Snapshot A 15-year-old boy presents to his pediatrician’s office for exercise intolerance. He says he is unable to keep up with his friends during physical activities such as sports, which is new to him. On physical exam, a loud S1 and a fixed split S2 is appreciated during cardiac auscultation. He is sent for a chest radiograph, electrocardiogram, and echocardiogram for further evaluation. Introduction Clinical definition a congenital defect resulting in an opening in the interatrial septum of the heart Epidemiology demographics present at birth risk factors family history exposure to alcohol or cigarette smoking in utero Etiology ostium secundum defect (most common) secundum ASD is often an isolated congenital defect can result in paradoxical emboli from deep venous thromboses ostium primum defect primum ASD is often associated with other cardiac defects Pathogenesis atrial septal defect results from missing tissue rather than unfused tissue left-to-right shunting in the heart, causing increased pulmonary blood flow and alterations in the pulmonary vasculature over time, with severe defects, this eventually results in pulmonary hypertension and Eisenmenger syndrome Associated conditions fetal alcohol syndrome Down syndrome Patau syndrome Prognosis may be asymptomatic or may progress to heart failure mortality highest in infants and adults > 65 years of age Presentation Symptoms usually asymptomatic in childhood patients with large ASDs will develop symptoms later in life exercise intolerance poor weight gain frequent pulmonary infections Physical exam cardiac auscultation loud S1 wide and fixed splitting in S2 parasternal heave midsystolic pulmonary flow murmur (secondary to increased blood flow across the pulmonic valve) Imaging Radiography indication often an initial test to rule out other pathologies views chest findings right heart enlargement increased vascular markings Echocardiography indications diagnostic test most specific test findings ASD Studies Electrocardiogram indication to assess for any arrhythmias findings right atrial enlargement right bundle branch block Making the diagnosis based on clinical presentation and echocardiogram Differential Ventricular septal defect distinguishing factor high-pitched and harsh holosystolic murmur Aortic stenosis distinguishing factor paradoxical splitting of S2 (heard on expiration rather than inspiration) crescendo-decrescendo systolic ejection murmur Innocent/physiologic murmurs distinguishing factor most common murmur of childhood grade < 2 intensity, minimal radiation, musical quality, softer intensity when sitting upright Treatment Management approach mild defects can be left untreated 6 months after procedures, patients must receive prophylaxis for infective endocarditis after dental procedures Medical palivizumab indications infants with symptomatic ASD passive immunization against the respiratory syncytial virus (RSV) Operative percutaneous or catheter device closure indication smaller isolated effects evidence of right heart overload secundum ASD complications arrhythmias thrombosis from the device surgical repair indication shunt ratio > 1.5:1 primum ASD evidence of right heart overload Complications Heart failure Eisenmenger syndrome Paradoxical emboli venous emboli may run through ASD to become systemic arterial emboli