Atypical Acute Coronary Syndrome: A Diagnostic Enigma in Immunosuppressed Patients

Infective endocarditis (IE) due to Listeria monocytogenes is rare, with 62 reported cases between 1955 and 2024. Coinfection with Aspergillus fumigatus is even more uncommon and poses a diagnostic and therapeutic challenge. We report the case of an oncology patient receiving immunosuppressive chemotherapy whose presentation mimicked acute myocardial infarction (AMI). A 47-year-old woman with multiple endocrine neoplasia type IIA, with a history of pheochromocytoma and medullary thyroid carcinoma, undergoing treatment for mixed ductal and mucinous breast carcinoma with capecitabine, paclitaxel, trastuzumab, and pertuzumab. She presented to the emergency department of a tertiary private hospital with sudden onset of severe left shoulder pain a few hours earlier. Admission ECG showed ST-segment elevation in leads DI, DII, and aVF, and initial high-sensitivity troponin was 2,046 ng/L, rising to 108,626 ng/L. She was referred for coronary angiography, which showed no obstructive lesions. Further investigation with transthoracic echocardiography revealed multiple vegetations on the mitral and aortic valves and the aortic root, along with an image suggestive of an abscess in the mitral–aortic junction. Blood cultures were collected, empirical antibiotics were started, and the cardiovascular surgery team was consulted. Three blood culture samples grew Listeria monocytogenes after 21 hours of incubation. Antimicrobial therapy was de-escalated to ampicillin 2 g every 4 hours, and aortic and mitral valve replacement was performed; intraoperative findings included vegetations obstructing the right and left coronary ostia. Valves were sent for culture, which grew Aspergillus fumigatus. On postoperative day 2, the patient died due to refractory cardiogenic shock. The initial presentation mimicking AMI with no coronary obstruction, associated with elevated troponin, illustrates the importance of considering IE in the differential diagnosis of atypical acute coronary syndromes, especially in immunocompromised patients. Blood cultures, early appropriate antibiotic therapy, and surgical intervention when indicated are crucial for improving prognosis, although outcomes may still be unfavorable given the severity of the condition.