A 1-month-old boy is brought to the clinic due to poor feeding. When nursing, he becomes diaphoretic, and for the past week he has fed for only 5 minutes at a time before falling asleep. The patient was born full term via spontaneous vaginal delivery. Today, his weight is 30 g (1 oz) below birth weight. Temperature is 37 C (98.6 F). Blood pressure is normal. Examination shows a thin infant who is sleeping but easily arousable. Cardiac examination reveals tachycardia and a I/VI holosystolic murmur over the left lower sternal border with a diastolic rumble over the cardiac apex. The S2 is prominent. The patient is tachypneic, but the lung fields are clear to auscultation. There is no clubbing, cyanosis, or peripheral edema. Which of the following is the most likely cause of this patient's symptoms?

Question

A 1-month-old boy is brought to the clinic due to poor feeding.  When nursing, he becomes diaphoretic, and for the past week he has fed for only 5 minutes at a time before falling asleep.  The patient was born full term via spontaneous vaginal delivery.  Today, his weight is 30 g (1 oz) below birth weight.  Temperature is 37 C (98.6 F).  Blood pressure is normal.  Examination shows a thin infant who is sleeping but easily arousable.  Cardiac examination reveals tachycardia and a I/VI holosystolic murmur over the left lower sternal border with a diastolic rumble over the cardiac apex.  The S2 is prominent.  The patient is tachypneic, but the lung fields are clear to auscultation.  There is no clubbing, cyanosis, or peripheral edema.  Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

11ec25c8_d63d_e504_bc81_f53aab5c7a75_MD0003_00 This patient's examination is most consistent with a large ventricular septal defect (VSD), a common congenital heart malformation. VSDs range from small and asymptomatic to large with significant left-to-right shunting. The characteristic murmur is holosystolic at the left lower sternal border. murmur is holosystolic Small or moderate VSDs produce II-VI/VI holosystolic murmurs due to turbulence. In contrast, large VSDs are quieter due to lower resistance (and less turbulence) through a larger orifice. An apical diastolic rumble may also be heard from increased flow across the mitral valve (from increased left-to-right shunting across the VSD). As right ventricular pressure increases due to increased flow, the S2 will become more prominent due to increased pressure closing the pulmonary valve. Significant left-to-right shunting results in pulmonary overcirculation and pulmonary hypertension, growth failure, diaphoresis, easy fatigability, and congestive heart failure. Unrepaired, large VSDs result in permanent pulmonary hypertension and Eisenmenger syndrome (cyanosis from right-to-left shunting). Echocardiogram confirms the defect's size and location. Treatment of large VSDs is generally a combination of medications (eg, diuretics) and defect closure. (Choice A) Large atrial septal defects (ASDs) can cause tachypnea. However, ASDs lead to a widened and fixed S2, which is not present in this patient. This characteristic pattern is due to the enlarged right ventricle's prolonged emptying resulting in delayed closure of the pulmonic valve (widened S2), with no difference between inspiration and expiration (fixed S2). (Choice B) Coarctation of the aorta presents with absent or delayed femoral pulses, hypertension in the upper extremities, and low blood pressure in the lower extremities. (Choice C) Mitral stenosis also causes an apical diastolic rumble, but not a holosystolic murmur at the left lower sternal border. (Choice D) Tetralogy of Fallot consists of a VSD, right ventricular outflow tract obstruction (eg, pulmonic stenosis), overriding aorta, and right ventricular hypertrophy. The pulmonary stenosis component causes a harsh, systolic ejection murmur at the left upper sternal border. Tetralogy of Fallot (Choice E) Transposition of the great vessels is characterized by the aorta arising from the right ventricle and a pulmonary artery arising from the left ventricle. This patient's age and lack of cyanosis make this diagnosis unlikely. Transposition of the great vessels Educational objective: Large ventricular septal defects cause growth failure, easy fatigability, and heart failure. They classically produce a holosystolic murmur that is loudest at the left lower sternal border and an apical diastolic rumble due to increased blood flow across the mitral valve. References: Shunt lesions part I: patent ductus arteriosus, atrial septal defect, ventricular septal defect, and atrioventricular septal defect. (http://www.ncbi.nlm.nih.gov/pubmed/27490614) Ventricular septal defect. (http://www.ncbi.nlm.nih.gov/pubmed/25523232)

A 1-Month-Old Boy Is Brought to the Clinic Due to Poor