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a Division of Cardiac Surgery, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada
b Division of Cardiac and Vascular Surgery, Sunnybrook Health Sciences Centre, 2075 Bayview Ave; Rm H-410, Toronto, Ontario M4N 3M5, Canada
(Email: gilbert.tang{at}utoronto.ca; stephen.fremes{at}sunnybrook.ca).
Nardi and colleagues [1] reported the 10-year outcomes on 302 consecutive patients with left ventricular (LV) dysfunction, defined as a LV ejection fraction (LVEF) of 0.35 or less, who underwent isolated coronary artery bypass grafting (CABG). This is one of the first studies that has up to a 15-year longitudinal examination on 98% of its patients. In addition, long-term echocardiographic data were used to objectively assess the improvement in cardiac function in these patients. The authors are to be congratulated on their efforts of a comprehensive long-term follow-up.
The operative mortality of 5.3% in this patient group was respectable among other contemporary series. The 5-year and 10-year survival rates of 80% ± 2.5% and 63% ± 4% were higher than those reported in other studies. Approximately 60% of patients underwent preoperative viability studies. Patients who came to CABG presumably had evidence of hibernating myocardium, which may be present in as many as 50% of patients with ischemic cardiomyopathy [2]. Dobutamine echocardiography or rest-redistribution radionuclide testing to determine extent of hibernating myocardium has been shown to be valuable in selection of patients with LV dysfunction [2]. A number of other perioperative and postoperative factors might also have contributed to the good operative and long-term outcomes, such as the high percentage (97.4%) of internal thoracic artery grafting and routine intraoperative and postoperative use of inotropic drugs. However, the data suggest that patients with severe LV dysfunction should probably be stabilized initially rather than proceed with emergency operation, whenever possible.
Patients with low LVEF for CABG frequently have other comorbidities. It is instructive that in the study by Nardi and colleagues [1], renal dysfunction and diabetes mellitus were important predictors of late events, and not the severity of LV dysfunction. Recently, Halkos and colleagues [3] showed that a preoperative diagnosis of diabetes among 3201 patients did not affect 5-year survival after CABG, but an elevated hemoglobin A1c (HbA1c) level was an independent predictor of death. Diabetic management, as reflected by HbA1c measurement, may partly ameliorate the poor prognosis in diabetic patients. It would be interesting to see whether elevated HbA1c might have a worse affect on survival in patients with LV dysfunction.
Preoperative ventricular arrhythmia was an important risk variable for early and late events. Only 16 patients (5.3%) in this study had insertion of a permanent pacemaker or an internal defibrillator. The CABG Patch trial confirmed that epicardial defibrillators reduced arrhythmic cardiac death after revascularization [4]. It is likely many of the study patients [1] would have been candidates for a subsequent transvenous automatic implantable cardioverter defibrillator postoperatively [5], according to Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) criteria [6].
Notwithstanding the above points, as Nardi and colleagues [1] have shown, patients with poor LV function can undergo CABG safely, with good long-term outcomes. Proper screening and management of patients with diabetes, renal dysfunction, and ventricular arrhythmias may improve long-term survival among these patients. Forthcoming results of the Surgical Treatment for Ischemic Heart Failure (STICH) trial will offer further insights on the benefit of surgical revascularization in this population.
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