Pharmacologic suppression of atrial flutter induced by atrial stimulation

To examine the electrophysiologic properties of human atrial flutter and its response to various classes of antiarrhythmic drugs, 39 patients were identified as having inducible sustained atrial flutter with atrial extra-stimulation techniques. Measurement of intra-atrial, interatrial, atrioventricular node and His-Purkinje-conduction intervals, atrial refractory periods, and atrial flutter-cycle length were made before and after intravenous administration of verapamil, ouabain, or cedilanid, propranolol, and procainamide in these 39 patients, as well as in seven control patients. Verapamil significantly shortened flutter-cycle length but suppressed atrial-flutter induction in only one of seven patients. Two of nine patients who received propranolol proved resistant to flutter provocation; the seven patients who remained nonsuppressible exhibited greater prolongation of interatrial-conduction time. Ouabain and cedilanid suppressed flutter inducibility in four of seven patients, and flutter-cycle length increased in those patients remaining inducible. Procainamide suppressed flutter induction in nine of 11 patients. These results suggest that procainamide is the most effective agent of those agents tested in suppressing atrial flutter induced by atrial extra-stimulation. Verapamil and propranolol proved quite ineffective in suppressing inducible atrial flutter.