A novel rabbit model of variably compensated complete heart block

1 Cardiovascular Research Programme, Hospital for Sick Children Research Institute; 2 Pathology Division and 3 Cardiology Division, Hospital for Sick Children; 4 Department of Laboratory Medicine and Pathobiology, University of Toronto; and 5 Department of Pediatrics, University of Toronto, Toronto, Ontario, Canada M5G 1X8 Complete heart block (CHB) provides a useful substrate for study of bradycardia-dependent ventricular arrhythmias and cardiac function. Existing CHB animal models are limited by surgical recovery time and reliance on intrinsic escape rhythms. We describe a novel closed-chest rabbit model of CHB involving transcatheter radiofrequency (RF) atrioventricular (AV) node ablation and ventricular rate control with chronic transvenous pacing. Permanent CHB was achieved in 34 of 38 attempts overall. Procedural mortality due to cardiac tamponade ( n = 2), airway complications ( n = 2), and unknown causes ( n = 5) occurred in nine animals. Survivors with CHB ( n = 28) were maintained for 22 days, during which there were three late deaths related to infection ( n = 1) or respiratory distress ( n = 2). None of the survivors with CHB showed recovery of AV conduction or pacemaker capture loss during chronic ventricular pacing at about one-half normal sinus rates, and 25 animals surviving to death showed no overt signs of hemodynamic compromise such as lethargy, poor feeding, or respiratory distress. This approach provides a reproducible nonsurgical CHB model with adjustable ventricular rate control. atrioventricular node; ventricular pacing; radiofrequency ablation