A 28-year-old man comes to the emergency department with palpitations. For the past 6 months, he has had palpitations that were intermittent and short-lived but seem persistent today. Past medical history is unremarkable. His BMI is 24 kg/m². Cardiac auscultation reveals a II/VI mid-systolic murmur at the left upper sternal border. Electrocardiogram (ECG) shows atrial fibrillation with rapid ventricular response. Echocardiogram shows normal left ventricular size and function and right atrial and ventricular dilation. Which of the following is the most likely diagnosis? A)Atrial septal defect, secundum type B)Dilated cardiomyopathy C)Hypertrophic cardiomyopathy D)Membranous ventricular septal defect E)Patent ductus arteriosus

Question

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Explanation: This patient's clinical presentation - mid-systolic murmur at the left upper sternal border with right atrial and ventricular dilation - is most suggestive of atrial septal defect (ASD) with a left-to-right shunt. ASDs are the second most common congenital heart defect in adults (bicuspid aortic valve is the most common). Many patients remain asymptomatic until adulthood. Those with significant shunt flow may have decreased exercise tolerance (ie, dyspnea and fatigue) and other complications such as pulmonary hypertension, right heart failure, stroke due to paradoxical embolization, and atrial arrhythmias (atrial fibrillation or flutter). Cardiac auscultation in patients with ASD (with large left-to-right shunt and normal pulmonary artery pressure) typically reveals a characteristic wide and fixed splitting of the second heart sound. Patients may also have a mid-systolic ejection murmur over the left upper sternal border resulting from increased flow across the pulmonic valve, and a mid-diastolic rumble resulting from increased flow across the tricuspid valve. Transthoracic echocardiogram can show the abrupt discontinuity of the interatrial septum, with right atrial and ventricular dilation (from volume overload due to left-to-right shunt). (Choice B) Patients with dilated cardiomyopathy can develop atrial or ventricular arrhythmias; however, echocardiogram will typically show a dilated left ventricular (LV) cavity with reduced LV function. (Choice C) Cardiac auscultation in patients with hypertrophic cardiomyopathy (HCM) and LV outflow tract obstruction reveals a harsh crescendo-decrescendo systolic murmur heard best at the apex and lower left sternal border. The murmur increases in intensity with Valsalva and also when rising from a sitting or squatting position. Echocardiogram shows LV hypertrophy (often asymmetric and involving the septum), and increased LV outflow tract gradient. (Choice D) Patients with a ventricular septal defect (VSD) typically have a harsh holosystolic murmur with maximal intensity over the left 3rd and 4th intercostal spaces, often accompanied by a palpable thrill. The presence of a large VSD with significant left-to-right shunt causes right ventricle dilation, along with enlargement of the left ventricle, left atrium, and pulmonary arteries due to volume overload in pulmonary circulation. (Choice E) Patent ductus arteriosus (PDA) causes a characteristic continuous murmur that is heard best in the left infraclavicular area. Moderate to large PDAs with left-to-right shunting cause volume overload of the left atrium and ventricle, resulting in left atrial/ventricle dilation and LV dysfunction. Educational objective: Patients with unexplained right atrial or ventricular dilation should be evaluated for possible atrial septal defect (ASD). Cardiac auscultation in patients with ASD (with large left-to-right shunt and normal pulmonary artery pressure) typically reveals a characteristic wide and fixed splitting of the second heart sound. References: ESC guidelines for the management of grown-up congenital heart disease. (http://www.ncbi.nlm.nih.gov/pubmed/20801927) ACC/AHA 2008 guidelines for the management of adults with congenital heart disease. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. (http://www.ncbi.nlm.nih.gov/pubmed/18997169)

A 28-Year-Old Man Comes to the Emergency Department with Palpitations