Advances in aortic valve-preserving surgery

Classification of the etiology of AR

Previously, surgeons did not have a good understanding of the pathophysiology of AR. In 2009, classification of the etiology of AR was proposed by the Brussels group following Carpentier’s classification of the etiology of mitral regurgitation (Fig. 5)22. Heart teams then had a common language resulting in a better understanding of the pathophysiology of AR, which appears beneficial in improving the outcome of AVP23. The varied phenotypes of bicuspid aortic valve (BAV) have complicated further understanding of the pathophysiology of AR. Although widely used, Sievers’ classification of BAV phenotype is an anatomical classification according to the number of raphe (0 – 2) and is not practical for AVP (Fig. 6A)24. The Brussels and Homburg groups recently proposed a repair-oriented classification system based on the commissure angle (Fig. 6B)25. This is also anticipated to improve the outcome of AVP for BAV.

Objective assessment of cusp configuration

The post-repair cusp configuration had traditionally been assessed subjectively (i.e., by eyeballing). In 2006, Schäfers advocated measuring the height difference between the central free margins and the aortic insertion lines using a dedicated caliper (i.e., effective height) (Fig. 7)26. This novel concept has made assessment of the cusp configuration more objective and reproducible. Lansac and colleagues reported that systematic cusp effective height assessment was associated with not only an increased rate of AVP but also improvement of repair durability27. In 2013, Schäfers published the normal dimensions of human cusps, in particular the cusp height (i.e., geometric height)28. They defined retraction in adults as a geometric height ≤ 16 mm in tricuspid aortic valves and ≤ 19 mm in the BAVs, and recommended avoiding AVP in such cases. This concept has served as a useful basis for decision making in AVP. Recently, Komiya and colleagues suggested that patients with a small cusp size (geometric height < 16 mm) can be candidates for AVP by tight annuloplasty because these cases have “annulus cusp mismatch”29. However, cases with severe mismatch may not be appropriate candidates for AVP. They also emphasized that annular size reduction may be mandatory even in cases with large cusps when “annulus cusp mismatch” exists.

Advent of aortic annuloplasty

The most distinct difference between MVP and AVP had been the availability of annuloplasty in the former. In 1958, Taylor and colleagues performed external suture annuloplasty for 11 beating hearts. However, this technique was not widely adopted due to unfavorable outcomes30. In 1966, Cabrol and associates proposed subcommissural annuloplasty, which was widely adopted because of its simplicity31. However, inhomogeneous plication negatively affects cusp movement and emerged as a risk of recurrence32. Circular annuloplasty procedures, such as external suture annuloplasty33, external ring annuloplasty27, and internal ring annuloplasty34, have been applied clinically in experienced centers, and appear to improve clinical outcomes of AVP (Fig. 8). Please refer to another systematic review article for many other alternatives35.

Valve-sparing root replacement

Two innovative approaches were developed to treat aortic root enlargement with or without AR; David and Feindel proposed reimplantation of the aortic valve (hereinafter referred to as reimplantation) in 199236 and Sarsam and Yacoub advocated remodeling of the aortic root (hereinafter referred to as remodeling) in 1993 (Fig. 9)37. Then, valve stability after VSRR has improved dramatically and selection of VSRR among aortic root surgery procedures has become more common, as described before. The two approaches had both advantages and disadvantages, but they have been improved by a number of modifications38 – 40. Currently, reimplantation using a vascular prosthesis with neosinuses and remodeling with annuloplasty have become standard procedures and achieved reproducible outcomes27, 41, 42.