Exercise-induced ST-segment changes permit prediction of improvement in left ventricular ischemic dysfunction after revascularization: Evaluation with positron emission tomographic measurements of regional myocardial blood flow and cardiac output

Abstract

Background. Prediction of the recovery of left ventricular (IV) ischemic dysfunction after revascularization is important in patients with coronary artery disease (CAD). We investigated whether the improvement in LV ischemic dysfunction after revascularization could be predicted preoperatively by exercise-induced ST-segment changes. Methods and Results. Regional myocardial blood flow (RMBF) and cardiac output were measured with nitrogen 13—ammonia positron emission tomography at rest and during low-level exercise in 28 patients with angiographically proven CAD before and after successful revascularization and in 9 normal subjects. Before revascularization, exercise-induced upsloping ST-segment depression <1 mm 80 msec after the J-point was observed in 11 patients (group 1), horizontal depression of 1 to 1.5 mm was observed in 9 patients (group 2), and downsloping depression ≥1.5 mm was observed in 8 patients (group 3). The number of regions of critical CAD was greater in group 3 than in groups 1 and 2 (3.6 ± 1.4 vs 1.6 ± 0.7 and 2.2 ± 1.1, p < 0.001, p < 0.02). Increase of RMBF in regions of critical CAD with exercise was lower in group 3 than in groups 1 and 2 (0.15 ± 0.01 vs 0.22 ± 0.01 and 0.18 ± 0.02 ml/min per gram, p < 0.0001, p < 0.01). After revascularization, RMBF in regions of critical CAD both at rest and during exercise improved in groups 1 (0.49 ± 0.15 to 0.60 ± 0.18, 0.70 ± 0.26 to 0.86 ± 0.33 ml/min per gram, both p < 0.05) and 2 (0.50 ± 0.15 to 0.62 ± 0.19, 0.67 ± 0.26 to 0.89 ± 0.31 ml/min per gram, both p < 0.02), but was unchanged in group 3 (0.47 ± 0.09 to 0.47 ± 0.15, 0.62 ± 0.17 to 0.64 ± 0.23 ml/min per gram, both p = NS). Cardiac output at rest improved in groups 1 (4.98 ± 0.43 to 5.35 ± 0.50 L/min, p < 0.02) and 2 (5.08 ± 0.52 to 5.53 ± 0.28 L/min, p < 0.02), but was unchanged in group 3 (4.76 ± 0.48 to 4.88 ± 0.82 L/min, p = NS). Conclusions. Our results suggest that marked downsloping ST segment depression induced by preoperative low-level exercise may predict a lack of improvement in IV ischemic dysfunction after revascularization.