EFFECTS OF INTRINSIC SYMPATHETIC ACTIVITY OF BETA-BLOCKERS ON SA AND AV NODES IN MAN

  • 1 January 1981
    • journal article
    • research article
    • Vol. 12  (6) , 367-375
Abstract
The effects of beta-blockers without intrinsic sympathetic activity (ISA) (propranolol, 160 mg/day), moderate ISA (acebutolol, 800 mg/day) and high ISA (pindolol, 20 mg/day) were compared. The sinus rate decreases more with propranolol than with acebutolol, during the day (P < 0.01) and night (P < 0.001). Pindolol does not change the daytime rate and increases the nighttime rate (P < 0.001). The ventricular rate during atrial fibrillation (AV [atrio-ventricular] nodal transmission) is modified as is sinus rate. There is no significant difference between propranolol and acebutolol and a highly significant difference between pindolol and propranolol (P < 0.001) or acebutolol (P < 0.01). The eurythmic effect of beta-blockers, making RR intervals more regular, is maximal with propranolol and minimal with pindolol, as judged on RR interval histograms. The ISA of the beta-blockers is of major importance for the clinical use of these drugs. In the case of SA [sino-atrial] or AV node dysfunction ISA can be useful, but it can obscure the beneficial effects of beta-blocking therapy.