Basic Science and Epidemiology of Congenital Heart Disease
Burden of disease
Congenital heart disease (CHD) affects roughly 8–9 per 1000 live births - taught as "about 1 in 100," rising to nearly 1–2% when bicuspid aortic valve and tiny muscular ventricular septal defects (VSDs) are included. VSD is the most common lesion at birth; bicuspid aortic valve is the most common congenital cardiac anomaly in adults. About one quarter of affected infants have critical CHD needing intervention in the first year.
Survival has transformed the field: over 90% of children born with CHD now reach adulthood, and adults with CHD outnumber children with CHD. This shift explains why exam items emphasize late complications, reintervention, and acquired comorbidity rather than the index repair.
Genetics and inheritance
Learn syndrome–lesion pairs: trisomy 21 (atrioventricular septal defect, VSD), 22q11.2 deletion (conotruncal lesions - tetralogy of Fallot, truncus arteriosus, interrupted aortic arch), Williams syndrome (supravalvular aortic stenosis), Turner syndrome (coarctation, bicuspid aortic valve), Noonan syndrome (pulmonary stenosis, hypertrophic cardiomyopathy), Alagille syndrome (peripheral pulmonary stenosis), Marfan syndrome (aortic root dilation). Recurrence risk with an affected parent is about 3–5% and is highest for left-sided obstructive lesions.
Traps
Items conflate prevalence with incidence, or ask for the "most common lesion" without specifying age - check whether the stem says "at birth" or "in adults." Do not assume every lesion is heritable; most CHD is multifactorial. Familial clustering should prompt echocardiographic screening of first-degree relatives for left-sided lesions and aortopathy. Finally, remember that a normal newborn examination does not exclude critical CHD - ductal closure unmasks obstruction.
Rule of thumb
Anchor on three numbers: 1 in 100 births, 1 in 4 needing early intervention, and more than 90% surviving to adulthood.