Absolute blood flow and oxygenconsumption in stunned myocardiumin patients with coronary artery disease

Objectives In patients with coronary artery disease (CAD), we sought to demonstrate normal myocardial blood flow (MBF) and myocardial oxygen consumption (MMRO2) to post-ischemic myocardium that exhibited reversible dysfunction and the relation between the severity of the dysfunction and the preceding ischemia. Background In animal models of stunning, MBF and MMRO2 are normal or near normal, and the severity of stunning is related to the degree of the preceding ischemia. Methods Myocardial blood flow and MMRO2 were measured using positron emission tomography and oxygen 15-labelled water (H215O) and oxygen 15-labelled oxygen (15O2), respectively, in 14 patients with CAD and normal left ventricular (LV) function. Global ejection fraction and regional LV systolic function (SF) were measured using quantitative echocardiography during and after dobutamine-induced ischemia. Results Ejection fraction and SF were reduced 30 min after dobutamine (both: p < 0.01) but recovered by 120 min. Myocardial blood flow (ml/min per g) to regions with reversible LV dysfunction was normal at baseline and during dysfunction (0.88 [0.82 to 0.99] and 1.09 [0.75 to 1.37], respectively, P = NS) as was MMRO2 (ml/min per 100 g) (16.64 [10.16 to 16.18] and 11.68 [8.43 to 15.30] respectively, P = NS). Left ventricular dysfunction was related to stenosis severity and peak MBF. Regions were divided into those subtended by a stenosis of <50%, 50% to 80% and >80% luminal diameter. Systolic function 30 min after dobutamine was 93.9% (83.4% to 104.4%) (p = NS), 85.4% (80.0% to 90.9%) and 67.4% (56.2% to 78.7%) (both: p < 0.001), respectively. Peak MBF was 2.0 (1.71 to 2.31), 1.75 (1.65 to 1.85) (p = 0.01 compared with <50%) and 1.47 (1.33 to 1.60) (p = 0.03 compared with 50% to 80% and P = 0.002 compared with <50%), respectively. Conclusions In patients with CAD, dobutamine produces prolonged, but reversible, LV dysfunction when MBF is normal, confirming stunning. This stunning is related to the severity of the coronary stenosis and the reduction in peak MBF. Myocardial oxygen consumption to stunned myocardium is normal.