Infected left ventricular thrombus confirmed by FDG PET/CT presenting as persistent Streptococcus anginosus...

Infected left ventricular (LV) thrombus is a rare but serious complication in patients with heart failure with reduced ejection fraction (HFrEF). It is associated with persistent bacteraemia, systemic embolization, and stroke. Diagnosis requires a high index of clinical suspicion, supported by multimodal imaging and coordinated multidisciplinary management.

We report a 69-year-old man with ischaemic cardiomyopathy (EF 30%), prior multi-territory stroke due to LV thrombus, and multiple comorbidities, who was admitted with reduced GCS following ICU treatment for Streptococcus anginosus septic shock. Despite several antibiotic courses, he experienced recurrent bacteraemia over 6 months with no clear source. Given his history, an infected LV thrombus and infective endocarditis were considered. Transthoracic echocardiography (TTE) demonstrated recurrence of an apical thrombus, which was confirmed on transoesophageal echocardiography (TOE) without valvular vegetations. FDG positron emission tomography (PET) showed focal uptake at the LV apex in a circular pattern with central photopenia, consistent with an infected thrombus. He was managed with 6 weeks of intravenous benzylpenicillin followed by 6 months of oral amoxicillin, alongside warfarin anticoagulation. Surgery was not pursued due to frailty and comorbidities. He improved clinically with the resolution of bacteraemia. Follow-up PET and TTE were planned to assess the response.

This case represents one of the few PET-confirmed infected LV thrombus presenting with persistent S. anginosus bacteraemia. It highlights the diagnostic value of multimodal imaging, particularly PET/CT in distinguishing infected thrombus from sterile thrombus and endocarditis, and underscores the importance of prolonged antibiotic therapy, anticoagulation, and multidisciplinary management.