Incremental prognostic value of 99mTc-tetrofosmin myocardial SPECT after percutaneous coronary intervention

Percutaneous transluminal coronary angioplasty is a well-established therapeutic method in selected patients with coronary artery disease. The aim of this study was to assess the incremental prognostic value of technetium-99m (Tc-99m)-tetrofosmin myocardial gated-single- photon emission computed tomography (SPECT) in asymptomatic patients after coronary artery stenting. A total of 246 consecutive patients (aged 55.5 +/- 8.2 years, 182 men) participated in the study with a median follow-up of 9.5 years (interquartile ra 5.8-10.5 years). All patients underwent exercise gated-SPECT myocardial imaging within 5-7 months. Myocardial scintigrams were performed using 99mTctetrofosmin, and were evaluated calculating the summed stress score (SSS), summed rest score (SRS), and summed difference score (SDS) indexes. Cardiovascular death and non-fatal myocardial infarction were considered as hard cardiac events, and late revascularization (> 3 months after myocardial SPECT) procedures as soft events. Receiver-operating characteristic (ROC) analysis was used to test the prognostic ability of SSS and SDS for cardiac events. Cox proportional hazards models were used to evaluate the incremental value of SPECT variables. Cardiac death occurred in 12 (4.9%) patients and non-fatal myocardial infarction in 20 (8.1%) patients. In addition, 60 (24.4%) patients underwent a late revascularization procedure. Using ROC analysis the optimal cut-offs of SSS (AUC = 0.94; 95% CI 0.92-0.97) and SDS (AUC = 0. 76; 95% CI 0.70-0.82) for the prediction of cardiac events were 10 and 1.7, respectively. Multiple Cox regression analyses revealed that SSS > 10 (HR = 24.2; 95% CI 7.44-78.79) and SDS > 1.7 (HR = 2.72; 95% CI 1.23-6.00) provided incremental prognostic value over clinical and exercise test data for the composite end points of any cardiac event. Tc-99m-tetrofosmin myocardial gated- SPECT, performed 6 months post-percutaneous coronary intervention (PCI), provides incremental prognostic information for the prediction of cardiac events in asymptomatic patients after PCI.