CAROTID-ARTERY DISTENSIBILITY AND DISTENDING PRESSURE IN HYPERTENSIVEHUMANS

Whether the decrease in large-artery distensibility observed in hypert ensive patients is due primarily to an increase in distending pressure or to hypertension-induced changes in structural properties has been much debated. We determined noninvasively the diameter-pressure curve of the common carotid artery over the systolic-diastolic range by cont inuously recording both the pulsatile changes in internal diameter (hi gh-resolution echo-tracking system) and, simultaneously on the contral ateral artery, the pressure waveform (high-fidelity applanation tonome try). We then derived the distensibility/pressure curve and compared a rterial distensibility in 14 normotensive subjects and 15 age- and sex -matched hypertensive subjects at their respective mean arterial press ures (MAP) and at a common distending pressure: 100 mm Hg. Distensibil ity decreased as blood pressure increased, and distensibility at MAP w as significantly lower in hypertensive than in normotensive subjects ( 7.8+/-0.7 versus 11.7+/-1.7 kPa(-1).10(-3), mean+/-SEM; P<.05). In hyp ertensive subjects, the distensibility-pressure curve was shifted towa rd higher levels of blood pressure, and a large part of the curve over lapped that of normotensive subjects. No significant downward shift of the distensibility-pressure curve was observed in hypertensive subjec ts, and distensibility at 100 mm Hg was not significantly different fr om that of normotensive subjects (10.0+/-1.0 versus 9.0+/-1.1 kPa(-1). 10(-3)). Distensibility at 100 mm Hg decreased with aging (P<.05) and was not reduced in hypertensive subjects compared with normotensive su bjects after adjustment for age. These results suggest that the decrea se in common carotid artery distensibility in hypertensive subjects is due primarily to the increased distending blood pressure and that age -independent structural modifications of the arterial wall play only a minor role.