PERFUSION-MVO(2) MISMATCH DURING INOTROPIC STRESS IN CAD PATIENTS WITH NORMAL CONTRACTILE FUNCTION

With the use of [C-11] acetate, positron emission tomography (PET) per mits exploration of myocardial blood flow (MBF) and oxidative metaboli sm (MVo(2)) coupling. PET imaging was performed; at rest and under dob utamine infusion in 8 normal subjects and 10 coronary artery disease ( CAD) patients with significant single-vessel left anterior descending (LAD) stenosis (>70%) and normal regional left contractile function at rest. Resting MBF and MVo(2) were similar in remote and LAD regions o f normal subjects and patients. During dobutamine infusion, MBF and my ocardial flow reserve were lower in LAD regions of patients compared w ith remote regions (MBF: 1.49 +/- 0.42 and 2.06 +/- 0.57 ml . g(-1). m in(-1), P < 0.01; reserve: 1.73 +/- 0.59 and 2.14 +/- 0.47, P < 0.01, respectively), whereas MVo(2) expressed as k(mono) (an index of MVo(2) ) and metabolic reserve were similar (k(mono): 0.106 +/- 0.021 vs. 0.1 07 +/- 0.017 min(-1); reserve: 1.88 +/- 0.32 vs. 1.98 +/- 0.37, respec tively). This is the first human study showing that, in normal contrac tile regions at rest but perfused by stenosed artery, a disparate rise in MVo(2) relative to the rise in myocardial perfusion occurs during increased cardiac work induced by dobutamine. This flow-metabolism unc oupling probably reflects an increase in O-2 extraction.