Introduction: Left circumflex (LC)-related acute myocardial infarction (AMI) presenting without ST-T changes has been underdiagnosed in the emergency department. There is little information on its clinical features and significance. Aims: The aims of the study were to investigate the clinical characteristics and outcomes of LC-related AMI without ST-T changes. Population and Methods: Ninety-six patients were admitted for LC-related AMI. Comparisons between those with and without ST-T changes were analyzed. Results: Twenty-two patients (23%) did not have ST-T changes, whereas 74 patients (77%) had them. Patients without ST-T changes had younger age (55.6 ± 16.8 vs 62.6 ± 12.0 years, P = .03), fewer presented as Killip III/IV (4.5% vs 27.4%, P = .02) and with lower creatine kinase (1647.3 ± 1602.2 vs 2778.2 ± 2343.3 IU/L, P = .037) and creatine kinase-MB (136.8 ± 130.3 vs 247.7 ± 200.0 IU/L, P = .017), and more were with concurrent culprit lesion in the middle or distal LC and right- or balanced-dominant coronary circulation (86.4% vs 44.6%, P <.001). During follow-up, the need for repeat percutaneous coronary intervention (48.6% vs 45.5%, P = .40) and recurrent infarction (13.5% vs 13.6%, P = .62) were similar between the 2 groups. The 30-day mortality (0% vs 5.4%, P = .35) and overall mortality rate (4.5% vs 12.2%, P = .28) between them were not different statistically. Conclusion: The relatively lower prevalence of LC-related AMI without ST-T changes in the study might be underestimated. These patients have smaller infarct size than patients with ST-T changes without differences in the short- and long-term outcomes between them.
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