Partial atrioventricular canal is due to a defective fusion of the endocardial cushions with the atrial septum primum. In the normal heart this fusion constitutes the atrioventricular septum where the mitral and tricuspid annuli insert, dividing the septum into an interatrial and an atrioventricular component. It accounts for about 4% of all congenital heart defects and its incidence is estimated to be 2 per 10,000 live births. It includes a spectrum of anomalies that differ from those of the complete form because the ventricular septal defect is absent. In partial atrioventricular canal two separate atrioventricular valve annuli are usually present: forms with a common annulus are referred as intermediate. Patients with these lesions may be asymptomatic or present with a variety of symptoms depending mostly on the function of the atrioventricular valves and the associated anomalies. Treatment of partial atrioventricular canal is invariably surgical and can be done electively in the first few years of life (uncomplicated forms) or in the first few months of life when symptoms are severe. Operative risk of all atrioventricular septal defects is approximately 3%. Twenty-year survival is 96%.
Last update: March 2003