What are the expected consequences of a 10 mm ventricular septal defect (VSD) in a 12-year-old boy with no other congenital defects?

Expected Consequences of a 10 mm Ventricular Septal Defect in a 12-Year-Old Boy

In a 12-year-old boy with a 10 mm VSD causing some exercise limitation but no heart failure, you would expect right ventricular hypertrophy, thickened pulmonary artery walls, predominantly left-to-right blood flow, absence of cyanosis, and an increased risk of subacute bacterial endocarditis.

Hemodynamic Consequences and Shunt Direction

Statement 1: Hypertrophy of Right Ventricle - TRUE

• Right ventricular hypertrophy develops in response to the left-to-right shunt and increased pulmonary blood flow. 1
• The 10 mm defect allows free communication between ventricles, creating RV volume overload from the left-to-right shunt 1
• The presence of exercise limitation without heart failure suggests moderate hemodynamic significance with compensatory RV hypertrophy 1

Statement 2: Abnormally Thick Wall to the Pulmonary Artery - TRUE

• Chronic increased pulmonary blood flow from the left-to-right shunt causes pulmonary arterial medial thickening. 2
• Large VSDs with significant left-to-right shunts lead to pulmonary vascular changes, including thickening of the pulmonary artery walls 1
• This represents early pulmonary vascular remodeling in response to increased flow, though not yet Eisenmenger syndrome 1

Statement 3: Flow Predominantly Right-to-Left - FALSE

• The shunt direction in this patient is predominantly left-to-right, not right-to-left. 1
• The absence of cyanosis and heart failure indicates the patient has not developed Eisenmenger syndrome with shunt reversal 1
• Right-to-left shunting only occurs when severe pulmonary vascular disease develops, causing pulmonary vascular resistance to exceed systemic resistance 1
• The direction and magnitude of shunt are determined by pulmonary vascular resistance, defect size, and ventricular function 1

Statement 4: Absence of Cyanosis - TRUE

• Cyanosis is absent because the shunt remains predominantly left-to-right. 1
• Cyanosis only develops with Eisenmenger syndrome when shunt reversal occurs (right-to-left shunting) 1
• The patient's clinical presentation—exercise limitation without heart failure or cyanosis—is consistent with a moderate left-to-right shunt without pulmonary vascular disease 1

Statement 5: Risk of Subacute Bacterial Endocarditis - TRUE

• All patients with VSDs have an increased risk of endocarditis requiring prophylaxis. 1
• Endocarditis occurs in up to 2 per 1000 patient-years in VSD patients, which is six times higher than the normal population 1
• European guidelines recommend endocarditis prophylaxis in all patients with unrepaired VSDs 1
• Even small residual VSDs carry this risk, though the rate in children is relatively low (0.9‰ in one large cohort) 3

Clinical Context and Natural History

• This 10 mm VSD represents a moderate-to-large defect with hemodynamic significance, evidenced by exercise limitation 1
• The patient has not yet developed severe pulmonary vascular disease (Eisenmenger syndrome), as indicated by absence of cyanosis and heart failure 1
• Left ventricular volume overload from the left-to-right shunt is the primary hemodynamic consequence requiring monitoring for potential surgical intervention 1
• Additional potential complications include development of aortic regurgitation, double-chambered right ventricle, and arrhythmias, though these are less common 1

Summary of True/False Answers

1. Hypertrophy of right ventricle: TRUE
2. Abnormally thick wall to pulmonary artery: TRUE
3. Flow predominantly right-to-left: FALSE
4. Absence of cyanosis: TRUE
5. Risk of subacute bacterial endocarditis: TRUE