Myocardial washout rate of technetium-99m-sestamibi in the chronic phase predicts myocardial damage in patients with previous myocardial infarction

Objective This study aimed to clarify the correlation between the myocardial washout rate (WR) of technetium- 99mhexakis 2-methoxy-isobutyl-isonitrile (99mTc-sestamibi) and cardiac enzyme levels in patients with acute myocardial infarction (AMI) 6 months after the onset. Methods Sixty-one consecutive AMI patients (mean age, 66.2 ± 9.7 years) who underwent percutaneous coronary intervention (PCI) on admission were enrolled. Creatinine kinase MB isoenzyme (CK-MB) levels were measured every 3 h. 99mTc-sestamibi myocardial scintigraphic images were obtained at the early (30 min) and delayed (4 h) phases after tracer injection for calculating heart-to-mediastinum (H/M) ratios and global WRs at 2 weeks (0 M) and 6 months (6 M) after the onset of AMI. Regional WRs in the culprit lesions (culprit WR) and the extent score (ES) and severity score (SS) of myocardial damage were also calculated. Results PCI was performed 8.3 ± 7.7 h after AMI onset. At 6 M, the early H/M ratio (p = 0.04), delayed H/M ratio (p = 0.02), global WR (p = 0.01), culprit WR (p = 0.002), and delayed ES (p = 0.008) were alleviated. At 0 M, the peak CK-MB level correlated with the delayed H/M ratio (p = 0.003), global WR (p = 0.003), culprit WR (p\0.001), early ES (p = 0.03), delayed ES (p = 0.01), early SS (p = 0.001), and delayed SS (p\0.001). At 6 M, the peak CK-MB level correlated with the delayed H/M ratio (p\0.001), global WR (p = 0.005), culprit WR (p = 0.001), early ES (p = 0.001), delayed ES (p\ 0.001), early SS (p\0.001), and delayed SS (p\0.001). Conclusions These results demonstrated that 99mTc-sestamibi WR in the chronic phase as well as that in the acute phase reflects the extent of initial myocardial damage in AMI patients after PCI. Moreover, it might indicate the myocardial condition in the clinical course.