Left ventricular outflow tract obstruction in atrioventricular septal defects: a pathologic and morphometric evaluation

Subaortic stenosis has been described with increasing frequency as an ominous feature of atrioventricular septal defect (AVSD), especially following surgical correction of the anomaly in non-Down's syndrome patients. In order to study the surgical anatomy of the left ventricular outflow tract i...

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Bibliographic Details
Published in:	Clinical cardiology (Mahwah, N.J.) Vol. 14; no. 6; p. 513
Main Authors:	Gallo, P, Formigari, R, Hokayem, N J, D'Offizi, F, D'Alessandro, Francalanci, P, d'Amati, G, Colloridi, V, Pizzuto, F
Format:	Journal Article
Language:	English
Published:	United States 01-06-1991
Subjects:	Aortic Valve Stenosis - etiology Aortic Valve Stenosis - pathology Heart Septal Defects, Atrial - complications Heart Septal Defects, Atrial - pathology Heart Septal Defects, Ventricular - complications Heart Septal Defects, Ventricular - pathology Humans Infant Infant, Newborn Ventricular Outflow Obstruction - complications Ventricular Outflow Obstruction - pathology
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Summary:	Subaortic stenosis has been described with increasing frequency as an ominous feature of atrioventricular septal defect (AVSD), especially following surgical correction of the anomaly in non-Down's syndrome patients. In order to study the surgical anatomy of the left ventricular outflow tract in this malformation, 48 hearts featuring AVSD were examined. Obstructive lesions were classified into unequivocal forms (class A, 13.5%) and potential ones (class B, 10.8%). In the remaining hearts (class C, 75.7%) no obstruction was noted. In class A, subaortic stenosis was due to exaggeration of the anticipated anomalous arrangement of atrioventricular valve tensor apparatus, to the persistence of a subaortic muscular infundibulum, and to a discrete fibrous diaphragm. A potential for subaortic stenosis is provided by the unwedged position of the aortic valve. The left ventricular outflow tract is transformed into a long, forward-displaced fibromuscular channel. Morphometric analysis showed in AVSD (with both common annulus and separate orifices) a significantly (p less than 0.01) lower inflow/outflow tract ratio, and a significantly (p less than 0.01) lower right ventricular/left ventricular outflow length ratio than normal hearts. These results suggest that AVSD is characterized not only, as commonly stated, by inflow tract shortening, but by outflow tract lengthening as well. On these anatomical grounds, nearly all cases of AVSD could harbor the potential for subaortic stenosis; however, this becomes a real hazard (class B) only when associated with forward displacement of the left anterior papillary muscle, or direct insertion on the ventricular septum of the anterior bridging leaflet, and it may be converted to an actual obstruction by the effects of surgery.
ISSN:	0160-9289
DOI:	10.1002/clc.4960140611