Viability, Remodeling, and CABG

F ollowing myocardial infarction, left ventricular (LV) remodeling is characterized by increased LV end-diastolic and end-systolic volumes (ESV) and decreased LV ejection fraction (EF) (1). This process is driven by elongation of infarcted zones and changes within the unaffected myocardium, including myocyte hypertrophy and interstitial collagen deposition. With medical therapy, revascularization, or cardiac resynchronization, the probability of reversing this process is greater where there is a greater proportion of viable myocardium, as assessed by noninvasive imaging (2–4). Based on a series of observational analyses (2,5,6), the extent of viability has been used to predict a greater LV functional benefit and improved survival from coronary artery bypass graft (CABG) versus medical therapy. This practice is not supported by results of a prior analysis of data from the randomized, controlled STICH (Surgical Treatment for Systolic Heart Failure) trial (7). However, additional studies have suggested that LV functional improvement following CABG is diminished in patients with greater LV volumes (8,9). These findings suggest that CABG may confer survival benefit only among patients with substantial viability, in the absence of severe remodeling. A report by Bonow et al. (10) in this issue of iJACC does not support this hypothesis, examining