Prediction of Long-term Cardiac Events by 123I-meta-Iodobenzylguanidine Imaging after acute Myocardial Infarction and Reperfusion Therapy

OBJECTIVE(S): In heart failure, the heart-to-mediastinum (H/M) ratio of the delayed image and washout rate (WR) are well-known as a powerful cardiac event predictors. H/M ratio quantifies the accumulation rate of MIBG in the myocardium and WR quantifies reduction of meta-iodobenzylguanidine (MIBG) accumulation in the heart from the early planar image to the delayed planar images in the (123)I-MIBG scintigraphy. The present study was conducted to estimate the role of the parameters of cardiac sympathetic imaging by (123)I-MIBG myocardial scintigraphy in subacute phase of acute myocardial infarction (AMI) in the prediction of cardiac events, particularly in patients who are successfully responded to reperfusion therapy. METHODS: This study was conducted on 145 patients with initial AMI who underwent (123)I-MIBG myocardial scintigraphy and myocardial single-photon emission computed tomography (SPECT) after successful response to reperfusion therapy. The (123)I-MIBG myocardial scintigraphy was averagely performed 16±5.8 days after the onset of AMI. The early image was taken 15 min after the intravenous administration of (123)I-MIBG. Three hours after (123)I-MIBG administration, an anterior planar delayed SPECT image was obtained. The H/M ratio and WR were calculated based on planar images. In addition, the average WR, defect volume, and extent were calculated from the SPECT image. The end points of the cardiac event was defined as hospitalization due to unstable angina, heart failure progression, myocardial infarction recurrence, malignant arrhythmia and cardiac death. RESULTS: The follow-up period was 18.4±8.5 months on average, during which 38 (26.2%) cases experienced cardiac events. The results revealed a significant difference between the groups with and without cardiac events in terms of WR and WR (SPECT). Based on the multivariate analysis, WR was the only relevant factor predicting cardiac events. The cumulative event-free rate was significantly lower in the group with the delayed H/M ratio of < 1.74. The cumulative event-free rate were significantly lower in the groups with WR and WR (SPECT) more than 25% and 21.8%, respectively. There was no significant relationship between the cumulative event-free survival rate and the defect size. CONCLUSION: In the subacute phase of myocardial infarction, the increased WR of (123)I-MIBG from the myocardium in planar scintigraphy and SPECT is the predictor of heart failure and cardiac events such as myocardial infarction and recurrence of unstable angina.