Clinical study: coronary artery disease
Evidence of reduced resting blood flow in viable myocardial regions with chronic asynergy

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Abstract

OBJECTIVES

We tested the hypothesis in patients (n = 24) with ischemic heart disease that chronic contractile dysfunction occurs in myocardial regions with true reduction in rest blood flow.

BACKGROUND

Whether viable myocardial regions with chronic contractile dysfunction have true reduction in rest myocardial blood flow is controversial.

METHODS

Positron emission tomography (PET) 13N-ammonia was used to measure myocardial blood flow in combination with 18F-fluorodeoxyglucose (18FDG) 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 blood flow and rest asynergy on echo.

RESULTS

Regional myocardial viability was present in 20 of 23 patients by PET, 13 of 23 by dobutamine echo and 10 of 11 by postrevascularization criteria. Rest blood flow in normal regions was 1.14 ± 0.52 ml/min/g and by definition exceeded (p < 0.005) that in both viable (0.48 ± 0.15; n = 8 patients) and nonviable (0.45 ± 0.14; n = 8 patients) regions (post-CABG criteria), which did not differ. Correction of rest myocardial blood flow in viable 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 present in 15 of 23 (65%) patients.

CONCLUSIONS

Reduced rest blood flow in viable myocardial regions with chronic asynergy is common and cannot be accounted for by partial volume effect. Thus, hypotheses concerning physiologic mechanisms underlying chronic contractile dysfunction should consider the role played by chronic reduction of basal myocardial blood flow.

Abbreviations

ANOVA
analysis of variance
BP
blood pressure
CABG
coronary artery bypass grafting
CAD
coronary artery disease
18FDG
18F-fluorodeoxyglucose
IV
intravenous
LV
left ventricle, left ventricular
MI
myocardial infarction
PET
positron emission tomography
ROI
region of interest

Cited by (0)

Partial support for this study came from Fujisawa, Inc (James Kean) who kindly supplied adenosine.