Transitional atrioventricular septal defect

This code represents a congenital heart malformation where there is an incomplete fusion of the atrial and ventricular septa, along with abnormalities of the atrioventricular valves. Specifically, it involves a primum atrial septal defect and a ventricular septal defect, with a common atrioventricular valve that is partially divided into two distinct orifices. This defect allows for shunting of blood between all four heart chambers.

Use this code when documentation clearly indicates a diagnosis of a transitional or partial atrioventricular septal defect. This diagnosis is typically made through echocardiography and may be identified prenatally or in infancy due to symptoms like heart murmur, cyanosis, or heart failure. Ensure the physician's notes specify the "transitional" or "partial" nature of the defect, distinguishing it from complete forms.

• Differentiate from Q21.20 (Atrioventricular septal defect, unspecified) and Q21.21 (Complete atrioventricular septal defect) based on the specific anatomical description.
• Always review imaging reports (e.g., echocardiogram) and cardiology notes to confirm the precise type of atrioventricular septal defect.
• Code any associated cardiac anomalies separately, if documented and not inherent to the definition of a transitional AVSD.