Factors influencing predictive value of FDG imaging for evaluating myocardial viability.

Rational management of patients with coronary artery disease (CAD) and poor left ventricular (LV) function relies on proper identification of the subgroup at high risk and those who have the highest potential of benefiting from a particular type of treatment. Before the advent of imaging techniques to determine myocardial viability, many patients with CAD and low ejection fractions (EFs) were relegated to medical therapy. It is now well recognized that patients with CAD and LV dysfunction have a high but variable mortality rate while receiving medical therapy. Many of these patients who have intractable heart failure are considered candidates for cardiac transplantation. Despite favorable survival after cardiac transplantation, because of the shortage of donor hearts, this procedure cannot be performed in many heart failure patients who are potentially eligible. Cardiac transplantation is also an expensive procedure. In many patients with heart failure, LV dysfunction is reversible after myocardial revascularization. The potential for recovery of LV dysfunction after myocardial revascularization represents a practical clinical definition for myocardial viability. Since its initial clinical application nearly 2 decades ago, myocardial metabolism imaging with fluorine 18 fluorodeoxyglucose (FDG) and positron emission tomography (PET) or single photon emission computed tomography (SPECT) has undergone extensive validation for assessment of myocardial viability. In the earlier studies, recovery of regional LV dysfunction was used as the criterion for determining myocardial viability. Subsequently, recovery of LVEF, improvement in heart failure symptoms, and improvement in survival emerged as more clinically relevant endpoints with which to assess the utility of FDG