A rare congenital cardiovascular disorder characterized by the failure of the embryologic structure truncus arteriosus to divide into the aorta and pulmonary trunk. It results in the presence of a single vessel instead of two vessels leading out of the heart. Clinical signs and symptoms include cyanosis that is present at birth, poor growth, dyspnea, tachypnea, arrhythmia, cardiomegaly, and heart failure. If it is not surgically repaired, it leads to death.