Aortic function in arterial hypertension determined by pressure-diameter relation: effects of diltiazem.

Abstract

Aortic elastic properties, important determinants of left ventricular function and coronary blood flow, are compromised in hypertension. The aim of this study was to determine aortic function in hypertensive patients and in normal subjects before and after administration of diltiazem, a calcium antagonist widely used in the treatment of essential hypertension. The aortic pressure-diameter relation was obtained before and after diltiazem administration in 15 hypertensives and 15 control normotensives. Instantaneous diameter of the thoracic aorta was acquired with a high-fidelity intravascular catheter developed in our institution and previously validated. Instantaneous aortic pressure was measured simultaneously and at the same aortic level with a catheter-tip micromanometer. Energy loss due to the viscosity of aortic wall was measured from the area of the loop. Aortic distensibility was calculated using the formula 2 x (pulsatile change in aortic diameter)/([diastolic aortic diameter] x [aortic pulse pressure]). At baseline, aortic distensibility was lower and energy loss was greater in hypertensives than in normotensives (distensibility: 1.4+/-0.3 versus 3.5+/-0.7 cm2 x dyne(-1) x 10(-6), respectively, P<.001; energy loss: 14.1+/-3.3 versus 8.2+/-2.2 mm x mm Hg, respectively, P<.001). After diltiazem administration, aortic distensibility was increased, whereas energy loss was decreased in both hypertensives (peak response: distensibility, 2.0+/-0.4 cm2 x dyne(-1) x 10(-6), P<.001; energy loss, 9.3+/-1.6 mm x mm Hg, P<.001) and normotensives (peak response: distensibility, 5.2+/-0.5 cm2 x dyne(-1) x 10(-6), P<.001; energy loss, 5.0+/-1.2 mm x mm Hg, P<.001). Aortic elastic properties are compromised and energy loss due to aortic wall viscosity is increased in hypertensives compared with normotensives. Function of the aorta is improved in both hypertensive and normotensive subjects after the administration of diltiazem.