Cardioversion, defibrillation, and overdrive pacing of ventricular arrhythmias: the effect of moricizine in dogs with sustained monomorphic ventricular tachycardia.

The purpose of this investigation is to define whether the antiarrhythmic drug moricizine has beneficial or adverse effects on currently used antitachycardia and antifibrillatory devices. These studies were performed in a dog model of sustained monomorphic ventricular tachycardia (VT). In 11 dogs, the left anterior descending artery and all surrounding epicardial collateral feeder vessels were ligated. Defibrillator patches were implanted and the dogs were allowed to recover. After a 7-day recovery period, effective refractory period (ERP), end diastolic threshold (EDT), VT induction, and VT and ventricular fibrillation (VF) termination data were collected before and after moricizine infusion (2 mg/kg). In this experimental model, moricizine caused the following electrophysiological changes: a prolongation of the ERP from 173 +/- 14 to 182 +/- 15 (P < 0.02) with no significant effect on the EDT for pacing; a prolongation of the VT cycle length from 175 +/- 18 to 201 +/- 23 msec (P < 0.003); an increased cycle length required for overdrive pacing from 136 +/- 20 to 157 +/- 22 msec (P < 0.01); no effect on the energy required to cardiovert VT; an increase in the defibrillation threshold from 7.5 +/- 4 to 9.4 +/- 4 joules (P < 0.006) and; in 5 of the 8 dogs with VT, the VT could be initiated with somewhat less aggressive stimulation. Significant beneficial electrophysiological physiological effects were noted on the VT cycle length, including a proportionately prolonged overdrive pacing cycle length for VT termination.(ABSTRACT TRUNCATED AT 250 WORDS)

Physics and engineering of transcatheter cardiac tissue ablation.

Ablation of arrhythmogenic cardiac tissues has emerged as one of the most important advances in cardiac electrophysiology. With the introduction of transcatheter ablation, the treatment of ventricular tachycardia, Wolff-Parkinson-White syndrome and other cardiac arrhythmias has progressed from an expensive and painful surgical therapy accompanied by a long recovery period to the less expensive, less traumatic transcatheter approach. The feasibility of cardiac ablation, along with the increasing number of physicians using the technique, requires understanding of the anatomic and electrophysiologic bases of transcatheter ablation as well as the different technologies, their limitations and complications. This report provides an overview of the physical, scientific and technical aspects of cardiac ablation performed with the methods currently available and a summary of the limitations of each method and expected future technologic developments in this growing field. Emphasis is placed on radiofrequency and direct current energies, the primary methods now used. Methods such as cryoablation and laser, and microwave and chemical ablation are discussed with less detail because the method of delivering energy for these ablative procedures has not been fully developed.