AORTIC FUNCTION IN ARTERIAL-HYPERTENSION DETERMINED BY PRESSURE-DIAMETER RELATION - EFFECTS OF DILTIAZEM

Background Aortic elastic properties, important determinants of left v entricular function and coronary blood flow, are compromised in hypert ension. The aim of this study was to determine aortic function in hype rtensive patients and in normal subjects before and after administrati on of diltiazem, a calcium antagonist widely used in the treatment of essential hypertension. Methods and Results The aortic pressure-diamet er 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. Instan taneous aortic pressure was measured simultaneously and at the same ao rtic level with a catheter-tip micromanometer. Energy loss due to the viscosity of aortic wall was measured from the area of the loop. Aorti c distensibility was calculated using the formula 2x(pulsatile change in aortic diameter)/([diastolic aortic diameter]x[aortic pulse pressur e]). 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 cm(2) . dyne(-1) . 10(-6), respectively, P<.0 01; energy loss: 14.1 +/- 3.3 versus 8.2 +/- 2.2 mm . mm Hg, respectiv ely, P<.001). After diltiazem administration, aortic distensibility wa s increased, whereas energy loss was decreased in both hypertensives ( peak response: distensibility, 2.0 +/- 0.4 cm(2) . dyne(-1) . 10(-6), P<.001; energy loss, 9.3 +/- 1.6 mm . mm Hg, P<.001) and normotensives (peak response: distensibility, 5.2 +/- 0.5 cm(2) . dyne(-1) . 10(-6) , P<.001; energy loss, 5.0 +/- 1.2 mm . mm Hg, P<.001). Conclusions Ao rtic elastic properties are compromised and energy loss due to aortic wall viscosity is increased in hypertensives compared with normotensiv es. Function of the aorta is improved in both hypertensive and normote nsive subjects after the administration of diltiazem.