Abstract
Anomalous coronary arteries (ACA) represent a heterogeneous group of anatomical variants with a wide range of clinical implications. While many are benign, specific courses may predispose to ischemia, myocardial infarction, heart failure, or sudden cardiac death. We present a rare case of a 62-year-old man with an anomalous left main (LM) coronary artery originating from a shared right coronary ostium, demonstrating a mixed interarterial and transseptal course. Multimodality imaging with cardiac CT angiography (CTA), cardiac magnetic resonance imaging (CMR), and invasive coronary angiography with intravascular ultrasound (IVUS) and physiologic assessment revealed dynamic systolic compression of a prominent first septal perforator, associated with mid-myocardial fibrofatty infiltration and fibrosis. Resting hemodynamics were normal; however, provocative maneuvers elicited significant ischemia as evidenced by abnormal instantaneous wave-free ratio (iFR) changes. Despite the anatomical complexity and hemodynamic findings, the patient opted for conservative management following a detailed discussion of surgical revascularization options. This case highlights the nuanced spectrum of clinical significance in anomalous LM coronary arteries, challenging the traditional benign versus malignant classification. Comprehensive anatomical and physiological evaluation is critical, especially in mixed-course anomalies. Our findings underscore the role of multimodal imaging modalities and functional testing in guiding individualized patient management in rare coronary anomalies.