Sustained Ventricular Tachycardia in Recent

SUMMARY To study recurrent ventricular tachycardia in the late phase of myocardial infarction (MI), transmural anteroapical infarcts were created by ligation of the left anterior descending (LAD) coronary artery in 25 dogs. Twenty dogs survived LAD ligation and underwent an open-chest electrophysiologic study an average of 20 days after MI. Programmed electrical stimulation was carried out using the extrastimulus tech-nique and short bursts of rapid ventricular pacing via bipolar electrodes positioned at multiple left ventricular endocardial sites. Sixteen dogs had electrically induced ventricular tachycardia, and in 11, sustained ven-tricular tachycardia was reproducibly initiated and terminated by programmed ventricular stimulation. Short bursts of rapid left ventricular pacing from areas in periinfarct zone was the most effective technique for ini-tiating ventricular tachycardia. The electrophysiologic phenomena in this model of sustained ventricular tachycardia in 3-week-old MI included electrically induced changes in rate and morphology and biventricular capture without termination during tachycardia. VENTRICULAR ARRHYTHMIAS during acute myocardial ischemia and within the first week of ex-perimental canine myocardial infarction have been studied by Harris et al., ' El-Sherif et al.2-6 and other investigators.7 1 However, the electrophysiologic mechanisms that underlie ventricular arrhythmias in later stages of myocardial infarction have not been as extensively investigated because of the lack of an ex-perimental model of reproducible, sustained ven-tricular tachycardia. In this report we describe a model of nonspontaneous, electrically inducible, sustained ventricular tachycardia in dogs with 3-week-old anteroapical myocardial infarctions. The stability, reproducibility and relatively high yield of inducible sustained ventricular tachycardia make this model promising for further investigation of the electro-physiologic properties of sustained ventricular tachycardia during the late phase of myocardial in-farction