Left Atrial Thrombus in Rheumatic Mitral Stenosis: A Case of Therapeutic International Normalized Ratio Failure

BACKGROUND: Atrial fibrillation or flutter in rheumatic mitral stenosis (MS) increases left atrial appendage (LAA) thrombus risk despite therapeutic anticoagulation. CASE SUMMARY: A 72-year-old woman on warfarin with moderate MS and atrial flutter presented with dyspnea. Transesophageal echocardiogram (TEE) showed a large LAA thrombus despite an international normalized ratio >2.5. Cardioversion was deferred, and the international normalized ratio target was raised to a range of 2.5 to 3.5. TAKE-HOME MESSAGES: While cardioversion can be considered in patients with uninterrupted anticoagulation without TEE, those with rheumatic MS are at high risk of LAA and LA thrombus and should undergo TEE before the procedure. Further research is needed to explore whether LAA thrombus warrants surgical intervention for rheumatic MS.