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Obstruction of the left ventricular outflow tract: anatomical observations and surgical implications
A F Maizza1, S Y Ho, R H Anderson
1Department of Paediatrics, National Heart and Lung Institute, London.
Insights
Left ventricular outflow tract obstruction has diverse anatomical causes. Understanding these malformations is crucial for effective surgical treatment of stenosis.
Area of Science:
- Cardiovascular Anatomy
- Congenital Heart Disease Surgery
Background:
- Left ventricular outflow tract (LVOT) obstruction presents in various anatomical forms.
- Understanding normal aortic valve anatomy is key to identifying pathological variations.
Purpose of the Study:
- To review the anatomy of normal and malformed hearts causing LVOT obstruction.
- To identify the specific anatomical substrates of stenosis at different levels of the outflow tract.
- To correlate findings with surgical literature.
Main Methods:
- Examination of 75 malformed hearts.
- Review of relevant surgical literature on LVOT obstruction.
- Detailed analysis of aortic valve and subvalvar regions.
Main Results:
- Valvar abnormalities occurred in 45 cases (tricuspid, bicuspid, or unicuspid valves).
- Subvalvar stenosis was present in 30 hearts, primarily due to posterior malalignment of the outlet septum or muscular hypertrophy.
- Obstruction also associated with atrioventricular septal defects.
Conclusions:
- Accurate identification of the level and anatomical substrate of LVOT obstruction is essential for surgical planning.
- Valvar and subvalvar abnormalities are significant causes of LVOT stenosis.
Abstract:
Obstruction within the outflow tract from the left ventricle can take several anatomic forms. To understand better these substrates, we reviewed the anatomy in the normal heart and, with this background, focused on the malformations observed at each level of the outflow tract which produce stenosis. We examined 75 malformed hearts and reviewed the literature pertinent to surgical aspects of obstruction. Close study of the normal aortic valve shows the lack of any discrete fibrous structure which can be described in terms of a ring-like annulus. The semilunar attachment of the leaflets makes a crown-shaped arrangement at the ventriculo-arterial junction rather than a strict ring. In the pathological study, valvar abnormalities were found in 45 cases. The valve had three leaflets in 20 cases, two leaflets in 24 cases and one leaflet in to the other. In two cases, additional obstruction was found at the sinutubular junction. Subvalvar stenosis was found in 30 hearts, the aortic valve being trifoliate in 28 and bifoliate in 2. The main substrate of subvalvar obstruction was posterior malalignament of the outlet septum (40%), followed by muscular septal hypertrophy (23%); obstruction was also an intrinsic feature in association with atrioventricular septal defects (14%). Although rare in our material, it can also be due to a fibrous or fibromuscular shelf. In our review of the literature, we have highlighted the various forms of valvar malformation and commented on the surgical options. Clear analysis of both the level of obstruction, and its precise anatomic substrate are essential for optimal surgical intervention.