Surgical anatomy of the aortic annulus: landmarks for external annuloplasty in aortic valve repair.

Background: Although reduction of a dilated aortic annulus is becoming an essential parameter for durable valve repair, anatomical descriptions of the annulus and surgical landmarks of the subvalvular plane for an external aortic annuloplasty remain to be defined.

Methods: Twenty hearts with normal anatomy with tricuspid aortic valves were studied. Annulus diameter, cusp geometric height, and interleaflet triangles heights were measured. The aortic root was dissected externally down to the subvalvular plane as to perform an external aortic annuloplasty or reimplantation procedure proximal anastomosis. Tissue thickness and dissection heights relative to the annulus were measured at each cusp nadir and at the middle of each interleaflet triangle.

Results: The mean annulus diameter, cusp geometric height, and interleaflet triangle heights were, respectively, 24.9 ± 0.2 mm, 19.7 ± 0.3 mm, and 20.1 ± 0.5 mm. External dissection of the aortic root reached the subvalvular plane below the nadir of left coronary cusp (-2.7 ± 0.4 mm), noncoronary (NC) cusp (-3.1 ± 0.3 mm), and the base of left-NC interleaflet triangle (-2.1 ± 0.4 mm). External dissection remained above the nadir of the right coronary cusp (+1.4 ± 0.4 mm), base of left-right interleaflet triangle (+2.4 ± 0.6 mm), and right-NC interleaflet triangle (+3.4 ± 0.3 mm). Mean tissue thickness between the inner and external side of the subvalvular plane was 2.5 ± 0.1 mm.

Conclusions: External dissection of the aortic annulus allows subvalvular placement of an external aortic ring below the left and NC cusps and below or within 3 mm of the right cusp nadir in 80% of cases. An external aortic annuloplasty would induce at least a 5-mm reduction of annulus diameter, corresponding to tissue thickness. Precise anatomical landmarks are important to standardize aortic valve annuloplasty.