A comparison of methods for assessing total arterial compliance

Abstract

There are several methods of assessing total arterial compliance (TAC) based on the two element Windkessel model, which is a ratio of pressure and volume, but the optimal technique is unclear. In this study, three methods of estimating TAC were compared to determine which was the most robust in a large group of patients with and without cardiovascular risk. In all, 320 patients (170 men; age 55 ± 10) were studied; TAC was determined by the pulse-pressure method (PPM), the area method (AM) and the stroke volume/pulse-pressure method (SVPP). We obtained arterial waveforms using radial applanation tonometry, dimensions using two-dimensional echocardiography and flow data by Doppler. Clinical data, risk factors, echo parameters and TAC by all three methods were then compared. TAC (ml mm Hg -1 ) by the PPM was 1.24±0.51, by the AM 1.84±0.90 and by the SVPP 1.96±0.76 (Po0.0001 between groups). Correlation was good between all methods: PPM/AM r ¼ 0.83, PPM/SVPP r ¼ 0.94 and AM/SVPP r ¼ 0.80 (all Po0.0001). Subgroup analysis showed significant differences between patients with and those without cardiovascular risk for all three methods; TAC-AM and TAC-SVPP values were similar and significantly higher than TAC-PPM. The only significant relationships observed with TAC and echo parameters were in left ventricular (LV) septal thickness (R 2 ¼ 0.07; Po0.0001) and LV mass (R 2 ¼ 0.04; P ¼ 0.004). Normal and abnormal values of TAC vary according to method, which should be expressed. Each of the techniques shows good correlation with each other, however, values for TAC-PPM are significantly lower. TAC-PPM and TAC-SVPP are comparable in determining differences between groups with and without cardiovascular risk.

Use of the Frank-Starling mechanism during exercise is linked to exercise-induced changes in arterial load

“…Thus, to reproduce the 2-element Windkessel model, only the part of blood ejected within the time of peak pressure should be measured. Despite this overestimation, close relationships have been noted between the SV/PP ratio and more direct measures of Windkessel compliance i.e., the area (r ϭ 0.98 and r ϭ 0.58) (12,43), and the PP method (r ϭ 0.97, and 0.80) (23,43). Further, Resnick et al (41) demonstrated that the SV/PP ratio was correlated with both capacitive (reflecting the TACI component associated with the conduit, capacitive function of larger arteries) and oscillatory (depicting the reflective component of TACI) compliance of the arterial tree using a modified Windkessel model (r ϭ 0.92 and 0.68, respectively).…”

Association between variations in coagulation system genes and carotid plaque

“…A subset of the samples in the Dominican discovery set (153 of 287) was also genotyped on the Affymetrix 6.0 platform and used to compute the D-prime (D′) and R-squared (r 2 ) between SNPs from the Gen-Carotid substudy and the follow-up study. The first principal component from Eigenstrat was used as a covariate in addition to covariates as mentioned previously [11]. Multiple logistic regression, using an additive genetic model, was conducted in PLINK (http://pngu.mgh.harvard.edu/purcell/plink/) with the major allele as the reference [12].…”

“…For each carotid plaque phenotype and for each gene, up to a 5 SNP model was tested in order to find the best fit. These SNPs were then examined as a haplotype using the haplo.glm function of the haplo.stats package, adjusting for age, sex, smoking, hypertension, dyslipidemia, and diabetes [11]. …”

Total arterial compliance: the future of cardiovascular risk assessment?

“…8,9 The study presented in the current issue by Haluska et al 10 highlights the strength of TAC over more traditional evaluation techniques such as pulse pressure and echocardiography. The assessment of TAC has also proven to be capable of differentiating between hypertensive, elderly and healthy individuals, which is of particular importance in an increasingly ageing society.…”

“…10 In their study they examined three methods: area method (AM), pulse pressure method (PPM) and stroke volume/pulse pressure method (SVPP). All three methods yielded good correlation with each other and are based on a modified two-element Windkessel model, but PPM and SVPP have emerged to be more robust than the AM method.…”