Pindolol postmyocardial infarction study: evaluation of the drug's antiarrhythmic and antianginal activity.

The study was designed to assess the antiarrhythmic and antianginal properties of pindolol as well as the tolerance to the drug by patients who had experienced a myocardial infarction 5 to 6 months previously. Exercise tests were performed in 521 postinfarct patients before and after a single oral 5 mg dose of pindolol. Depending on the physical condition of the patient, the initial work load was 25 or 50 watts, which was increased by 25 watts every 5 minutes. In patients with an initial heart rate (HR) of more than 68 bpm on the average, HR at rest was reduced with pindolol. This reduction was more pronounced the higher the initial HR. If the initial HR was below 68 bpm, HR increased slightly with pindolol, reflecting the drug's intrinsic activity. The frequency-regulating effect of pindolol dependent on the level of exercise that produced the tachycardia: tachycardia at rest responded more markedly to pindolol than exercise-induced tachycardia; tachycardia due to low-level exercise responded better than that due to higher level exercise. Of the 88 patients who developed typical effort angina and/or ischemic ST-segment depression, 62 became symptom free during exercise when taking pindolol. The patient sample included 66 patients with effort-related premature ventricular contractions (PVCs), 44 of whom responded well to pindolol. Of the 453 patients with a stable HR, 15 exhibited PVCs during exercise for the first time while receiving pindolol. Overall, pindolol exerted a statistically highly significant antiarrhythmic effect. Tolerance to pindolol was good; no side effects were observed.