Pulse waveform analysis of arterial compliance: relation to other techniques, age, and metabolic variables

To assess the physiologic and clinical relevance of newer noninvasive measures of vascular compliance, computerized arterial pulse waveform analysis (CAPWA) of the radial pulse was used to calculate two components of compliance, C1 (capacitive) and C2 (oscillatory or reflective), in 87 normotensive (N1BP, n = 20), untreated hypertensive (HiBP, n = 21), and treated hypertensive (HiBP-Rx, n = 46) subjects. These values were compared with two other indices of compliance, the ratio of stroke volume to pulse pressure (SV/PP) and magnetic resonance imaging (MRI)-based aortic distensibility; and were also correlated with demographic and biochemical values. The HiBP subjects displayed lower C1 (1.34 +/- 0.09 v. 1.70 +/- 0.11 mL/mm Hg, significance [sig] = .05) and C2 (0.031 +/- 0.003 v 0.073 +/- 0.02 mL/mm Hg, sig = .005) than N1BP subjects. This was not true for C1 (1.64 +/- 0.08 mL/mm Hg) and C2 (0.052 +/- 0.005 mL/mm Hg) values in HiBP-Rx subjects. The C1 (r = 0.917, P < .0001) and C2 (r = 0.677, P < .0001) were both closely related to SV/PP, whereas C1 (r = 0.748, P = .002), but not C2, was significantly related to MRI-determined aortic distensibility. Among other factors measured, age exerted a strong negative influence on both C1 (r = -0.696, P < .0001) and C2 (r = -0.611, P < .0001) compliance components. Positive correlations were observed between C1 (r = 0.863, P = .006), aortic distensibility (r = 0.597, P = .19) and 24-h urinary sodium excretion, and between C1- and MR spectroscopy-determined in situ skeletal muscle intracellular free magnesium (r = 0.827, P = .006), whereas C2 was inversely related to MRI-determined abdominal visceral fat area (r = -0.512, P = .042) and fasting blood glucose (r = -0.846, P = .001). Altogether, the close correspondence between CAPWA, other compliance techniques, and known cardiovascular risk factors suggests the clinical relevance of CAPWA in the assessment of altered vascular function in hypertension.