Sympathetic activity in idiopathic dilated cardiomyopathy. Influence of captopril and hydralazine.

To study the interrelationship between myocardial norepinephrine content, left ventricular (LV) and right ventricular (RV) function, morphological changes, and plasma catecholamine concentrations, 20 patients with idiopathic dilated cardiomyopathy underwent endomyocardial biopsy and ventricular angiography. The strongest correlation was found between LV ejection fraction (EF) and myocardial norepinephrine content (r = 0.87; p less than 0.001). Myocardial norepinephrine content was much weaker correlated to RV EF (r = .55; p less than 0.005), and no correlation was found to morphological changes or plasma norepinephrine concentration. The hemodynamic and neurohumoral effects of hydralazine versus captopril after the first dose were compared in a crossover trial including 15 patients with idiopathic dilated cardiomyopathy. Hydralazine induced increases in heart rate and cardiac index (p less than 0.01) and decreases in mean arterial pressure and pulmonary wedge pressure (p less than 0.01 and p less than 0.005, respectively). These hemodynamic effects were associated with increased plasma norepinephrine concentrations during upright exercise (p less than 0.05) and increased plasma renin activity (p less than 0.01). After captopril, norepinephrine plasma concentrations showed a tendency to lower levels during upright exercise, although mean arterial pressure decreased significantly (p less than 0.01). These data suggest that, in patients with idiopathic dilated cardiomyopathy, myocardial norepinephrine depletion strongly reflects left ventricular dysfunction. The different patterns of neurohumoral response to hydralazine versus captopril may be important for their long-term effect and for the prognosis of patients with idiopathic dilated cardiomyopathy. It remains to be established whether the myocardial catecholamine content is differently influenced by either drug, and whether this effect is related to the drug response after long-term treatment.