Evidence of reduced resting blood flow in viable myocardial regions with chronic asynergy

OBJECTIVES We tested the hypothesis in patients (n = 24) with ischemic hear t disease that chronic contractile dysfunction occurs in myocardial regions with true reduction in rest blood flow. BACKGROUND Whether viable myocardial regions with chronic contractile dysfu nction have true reduction in rest myocardial blood flow is controversial. METHODS Positron emission tomography (PET) N-13-ammonia was used to measure myocardial blood flow in combination with F-18-fluorodeoxyglucose ((18)FDG ) to assess myocardial viability. Viability also was assessed by dobutamine echo and recovery of function after coronary artery bypass grafting (CABG) . Segments (n = 252) were selected based on PET measured reduced resting bl ood flow and rest asynergy on echo. RESULTS Regional myocardial viability was present in 20 of 23 patients by P ET, 13 of 23 by dobutamine echo and 10 of 11 by postrevascularization crite ria. Rest blood how in normal regions was 1.14 +/- 0.52 ml/min/g and by def inition exceeded (p < 0.005) that in both viable (0.48 +/- 0.15; n = 8 pati ents) and nonviable (0.45 +/- 0.14; n = 8 patients) regions (post-CABG crit eria), which did not differ. Correction of rest myocardial blood flow in vi able asynergic segments, only, for fibrosis and incomplete tracer recovery raised the level to 0.67 +/- 0.21 (p < 0.005 vs. normal). Finally, evidence of both stunning (rest asynergy with normal flow) and hibernation was pres ent in 15 of 23 (65%) patients. CONCLUSIONS Reduced rest blood flow in viable myocardial regions with chron ic asynergy is common and cannot be accounted for by partial volume effect. Thus, hypotheses concerning physiologic mechanisms underlying chronic cont ractile dysfunction should consider the role played by chronic reduction of basal myocardial blood flow. (C) 2000 by the American College of Cardiolog y.