Metabolic imaging to assess myocardial viability.

A potentially reversible impairment of contractile function in patients with chronic coronary artery disease characteristically exhibits a regional increase in glucose utilization or, more precisely, glucose extraction, as evidenced by the presence of a blood flow-glucose metabolism mismatch. The predictive accuracy of patterns of blood flow and glucose metabolism has now been established in more than 107 patients with 384 dysfunctional myocardial segments against the gold standard of myocardial viability, the functional outcome of contractile function after revascularization. According to long-term albeit retrospective follow-up studies, correlations exist between the blood flow-metabolism patterns and patient survival or cardiac morbidity. The same studies point out the high risk of patients with blood flow-metabolism mismatches and, at the same time, the considerable benefits derived from revascularization, i.e., reduced mortality and improvement in symptoms related to congestive heart failure. Imaging of the relative distribution of blood flow and of exogenous glucose utilization with PET therefore appears to be of considerable value for identifying high-risk patients as well as for stratifying patients to the most appropriate therapeutic management. This pertains especially to patients with poor left ventricular function and symptoms related to congestive heart failure. Assessment of myocardial viability in this particular patient group remains diagnostically challenging. On the other hand, as demonstrated by several investigations, blood flow metabolism imaging with 18F-deoxyglucose and PET is highly accurate in these patients for the identification of viable or reversibly dysfunctional myocardium.