Continuous telemetry from a chronic canine model of sudden cardiac death

Introduction: We sought to develop a continuously telemetered animal model of sudden cardiac death (SCD) to study the role of existing infarcts and ac ute ischemia in fatal arrhythmias. Methods and Results: A telemetry system capable of recording eight channels of electrophysiologic data continuously and chronically has been developed . To demonstrate the use of this technology in an animal model of sudden de ath, 12 anesthetized dogs were instrumented with eight electrodes located i n endocardium of the right side of the heart, epicardium of the left ventri cle (LV), or in the subcutaneous tissues. The left anterior descending (LAD ) coronary artery was occluded for 90 minutes and reperfused to produce LV infarction, A copper wire was placed in the left circumflex (LCX) coronary artery to cause intimal injury in a second arterial bed. The telemetry unit recorded deaths in seven animals between 19 to 64 hours after surgery. Fiv e animals that did not experience SCD by the fifth postoperative day served as controls. There were three modes of SCD: complex ventricular ectopy tha t degenerated into ventricular fibrillation (VF, n = 4); normal sinus rhyth m that suddenly degenerated into VF (n = 1); and bradycardia (RR intervals >1,000 msec) that lasted >3 minutes and preceded VF (n = 2), ST segment cha nges were significantly greater in the LCX-bed electrograms for tachyarrhyt hmic compared to bradyarrhythmic deaths (mean +/- SD; 4.0 +/- 3.4 mV and 0. 2 +/- 0.8 mV, respectively). Fast Fourier transform showed the peak frequen cy of VF 10 seconds after onset was significantly higher in the five dogs w ith initial tachyarrhythmias compared with the VF that followed profound br adycardia (6.5 +/- 3.1 Hz and 3.7 +/- 0.6 Hz, respectively). Computer-assis ted planimetry of postmortem heart slices revealed that infarcts in the two dogs with bradycardic events were larger (19.7 % +/- 2.2 % of the LV and s eptal mass) than in the five dogs with tachyarrhythmias (7.7% +/- 2.4%) or in the five control dogs (11.9% +/- 8.1%). Conclusion: It is possible to record via telemetry the events leading to SC D in an animal model, Continuous telemetry monitoring demonstrated that bot h tachyarrhythmias and bradyarrhythmias ultimately resulted in VF in an ani mal model of SCD, Animals with tachyarrhythmic deaths had greater ischemia in the LCX bed, smaller preexisting infarcts, and higher VF peak frequency than animals with bradyarrhythmic deaths.