A comparison of methods for assessing total arterial compliance.

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 (P<0.0001 between groups). Correlation was good between all methods: PPM/AM r=0.83, PPM/SVPP r=0.94 and AM/SVPP r=0.80 (all P<0.0001). 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)=0.07; P<0.0001) and LV mass (R(2)=0.04; P=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.

Influence of arterial compliance on presence and extent of ischaemia during stress echocardiography.

OBJECTIVE: To seek an association between total arterial compliance (TAC) and the extent of ischaemia at stress echocardiography. DESIGN: Cohort study. SETTING: Regional cardiac centre. METHODS: 255 consecutive patients (147 men; mean (SD) age 58 (8)) presenting for stress echocardiography for clinical indications were studied. Wall motion score index (WMSI) was calculated and ischaemia was defined by an inducible or worsening wall motion abnormality. Peak WMSI was used to reflect the extent of dysfunction (ischaemia or scar), and DeltaWMSI was indicative of extent of ischaemia. TAC was assessed at rest by simultaneous radial applanation tonometry and pulsed wave Doppler in all patients. RESULTS: Ischaemia was identified by stress echocardiography in 65 patients (25%). TAC was similar in the groups with negative and positive echocardiograms (1.08 (0.41) v 1.17 (0.51) ml/mm Hg, not significant). However, the extent of dysfunction was associated with TAC independently of age, blood pressure, risk factors, and use of a beta blocker. Moreover, the extent of ischaemia was determined by TAC, risk factors, and use of a beta blocker. CONCLUSION: While traditional cardiovascular risk factors are strong predictors of ischaemia on stress echocardiography, TAC is an independent predictor of the extent of ischaemia.

Relation of arterial stiffness to diastolic dysfunction in hypertensive heart disease.

OBJECTIVES: To examine the relation of arterial compliance to diastolic dysfunction in hypertensive patients with suspected diastolic heart failure (HF). PATIENTS: 70 medically treated hypertensive patients with exertional dyspnoea (40 women, mean (SD) age 58 (8) years) and 15 normotensive controls. MAIN OUTCOME MEASURES: Mitral annular early diastolic velocity with tissue Doppler imaging and flow propagation velocity were used as linear measures of diastolic function. Arterial compliance was determined by the pulse pressure method. RESULTS: According to conventional Doppler echocardiography of transmitral and pulmonary venous flow, diastolic function was classified as normal in 33 patients and abnormal in 37 patients. Of those with diastolic dysfunction, 28 had mild (impaired relaxation) and nine had advanced (pseudonormal filling) dysfunction. Arterial compliance was highest in controls (mean (SD) 1.32 (0.58) ml/mm Hg) and became progressively lower in patients with hypertension and normal function (1.04 (0.37) ml/mm Hg), impaired relaxation (0.89 (0.42) ml/mm Hg), and pseudonormal filling (0.80 (0.45) ml/mm Hg, p = 0.011). In patients with diastolic dysfunction, arterial compliance was inversely related to age (p = 0.02), blood pressure (p < 0.001), and estimated filling pressures (p < 0.01) and directly related to diastolic function (p < 0.01). After adjustment for age, sex, body size, blood pressure, and ventricular hypertrophy, arterial compliance was independently predictive of diastolic dysfunction. CONCLUSIONS: In hypertensive patients with exertional dyspnoea, progressively abnormal diastolic function is associated with reduced arterial compliance. Arterial compliance is an independent predictor of diastolic dysfunction in patients with hypertensive heart disease and should be considered a potential target for intervention in diastolic HF.

Pulse pressure vs. total arterial compliance as a marker of arterial health.

BACKGROUND: Brachial pulse pressure (BPP) is a predictor of outcome in epidemiologic studies, but brachial and aortic pulse pressure (AoPP) may not correspond and both are influenced by multiple parameters including arterial properties and cardiac output. We sought to what extent pulse pressure (PP) measurements reflected direct measurement of arterial properties, assessed as total arterial compliance (TAC). METHODS: We studied 123 patients (76 men; age 55 +/- 11); 31 normal controls, 46 patients with coronary artery disease and 46 patients with hypertension. PP was determined from brachial cuff pressure and TAC was measured by simultaneous radial applanation tonometry and pulsed wave Doppler of the LV outflow. AoPP was calculated using a transfer function from the radial waveform. RESULTS: There was a significant difference between BPP and AoPP (57 +/- 16 vs. 45 +/- 14; P < 0.0001), although TAC correlated with BPP (r = -0.72; P = 0.01) and AoPP (r = -0.66; P = 0.01). In a multiple linear regression, the difference between BPP and AoPP was predicted by cardiac output (CO) (P = 0.002) and gender (P = 0.03). Bland-Altman analysis showed the best correspondence between BPP and AoPP in the middle tertile (CO 4.7 to 5.7 L min(-1)) with less correlation in the low and high tertiles. The same analysis by gender showed a higher difference in women than men (14 +/- 6 vs. 10 +/- 5; P < 0.0001). The difference between BPP and AoPP showed the best correlation in the control group and the worst in the hypertension group. CONCLUSION: BPP correlates with TAC in men with normal cardiac function. However, in women, in patients at the low and high extremes of function, and in patients with preclinical and overt cardiovascular disease, there appears to be incremental value in measuring TAC.