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

Background. Prediction of the recovery of left ventricular (LV) ischem ic dysfunction after revascularization is important in patients with c oronary 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 Res ults. Regional myocardial blood flow (RMBF) and cardiac output were me asured with nitrogen 13-ammonia positron emission tomography at rest a nd during low-level exercise in 28 patients with angiographically prov en CAD before and after successful revascularization and in 9 normal s ubjects. Before revascularization, exercise-induced upsloping ST-segme nt depression < 1 mm 80 msec after the J-point was observed in 11 pati ents (group 1), horizontal depression of 1 to 1.5 mm was observed in 9 patients (group 2), and downsloping depression greater than or equal to 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 th an 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 de pression induced by preoperative low-level exercise may predict a lack of improvement in LV ischemic dysfunction after revascularization.