CORONARY VASODILATING ACTION OF DOBUTAMINE IN PATIENTS WITH IDIOPATHIC DILATED CARDIOMYOPATHY

To assess the coronary hemodynamic effects of dobutamine in patients with idiopathic dilated cardiomyopathy, dobutamine was infused at the incremental infusion rates of 25, 50, 100, and 200 mug/min into the left main coronary artery of nine patients undergoing cardiac catheterization. In response to dobutamine infusion, systemic hemodynamic effects were dose related. At the highest infusion rate cardiac index and left ventricular peak positive rate of rise in ventricular pressure increased from 2.33 +/- 0.54 to 2.97 +/- 0.65 L/min/m (p = 0.001) and from 690 +/- 177 to 1157 +/- 275 mm Hg/sec (p = 0.001), respectively. Left ventricular end-diastolic pressure decreased from 17 +/- 8 to 8 +/- 7 mm Hg (p = 0.001) and a trend toward decrease in left ventricular wall stress was observed (from 166 +/- 75 to 148 +/- 66 gm/cm2, not significant). Heart rate and mean arterial pressure remained unchanged. The coronary hemodynamic response to dobutamine infusion was also dose related. At the highest infusion rate coronary sinus blood flow increased from 133 +/- 35 to 179 +/- 47 ml/min (p < 0.01) and was associated with an increase in coronary oxygen blood content from 4.5 +/- 0.6 to 7.8 +/- 1.7 ml per 100 ml (p < 0.01) whereas myocardial oxygen consumption remained unchanged. During dobutamine infusion norepinephrine decreased in the femoral artery and in the coronary sinus from 1.03 +/- 0.34 to 0.641 +/- 0.179 ng/ml (p < 0.05) and from 1.76 +/- 0.98 to 1.38 +/- 0.65 ng/ml (p < 0.05), respectively. The level of atrial natriuretic factor decreased in the femoral artery and in the coronary sinus from 780 +/- 390 to 523 +/- 304 pg/ml (p = 0.005) and from 2314 +/- 706 to 1629 +/- 719 pg/ml (p = 0.005), respectively. These results suggest a direct coronary vasodilator effect of dobutamine in patients with idiopathic dilated cardiomyopathy. These coronary hemodynamic changes were associated with a decrease in both the cardiac adrenergic drive and the atrial natriuretic factor release.