Ventricular Septal Defect (VSD) is the Most Common Congenital Heart Disease Associated with Infective Endocarditis
The most common congenital heart disease associated with infective endocarditis (IE) is ventricular septal defect (VSD). According to the ACC/AHA guidelines, VSD represents 24% of IE cases in patients with unoperated or palliated congenital heart disease, making it the leading congenital cardiac lesion predisposing to infective endocarditis 1.
Epidemiology and Risk Factors
VSD carries a substantially increased risk of IE compared to other congenital heart defects for several reasons:
- The risk of IE in patients with VSD is 11-15 fold higher than in the general population, with an incidence of approximately 1.90/1000 patient-years in unrepaired VSDs 2
- For VSDs, the risk of IE before surgical closure is more than twice that for surgically closed VSDs 1
- Even after surgical repair, residual VSD leaks increase IE risk - at least 22% of patients with surgically repaired VSDs who developed IE were known to have residual VSD leaks 1
- The presence of aortic regurgitation independently increases the risk of IE in patients with VSD 1
Pathophysiology of IE in VSD
The mechanism of IE development in VSD involves:
- High-velocity jets of blood through the VSD causing endothelial damage
- Vegetations typically form where the high-velocity left-to-right jet impacts on the right side of the heart (tricuspid valve septal leaflet or mural right ventricular endocardium) 1
- Damaged endothelium leads to platelet and fibrin deposition, creating nonbacterial thrombotic endocarditis that serves as a nidus for bacterial colonization 1
Comparison with Other Congenital Heart Defects
When comparing the prevalence of IE across different congenital heart defects:
- VSD: 24% of IE cases in unoperated/palliated CHD 1
- Left ventricular outflow tract lesions: 17% 1
- Tetralogy of Fallot: 19% (in repaired cases) 1
- Atrioventricular defects: 14% (in repaired cases) 1
Notably, IE is rarely reported in atrial septal defect (ASD), closed VSD without residual leak, isolated pulmonary stenosis, or unrepaired Ebstein's anomaly 1.
Microbiology
The most common causative organisms in IE associated with congenital heart disease are:
Prevention and Management Considerations
Prevention of IE in patients with VSD includes:
- Good dental health and skin hygiene 4
- Antibiotic prophylaxis is recommended for high-risk patients undergoing oral mucosal procedures, particularly those with:
- Unrepaired cyanotic CHD
- Repaired CHD with prosthetic material during the first 6 months after procedure
- Repaired CHD with residual defects adjacent to prosthetic patches 1
Clinical Pearls and Pitfalls
- Important pitfall: Clinical presentation of IE in VSD can be atypical, leading to delayed diagnosis - the delay from symptom onset to diagnosis can be as long as 60 days in unoperated/palliated CHD 1
- Key consideration: Echocardiography plays a vital role in diagnosis, particularly in cases with atypical presentation 5
- Critical warning sign: The presence of heart failure at diagnosis of IE is an independent factor associated with mortality 3
- Management challenge: Surgery is required to treat IE in approximately 47% of patients with CHD 3
In conclusion, VSD (answer A) is the correct answer as the most common congenital heart disease associated with infective endocarditis, with significantly higher prevalence than ASD, TOF, or PDA.