INCREMENTAL PROGNOSTIC VALUE OF EXERCISE TL-201 MYOCARDIAL SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY LATE AFTER CORONARY-ARTERY BYPASS-SURGERY

Objectives. This study assessed the incremental prognostic value of ex ercise thallium-201 myocardial perfusion single-photon emission comput ed tomography (SPECT) performed greater than or equal to 5 years after coronary artery bypass surgery. Background. Thallium-201 scintigraphy has shown significant prognostic value in a variety of populations wi th suspected and known coronary artery disease. However, its value in patients with previous bypass surgery remains unknown. Methods. We stu died 294 patients who were prospectively followed up. Cox proportional hazards models for prediction of ''hard'' events (cardiac death and n onfatal infarctions) sere constructed, with variables considered for i nclusion in hierarchic order: clinical and exercise data first, follow ed by scintigraphic information. Results. Mean (+/-SD) follow up durat ion after scintigraphy was 31 +/- 11 months. There were 20 cardiac dea ths and 21 nonfatal acute myocardial infarctions. Twenty nine patients had late (>60 days after thallium-201 SPECT) revascularization proced ures or underwent repeat bypass surgery or percutaneous transluminal a ngioplasty. Shortness of breath and peak exercise heart rate were the most important clinical predictors of hard events. Two scintigraphic v ariables added significant prognostic information to the clinical mode l: the thallium-201 summed reversibility score (summation of segmental differences between stress and redistribution scores) and the presenc e of increased lung uptake of the radiotracer. The global chi-square s tatistic for this model was twice as high as that for the clinical/exe rcise model alone (49.7 vs. 24.2). When a second multivariate Cox mode l was built adding ''soft'' events (i.e., late revascularization proce dures) as outcomes of interest, the summed reversibility score was sel ected as an independent scintigraphic predictor of events. The global chi-square statistic for this model was 50.7, three times as high as t hat for the clinical/exercise model alone. Conclusions. After evaluati on of treadmill and exercise data, thallium-201 myocardial perfusion S PECT provided incremental prognostic information in patients late afte r bypass.