An Unusual Cause of Functional Mitral Stenosis: A Left Atrial Intimal Sarcoma.

Primary cardiac tumors are rare, with an incidence of <0.1% in postmortem series; sarcomas comprise 75% of these. Cardiac sarcomas may be life-threatening at the time of presentation. We describe a left atrial intimal sarcoma presenting with constitutional symptoms, obstructive shock, and systemic emboli, and treated with proton beam therapy. (Level of Difficulty: Intermediate.).