The influence of intrinsic sympathomimetic activity on regional left ventricular function; use of regional ejection fraction to demonstrate a beneficial action by pindolol over propranolol on hypokinetic segments.

In a previous report from our laboratory, visual assessment of wall motion in patients with coronary artery disease demonstrated no advantage for pindolol, a beta blocking agent with intrinsic sympathomimetic activity (ISA), over propranolol on impaired regional left ventricular (LV) function. In this study, we reanalyzed the radionuclide ventriculograms using a computer-assisted method of deriving regional ejection fraction. Use of normalized values allowed hypokinetic and normokinetic segments to be identified and examined separately. Pindolol (5-10 mg twice a day) was compared to propranolol (40-80 mg 4 times a day) in 23 patients using a randomized, crossover study design. Supine resting heart rate was reduced less (70 +/- 12 beats/min vs 63 +/- 10 beats/min, p less than 0.01) by pindolol; exercise heart rate was reduced equally by both agents. Derivation of normalized regional LV ejection fractions showed that 17 segments were hypokinetic at rest. Function of these segments increased (p less than 0.02) with pindolol. This improvement was not detected by visual assessment of regional wall motion. Thirty-seven segments were found to be hypokinetic during exercise and a significant (p less than 0.05) improvement in function occurred with pindolol and propranolol. In summary, derivation of normalized regional LV ejection fraction values allows the demonstration of significant improvement in resting LV function with pindolol, but not with propranolol in patients with regional dysfunction due to coronary artery disease. This advantage may provide a rationale for further evaluation of this agent in patients with more widespread ventricular dysfunction.