Usefulness and Limitation of 24 Hour Reinjection Images to Assess Myocardial Viability in Patients with Acute Myocardial Infarction

ABSTRACT

OBJECTIVE: The study was performed to evaluate whether thallium reinjection (RI) distinguishes viable from nonviable myocardium among myocardial segments which showed persistent perfusion defect (PD) in patients with acute myocardial infarction (AMI). MATERIALS AND METHODS: We studied 22 patients underwent PTCA after AMI. SPECT was performed in all patients using dipyridamole stress- 4 hour redistribution (RD) followed by 24 hour RI protocols. Dysfunctional segs were classified into 5 groups: 1) normal, 2) reversible, 3) mild to moderate PD, 4) severe PD and 5) reverse redistribution (RR). All patients underwent follow up echocardiography after 4 months to assess regional wall motion (WM) improvement such as a criteria of viable myocardium. RESULTS: A total of 127 segs with abnormal WM was analyzed. Of 74 segs with PD, 17 (23%) showed enhanced uptake after 24 hour RI. Five of 17 segs (29%) with PD that responded to RI with enhanced thallium uptake showed WM improvement. WM improvement were seen in the 24 of 57 segs (42%) not responding to RI. All four segs (100%) with RR that responded to RI showed improvement. WM improvement were not seen in the 5 of 8 segs (71%) with RR not responding to thallium RI. Eleven (73%) of 15 segs with mild-moderate PD after RI showed improvement, but 33% of segs with severe PD after RI did not showed improvement. Segs with mild-moderate PD after RI and fill in after RI showed improvement in comparison to segs with severe PD after RI(p<0.05). CONCLUSIONS: These data indicate that because only small proportion of PD showed further perfusion improvement after RI and predictive value by the uptake after RI was low, there was limited role of RI after myocardial infarction. Usefulness of RI could be found in segs showing RR responding to RI in AMI reflects viable myocardium.