FAVORABLE EFFECTS OF HYDRALAZINE ON THE HEMODYNAMIC-RESPONSE TO ISOMETRIC-EXERCISE IN CHRONIC SEVERE AORTIC REGURGITATION

The hemodynamic effects of isometric exercise and the repsonse to hydralazine therapy were evaluated in 11 patients with chronic, severe aortic regurgitation (AR). Isometric exercise produced a significant increase in heart rate (from 78 .+-. 11 to 93 .+-. 19 beats/min [mean .+-. SD], P < 0.05), mean blood pressure (from 83 .+-. 8 to 104 .+-. 20 mm Hg, P < 0.05), mean right atrial pressure (from 3 .+-. 2 to 7 .+-. 5 mm Hg, P < 0.05) and mean pulmonary artery wedge pressure (from 12 .+-. 7 to 18 .+-. 10 mm Hg, P < 0.05). Small and insignificant changes were seen in cardiac index (from 3.4 .+-. 0.8 to 3.9 .+-. 1.0 l/min per m2), systemic vascular resistance (from 1097 .+-. 257 to 1171 .+-. 284 dyn s cm-5), pulmonary vascular resistance (from 120 .+-. 76 to 130 .+-. 89 dyn s cm-5) and stroke volume index (from 44 .+-. 10 to 43 .+-. 12 ml/m2). After oral hydralazine administration (100-300 mg), hemodyanmic values during isometric exercise were: Heart rate increased further, to 105 .+-. 14 beats/min (P < 0.05), mean blood pressure was 102 .+-. 16 mm Hg (difference not significant [NS]) cardiac index increased markedly, to 5.2 .+-. 1.4 l/min per m2 (P < 0.05), stroke volume index increased to 49 .+-. 12 ml/m2 (P < 0.05), right atrial pressure decreased slightly, to 5 .+-. 5 mm Hg (NS), pulmonary artery wedge pressure decresaed to 14 .+-. 7 mm Hg (P < 0.05), systemic vascular resistance decreased to 903 .+-. 288 dyn s cm-5 (P < 0.05), and pulmonary vascular resistance changed to 100 .+-. 66 dyn s cm-5 (NS). Thus, isometric exercise in patients with chronic severe AR is associated with only a slight and insignificant increase in systemic vascular resistance, but a marked increase in pulmonary artery wedge pressure. Direct arteriolar vasodilation with hydralazine results in a significant attenuation of pulmonary artery wedge pressure increase during isometric exercise and leads concomitantly to a significant augmentation of stroke volume and cardiac output. These findings substantiate the value of hydralazine therapy in patients with chronic, severe AR.