Influence of atenolol and bopindolol on circadian heart rate

The effects of a cardioselective beta-adrenoceptor blocker without intrinsic sympathomimetic activity (ISA) (atenolol) and a noncardioselective beta-adrenoceptor blocker with ISA (bopindolol) on circadian heart rate were studied in 10 patients (2 women and 8 men) with an average age of 52 years and the following diagnoses: coronary heart disease (n = 4) and hypertension (n = 6). The patients were treated in a randomized crossover study with 100 mg atenolol p.o. and 1 mg bopindolol p.o. Atenolol lowered the averaged circadian heart rate (HR) significantly (p less than 0.001), from 70-59 beats/min. The HR decreased during the day and also at night. After bopindolol the average circadian HR decreased only slightly, from 69-64 beats/min. HR was reduced during the day but not during the night. Nine out of 10 patients receiving atenolol developed hourly HRs less than 55 beats/min compared to 3 patients on bopindolol. There was a significant increase of hourly segments (HR less than 55 beats/min) from 11-85 and also for hourly segments with HR less than 50 beats/min from 0-46 with atenolol, whereas no significant change could be detected under bopindolol. Both drugs produced similar reductions in exercise-induced increases in HR and systolic blood pressure and these effects persisted for more than 24 h.