Mechanism for improved cardiac performance with arteriolar dilators in aortic insufficiency.

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Abstract
To determine how arteriolar dilation improves cardiac performance in aortic insufficiency, we evaluated the acute effects of hydralazine in 10 patients with chronic severe aortic insufficiency. Control measurements of intracardiac and intravascular pressures, cardiac output and left ventricular volumes were obtained at cardiac catheterization. Hydralazine, 0.3 mg/kg i.v. (maximal dose 20 mg), was administered and all measurements were repeated 30 minutes later. A reduction in systemic vascular resistance from 1264 to 710 dyn-sec-cm-5 was associated with significant increases in forward cardiac index (2.9 to 5.1 l/min/m2) and stroke volume index (37 to 55 ml/m2). Left ventricular end-diastolic pressure was reduced from 19 to 12 mm Hg. There was a significant reduction in mean arterial pressure (88 to 83 mm Hg) and a significant increase in heart rate (81 to 94 beats/min). Regurgitant stroke volume was reduced by more than 10 ml/m2 in seven patients and for the group was significantly reduced, from 65 to 53 ml/m2. Regurgitant fraction was reduced in all patients; the overall reduction from 0.64 to 0.48 was highly significant. Ejection fraction increased more than 0.10 in four patients, by 0.08 in an additional patient and for the group increased significantly from 0.50 to 0.57. Left ventricular end-diastolic volume decreased by more than 25 ml/m2 in four patients, by 19 ml/m2 in an additional patient and was decreased significantly, from 208 to 190 ml/m2, for the group. Arteriolar dilators improve cardiac performance in aortic insufficiency by reducing the amount of aortic regurgitation and, in some patients, by substantially improving systolic pump fraction. These data suggest a role for arteriolar dilators in the management of selected patients with aortic insufficiency.