Ischemic ventricular arrhythmias during heart failure: a canine model to replicate clinical events.

Abstract

BACKGROUND: Development of experimental animal models has played an invaluable role in understanding the mechanisms of ventricular arrhythmias. OBJECTIVES: The purpose of this study was to evaluate a new canine model of myocardial infarction (MI), heart failure, and ischemic ventricular arrhythmias in an attempt to replicate clinical conditions. METHODS: Thirty-six mongrel dogs underwent placement of a permanent ventricular pacemaker and induction of an anterior MI by percutaneous transcatheter embolization of polyvinyl foam particles into the left anterior descending coronary artery (just distal to the first septal branch). After a 2-week recovery period, heart failure was induced by continuous rapid ventricular pacing at 200 to 240 ppm for 3 weeks. Transient (4-minute) myocardial ischemia was induced via balloon occlusion of the proximal left circumflex coronary artery. Echocardiographic and electrophysiologic testing was performed before MI creation and repeated prior to acute ischemia induction. RESULTS: Seven dogs (19%) died within several hours of MI creation. All surviving dogs developed severe left ventricular systolic dysfunction. Significant increases in the intraatrial and intraventricular conduction intervals were observed following MI creation and heart failure induction compared with baseline values, as evidenced by increases in the duration of the P wave and QRS complex. Significant increases in corrected QT interval and ventricular refractoriness were observed. Acute transient ischemia induced sustained ventricular tachycardia or ventricular fibrillation in 21 of 29 dogs (72%). CONCLUSION: This canine model can serve as a useful tool for studying ventricular arrhythmias during the interactions of healed infarction, heart failure, increased sympathetic tone, and myocardial ischemia.