A case report of myocardial infarction with non-obstructive coronary arteries caused by severe myocardial bridging: insights from resting full-cycle ratio and perfusion imaging

Myocardial bridging (MB) is often considered a benign anatomical variant, yet deep or long bridges can result in dynamic coronary compression and ischaemia. In rare instances, MB may lead to myocardial infarction with non-obstructive coronary arteries (MINOCA), posing a diagnostic challenge.

We report the case of a 59-year-old man who presented with chest pain and elevated cardiac troponin following exertion. Coronary angiography showed no obstructive coronary artery disease but revealed an MB in the mid-left anterior descending (LAD) artery with complete systolic compression. Intravascular ultrasound (IVUS) confirmed the presence of MB without underlying atherosclerosis. Functional assessment using the resting full-cycle ratio (RFR) demonstrated a value of 0.91. Single-photon emission computed tomography (SPECT) revealed no perfusion defects, supporting the absence of significant ischaemia. The patient was diagnosed with MINOCA secondary to MB and treated conservatively with beta-blockers. He remained free of recurrent myocardial infarction, and the exertional chest pain was markedly improved.

This case highlights the potential of severe MB to cause infarction in the absence of fixed coronary lesions. It also underscores the diagnostic utility of RFR in assessing MB physiology and its concordance with perfusion imaging.