A 20-year-old man comes to the office due to occasional palpitations. He describes them as "skipped beats." He has no chest pain or shortness of breath. Medical history is unremarkable. On physical examination, he has wide, fixed splitting of the second heart sound (S2). No murmurs are heard. Chest x-ray reveals enlargement of the right heart contour. Echocardiogram is consistent with a congenital heart defect. Repair of this patient's congenital disease is aimed at preventing irreversible changes to which of the following?

Question

A 20-year-old man comes to the office due to occasional palpitations.  He describes them as "skipped beats."  He has no chest pain or shortness of breath.  Medical history is unremarkable.  On physical examination, he has wide, fixed splitting of the second heart sound (S2).  No murmurs are heard.  Chest x-ray reveals enlargement of the right heart contour.  Echocardiogram is consistent with a congenital heart defect.  Repair of this patient's congenital disease is aimed at preventing irreversible changes to which of the following?

Quizplus · Accepted Answer

11ec160b_3a7f_ad88_9249_8dd1ffc55513_MD0001_00 This patient has wide, fixed splitting of the second heart sound (S2), a characteristic auscultatory finding of an atrial septal defect (ASD). ASD is characterized by left-to-right shunting due to the higher pressure in the left atrium compared to the right atrium. The resulting increase in blood flow causes right-sided volume overload, leading to delayed closure of the pulmonic valve (wide S2) that does not vary with respirations (fixed S2). Right-sided volume overload leads to right atrial and ventricular enlargement, which may be seen as an enlarged right heart contour on chest x-ray. Atrial arrythmia (eg, atrial fibrillation), which is likely causing this patient's palpitations, is a common complication of atrial enlargement. With longstanding ASD, the increased blood flow through the pulmonary circulation can result in laminated medial hypertrophy of the pulmonary arteries. This increases pulmonary vascular resistance (PVR) and causes pulmonary hypertension. Eventually, PVR can exceed systemic vascular resistance, reversing the direction of the intracardiac shunt and creating net right-to-left flow through the ASD. This reversal, known as Eisenmenger syndrome, allows blood to bypass the pulmonary circulation and can cause adult-onset cyanosis, clubbing, and polycythemia. The pulmonary vascular remodeling is irreversible. Once Eisenmenger syndrome is present, closure of the ASD is not possible because it can increase right-sided pressures even further and lead to acute right-sided heart failure. Therefore, early closure of a hemodynamically significant ASD is needed to avoid irreversible changes to the pulmonary vessels. (Choices A, B, and C) ASD does not typically cause volume overload or enlargement of the left-sided heart chambers because excess blood flow is shunted to the right atrium before reaching the left ventricle. The coronary vessels are also not typically affected. (Choice E) ASD causes right atrial dilation. However, these changes are mostly reversible because, unlike in the pulmonary arteries and often the right ventricle, significant muscular hypertrophy of the right atrium does not take place. Educational objective: Atrial septal defects cause wide, fixed splitting of the second heart sound due to right-sided volume overload from left-to-right shunting. Uncorrected defects can lead to irreversible medial hypertrophy of the pulmonary arteries with pulmonary hypertension and reversal to right-to-left shunting (ie, Eisenmenger syndrome). __________ References: Atrial septal defect (ASD). (http://www.ncbi.nlm.nih.gov/pubmed/30571061)

A 20-Year-Old Man Comes to the Office Due to Occasional