Systemic embolism occurring in patients with mitral stenosis is often devastating. Unfortunately, predicting the risk for systemic embolism in patients with mitral stenosis and sinus rhythm is often imprecise. Faced with this uncertainty, clinicians frequently institute empirical anticoagulant therapy in patients with clinically significant mitral stenosis and sinus rhythm. Chiang and colleagues [1] are therefore to be commended on their prospective study on predictors of systemic embolism in patients with mitral stenosis. However, important questions still remain. The authors identified left atrial thrombus as one predictor of systemic embolism in patients in sinus rhythm. They report that 30.5% of their patients had a left atrial thrombus detected by transthoracic echocardiography (TTE). Transthoracic echocardiography is relatively insensitive for detection of left atrial appendage thrombi, and transesophageal echocardiography (TEE) significantly improves the detection rate. What were the rates of detection of left atrial and left atrial appendage thrombi by TEE in the subgroup of patients who underwent TEE at baseline in the current study? Are the authors implying that TTE is sufficient to detect left atrial thrombi and left atrial appendage thrombi, or should TEE be performed in all patients with significant mitral stenosis who are in sinus rhythm? Because most systemic emboli are thought to originate from left atrial thrombi and left atrial appendage thrombi, why was the presence of left atrial thrombi not predictive of emboli in patients with atrial fibrillation? Answers to these questions will facilitate management decisions in patients with mitral stenosis and sinus rhythm.