Delineation of myocardial viability with PET

Relative flow and metabolic imaging (the "mismatch pattern") with PET have been proposed to identify the presence of viable myocardium in patients with ischemic left ventricular dysfunction. Yet, optimal criteria to identify dysfunctional but viable myocardium and predict significant functional improvement have not been fully defined.

Dynamic PET imaging with 13N-ammonia and 18F-deoxyglucose to assess absolute myocardial perfusion and glucose uptake was performed in 25 patients (20 men, 5 women; mean age 57 +/- 12 yr, range 30-72 yr) scheduled for coronary revascularization because of coronary artery disease, anterior wall dysfunction and mildly depressed left ventricular ejection fraction (49% +/- 11%). Global and regional left ventricular function was evaluated by contrast left ventriculography at baseline and after revascularization.

As judged from the changes in end-systolic volume and resting anterior wall motion before and after revascularization, 17 patients with improved wall motion score and decreased end-systolic volume were considered to have viable myocardium, whereas 8 patients with either no change in regional wall motion or increased end-systolic volume were considered to have nonviable myocardium. Before revascularization, viable myocardium showed higher absolute myocardial blood flow (77 +/- 20 versus 51 +/- 9 ml (min.100 g)-1, p = 0.004) and absolute regional myocardial glucose uptake (36 +/- 14 versus 24 +/- 11 mumole (min.100 g)-1, p = 0.04) than nonviable myocardium.

This study identified absolute myocardial blood flow and normalized glucose extraction as the most powerful predictors of the return of contractile function after coronary revascularization in patients with ischemic anterior wall dysfunction.