A 6-month-old boy is brought to the office for a routine checkup. He has met all expected developmental milestones, and all of his vaccinations are up to date. On physical examination, the patient's peripheral pulses are somewhat accentuated. Cardiac auscultation findings at the left sternal border are given below. What is the most likely diagnosis in this patient?

Question

A 6-month-old boy is brought to the office for a routine checkup.  He has met all expected developmental milestones, and all of his vaccinations are up to date.  On physical examination, the patient's peripheral pulses are somewhat accentuated.  Cardiac auscultation findings at the left sternal border are given below.  What is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

This patient's auscultation findings reveal a continuous murmur with maximal intensity at S2, which is characteristic of a patent ductus arteriosus (PDA). The murmur is caused by continuous blood flow through the PDA (because aortic pressure exceeds pulmonary arterial pressure throughout the cardiac cycle). It is usually best heard at the left infraclavicular or posterior interscapular region. Its maximal intensity is typically at S2, when pressure in the aorta is at its peak. continuous murmur best heard The symptoms caused by a PDA are variable depending on its size and the resulting degree of left-to-right shunting from the aorta to the pulmonary arterial trunk. A small PDA is often asymptomatic and detected incidentally via cardiac auscultation whereas a larger PDA may present with respiratory distress, poor feeding, and/or retracted growth within the first year of life. Relatively large PDAs can cause high cardiac output and hyperdynamic circulation (eg, accentuated peripheral pulses) due to the left ventricle compensating for the significant reduction in systemic vascular resistance created by the PDA shunt. The resulting overcirculation of the lungs and left side of the heart can eventually lead to left ventricular failure. overcirculation (Choice A) Endocardial cushion defects are common with Down syndrome (eg, septum primum defects) and can cause an atrial septal defect (ASD) often with involvement of the atrioventricular valves (eg, causing mitral or tricuspid regurgitation). These defects do not cause a continuous murmur. The typical murmur of an ASD is not caused by blood flow through the defect itself (as there is a low-pressure difference between the atria) but results from right-sided volume overload with increased blood flow across the pulmonic valve (ie, pulmonic flow murmur). ASD (Choice B) Mitral valve prolapse classically causes a midsystolic click followed by a late systolic murmur of mitral regurgitation (best heard at the cardiac apex). The timing of the click (and murmur) varies with changes in left ventricular blood volume. Mitral valve prolapse timing of the click (Choice D) Williams syndrome is commonly associated with supravalvular aortic stenosis (due to narrowing of the proximal aorta), which creates a crescendo-decrescendo systolic murmur similar to that of valvular aortic stenosis. aortic stenosis Educational objective: A patent ductus arteriosus causes a continuous flow murmur due to constant movement of blood from the high-pressure aorta to the low-pressure pulmonary arterial trunk.

A 6-Month-Old Boy Is Brought to the Office for a Routine