PREDICTION OF ARRHYTHMIC EVENTS WITH POSITRON EMISSION TOMOGRAPHY
Michael E. Cain, M.D., University at Buffalo, Buffalo, NY, USA
Between 184,000 and 462,000 Americans die suddenly each year. Fifty to seventy percent of these deaths are due to ventricular tachycardia/fibrillation (VT/VF). We tested whether hibernating myocardium or myocardial sympathetic denervation identifies patients at high-risk for developing VT/VF independently of EF. Positron emission tomography (PET) was used to quantify myocardial sympathetic denervation (11C-meta-hydroxyephedrine, 11C-HED), perfusion (13N-ammonia, 13NH3), and viability (insulin-stimulated 18F-2-deoxyglucose, 18FDG) in patients with ischemic cardiomyopathy (EF<35%) eligible for a primary prevention implantable cardioverter defibrillator (ICD). The primary end-point was sudden cardiac arrest (SCA) defined as arrhythmic death or ICD discharge for VT/VF >240 bpm. Volumes of total denervated (p=0.001) and viable denervated myocardium (11C-HED-18FDG mismatch, p=0.03) predicted SCA, while hibernating and infarcted myocardium did not. Multivariate analysis identified four independent predictors of SCA: denervated myocardium >37.6% LV, LV end-diastolic volume >98 ml/m2, creatinine >1.49 mg/dl, and no ACE- inhibition therapy. Denervated myocardium had a hazard ratio of 3.5 for SCA (10.3%/year vs. 3.0%/year, p=0.001). Absence of all four factors predicted low risk (44% of cohort; SCA <1%/year) while =2 identified subjects at high-risk (20% of cohort; SCA 12%/year). Denervated myocardium quantified using PET strongly predicts risk of SCA, and is independent of EF, infarct volume, and other clinical variables.