Prevalence of left-sided obstructive lesions in patients with atrioventricular canal without Down's syndrome.

Ninety consecutive patients with atrioventricular canal were studied to identify the association between left-sided obstructive lesions and Down's syndrome. Three groups were recognized: Group I, 76 patients with atrioventricular canal and no left-sided obstructions; Group II, nine patients with atrioventricular canal and left-sided inlet obstructions; Group III, five patients with atrioventricular canal and left-sided outlet obstructions. Of the 90 patients studied, 47 had Down's syndrome and only one of these had a left-sided obstructive lesion. Of 43 without Down's syndrome, 13 or 30% had left-sided obstructive lesions with predominating lesions at the inlet level caused by right ventricular dominance.