A 4-year-old boy with Down syndrome presents to clinic with progressive exertional dyspnea and fatigue over the past 6 months. His mother reports he tires easily compared to his siblings and has difficulty keeping up during play. Physical examination reveals a systolic murmur best heard at the left lower sternal border, a fixed split S2, and mild hepatomegaly. Chest X-ray demonstrates cardiomegaly with increased pulmonary vascular markings. Echocardiography shows an ostium primum atrial septal defect (ASD) with a left-to-right shunt and signs of pulmonary overcirculation. Which of the following complications is this patient at highest risk of developing if the defect is not closed?

1. A)Mitral stenosis from rheumatic heart disease
2. B)Acute bacterial endocarditis affecting the mitral valve
3. C)Spontaneous closure of the defect leading to normalization of pulmonary pressures
4. D)Progressive pulmonary hypertension with eventual reversal of shunt flow (Eisenmenger syndrome)GABARITO
5. E)Aortic root dilation and acute aortic dissection