SUMMARY Termination of ventricular tachycardia by low-energy shocks delivered during the ventricular refractory period has been reported. We describe a case of reproducible termination of multiple episodes of sustained ventricular tachycardia by a low-current extrastimulus delivered during the effective refractory period of the right ventricle, from the distal bipole of a quadripolar electrode catheter.NONPROPAGATED electrical activity of diseased myocardial cells has been well demonstrated, particularly in canine' and human ischemic myocardium.2 The role of such activity in the modulation of paroxysmal dysrhythmia in man, although strongly suspected, is undefined. We describe the reproducible termination of multiple episodes of sustained ventricular tachycardia (VT) by a single, nonpropagated pacing stimulus delivered during the effective refractory period of the right ventricle.Case Report GF was a 57-year-old man with ischemic heart disease, an old anterior myocardial infarction and severe left ventricular dysfunction. He had been treated for 2 years with various antiarrhythmic drugs for several episodes of VT and ventricular fibrillation that occurred within 1 month after the infarction. At the time of the study, the patient was receiving no antiarrhythmic therapy. An atrioventricular sequential permanent pacemaker had been implanted several months earlier, and amiodarone had been discontinued for 3 weeks because of severe neurotoxicity. The patient was taken to the electrophysiology laboratory unsedated and, after local anesthesia (1% lidocaine) of the right femoral area, a #7F (USCI) quadripolar electrode catheter was advanced into the right ventricle under fluoroscopic control. A #5F cannula was placed in the right femoral artery for monitoring the systemic blood pressure. The distal pair of poles of the electrode catheter was connected to a programmable stimulator (Bloom DTU-101), and the proximal pair was used for electrogram recording. Leads I, aVF and V, of the surface ECG, the right ventricular (RV) electrogram (filtered between 100 and 500 Hz), the stimulation artifact and the blood pressure tracing were displayed on an oscilloscope (Electronics for Medicine VR-16) and recorded on photographic paper at speeds of 25-100 mm/sec.
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