Effect of primary pci in asymptomatic stemi patients presenting 12 to 48 hours of symptom onset, on myocardial viability assessed by spect tc 99m sestamibi scan epitome99

Abstract Background Guidelines on revascularization of asymptomatic stable STEMI patients presenting 12-48 hours of symptom onset are limited. We utilized TC-99mSestaMIBI scan to study the impact of primary PCI on myocardial viability by deriving myocardial salvage index (MSI) from area at risk (AAR), prior to revascularization and final infarct size (FIS) at follow up, in asymptomatic stable STEMI patients presenting between 12-48 hours of symptom onset to PCI. Purpose Evidence contributing lack of symptoms to a non-viable myocardium is lacking and it would be unethical to randomize patients with myocardial infarction (< 48 hours old) to a control arm or a non-intervention arm without evaluating the possibility of salvageable myocardium. Our study aims to inculcate evidence based management of late presenting stable asymptomatic STEMI patients. Methods We enrolled 141 patients presenting with STEMI (12-48 hours), from January 2021 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. Subjects were subcategorised into cohort A(12-24 hrs.), B(25-36 hrs.), and C(37-48 hrs.) according to the duration of symptom onset. Results A substantial MSI of > 0.50 was achieved by 36 %, 8% and 5 % of patients from cohort A, cohort B, and cohort C respectively. Although the AAR was comparable throughout cohorts, on post HOC analysis a statistically significant reduction in the final infarct size was seen among patients in cohort A vs C [Q = 4.72 (p = .00309)], while a reduction of FIS in cohort B and cohort C were obvious but statistically insignificant. Myocardial salvage index was smaller in late presenters, with no statistically significant difference among cohort B & cohort C [Q = 0.96 (p = .77697)]. Delaying the timing of Primary PCI from symptom onset was associated with larger AAR (R= - 0.01) & FIS (R= 0.35) although with a lower correlation coefficient. While evaluating MSI against timing of Primary PCI, a moderately negative (R= - 0.41) relation exists, indicating a linear correlation to reduced myocardial salvage Index with delay in the timing of primary PCI to symptom onset. 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.