Mobile Thrombus in Sinuses of Valsalva in a 1-Year-Old-Cat: Case Report

Feline aortic thromboembolism is a life-threatening condition most commonly associated with cardiomyopathy and typically localised at the aortic trifurcation. Direct visualisation of a mobile thrombus within the aortic root prior to the development of clinical embolic signs has rarely been reported in cats. This case report describes the clinical course of a one-year-old male British Shorthair cat in which a mobile thrombus was detected at the level of the sinuses of Valsalva during echocardiographic examination before the onset of arterial thromboembolism. The cat was referred for respiratory distress following elective castration. Thoracic radiography revealed pulmonary oedema. Echocardiography demonstrated marked left atrial enlargement, borderline systolic function and a severe restrictive diastolic filling pattern consistent with a restrictive cardiomyopathy phenotype. A mobile thrombus was identified within the aortic root. Multimodal antithrombotic therapy, including low molecular weight heparin and rivaroxaban, was initiated. Despite treatment, clinical arterial thromboembolism affecting both pelvic limbs developed seven days later. Repeat echocardiography revealed resolution of the aortic thrombus but the presence of a new thrombus within the left atrium. Coagulation testing showed normal prothrombin time, shortened activated partial thromboplastin time and markedly increased fibrinogen concentration. The patient died six days after the embolic event. This case highlights the dynamic and unpredictable nature of thromboembolism in cats and suggests that mobile thrombi located within the aortic root may be associated with a poor prognosis, even in the absence of significant haemodynamic obstruction. Early detection and aggressive therapy may not always prevent embolisation of pre-existing thrombi, underscoring the limitations of current treatment strategies.