A case with suspected ruptured mycotic coronary aneurysm presenting as purulent bloody pericarditis

Abstract Background Coronary artery aneurysms are rare, and mycotic coronary aneurysms arising secondary to bacterial infection are even rarer. Case summary A 77-year-old woman with end-stage renal disease presented with a 1-week history of persistent fever following arteriovenous fistula creation. Transthoracic echocardiography revealed a mild pericardial effusion. On the day after admission, a blood culture yielded methicillin-sensitive Staphylococcus aureus. Transoesophageal echocardiography revealed a well-demarcated hypoechoic lesion encasing the right coronary artery and moderate pericardial effusion. Owing to further accumulation of pericardial effusion, urgent pericardial drainage was performed, and purulent bloody pericardial fluid was evacuated, from which S. aureus was isolated. Computed tomography revealed a saccular right coronary aneurysm, suggestive of a diagnosis of a “mycotic coronary aneurysm” concomitant with purulent pericarditis. Despite the urgent transfer, the aneurysm ruptured before the planned surgery, and the patient subsequently died after surgical repair. Discussion Autopsy studies have revealed that most mycotic coronary aneurysms represent “pseudoaneurysms”, characterised by thinning of the arterial wall with outward bulging due to disruption of the elastic tissue layers. Thus, rapid dilation of the aneurysm and eventual rupture into the pericardial cavity may be key characteristics of this pathological condition. Clinicians should maintain a high index of suspicion for mycotic coronary aneurysms in patients with persistent bacteraemia and pursue prompt multimodal imaging for early detection, particularly when the standard evaluations for infective endocarditis are unknown. Furthermore, in the presence of haemorrhagic pericardial effusion, timely surgical intervention is imperative, because it indicates aneurysmal rupture.