Prognostic Value of Rest ²⁰¹Tl-Dipyridamole Stress ^99mTc-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. Methods: 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 ²⁰¹Tl-dipyridamole stress ^99mTc-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. Results: 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 (≥4 segments) and reversibility (≥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 (≥0.84) showed better event-free survival than did those with a lower logistic function value (<0.84) (log-rank test, P < 0.05). Conclusion: The number of viable segments should be >4 for rest ²⁰¹Tl 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.