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

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.

Usefulness of 201Tl Myocardial Perfusion SPECT in Prediction of Left Ventricular Remodeling following an Acute Myocardial Infarction / 대한핵의학회잡지

PURPOSE: We investigated the role of myocardial perfusion SPECT in prediction of ventricular dilatation and the role of revascularization including thrombolytic therapy and PTCA in prevention of ventricular dilatation after an acute myocardial infarction (AMI). MATERIALS AND METHODS: We performed dipyridamole stress, 4 hour redistribution, and 24 hour reinjection Tl-201 SPECT in 16 patients with AMI two to nine days after attack. Perfusion and wall motion abnormalities were quantified by perfusion index (PI) and wall motion index (WMI). Left ventricular ejection fraction (LVEF), WMI and ventricular volume were measured within 1 week of AMI and after average of 6 months. According to serial changes of left ventricular end-diastolic volume (LVEDV), patients were divided into two groups. We compared WMI, PI and LVEF between the two groups. Relationships among degree of volume, stress-rest PI, WMI, CKMB, Q wave, LVEF and revascularization were analysed using multivariate analysis. RESULTS: Only initial rest perfusion index was significantly different between the two groups (p<0.05). While initial LVEF, stress PI, CKMB, trial of revascularization procedure, presence of Q wave and WMI were not significantly different between the two groups. Eight of 16 patients (50%) showed LV dilatation on follow-up echocardiography. Three of 3 patients (100%) who did not undergo revascualrization procedure documented LV dilatation. And only 5 (38%) of the remaining 13 patients who underwent revascularization revealed LV dilatation. There was no difference in infarct location between the two groups. By multivariate linear regression analysis in patients only undergoing revascularization, rest perfusion index was the only significant factor. CONCLUSION: Myocardial perfusion SPECT performed prior to revascularization was useful in prediction of LV dilatation after an AMI. Rest perfusion index on myocardial perfusion plays as a significant predictor of left ventricular dilatation after AMI. And revascularization appears to be a valuable procedure in alleviating LV dilatation after AMI with or without viable myocardium in a limited number of patients studied retrospectively.