A 6-month-old infant with Down syndrome presents with recurrent respiratory infections, poor feeding, and failure to thrive. Echocardiography reveals a complete atrioventricular septal defect (AVSD) with both atrial and ventricular components and a common AV valve. Which of the following is a cardinal feature distinguishing complete AVSD from partial AVSD on echocardiography?
- A Presence of a primum atrial septal defect
- B Left ventricular outflow tract elongation ('gooseneck deformity')
- C A common AV valve (instead of separate mitral and tricuspid valves) ✓
- D Inlet VSD component
Correct answer: C. A common AV valve (instead of separate mitral and tricuspid valves)
Explanation
The defining feature of complete AVSD is the presence of a single, common AV valve (five leaflets) bridging both ventricles, as opposed to partial AVSD where there are still two separate AV valve annuli (the 'cleft' mitral valve in partial AVSD). Both forms share a primum ASD and the 'gooseneck deformity' of the LVOT on angiography. Only the complete form has a significant inlet VSD with a common AV valve. Surgical repair is recommended before 6 months to prevent pulmonary hypertension, which develops rapidly in complete AVSD, especially in Down syndrome.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.