Acute myocardial perfusion imaging – A useful tool for evaluation of therapeutic modalities & a predictor of urgent need for revascularization in acute coronary syndromes

We have been evaluating different therapeutic modalities using acute MPI, & we aimed at the use of acute MPI as a predictor of patients in need for urgent revascularization.MethodsA total of 85 patients with ACS were included in our study, 57 males, mean age 52.9 ± 10.6 years, 35% were diabetics, 50% hypertensive, 54% smokers, 30% dyslipidemic & 33% had +ve family history of CAD. Acute MPI was done by SPECT technique using triple head Gamma Camera. Every patient had two sets of images, first set done on admission by injecting 25 mCi Tc99m SestaMIBI intravenously before initiating therapeutic intervention and acquired within 6 h of injection. Second set of images was acquired 2 days later. Myocardium at risk (MAR) was calculated using 20 segment scoring system from the 1st set of images (scale 0–4/segment). Residual ischemia (RI) was calculated from the second set of images. Salvage index (SI = MAR − RI/MAR × 100) was taken as an end point for successful reperfusion (SI > 30%). All risk factors and MPI parameters were analyzed as independent predictors for the need for urgent revascularization vs. conservative strategy.ResultsPatients were subdivided according to therapeutic modalities used into three groups, group I: (50 pts) received unfractionated heparin, group II: (20 pts) received low molecular weight heparin & group III: (15 pts) received GPIIb/IIIa. There was no statistical difference as regards risk factors, age, sex, & MAR. Salvage index was highest in group II & lowest in group I (39 ± 21% vs. 64 ± 33.6% vs. 58 ± 25%) P = 0.07. Successful reperfusion was achieved in 67.3% in group I & 90% of group II, 86.7% in group III (P = 0.06). Out of 85 pts, 31 patients (group A) were in need for inhospital target vessel revascularization & 54 patients (group B) showed a good response on medical treatment (conservative strategy). Compared to group B, group A had higher values of RI (11 ± 7 vs. 5 ± 4%, P < 0.0001) & lower SI (15 ± 6 vs. 67 ± 24%, P < 0.0001) despite similar MAR (14 ± 7 vs. 15 ± 8) P > 0.05. High SI > 60%, and absence of diabetes (DM) were good predictors for conservative management strategy (specificity 96%); however, SI < 30% as well as presence of DM may recognize patients in need for urgent revascularization (sensitivity 50%) with overall predictive accuracy of 78.8%.ConclusionAcute MPI is a useful tool for evaluating therapeutic interventions. SI > 60% as well as absence of DM could recognize the subset of patients who can be managed conservatively whereas SI < 30% as well as presence of DM may recognize patients in need for urgent revascularization.