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A 12-month-old boy is brought to the pediatrician by his parents for an upper respiratory infection. Temperature is 38.3 C (101 F), blood pressure is 92/45 mm Hg, pulse is 110/min, and respirations are 25/min. Physical examination shows erythema and swelling of the nasal mucosa and nasal discharge. Cardiac auscultation findings at the left sternal border are given below. Pulses are equal in all 4 extremities. The remainder of the examination is unremarkable. Which of the following is the most likely diagnosis?
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This patient's auscultation findings reveal a continuous murmur with maximal intensity at S2 (when pressure in the aorta is at a peak), which is characteristic of a patent ductus arteriosus (PDA). The murmur is usually best heard at the left infraclavicular or posterior interscapular region. The symptoms caused by a PDA are variable depending on its size and resulting degree of left-to-right shunting from the aorta to the pulmonary arterial trunk. Because this patient was asymptomatic and the PDA was detected incidentally, he most likely has a small PDA. Larger PDAs typically present with respiratory distress, poor feeding, and/or retracted growth during the first year of life. Patients at greatest risk of PDA are those born prematurely and those with cyanotic congenital heart disease.
(Choice A) Aortic coarctation is usually associated with a systolic murmur best heard at the left infraclavicular area. It can sometimes cause a continuous murmur due to blood flow through large collateral vessels, but this is a much less common cause of continuous murmur than a PDA. In addition, equal pulses in the upper and lower extremities make aortic coarctation unlikely.
(Choice B) An ascending aortic aneurysm is often associated with aortic regurgitation, which causes a decrescendo early diastolic murmur as opposed to a continuous murmur. Aortic regurgitation resulting from aortic root (as opposed to valvular) pathology is typically best heard at the right upper sternal border.
(Choice C) An atrial septal defect typically causes a faint, crescendo-decrescendo systolic murmur (best heard at the left upper sternal border) caused by increased blood flow through the pulmonic valve (ie, pulmonic flow murmur). Splitting of S2 is wide and fixed.
(Choice D) 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.
Educational objective:
A patent ductus arteriosus (PDA) causes a continuous murmur best heard at the left infraclavicular or posterior interscapular region. A small PDA is often asymptomatic and detected incidentally during routine cardiac auscultation. It most commonly occurs in patients born prematurely and those with cyanotic congenital heart disease.