Detection of stent restenosis in single vessel CAD: comparison of Thallium-201 and gated Tc-99m MIBI SPECT

After successful PTCA, stent restenosis is observed in up to 40% of patients during the first year. Aim: The prior objective was to determine the value of myocardial perfusion studies (MPS) in detection of stent restenosis in a symptomatic patient cohort. Methods: A total of 80 pts. without prior MI and who underwent one vessel PTCA with stent implantation were studied. Diagnostic accuracy of two study protocols; standard Tl-201 (38 pts.) and rest-stress same day Tc-99m gated-MIBI (42 pts.) were compared. MPS data were visually evaluated by two experienced observers and stress induced perfusion defects with reversibility at rest was considered as restenosis. In gated-MIBI data wall motion (WM) and EF were also noted. Diagnostic value of a semiquantitative method based on 20 segment model and summed stress scores (SSS) were also tested and a score of ≥ 8 was considered as abnormal. MPS diagnosis were compared with control coronary angiography (CA) in all pts and agreement was defined as kappa value (K). Results: Average time interval between stent implantation and MPS was 9±2 months. Restenosis detected in 58% of patients in CA. No significant differences were observed regarding age, sex, achieved exercise levels, vascular territorial distribution of lesions, imaging time interval after PTCA and restenosis degree between Tl-201 and gated-MIBI groups. MPS identified stent restenosis in 41 of 47 patients (sens:87%, spec:82%, acc:85% K:0.69). Four of 6 occluded stents that could not be detected in MPS had intermediate degree stenosis (50-70%). Sensitivity, specificity and accuracy were not significantly different but better for gated-MIBI group when compared to Tl-201 (sens:90-83%, spec:85-80%, acc:88-82%). Semiquantitative evaluation using SSS reached lower sensitivity (MIBI: 90% vs 69%, Tl-201 83% vs 72%) but higher specificity (MIBI: 85% vs 92%, Tl-201 80% vs 90%) for both tracers and SSS were significantly correlated with occlusion degree (r:0.84). EF values calculated from gated-MIBI study were also inversely correlated with occlusion degree (r:0.55) and significantly different in pts. with occluded stents (p<0.001). Agreement with CA for both tests were adequate (K; MIBI:0.73, Tl-201:0.63). Conclusion: Semiquantitative evaluation of MPS using SSS may enhance diagnostic specificity in the detection of stent restenosis. Although, Tl-201 and gated-MIBI studies both had accurately detected stent restenosis, gated-MIBI method has clear advantages of WM analysis in restenosis area and evaluation of EF, with higher diagnostic sensitivity