To explore the clinical characteristics and misdiagnosis reasons of acute myocardial infarction with cardiac enlargement as the first manifestation.

The clinical data of a patient with acute myocardial infarction admitted to the Cardiac Care Unit of Affiliated Hospital of Jining Medical University on July 30, 2020 was retrospectively analyzed, and relative literatures were reviewed.

The 41-year-old patient developed a cough and a small amount of white phlegm for 10 days before admitted to the hospital, with gradually increasing chest tightness, and decreasing activity endurance. Echocardiography showed left ventricle and right atrium was enlarged, left ventricle contraction was markedly impaired, and left ventricular ejection fraction (LVEF) was 43%. He was diagnosed with dilated cardiomyopathy, and still felt chest tightness and discomfort after 3 days of treatment. After admission, echocardiography showed that LVEF decreased to 22% and the manifestations of cardiac MRI were consistent with the changes of acute myocardial infarction. Coronary angiography showed that the stenosis in LAD after D1 was 95%, the proximal part of D1 stenosis was 80%, and a drug-eluting stent was implanted at the stenosis of LAD. Following discharge, follow-up echocardiography revealed good heart function recovery, with LVEF increasing to 56% 8 months later.

Cardiac MRI is of great significance in the diagnosis of atypical acute myocardial infarction. Revascularization and adequate medical treatment can reverse ventricular remodeling in acute myocardial infarction.