ISOBARIC ARTERIAL COMPLIANCE IS NOT REDUC ED IN ESSENTIAL HYPERTENSIVES

Whether the decrease in large artery compliance, observed in hypertens ive patients (HT). is due to an increase in distending pressure or to intrinsic alterations of the vascular wall remains much debated. We de termined the diameter-pressure curve of the common carotid artery over the systolic-diastolic range, then derived the compliance-pressure cu rve, in order to compare arterial compliance in normotensive subjects (NT) and in HT. for a common level of distending blood pressure : 100 mmHg (isobaric compliance). Fourteen NT and 15 never treated essential HT were included in the study. The diameter-pressure curve of the com mon carotid artery was determined non-invasively by simultaneously and continously recording the systolic-diastolic changes in internal diam eter (using a high resolution echotracking system) and pressure wavefo rm (using high fidelity applanation tonometry on the contralateral art ery) over 4-6 cardiac cycles. The level of MAP of the carotid pressure waveform was determined electronically and set equal to mean brachial pressure. Compliance pressure curve was then derived from the pressur e-diameter curve in order to determine compliance (C) for any given le vel of blood pressure. particularly MAP (C(MAP)) and 100 mmHg (C100). Despite the considerable differences in blood pressure, the compliance -pressure curve of HT was not different from that of NT. CMAP decrease d with aging (p < 0.001) and MAP (p < 0.001). According to age, C(MAP) was reduced in HT as compared to NT (84 +/- 49 vs 116 +/- 52 mm2.mmHg . 10(-3) p < 0.01) C100 decreased with aging (p < 0.05) but not with M AP. According to age, C10;0 was not reduced in hypertensives. These re sults suggest that, in hypertensive patients, the decrease in common c arotid artery compliance is mainly due to the increase in distending b lood pressure, and that intrinsic pressure-independent modifications o f the arterial wall play only a minor role.