A rare case with Uhl's anomaly whose hemodynamics largely dependent on right atrial hyper-contraction and a patent foramen ovale - A "double-edged sword" of ventricularized right atrium.

We report the case of a 31-year-old man with Uhl's anomaly. Echocardiography revealed severely enlarged nonfunctioning right ventricle and unusual findings of the premature opening of the pulmonary valve along with substantial forward flow during late-diastole, indicating that pulmonary circulation was largely dependent on compensatory right atrial contraction. Moreover, right-to-left shunt through the patent foramen ovale (PFO) achieved systemic circulation at the expense of severe hypoxia. During accelerated idioventricular rhythm (AIVR) accompanied by ventriculo-atrial (VA) conduction, hypoxemia deteriorated further because of an increased right-to-left shunt through the PFO. We report the case of an adult with Uhl's anomaly whose hemodynamics was largely dependent on the ventricularized right atrium and PFO. Although the unique hemodynamics contributed to his survival into adulthood, detrimental aspects manifested themselves during AIVR with VA conduction like a "double-edged sword." <Learning objective: Uhl's anomaly is a rare congenital heart disease, characterized by the absence of right ventricular myocardium. Thus, once diagnosed with Uhl's anomaly in childhood, patients rarely survive to attain adulthood owing to progressive right ventricular deterioration. Although this patient could survive into adulthood by virtue of the "ventricularized right atrium" and the presence of a patent foramen ovale, these unique hemodynamics could be a "double-edged sword" during repeated accelerated idioventricular rhythm with ventriculo-atrial conduction.>.