Effective removal of a large, mobile right atrial thrombus with the ŌNŌ retrieval device: a novel case report

Background: Large right atrial thrombi represent medical emergencies due to their potential for fatal embolization. Treatment options vary based on thrombus etiology and morphology, and include: (i) anticoagulation alone, (ii) a combination of anticoagulation and thrombolysis, (iii) transcatheter thrombectomy, and (iv) surgical thrombectomy. Here, we report the youngest and smallest patient to date to successfully undergo right atrial thrombectomy using the novel ŌNŌ transcatheter retrieval system (ŌNŌCOR LLC). Case summary: An 8-year-old male with Hodgkin's lymphoma was diagnosed with a new large, mobile thrombus associated with a port-a-cath in the right atrium on routine pre-chemotherapy echocardiogram. He was otherwise asymptomatic with a structurally normal heart. Thrombolysis with alteplase was initially attempted but was unsuccessful due to anaphylaxis. The patient subsequently underwent a partial thrombectomy of the mobile portion of the thrombus using the ŌNŌ retrieval device, successfully reducing the risk of catastrophic embolization. Follow-up echocardiography at twelve weeks and seven months confirmed further reduction in thrombus size and calcification of the remnant. Discussion: This patient presented a unique therapeutic dilemma due to several factors, including hypermobile thrombus of substantial size, recent oncologic diagnosis, and anaphylaxis to alteplase. The novel ŌNŌ was effective in encapsulating the entire thrombus, securing fragments, and thereby reducing risk of embolization during retrieval. This approach also minimized blood loss and avoided the complications associated with invasive cardiothoracic surgery in a patient with underlying malignancy.