Congenital Heart Disease and Infective Endocarditis Risk
A 10-year-old boy attends a pediatric cardiology clinic after completing 4 weeks of intravenous antibiotics for culture-positive infective endocarditis caused by viridans group streptococci, which followed a dental extraction performed 3 weeks before his illness. He was born with an unrepaired congenital cardiac defect detected at 6 months of age. Which unoperated congenital lesion is most commonly associated with infective endocarditis?
- A.Secundum atrial septal defect
- B.Ventricular septal defectCorrect
- C.Patent ductus arteriosus
- D.Coarctation of the aorta
Explanation
Ventricular septal defect is the single most common congenital lesion underlying infective endocarditis in children, both because it is the most frequent congenital heart defect and because it generates the high-velocity turbulent jet that damages endocardium. A restrictive defect produces a large pressure gradient between the left and right ventricles, and the resulting jet strikes the right ventricular septal surface or the tricuspid apparatus, denuding endothelium and exposing subendothelial collagen. Platelets and fibrin then deposit to form a sterile nonbacterial thrombotic vegetation, which is seeded during transient bacteremia such as that following dental extraction, most often by viridans group streptococci. This lesion-plus-turbulence model explains why endocarditis risk correlates with the presence of a pressure gradient rather than with defect size alone, and why a small restrictive ventricular septal defect can carry more risk than a large non-restrictive one. Secundum atrial septal defect is a low-pressure, low-velocity shunt and carries essentially no endocarditis risk, which is why it is the classic exception among congenital lesions. Patent ductus arteriosus and coarctation of the aorta do create turbulence and can be complicated by endarteritis or endocarditis, but both are far less common overall than ventricular septal defect. Current guidelines restrict antibiotic prophylaxis before dental procedures to the highest-risk groups: prosthetic valves or prosthetic material used in valve repair, previous infective endocarditis, unrepaired cyanotic congenital heart disease, and repaired defects with residual shunt adjacent to prosthetic material or within 6 months of repair. Because this child has had endocarditis before, he now qualifies for prophylaxis regardless of his underlying lesion.
Why each option
- A.
- Secundum atrial septal defect is a low-pressure shunt without a damaging jet and is the classic congenital lesion that does not predispose to endocarditis.
- B.
- Correct. Ventricular septal defect is the commonest congenital heart lesion and its high-velocity jet makes it the commonest substrate for infective endocarditis in children.
- C.
- Patent ductus arteriosus can cause endarteritis but is far less common than ventricular septal defect as an underlying lesion.
- D.
- Coarctation of the aorta carries some risk of endarteritis at the coarctation site but accounts for a small minority of cases.
Reference: Nelson Textbook of Pediatrics, 22nd ed., 2024, Infective Endocarditis; AHA Scientific Statement on Prevention of Infective Endocarditis, 2021 update
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