Myocardial viability did not predict a survival benefit from surgical revascularization among patients with ischemic heart disease and left ventricular (LV) dysfunction, according to the findings of a substudy of the Surgical Treatment for Ischemic Heart Failure Trial (STICH). Robert O. Bonow, MD, Northwestern University, Chicago, Illinois, USA, reported the results of the study, which is the largest report to date that relates myocardial viability to clinical outcomes in this population and the first to do so in the setting of a prospective randomized trial of coronary artery bypass grafting (CABG) versus medical therapy.

The study included 601 of the 1212 patients who were enrolled in the STICH trial in whom myocardial viability was assessed. Viability assessment was done by single-photon emission computed tomography (SPECT) in 471 patients and by low-dose dobutamine echocardiography in 280 patients, with 150 patients undergoing both tests. Assessment was optional and was done at the discretion of the recruiting investigators. The patients were randomly assigned to receive aggressive medical therapy alone (n=303) or CABG (n=298).

There were 487 (81%) patients with viable myocardium. The primary endpoint of all-cause mortality was less frequent in patients with myocardial viability in the unadjusted analysis (5-year mortality 37% vs 51%; p=0.003); however, myocardial viability was not significantly related to mortality (p=0.21) in a multivariable analysis that adjusted for other markers of risk, including LV ejection fraction, LV end-systolic and end-diastolic volume indexes, and a “risk at randomization” score (calculated with variables of age, renal disease, heart failure, ejection fraction, Duke coronary artery disease index, mitral insufficiency, and cerebrovascular disease).

Similarly, the secondary endpoint of cardiovascular (CV)-related mortality was significantly lower in patients with viability on univariate analysis (5-year mortality 29% vs 43%; p=0.003) but not on multivariable analysis (p=0.34). The secondary combined endpoint of mortality plus CV-related hospitalization occurred less frequently in patients with viability (5-year events 63% vs 82%), even after adjustment (p < 0.001).

These findings indicate that assessment of myocardial viability does not provide incremental independent information in identifying patients with coronary artery disease and LV dysfunction who will have the greatest survival benefit from adding CABG. The researchers suggest that the assessment of myocardial viability should not be the sole deciding factor in selecting the best therapy for patients in this population.

The study has several limitations, including the lack of randomization for viability testing, the small number of patients, and the small proportion of patients who were judged not to have substantial viability. Although viability assessment using other modalities (eg, MRI and PET) was not evaluated in this study, current meta-analyses and reviews indicate that the potential of SPECT and dobutamine echocardiography does not differ from PET in predicting survival in patients with LV dysfunction.

Further Reading: Bonow R et al. N Engl J Med 2011.