This patient's presentation of a systolic murmur with a widely split, fixed S2 and the above echocardiogram findings is consistent with a diagnosis of atrial septal defect (ASD). Patients with ASD are at risk of developing pulmonary hypertension due to the chronic left-to-right intracardiac shunt.
Whether or not a patient is symptomatic or develops complications from an ASD is often dependent on the size of the defect. In the many cases, initially the left-to-right shunting of the blood between the atria through the defect leads to an asymptomatic increase in blood flow to the pulmonary vasculature. Over time and with increasing blood flow, the pulmonary vessels begin to stiffen, resulting in pulmonary hypertension. The elevated pulmonary vasculature pressures lead to increased right-sided heart pressures and eventually reversal of the shunt to a right-to-left direction. Although rare, this shunt reversal, called Eisenmenger's syndrome, is a late and serious complication of an untreated ASD.
McConnell et al. review the differentiation of innocent from pathologic heart murmurs in pediatric patients. Pathologic systolic heart murmurs in children are most commonly caused by atrial or ventricular septal defects, pulmonary or aortic outflow abnormalities, or a patent ductus arteriosus. Physical exam findings of an ASD are often subtle and easily confused with an innocent murmur. The murmur of ASD differs from that of an innocent murmur, in that an ASD is associated with increased precordial activity, a widely split and fixed S2, a systolic flow murmur at the left upper sternal border that does not change with position, and possibly an inflow diastolic rumble in the tricuspid valve area.
Geva et al. review the complications that may stem from ASDs. For patients with ASDs, exercise intolerance, atrial arrhythmias, right ventricular dysfunction, and pulmonary hypertension are all complications that increase in frequency and severity with increasing age. Adults with untreated ASDs have a reduced life expectancy. When surgical closure of an ASD is achieved before age 25, patients have a normal life expectancy. In addition to a untreated defect in an adult, female gender also is associated with an increased risk of developing pulmonary vascular disease as a result of the ASD.
Illustration A shows the altered anatomy and blood flow associated with an ASD. Illustration B is an echocardiogram showing an atrial septal defect (arrow) with Doppler demonstrating a left-to-right shunt. Illustration C shows the development of Eisemenger's syndrome; although this illustration shows a ventricular septal defect instead of an ASD, the principles of flow reversal due to increasing pulmonary vascular resistance hold true for both cases.
Answer 1: While an ASD is an intracardiac shunt, an AV fistula is an extracardiac, peripheral shunt. ASD does not predispose to the development of an arteriovenous fistula.
Answer 2: ASD initially results in a left-to-right shunt that increases flow through the pulmonary valve. ASD does not predispose to the development of pulmonic valve stenosis. If pulmonary stenosis and ASD are coexistent, this might act to increase the right heart outflow obstruction and thereby somewhat protect the pulmonary bed vasculature from increased stress/blood flow.
Answer 3: This patient is not at elevated risk of coronary artery disease based on having an ASD.
Answer 5: Aortic root dilation is not a known complication of an ASD.
McConnell ME, Adkins SB 3rd, Hannon DW. Heart murmurs in pediatric patients: when do you refer? Am Fam Physician. 1999 Aug;60(2):558-65.
PMID:10465230 (Link to Abstract)
Geva T, Martins JD, Wald RM. Atrial septal defects. Lancet. 2014 May 31;383(9932):1921-32.
PMID:24725467 (Link to Abstract)