Prognostic value of rest (201)Tl-dipyridamole stress (99m)Tc-sestamibi gated SPECT for predicting patient-based clinical outcomes after bypass surgery in patients with ischemic left ventricular dysfunction.

Abstract

We investigated the postoperative prognostic value of preoperative myocardial SPECT for predicting clinical outcomes, including event-free survival and functional improvement. A total of 123 patients with ischemic heart disease and left ventricular dysfunction were enrolled. The ratio of men to women was 103:20, and the mean (+/-SD) age was 61 +/- 8 y. The disease involved 3 vessels in 95 patients, 2 vessels in 27 patients, and 1 vessel in 1 patient. Rest (201)Tl-dipyridamole stress (99m)Tc-sestamibi gated 24-h-delayed SPECT was performed before and 3-4 mo after bypass surgery. With a 20-segment model, a dysfunctional segment was defined as that with systolic wall thickening of <20%. Dysfunctional but viable segments were defined for each viability predictor, including rest thallium uptake of >60%, reversibility score (rest perfusion minus stress perfusion) of >7, systolic wall thickening of >10%, and 24-h-delayed thallium uptake of >60%. Global left ventricular functional improvement was defined as a 5% increase in the left ventricular ejection fraction (LVEF) or a 10-mL decrease in the end-systolic volume (ESV). A long-term follow-up evaluation was performed by chart reviews and telephone interviews over a period of up to 6 y. Cardiac events were defined as cardiac death, myocardial infarction, or heart failure requiring hospitalization. After bypass surgery, the LVEF was improved from 36.4% +/- 8.8% (mean +/- SD) to 44.3% +/- 11.1%, and the ESV was improved from 96.6 +/- 46.7 mL (mean +/- SD) to 75.1 +/- 44.0 mL. Global left ventricular function was improved in 96 patients but not improved in 27. Rest thallium uptake (>or=4 segments) and reversibility (>or=5 segments) were found to be significant variables in the receiver-operating-characteristic (ROC) curve analysis, with area-under-the-curve (AUC) values of 0.755 (P < 0.05) and 0.735 (P < 0.05), respectively. The values for preserved systolic wall thickening and delayed thallium uptake had no statistical significance. Using a multivariate logistic function, we created a single variable consisting of rest thallium uptake and reversibility; this variable had better prediction power than any other single variable (AUC value for the ROC curve, 0.794). Patients with a higher logistic function value (>or=0.84) showed better event-free survival than did those with a lower logistic function value (<0.84) (log-rank test, P < 0.05). The number of viable segments should be >4 for rest (201)Tl SPECT or >5 for the reversibility parameter for the prediction of global functional improvement in a patient-based evaluation. With a logistic function created from these parameters, the long-term clinical prognosis after bypass surgery could be predicted by the presence of viability on preoperative rest-stress myocardial SPECT.