Effect of Pindolol and Propranolol on Sinus Node Recovery Time and Atrioventricular Conduction Intervals

Abstract

In a randomized, observer-blind study, the effect of incremental doses of pindolol 0.001, 0.002, 0.003, and 0.004 mg/kg IV and propranolol 0.01, 0.02, 0.03, and 0.04 mg/kg IV on SA nodal recovery time (SNRT) and atrioventricu lar conduction interval (AH) was assessed in 20 patients (15 men and 5 women age range thirty to seventy-two, mean age fifty-three). AH and His bundle-to- ventricle (HV) intervals and SNRT were measured at spontaneous heart rate and at incremental atrial pacing rates (80, 100, 120, 140 bpm). Both drugs caused significant beta blockade as estimated by the percentage suppression of heart rate increment induced by 3 mcg isoproterenol administered intraven ously (pindolol 67.6±5.3%, P < 0.007; propranolol 38.6±10.6%, P < 0.001).

Propranolol significantly prolonged SNRT (P < 0.05) and AH interval (P < 0.05).

Pindolol did not significantly affect either SNRT (P=0.25) or AH intervals (P=0.78).

Significant effects on HV interval were not seen.

Thus, in the doses tested that resulted in significant beta blockade, pro pranolol prolonged SA nodal recovery times and depressed AV nodal conduc tion while pindolol did not affect these variables.