Effect of Primary PCI in asymptomatic STEMI patients presenting 12-48 hours of symptom onset, on myocardial viability assessed on SPECT - ‘EPITOME-99’

Background : Guidelines on revascularization of asymptomatic STEMI patients presenting 12-48 hours of symptom onset are limited, evidence contributing lack of symptoms to non-viable myocardium are scarce. We utilized TC-99mSestaMIBI scan to study the impact of primary PCI on myocardial viability by deriving myocardial salvage index (MSI) in asymptomatic STEMI patients presenting between 12-48 hours of symptom onset to PCI. Methods and results : We enrolled 141 patients with STEMI (12-48 hours), from January 2020 to December 2023, who then underwent TC-99mSestaMIBI scan, followed by revascularization of IRA with 138 patients completing the designed study with follow-up scan at 3 months. A substantial MSI of > 0.50 was achieved by 36 %, 8% and 5 % of patients from cohort A(12-24 hrs.), B(25-36 hrs.), and C(37-48 hrs.) respectively.Post Hoc analysis determined a comparable AAR of 34.47 %( ±11.70) throughout cohorts, however a greater reduction in FIS [Q=4.72 (p=.00309)]and MSI gain was noted among patients of cohort A alone [Q=4.18 (p=.01025)]. Regression analysis of MSI against PCI timing was negatively correlated (R= -0.41). Conclusion : Asymptomatic stable STEMI patients presenting 12-24 hours of symptom onset to PCI, benefited from primary PCI with lesser final infarct size and larger MSI. Despite a comparable AAR across cohorts, MSI fell sharply among patients undergoing primary PCI 24-48 hours of symptom onset with a larger final infarct size, warranting viability guided revascularization. Although primary PCI improved final LVEF and MSI in patients with ischemic heart failure, parameter gain alone was insufficient in endeavoring a positive clinical impact.