pressure (XSP)] measured using tonometry predict cardiovascular events beyond conventional risk factors. However, the operator dependency of tonometry impedes widespread use. An operator-independent cuff-based device can reasonably estimate the intra-aortic RP and XSP from brachial volumetric waveforms, but whether these estimates are clinically relevant to preclinical phenotypes of cardiovascular risk has not been investigated.Methods: The RP and XSP were derived from brachial volumetric waveforms measured using cuff oscillometry (SphygmoCor XCEL) in 1691 mid-life adults from the CheckPoint study (a population-based cross-sectional study nested in the Longitudinal Study of Australian Children). Carotid intima--media thickness (carotid IMT, n = 1447) and carotid--femoral pulse wave velocity (PWV, n = 1632) were measured as preclinical phenotypes of cardiovascular risk. Confounders were conventional risk factors that were correlated with both exposures and outcomes or considered as physiologically important.Results: There was a modest association between XSP and carotid IMT (beta = 0.76 mu m, 95% CI, 0.25-1.26 partial R-2 = 0.8%) after adjusting for age, sex, BMI, heart rate, smoking, diabetes, high-density lipoprotein cholesterol and mean arterial pressure. Neither RP nor XSP were associated with PWV in the similarly adjusted models (beta = -0.47 cm/s, 95% CI, -1.15 to 0.20, partial R-2 = 0.2% for RP, and beta = 0.04 cm/s, 95% CI, -0.59 to 0.67, partial R-2 = 0.01% for XSP). Conclusion: Cuff-based XSP associates with carotid IMT independent of conventional risk factors, including traditional BP, but the association was weak, indicating that further investigation is warranted to understand the clinical significance of reservoir pressure parameters.</div

Computer modelling and wave intensity analysis of perinatal cardiovascular function and dysfunction

© 2011 Dr. Jonathan Paul MynardRecent experimental work has highlighted a number of complex issues relating to blood flow dynamics in the normal fetus, where the structure and function of the cardiovascular system differs substantially from the normal adult or neonate. Neonates with congenital heart disease may also display quite complex haemodynamics due to a persistence of some features of the fetal circulation after birth, along with heart and vascular abnormalities that disturb normal blood flow patterns. For example, in pulmonary atresia with intact ventricular septum (PAIVS), the right ventricular outflow path fails to develop, while the combination of an underdeveloped right ventricle and profound coronary abnormalities may give rise to quite unusual coronary arterial flow patterns. This thesis employs two research tools that are ideal for clarifying the processes that govern haemodynamics in these contexts. The first is computer modelling, in which cardiac and vascular variables and configuration can be directly manipulated in a simulated physiological system without ethical concern. The second is wave intensity analysis, which is a powerful technique for discerning the origin of pressure/flow waves, as well as wave interactions, that occur at or between different vascular measurement sites. To enable investigation of a wide range of circulatory interactions in the perinatal period, this thesis describes computer models of the entire circulation for the normal fetus and neonate, these being derived from a model of the adult circulation that also provides an essential haemodynamic reference point. The normal fetal and neonatal models are adapted to form a model of PAIVS, which includes commonly occurring coronary abnormalities such as a fistula connecting to the right ventricular cavity and an interruption of the normal aorto-coronary pathway. These `comprehensive' models contain all of the major functional and anatomical segments of the circulation, including one-dimensional (1D) representations of the arterial and venous networks, and lumped parameter (0D) representations of the heart, valves and microvascular beds. In combination with wave intensity analysis and available experimental data, the normal fetal model is used to further investigate the determinants of the distinctive pressure/flow waveforms and wave intensity patterns in the pulmonary trunk, proximal branch pulmonary arteries and ductus arteriosus that have been observed in recent experimental studies in fetal lambs. Additionally, the fetal model is harnessed to investigate factors that contribute to a so-called fetal right-ventricular dominance, and to delineate the likely physical basis of mean aorto-pulmonary pressure differences and a functional separation of the upper body and lower body circulations in the fetus. The model of neonatal PAIVS is then used to elucidate the determinants of coronary arterial blood flow patterns and regional myocardial perfusion in the presence or absence of coronary abnormalities, both before and after surgical opening of the right-ventricular outflow path. The potential for coronary collateral connections to provide protection against myocardial ischemia is also explored. The findings of this thesis underscore the potential for both computer modelling and wave intensity analysis to provide insights into complex haemodynamic interactions that may occur normally or abnormally in the perinatal period

The ebbing tide of the reservoir-wave model [editorial]

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