952-28 Monomorphic versus Polymorphic Ventricular Tachycardia After Coronary Artery Bypass Grafting

We hypothesized that 1) ventricular tachycardia and fibrillation (VT/VF) developing after coronary artery bypass grafting (CABG) are due to either restoration of perfusion to a chronic infarction or to peri-operative ischemia/infarction and 2) that VT morphologic and electrophysiologic characteristics would depend upon which mechanism was causal. Records of 17 pts referred for electrophysiologic studies (EPS) whose first episode of VT/VF ocurred peri-operatively were compared to a control group of 119 consecutive CABG pts without VT/VF. Results Pts with VT/VF had more depressed pre-operative ejection fraction (0.32 vs 0.49, p = 0.0001) and a higher incidence of peri-operative myocardial infarction (MI) (47% vs 8%, p = 0.0001) compared to control pts. The majority of VT/VF pts (88%) had a zone of prior infarction and placement of a bypass graft to an occluded vessel occurred more frequently in these Subjects compared to controls (p = 0,03). The majority of pts having monomorphic VT (64%) did not suffer a peri-operative MI and 80% had inducible monomorphic VT at EPS. Only 37% of pts having polymorphic VT were inducible and 67% had a peri-operative MI. Conclusion New onset monomorphic VT after bypass surgery is associated with an old infarct scar and may, in some cases, be due to revascularization of an area of prior infarction. Polymorphic VT/VF is usually associated with acute ischemia/infarction.