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 characte rized by classical and new positron emission tomographic (PET) pattern s in patients with chronic ischemic left ventricular dysfunction. Back ground. PET is considered the most accurate method for assessment of m yocardial viability, which is traditionally identified by perfusion-me tabolism 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 region al myocardial uptake of potassium-38 and fluorine-18 fluorodeoxglucose (F-18 FDG) during glucose clamp were compared in 16 corresponding seg ments. Results. Of a total of 368 segments, data analysis focused on 2 14 (58%) dyssynergic segments at baseline. Contractile reserve was ide ntified with increasing incidence according to the six following PET p atterns: 1) diminished perfusion and moderate reduction of F-18 FDG up take (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 modera te reduction of F-18 FDG uptake (13 [46%] of 27 segments); 5) preserve d perfusion and F-18 FDG uptake (37 [59%] of 63 segments) compared wit h 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 wi th F-18 FDG uptake greater than or equal to 50% supplied by vessels wi th 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 patter n of viability show contractile reserve in slightly <50%, In segments with moderate reduction of F-18 FDG uptake, the contractile response t o dobutamine is linked to the level of rest perfusion. Most segments w ith preserved perfusion and increased F-18 FDG uptake have impaired re st function, but contractile reserve is still present. These data sugg est that in chronic ischemic left ventricular dysfunction, myocardial hibernation is a heterogeneous condition. (C) 1997 by the American Col lege of Cardiology.