A 2-month-old infant with pulmonary atresia, ventricular septal defect, and major aortopulmonary collateral arteries developed an aneurysmatic elongation of the tricuspid valve tissue that partially closed and dynamically protruded through the ventricular septal defect, beneath the aortic valve. This rare finding caused dynamic left ventricle outflow tract obstruction and recurrent cardiac arrests and ultimately required surgical intervention.