title: Termination of ventricular tachycardia by an increase in cardiac vagal drive.
abstract: Out of 12 patients in whom phenylephrine terminated ventricular tachycardia, four were selected for detailed studies of its mechanism of action. Pretreatment with edrophonium (15-20 mg, i.v.) decreased, while atropine (2.4 mg, i.v.) increased by at least a factor of two, the dose of phenylephrine required to break ventricular tachycardia. Carotid sinus massage following pretreatment with edrophonium in unusually high (15-20 mg, i.v.) doses broke ventricular tachycardia in all four patients. The evidence presented supports the assumption that a vagal mechanism caused both instances of termination. These findings significantly alter our interpretation of vagal interventions in the bedside clinical diagnosis of wide QRS complex tachycardias.
mesh_terms: D001285:Atropine / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004357:Drug Synergism; D004491:Edrophonium / Q000494:pharmacology; D004562:Electrocardiography; D006321:Heart / Q000294:innervation; D006336:Heart Massage; D006801:Humans; D007275:Injections, Intravenous; D010656:Phenylephrine / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D011433:Propranolol / Q000494:pharmacology; D013610:Tachycardia / Q000188:drug therapy*; D014630:Vagus Nerve / Q000187:drug effects*
chemical_list: D010656:Phenylephrine; D004491:Edrophonium; D001285:Atropine; D011433:Propranolol