A 10-week-old male infant is brought to the pediatric emergency department by his parents … — USMLE Step 2 CK

A $10$ -week-old male infant is brought to the pediatric emergency department by his parents due to a $3$ -day history of rapid breathing, poor feeding, and increased fussiness. The parents report that the infant takes twice as long to finish a bottle and frequently stops to catch his breath while sweating profusely over his forehead. He has had a mild cough but no fever. Medical history is notable for an uncomplicated full-term birth. A cardiac murmur was mentioned at his $1$ -month well-child visit, but the family missed the follow-up appointment. Temperature is $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), pulse is $168/\text{min}$ , respiratory rate is $68/\text{min}$ , and blood pressure is $85/50\text{ mmHg}$ . Pulse oximetry shows $94\%$ on room air. Physical examination reveals an infant in moderate respiratory distress with intercostal retractions. Lung auscultation reveals diffuse bilateral wheezes and fine crackles at the bases. Cardiovascular examination shows a hyperactive precordium, a loud S2, and a grade $3/6$ harsh holosystolic murmur at the left lower sternal border. The liver edge is palpated $3.5\text{ cm}$ below the right costal margin. Which of the following is the most appropriate next step in the management of this patient?

Transthoracic echocardiographyAnswer
B
Administration of nebulized albuterol
C
Administration of intravenous methylprednisolone
D
Empiric administration of intravenous ceftriaxone
E
Reassurance and scheduling a developmental assessment

Answer

Transthoracic echocardiography is the most appropriate next step to diagnose and confirm the structural cause of the patient's acute congestive heart failure.

This infant is presenting with classic signs of acute congestive heart failure (CHF) secondary to a congenital heart defect, most likely a ventricular septal defect (VSD). Hallmarks of infant CHF include tachypnea, poor feeding, diaphoresis with exertion (such as feeding), failure to thrive, and hepatomegaly due to venous congestion. Furthermore, the grade

3/6

harsh holosystolic murmur at the left lower sternal border is highly specific for a VSD. Infants with large VSDs often do not present at birth because their pulmonary vascular resistance (PVR) is still physiologically elevated, restricting the left-to-right shunt. As PVR naturally falls over the first

2

3

months of life, the shunt increases, leading to pulmonary overcirculation and subsequent heart failure. The most appropriate next step in management is a transthoracic echocardiogram to visualize the defect, assess the direction and magnitude of the shunt, and evaluate overall cardiac function.

Step-by-Step Solution

Evaluate the patient's constellation of clinical signs and symptoms.

Identify the clinical syndrome as acute congestive heart failure rather than a primary respiratory illness.

The combination of tachypnea, diaphoresis during exertion (feeding), crackles, wheezing, and significant hepatomegaly strongly points to right-sided volume overload and pulmonary edema.

Correlate the cardiovascular exam findings with the infant's age.

Suspect a significant left-to-right cardiac shunt, most likely a ventricular septal defect (VSD).

A harsh holosystolic murmur at the left lower sternal border is characteristic of a VSD. Symptoms typically manifest at 6 to 10 weeks of life when normal physiologic pulmonary vascular resistance drops, allowing for a massive left-to-right shunt.

Determine the optimal next step in management.

Select transthoracic echocardiography.

Echocardiography is the gold standard, non-invasive imaging modality required to definitively define the cardiac anatomy, quantify the shunt, and guide subsequent medical and surgical interventions.

Key Concept

Clinical presentation and initial diagnostic workup of pediatric congestive heart failure secondary to a left-to-right shunt.

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