Beyond Atherosclerosis: Tumoral Coronary Infiltration as a Rare Cause of Myocardial Infarction

Description of Clinical Presentation: A 44-year-old woman with no significant cardiovascular history presented with chest pain, inferior T-wave inversion on ECG, and elevated troponins. She was diagnosed with non–ST-elevation myocardial infarction (NSTEMI) involving the right coronary artery, posterior descending artery, and posterolateral branch territories, and underwent successful angioplasty with stent implantation. During hospitalization, echocardiography revealed preserved LVEF (55%), regional wall motion abnormalities, and a large heterogeneous mass compressing the right atrium, accompanied by pericardial thickening and moderate effusion.

Diagnostic Techniques and Their Most Important Findings: Multimodality imaging was performed. CT revealed a large infiltrative mass involving the right atrioventricular and posterior interventricular grooves, encasing previously stented coronary segments, with mediastinal/axillary adenopathy, pericardial effusion, pleural effusion, and a liver lesion. Cardiac MRI confirmed extensive infiltrative involvement of the right atrium, right ventricle, and basal inferior LV, with associated pericardial infiltration and large effusion, highly suggestive of malignancy. Biopsy of the liver lesion demonstrated a well-differentiated neuroendocrine tumor (grade II, Ki-67 10%, positive for synaptophysin and chromogranin). Octreotide scintigraphy (Octreoscan) confirmed somatostatin receptor–expressing metastases in the heart, pericardium, mediastinal nodes, and liver. The infarction was ultimately attributed not to atherosclerotic disease but to tumoral encasement of the right coronary artery.

Learning Points from this Case: This case illustrates a rare presentation of metastatic cardiac involvement from a neuroendocrine tumor, manifesting initially as acute coronary syndrome due to tumor infiltration of the coronary arteries. Multimodality imaging was critical in characterizing the mass, defining its extent, guiding biopsy, and confirming systemic disease. The case underscores the importance of considering non-atherosclerotic causes of myocardial infarction, particularly in patients with unusual imaging findings, and highlights the value of combining cardiac MRI, CT, and nuclear medicine techniques in the diagnostic pathway.

A large infiltrative tumor mass is located in the right atrioventricular and posterior interventricular grooves at the basal level. It extends into the inferior and lateral walls of the right atrium, the diaphragmatic and lateral basal walls of the right ventricle, the basal inferior wall of the left ventricle, and the posterior and septal leaflets of the tricuspid valve
Redemonstration of the large atrioventricular groove mass with edema and enhancement. large nonhemorrhagic pericardial effusion with edema and enhancement. There are no nodular thickening of the pericardium consistent with tumour infiltration.
hepatic primary tumor demonstrated. No pulmonary nodules suggesting metastatic involvement are seen. A conglomerate of mediastinal lymphadenopathy is present anterior to the aortic arch (station 6), along with a hypodense focal liver lesion in segment VI, likely representing metastasis.