Electrophysiological effects of cardioselective and non‐cardioselective beta‐adrenoceptor blockers with and without ISA at rest and during exercise.

Abstract

1 In 46 patients (16 female and 30 male), aged between 18 and 73 years the effect of acute P-adrenoceptor blockade with i.v. pindolol, acebutolol and atenolol has been studied at rest and during ergometric exercise, during routine intracardiac His bundle investigations. 2 At rest the functional parameters of the sinus node were impaired most markedly by atenolol. A-V nodal conduction was more depressed with acebutolol and atenolol than with pindolol. The His-Purkinje system conduction remained unaffected by all three 3-adrenoceptor blocking agents.3 During ergometric exercise the depressant action of P-adrenoceptor blockade on sinus nodal function with lower heart rates and on A-V nodal conduction with slower conduction velocities was equieffective with pindolol, acebutolol and atenolol. His-Purkinje system conduction again remained unchanged with one exception that after administration of pindolol, conduction rate during exercise was faster than before P-adrenoceptor blockade.

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

“…The responses of atrioventricular conduction intervals and sinus node recovery times to atrial pacing at increasing rates were as expected from previous studies. 10,13,14 Increasing heart rate resulted in prolongation of AH interval as succeeding atrial impulses occurred during the relative refractory period of the AV node. A decline in sinus node recovery time with increasing heart rates after a certain peak has been reached has been attributed to sympathetic stimulation or vagal withdrawal from a decline in stroke volume and blood pressure by pacing at higher rates.&dquo; Based on previous studies, a potency ratio of 1 to 10, pindolol to propranolol, was utilized in designing this study.15,16 A higher ratio (eg, 1:20) may be more appropriate if one considers the results of the beta blockers on the suppression of the isoproterenol-induced tachycardia observed in this study.…”

“…'-' In these instances the selection of a beta blocker may depend on its more or less pronounced effect on AV nodal or SA nodal function. [10][11][12][13] The purpose of this investigation was to compare the effects of pindolol, a beta blocker with intrinsic sympathomimetic activity (ISA), and propranolol, a beta blocker without this property, on sinus node recovery times and AV nodal conduction intervals. The population consisted of 20 consecutive patients (15 men, 5 women, mean age fiftythree, range thirty to seventy-two) undergoing cardiac catheterization who also agreed to participate in the study; 11 had coronary artery disease, 7 had history of hypertension (4 with coronary artery disease), 2 had mitral valve prolapse, and 4 had chest pain with normal catheterization findings.…”

Electrophysiologic effects of intravenous xamoterol in patients with sinus node dysfunction

“…In contrast, pindolol, a beta-blocking agent with a marked degree of ISA, had little effect on the resting heart rate and on the sinoaUial conduction time in patients without evidence of the sick sinus syndrome [7]. Moreover, oral treatment with pindolol in patients with clinical [13] or electrophysiologic [14] evidence of sinus node dysfunction induced a significant increase in the resting heart rate and a shortening of the maximal corrected sinus node recovery time, the mean of the three longest corrected sinus node recovery times, and the sinoatrial conduction time.…”

“…In human studies, beta-blocking agents with a marked degree of intrinsic sympathomimetic activity (ISA) have been shown to depress heart rate less than beta blockers devoid of this property [7,8]. Such betaadrenoceptor partial agonists act according to the prevailing sympathetic tone; indeed, the effect of ISA is particularly evident during the nocturnal phase, when sympathetic activity is low [9][10][11].…”

Comparative efficacy of nicardipine hydrochloride and atenolol in the treatment of chronic stable angina

“…The data suggest that atenolol may prolong the PR interval and electrophysiological studies indicate that atenolol prolongs atrio-ventricular nodal impulse conduction time (Hombach et al, 1982;Hotvedt et al, 1984). These characteristics may be clinically significant for some patients.…”