Surgery in Patients with Ischemic Cardiomyopathy

Posted by • April 22nd, 2016

2016-04-19_9-59-01The original Surgical Treatment for Ischemic Heart Failure (STICH) trial by Velazquez et al. was designed to test the hypothesis that coronary-artery bypass grafting (CABG) plus guideline-directed medical therapy for coronary artery disease, heart failure, and left ventricular dysfunction would improve survival over that with medical therapy alone. The authors now report the results of the STICH Extension Study (STICHES), which was conducted to evaluate the long-term (10-year) effects of CABG in patients with ischemic cardiomyopathy.

Among patients with ischemic cardiomyopathy, coronary-artery bypass grafting added to medical therapy led to significantly lower rates of death from any cause and of cardiovascular death over 10 years than did medical therapy alone. A new Original Article summarizes.

Clinical Pearl

• Why is there a need for contemporary trials that compare coronary-artery bypass grafting with medical therapy for patients with coronary artery disease and heart failure?

Landmark clinical trials have established CABG as an effective treatment for patients with disabling angina symptoms. In these trials, CABG was associated with longer survival than was medical therapy alone among the subgroups with more extensive coronary artery disease and worse left ventricular dysfunction. However, the trials were conducted more than 40 years ago, before the availability of current guideline-based medical therapy for coronary artery disease and heart failure, and they did not include patients with severe left ventricular dysfunction; only 4% of participants had symptomatic heart failure. More recently, an increasing proportion of patients with heart failure and left ventricular dysfunction are referred for CABG.

Clinical Pearl

• What were the results of the STICH trial at a median follow-up of 56 months?

In the analysis of data from that trial, at a median follow-up of 56 months, there was no significant difference between the CABG group and the medical-therapy group in the rate of death from any cause, although the rates of death from cardiovascular causes and of death from any cause or hospitalization for cardiovascular causes were lower among patients in the CABG group.

Morning Report Questions

Q: Is CABG associated with a long-term survival benefit as compared to medical therapy alone in patients with coronary artery disease and left ventricular dysfunction?

A: In the trial by Velazquez et al. involving patients with heart failure, left ventricular dysfunction, and coronary artery disease, the rate of death from any cause over 10 years was lower by 16% (an 8-percentage-point absolute difference in the 10-year Kaplan–Meier rates) among patients who underwent CABG in addition to receiving medical therapy than among those who received medical therapy alone. Overall, CABG was associated with an incremental median survival benefit of nearly 18 months and prevention of one death due to any cause for every 14 patients treated and of one death due to a cardiovascular cause for every 11 patients treated. The authors previously reported that CABG was associated with a risk of death within the initial 30 days after randomization that was triple the risk with medical therapy alone, with similar differences in risk up to the second year of follow-up, before a significant benefit began to accrue after 2 years. Thus, it appears that the operative risk associated with CABG is offset by a durable effect that translates into increasing clinical benefit to at least 10 years.

Figure 2. Kaplan–Meier Estimates of the Rates of Death from Any Cause, Death from Cardiovascular Causes, and Death from Any Cause or Hospitalization for Cardiovascular Causes.

Table 2. Primary and Secondary Outcomes.

Q: What are some of the factors that are felt to have contributed to the effectiveness of CABG in the Velazquez study?

A: Substantial declines in risk-adjusted mortality associated with CABG have occurred since the 1970s, when the landmark trials comparing CABG and medical therapy were performed. Improvements in myocardial protection techniques, surgical skill, and perioperative care, coupled with the near-universal use of the left internal mammary artery (LIMA) conduit are probably responsible. Among the patients randomly assigned to undergo CABG, 91.0% of patients in STICH received a LIMA graft, as compared with 9.9% of patients in the early CABG trials. Although there are limited data on the long-term patency of LIMA or saphenous vein grafts in patients at high risk for death or complications, like those enrolled in STICH, evidence from studies involving lower-risk patients supports the superior 1-year angiographic results with the LIMA. In addition, the high rate of use of statins, which have been shown to reduce the rate of vein-graft failure, is likely to have contributed to the durable effect of CABG and the low rates of repeat revascularization observed in this group.

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