Electrophysiology-guided defibrillator implantation early after ST-elevation myocardial infarction

Background Sudden death risk is highest early after myocardial infarction (MI). Inducible ventricular tachycardia (VT) confers increased risk of spontaneous ventricular arrhythmias. Objective The purpose of this study was to evaluate outcomes of electrophysiology (EP)-guided defibrillator implantation early after ST-elevation MI in patients with ejection fraction ≤40%. Methods EP study was performed 9 days after MI (n = 360). Predischarge defibrillator was recommended if VT with cycle length <200 ms was induced with ≤4 extrastimuli (EP-positive [EP_pos], n = 142). EP-negative (EP _neg) patients were discharged without a defibrillator (n = 218). Primary endpoint was either sudden death or spontaneous ventricular arrhythmia. Results Defibrillator was implanted in 71% of EP_pos patients (median 21 days post-MI) and withheld in 94% of EP_neg patients. At 2 years, primary endpoint was 4.3% in the EP_neg group and 22% in the EP _pos group (adjusted hazard ratio 0.46, P = .035, EP_neg vs EP_pos). Lack of a defibrillator in EP_pos patients conferred a fourfold increased risk of sudden death (P = .014). EP_neg patients without a defibrillator were at significantly lower risk for the primary endpoint than were EP_pos patients without a defibrillator (adjusted HR 0.34, P = .011). Short inducible VT cycle length (200230 ms) and use of the fourth extrastimulus identified patients at significant arrhythmic risk. Conclusion EP study performed early after MI identified patients at significant long-term arrhythmic risk at a critical time after MI in whom defibrillator implantation was protective. A large majority of patients (EP _neg; two thirds) were at significantly lower risk of arrhythmic events without a defibrillator in the long term.