Dose-dependent haemodynamic response to prenalterol in patients with congestive heart failure.

The effect of three doses of prenalterol, 12.5, 25 and 50 micrograms, on cardiac index (CI), pulmonary artery pressure (PAP), heart rate (HR), and stroke volume index (SVI) was investigated in 18 patients with congestive heart failure (CHF). Twelve patients received only prenalterol, while 6 patients received prenalterol 1 hour after an oral dose of hydralazine and isosorbid dinitrate. In 7 out of 12 patients a dose-dependent increase in HR was observed. The response of HR was inversely correlated to resting catecholamine levels; patients with high resting catecholamines--these are patients with severe CHF--did not show any increase in HR. CI increased in 8 out of 12 patients (average 1 . 1/min m) and SVI in 5 out of 12 patients. This inconsistent response was not dependent on left ventricular ejection fraction or plasma catecholamines at rest. Pretreatment with vasodilators did not improve the haemodynamic response to prenalterol. Four out of 17 patients demonstrated an increase in severity of arrhythmias suggestive of arrhythmogenic properties of prenalterol.