Relation between contractile reserve and positron emission tomographic patterns of perfusion and glucose utilization in chronic ischemic left ventricular dysfunction - Implications for identification of myocardial viability

Objectives. This study sought to determine the incidence and extent of dobutamine induced contractile reserve in myocardial regions characterized by classical and new positron emission tomographic (PET) patterns in patients with chronic ischemic left ventricular dysfunction. Background. PET is considered the most accurate method for assessment of myocardial viability, which is traditionally identified by perfusion-metabolism mismatch. Methods. In 23 patients, segmental wall thickening expressed by four echocardiographic scores at rest and during low dose (5 and 10 mu g/kg body weight per min) dobutamine infusion and regional myocardial uptake of potassium-38 and fluorine-18 fluorodeoxglucose (F-18 FDG) during glucose clamp were compared in 16 corresponding segments. Results. Of a total of 368 segments, data analysis focused on 214 (58%) dyssynergic segments at baseline. Contractile reserve was identified with increasing incidence according to the six following PET patterns: 1) diminished perfusion and moderate reduction of F-18 FDG uptake (3 [11%] of 28 segments); 2) proportional reduction of perfusion and F-18 FDG uptake (10 [23%] of 43 segments); 3) perfusion-metabolism mismatch (19 [46%] of 41 segments); 4) preserved perfusion but moderate reduction of F-18 FDG uptake (13 [46%] of 27 segments); 5) preserved perfusion and F-18 FDG uptake (37 [59%] of 63 segments) compared with our normal database; and 6) normal perfusion but absolute increased F-18 FDG uptake (8 [73%] of 11 segments), In the latter category, only 7 of 24 segments had normal rest function. In dyssynergic segments with F-18 FDG uptake greater than or equal to 50% supplied by vessels with greater than or equal to 75% stenosis, improvement in contractility during dobutamine correlated with the presence of collateral channels. Conclusions. Myocardial regions with the traditional mismatch pattern of viability show contractile reserve in slightly <50%, In segments with moderate reduction of F-18 FDG uptake, the contractile response to dobutamine is linked to the level of rest perfusion. Most segments with preserved perfusion and increased F-18 FDG uptake have impaired rest function, but contractile reserve is still present. These data suggest that in chronic ischemic left ventricular dysfunction, myocardial hibernation is a heterogeneous condition. (C) 1997 by the American College of Cardiology.