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 (200-230 ms) and use of the fourth extrastimulus identified patients at significant arrhythmic risk.


CONCLUSIONS
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.
Kumar
Saurabh
S
Department of Cardiology, Westmead Hospital, Sydney, New South Wales, Australia.
Sivagangabalan
Gopal
G
Zaman
Sarah
S
West
Elizabeth B
EB
Narayan
Arun
A
Thiagalingam
Aravinda
A
Kovoor
Pramesh
P
D000368:Aged; D054849:Cardiac Electrophysiology; D017147:Defibrillators, Implantable; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000503:physiopathology* / Q000628:therapy*; D013318:Stroke Volume; D013997:Time Factors; D016896:Treatment Outcome