ABSTRACT
In order to evaluate the mechanism by which beta blockers with intrinsic sympathomimetic activity preserve left ventricular systolic function at rest, 46 patients with coronary artery disease were studied by right and left heart catheterization and left ventriculography. Patients were studied using a double-blind, randomized protocol before and after a single intravenous dose of 3 mg propanolol (N = 22) or 0.5 mg pindolol (N = 24). Mean right atrial pressure increased similarly after both drugs. Mean pulmonary artery pressure, left ventricular end-diastolic pressure, mean aortic pressure, and peripheral vascular resistance did not change significantly after either drug. Cardiac index (before: 3.0 + or - 0.7(mean + or - SEM); after: 2.8 + or - 0.2 1 min **-1 m**-2) and heart rate (before: 78 + or - 15; after: 72 + or - 12 bpm) deveased only after propranolol administration. Ejection fraction decreased only after propranolol (48 + or - 16 to 41 + or - 15%). Improvement in segmental wall motion abnormalities was noted (23 of 47 segments) only after pindolo. The total left ventricular wall motion score improved after pindolol and worsened after propranolol (P<0.5). In patients with impaired left ventricular function, pindolol administration resulted in improved resting ejection fraction. Thus, the acute hemodynamic consequences of pindolol administration differ from those of propranolol owing to the preservation of left ventricular systolic function which seem to be related to the...