CABG Improves Long-term Survival in Severe Left Ventricular Dysfunction

By Van Selby, MD

Assistant Professor of Medicine, University of California, San Francisco, Cardiology Division, Advanced Heart Failure Section

Dr. Selby reports no financial relationships relevant to this field of study.

SYNOPSIS: In patients with coronary artery disease, heart failure, and left ventricular ejection fraction < 35%, coronary artery bypass grafting plus medical therapy was associated with improved survival compared to medical therapy alone.

SOURCE: Velazquez EJ, Lee KL, Jones RH, et al. Coronary-artery bypass surgery in patients with ischemic cardiomyopathy. N Engl J Med 2016 Apr 3 [Epub ahead of print].

Whether adding coronary artery bypass grafting (CABG) to optimal medical therapy is associated with increased survival in patients with coronary artery disease and severe left ventricular dysfunction remains unclear. The Surgical Treatment for Ischemic Heart Failure (STICH) trial, originally reported in 2011, randomized 1,212 patients with coronary artery disease amenable to CABG, heart failure, and left ventricular ejection fraction (EF) < 35% to CABG plus medical therapy or medical therapy alone. Patients with significant left main stenosis or Canadian Cardiovascular Society class III or IV angina were excluded. The mean age was 60 years and the mean EF was 28%. During five years of follow-up, there was no significant improvement in the primary outcome of all-cause death.

The STICH Extension Study (STICHES) reported 10-year outcomes for these patients. During a median follow up of 9.8 years, 58.9% of patients in the CABG group and 66.1% of patients in the medical therapy group died (hazard ratio [HR], 0.84; 95% confidence interval [CI], 0.73-0.97; P = 0.02). Median survival was 1.44 years longer in the CABG group. CABG was similarly associated with reduced rates of cardiovascular mortality (HR, 0.79; P = 0.006) and the composite outcome of death or hospitalization for cardiovascular causes (HR, 0.72; P < 0.001). Patients with three vessel diseases derived the greatest survival benefit from CABG.

There were no significant differences between the groups with regard to background medical therapy. Nineteen percent of patients in the medical therapy arm crossed over and underwent CABG during the follow-up period. The authors concluded the findings of STICHES support a benefit of CABG plus medical therapy over medical therapy alone among patients with ischemic cardiomyopathy.

COMMENTARY

Landmark trials performed in the 1970s showed the superiority of CABG over medical therapy alone for treatment of ischemic cardiomyopathy. However, only a small minority of patients enrolled in these studies had severe left ventricular systolic dysfunction. Furthermore, subsequent decades have brought substantial improvements in medical therapy for both coronary artery disease and systolic heart failure. The survival benefit of CABG for patients with severe ischemic cardiomyopathy in the current era is unproven. The original STICH trial found no significant benefit in the primary outcome of all-cause survival, although there were improvements in several secondary endpoints. STICHES now shows a statistically significant survival benefit associated with CABG that is substantial and likely to affect clinical practice.

STICHES has many strengths. Implementation of guideline-based medical therapy in both groups was excellent. Approximately 90% of patients were receiving beta-blockers, angiotensin-converting enzyme inhibitors/angiotensin-receptor blockers, and statins. Use of implantable cardioverter-defibrillators was low at 18% of the study population. Otherwise, STICHES accurately reflects real-world ischemic cardiomyopathy patients. Follow-up status was ascertained for 98% of randomized patients, impressive for a 10-year extension study.

Current American College of Cardiology/American Heart Association guidelines assign a class IIb recommendation (might be considered) for CABG in patients with ischemic cardiomyopathy and severely reduced ejection fraction. Based on the findings from STICHES, future guidelines likely will be altered to provide stronger encouragement for CABG. The results also underscore the need to identify the presence and angiographic severity of coronary artery disease in patients with systolic heart failure. It is important to remember that STICHES only evaluated the utility of CABG in this population, and the same survival benefit cannot be assumed for multivessel percutaneous coronary intervention.

The findings from STICH and STICHES guide individual patient discussions regarding treatment options for ischemic cardiomyopathy. Early (one month) mortality was 3.6% in the CABG arm, significantly higher than the medical therapy group. In patients at lower perioperative risk (i.e., younger and with few comorbidities), the expected long-term survival benefit with CABG would be even greater. Patients with more extensive coronary artery disease and diabetes also have a greater expected benefit with CABG. Choice of therapy will continue to be a patient-specific decision, but the results of STICHES suggest early evaluation for coronary artery disease and discussion regarding the potential benefits of CABG should be strongly considered in patients with ischemic cardiomyopathy and severe systolic dysfunction.