A 32-Year-Old Female Patient Presents With Palpitations

A 32-year-old female patient presented with complaints of palpitations and exercise intolerance for the past 6 months. Palpitations were intermittent and irregular and lasted for hours. She has had New York Heart Association class 1 dyspnea on exertion for the past 6 months. She had been very active and was previously able to run a marathon. There was no history of syncope or chest pain. She had no other chronic medical problems and had no prior cardiac history. She did not smoke or use illicit drugs, and there was no family history of sudden cardiac death. Her vitals were normal. There was no jugular venous distension or pedal edema. Cardiac examination revealed a nondisplaced apical impulse, normal S1 and S2, and no murmurs. The remainder of the physical examination was unremarkable. Complete blood count and basic metabolic profile were within normal reference range. An electrocardiogram revealed normal sinus rhythm without ST-T changes. A transthoracic echocardiogram (Figure 1) was performed, followed by transesophageal echocardiogram (Figure 2).

Figure 1

Figure 2

What is the diagnosis?

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