Single papillary muscle ("parachute valve") and double-orifice left ventricle in atrioventricular septal defect convergence of chordal attachment: surgical anatomy and results of surgery.

A review of 59 anatomical specimens and of the findings in 65 surgically repaired patients with atrioventricular septal defect (AVSD), revealed four patients with a single papillary muscle and 11 with a double-orifice left ventricle. A single papillary muscle of the left ventricle occurred in 1.7% (1 of 59) of the anatomical specimens, and 6% (4 of 65) of the surgical cases. A double orifice of the left ventricle was found in 13.6% (8 of 59) of the anatomical specimens, and 7.7% (6 of 65) of the surgical cases. A single papillary muscle was only seen in cases with a complete defect. Double orifice was associated with partial, complete, or intermediate type of defect, with the highest incidence in the intermediate forms: 40% (4 of 10) of the anatomical specimens and 22% (2 of 9) of the surgical cases. In the anatomical study the specimens, with either single papillary muscle or double-orifice left ventricle, appear to be variants of the same malformation characterized by convergence of chordal insertion and underdevelopment of the left lateral leaflet. Pathology belonging to this spectrum was seen in 15% of our autopsy specimens and 14% of the surgical cases. In the surgical series good operative results were obtained with a conservative approach in cases with a favorable surgical anatomy.