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

BackgroundSudden death risk is highest early after myocardial infarction (MI). Inducible ventricular tachycardia (VT) confers increased risk of spontaneous ventricular arrhythmias.ObjectiveThe 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%.MethodsEP 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 [EPpos], n = 142). EP-negative (EPneg) patients were discharged without a defibrillator (n = 218). Primary endpoint was either sudden death or spontaneous ventricular arrhythmia.ResultsDefibrillator was implanted in 71% of EPpos patients (median 21 days post-MI) and withheld in 94% of EPneg patients. At 2 years, primary endpoint was 4.3% in the EPneg group and 22% in the EPpos group (adjusted hazard ratio 0.46, P = .035, EPneg vs EPpos). Lack of a defibrillator in EPpos patients conferred a fourfold increased risk of sudden death (P = .014). EPneg patients without a defibrillator were at significantly lower risk for the primary endpoint than were EPpos patients without a defibrillator (adjusted HR 0.34, P = .011). Short inducible VT cycle length (200–230 ms) and use of the fourth extrastimulus identified patients at significant arrhythmic risk.ConclusionEP 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 (EPneg; two thirds) were at significantly lower risk of arrhythmic events without a defibrillator in the long term.