Differential sensitivity of sinus node, atrioventricular node, atrium, and ventricle to propranolol.
The purpose of this study was to test the hypothesis that less propranolol was required to block stellate-induced shortening of atrial and ventricular effective refractory periods (ERPs) than was required to prevent stellate-induced shortening of the spontaneous sinus nodal cycle length and atrioventricular (AV) nodal conduction time. Studies were performed in open-chest, neurally decentralized dogs anesthetized with secobarbital. We determined the dose of propranolol (propranolol dose-response curves) required to block the effects of 1 Hz, 2 Hz, and 4 Hz bilateral ansae subclaviae stimulation on sinus nodal automaticity, AV nodal conduction, and atrial and ventricular ERPs. We found that propranolol at a dose of 0.5 mg/kg eliminated ansae subclaviae-induced shortening of atrial and ventricular ERPs, whereas sinus nodal cycle length and AV nodal conduction time still shortened. These data indicate a differential sensitivity of the sinus and AV nodes compared with atrial and ventricular myocardium to the beta-adrenergic receptor-blocking effects of propranolol in response to efferent sympathetic neural stimulation. Clinical implications are that it might be possible to treat sympathetically mediated ventricular arrhythmias with doses of propranolol that still preserve sinus and AV nodal responses.
Chang
M S
MS
Krannert Institute of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis 46202.
Zipes
D P
DP
D000818:Animals; D016275:Atrial Function; D001283:Atrioventricular Node / Q000187:drug effects / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D002304:Cardiac Pacing, Artificial; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006325:Heart Atria / Q000187:drug effects; D006329:Heart Conduction System / Q000502:physiology*; D006352:Heart Ventricles / Q000187:drug effects; D008297:Male; D011433:Propranolol / Q000494:pharmacology*; D012032:Refractory Period, Electrophysiological / Q000187:drug effects; D012849:Sinoatrial Node / Q000187:drug effects / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology; D016276:Ventricular Function
D011433:Propranolol