DELINEATION OF MYOCARDIAL VIABILITY WITH PET

Relative flow and metabolic imaging (the ''mismatch pattern'') with PE T have been proposed to identify the presence of viable myocardium in patients with ischemic left ventricular dysfunction. Yet, optimal crit eria to identify dysfunctional but viable myocardium and predict signi ficant functional improvement have not been fully defined. Methods: Dy namic PET imaging with N-13-ammonia and F-18-deoxyglucose to assess ab solute myocardial perfusion and glucose uptake was performed in 25 pat ients (20 men, 5 women; mean age 57 +/- 12 yr, range 30-72 yr) schedul ed far coronary revascularization because of coronary artery disease, anterior wall dysfunction and mildly depressed left ventricular ejecti on fraction (49% +/- 11%). Global and regional left ventricular functi on was evaluated by contrast left ventriculography at baseline and aft er revascularization. Results: As judged from the changes in end-systo lic volume and resting anterior wall motion before and after revascula rization, 17 patients with improved wall motion score and decreased en d-systolic volume were considered to have viable myocardium, whereas 8 patients with either no change in regional wall motion or increased e nd-systolic volume were considered to have nonviable myocardium. Befor e revascularization, viable myocardium showed higher absolute myocardi al blood flow (77 +/- 20 versus 51 +/- 9 ml (min . 100 g)(-1), p = 0.0 04) and absolute regional myocardial glucose uptake (36 +/- 14 versus 24 +/- 11 mu mole (min . 100 g)(-1) p = 0.04) than nonviable myocardiu m. Conclusion: This study identified absolute myocardial blood flow an d normalized glucose extraction as the most powerful predictors of the return of contractile function after coronary revascularization in pa tients with ischemic anterior wall dysfunction.