This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Infective Endocarditis, Subject name: Medicine
The risk of developing infective endocarditis is the least in a patient with: 
Select and explain. 
A. Small ventricular septal defect, B. Severe aortic regurgitation., C. Severe mitral regurgitation, D. Large atrial septal defect.
D: Large atrial septal defect.
Answer: D: Large atrial septal defect. 
Explanation: Ans. is 'd' i.e. Large atrial septal defect Infective endocarditis usually occurs in C. H. D.'s where Blood flow occurs d/t high pressure gradient e.g. Aortic Stenosis or V.S.D. The high pressure jet of blood hits the endocardium and endothelium damaging them. The infection generally starts at this lesion.In Atrial septal defect the blood flow occurs at very low pressure gradient. Therefore there is less chance of damaging the walls of the heart.* Risk of infective endocarditis in various lesions:High RiskModerate RiskLow RiskProsthetic heart value Tetralogy of fallot PDA AR ASCoarctation of Aorta VSDMVP + M.R. T.S.T.R.P.S.M.S.Mitral value prolapse without mitral Regurgitation. ASD