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

Area of Science:

• Cardiovascular Surgery
• Pediatric Cardiology
• Congenital Heart Disease

Background:

• Subaortic stenosis is an increasingly recognized complication of atrioventricular septal defect (AVSD).
• This association is particularly concerning in non-Down's syndrome patients post-surgical correction.
• Understanding the surgical anatomy of the left ventricular outflow tract in AVSD is crucial.

Purpose of the Study:

• To investigate the surgical anatomy of the left ventricular outflow tract in hearts with atrioventricular septal defect (AVSD).
• To classify and identify anatomical features contributing to subaortic stenosis in AVSD.
• To elucidate the morphometric characteristics of the outflow tract in AVSD.

Main Methods:

• Examination of 48 hearts with atrioventricular septal defect (AVSD).
• Classification of obstructive lesions into unequivocal (Class A) and potential (Class B) forms.
• Morphometric analysis of inflow/outflow tract and ventricular outflow lengths.

Main Results:

• Unequivocal subaortic stenosis (Class A) identified in 13.5% of cases, with potential stenosis (Class B) in 10.8%.
• Anatomical causes included anomalous valve tensor apparatus, muscular infundibulum, fibrous diaphragm, and aortic valve position.
• AVSD hearts showed significantly lower inflow/outflow tract and right/left ventricular outflow length ratios compared to normal hearts.
• Outflow tract lengthening was observed in AVSD, alongside the commonly noted inflow tract shortening.

Conclusions:

• Atrioventricular septal defect (AVSD) anatomy inherently carries a potential for subaortic stenosis.
• Specific anatomical variations, like papillary muscle displacement or leaflet insertion, increase the risk of actual obstruction.
• Surgical intervention can exacerbate this potential, leading to clinically significant subaortic stenosis.