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Cardiac Surgery, Cleveland Clinic Foundation, 9500 Euclid Ave, Desk H-35, Cleveland, OH 44122
(Email: abeel.mangi{at}gmail.com).
Coronary artery bypass grafting in the setting of ischemic ventricular fibrillation independently protects against future episodes of ventricular arrhythmia and future episodes of sudden cardiac death [1–3]. Secondary prophylaxis by implantable cardioverter-defibrillator (ICD) resulted in 31% reduction in mortality in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial, a 23% in The Canadian Implantable Defibrillator Study (CASH) trial [4], and 20% in the Canadian Implantable Defibrillator Study (CIDS) trial [5]. In the Coronary Artery Bypass Graft (CABG) Patch trial [6], patients who were believed to be at high risk for sudden death were randomized to CABG only and CABG plus ICD. The study demonstrated a 7% increment in mortality (p = 0.64), and post hoc analysis demonstrated a reduction in risk of sudden cardiac death with ICD in addition to CABG as compared with CABG alone [7]. These studies do not address the role of electrophysiology (EP) testing as a tool for patient stratification, the impact of ICD placement, or medical therapy on influencing freedom from sudden death and survival after CABG, or the adequacy of CABG alone for secondary prophylaxis of sudden cardiac death.
This report by Ngaage and colleagues [8] suggests that CABG alone serves as adequate secondary prophylaxis in the majority of patients studied. It is impossible to comment on whether the addition of either ICD or medical management impacted overall survival. However, if we were to extrapolate from previous studies, we might be able to assert that prevention of death due to cardiac arrhythmia by ICD implantation or medical management seems to translate into a benefit in terms of overall survival.
The survivor of cardiac sudden death who qualifies for ICD placement in addition to CABG remains elusive. Survivors of pre-hospital cardiac arrest should be evaluated for the presence of coronary artery disease and treatable ischemia. An EP study before CABG surgery in these patients is not always helpful or necessary, and may be contraindicated in patients with critical left main disease or unstable angina. In the presence of reversible ischemia and appropriate anatomy, revascularization should be performed. This is adequate therapy for many patients as Ngaage indicates. Patients who are at incremental risk for recurrent sudden death, such as those greater than 65 years of age, female patients, those with Cleveland Severity Score greater than 8, patients requiring perioperative intra-aortic balloon counterpulsation, those undergoing redo CABG, and those with left ventricular ejection fraction < 40% [9] should probably undergo postoperative EP testing as inducibility at postoperative EP study is powerfully predictive of therapeutic device discharge, and patients who were not inducible at postoperative EP testing will generally remain free of sudden death. However, EP testing may be waived if there are already definite indications for ICD implantation or if the original event was clearly provoked by ischemia, and if an ICD is believed to be unnecessary (eg, in a patient with normal left ventricular function and critical coronary disease who arrested during or soon after vigorous exercise). Finally, any patient with a positive postoperative EP study should probably be treated with an ICD with or without concomitant medical anti-arrhythmic management.
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