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Difficulty: EasyPediatric Cardiovascular Disorders

A 3-month-old girl is brought to the clinic by her parents because they are concerned about her feeding. The parents report that she tires easily, breaks into a sweat during feedings, and takes over 45 minutes to finish a 3-ounce bottle. Her weight has dropped from the 50th percentile at birth to the 5th percentile. Vital signs show a heart rate of 160/min and a respiratory rate of 65/min. Physical examination reveals a harsh, holosystolic murmur at the left lower sternal border with a palpable thrill. The liver edge is palpable 3 cm below the right costal margin, and bilateral fine crackles are heard on lung auscultation. Which of the following is the primary pathophysiological mechanism underlying this patient's current symptoms?

  1. Pulmonary volume overload due to a left-to-right intracardiac shuntAnswer
  2. B
    Reversible airway hyperreactivity and bronchospasm
  3. C
    Benign variation in normal pediatric growth and development
  4. D
    Systemic inflammatory reaction to a live-attenuated mucosal vaccine
  5. E
    Exudative alveolar consolidation from a bacterial pathogen

Answer

Pulmonary volume overload due to a left-to-right intracardiac shunt
The patient's presentation of poor feeding, failure to thrive, diaphoresis during feeds, tachypnea, and hepatomegaly, combined with a harsh holosystolic murmur at the left lower sternal border, is the classic clinical picture of a Ventricular Septal Defect (VSD) complicated by congestive heart failure. Because systemic vascular resistance is higher than pulmonary vascular resistance, a VSD creates a left-to-right intracardiac shunt. This shunting leads to excessive blood flow into the pulmonary circulation (volume overload), resulting in pulmonary edema (manifesting as tachypnea and crackles) and right-sided volume overload leading to systemic venous congestion (manifesting as hepatomegaly).

Step-by-Step Solution

1
Identify the key clinical findings in the physical examination.
Harsh holosystolic murmur at the left lower sternal border with a palpable thrill.
This specific murmur is the hallmark sign of a Ventricular Septal Defect (VSD).
2
Analyze the systemic symptoms and signs.
Diaphoresis during feeds, failure to thrive (dropping weight percentiles), tachypnea, crackles, and hepatomegaly.
These findings indicate congestive heart failure, which is the primary complication of a hemodynamically significant VSD in infancy.
3
Determine the pathophysiological mechanism linking the defect to the heart failure symptoms.
A VSD allows blood to flow from the high-pressure left ventricle to the lower-pressure right ventricle.
This left-to-right shunt leads to pulmonary overcirculation, pulmonary edema (crackles), and eventual right-sided volume overload (hepatomegaly).

Key Concept

Ventricular Septal Defect (VSD) with Heart Failure
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Topics

Pediatric Cardiovascular Disorders

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