Preserved Ejection Fraction Despite Progressive Functional Decline in a Patient With Single-Ventricle Physiology Without Documented Successful Surgical Palliation.

Seventh-decade survival with single-ventricle congenital heart disease (CHD) without documented successful surgical palliation is exceedingly rare. The prognostic value of ejection fraction (EF) in this population remains poorly characterized, and validated staging tools are absent from current guidelines. We report a 62-year-old man with complex single-ventricle CHD who survived without documented successful surgical palliation and had a common atrium, systemic right ventricle, and severe common atrioventricular valve regurgitation. Despite a preserved EF of 55-60%, he was NYHA Class IV with chronic hypoxemia. Four hospitalizations over 26 months were driven by atrial fibrillation with rapid ventricular response and community-acquired pneumonia; medication nonadherence was a documented precipitant in at least two admissions. He died during the fourth admission of refractory hypoxemic respiratory failure. In this patient, preserved EF did not reflect functional reserve in the context of single-ventricle physiology. AV valve regurgitation, obligate right-to-left shunting, and preload dependence may collectively decouple systolic function from effective cardiac output. Arrhythmia and infection were the dominant modifiable tipping points in this case. This case illustrates the potential inadequacy of EF-centered staging and the critical role of medication adherence, arrhythmia management, and infection prevention in deferring irreversible functional decline.