Cardiovascular · Year 1 · from Cardiovascular
Case 2: Ventricular Septal Defect - Left-to-Right Shunt with Heart Failure
Clinical Image
Source: Wikimedia Commons - VSD diagram - CC BY-SA 3.0
Patient Presentation
A 6-week-old female infant is brought to the pediatrician for poor feeding and failure to thrive. The mother reports that the baby takes a very long time to finish bottles (45-60 minutes), sweats during feeding, and breathes rapidly. She has gained only 300 grams since birth. A heart murmur was noted at the 2-week check-up.
Demographics
- Age: 6 weeks
- Sex: Female
- Birth History: Term, uncomplicated vaginal delivery, birth weight 3.2 kg
- Current weight: 3.5 kg (below 3rd percentile)
Chief Complaint
Poor feeding, diaphoresis with feeds, and failure to thrive
Physical Examination
- Heart rate: 160 bpm
- Respiratory rate: 60/min
- Oxygen saturation: 98% on room air
- Weight: 3.5 kg (below 3rd percentile)
- General: Tachypneic, mild subcostal retractions, diaphoretic
- Cardiovascular: Hyperdynamic precordium, grade 4/6 harsh holosystolic murmur at left lower sternal border with thrill, loud P2, diastolic rumble at apex
- Lungs: Bilateral crackles
- Liver: 3 cm below costal margin (hepatomegaly)
Workup
- Chest X-ray: Cardiomegaly, increased pulmonary vascular markings, pulmonary edema
- ECG: Biventricular hypertrophy, left atrial enlargement
- Echocardiography: Large (8 mm) perimembranous VSD with left-to-right shunt, dilated left atrium and left ventricle, elevated pulmonary artery pressure (estimated PASP 55 mmHg)
- BNP: Elevated (heart failure marker)
Diagnosis
Large Ventricular Septal Defect with Congestive Heart Failure
Treatment
- Diuretics (furosemide) to manage pulmonary congestion
- ACE inhibitor (captopril) for afterload reduction
- High-calorie formula to maximize nutrition
- Close monitoring of weight gain and respiratory status
- Surgical VSD closure indicated due to:
- Heart failure symptoms
- Failure to thrive
- Elevated pulmonary artery pressures
- Surgery typically performed at 3-6 months if medical management fails
Physiological Principles Demonstrated
- Left-to-right shunt physiology: When a VSD is large, blood flows from the higher-pressure left ventricle to the lower-pressure right ventricle during systole, causing volume overload of the pulmonary circulation.
- Pulmonary vascular resistance and shunt timing: In the newborn period, PVR is still elevated, limiting the shunt. As PVR falls normally over weeks, the shunt increases, and symptoms appear at 4-8 weeks of age.
- Heart failure mechanism: Excessive pulmonary blood flow causes pulmonary venous congestion. The left heart must handle both systemic output and shunted blood, leading to volume overload and failure.
- Eisenmenger physiology prevention: Early repair prevents irreversible pulmonary vascular disease that would lead to shunt reversal (Eisenmenger syndrome).