Why can't the aortic valve be more like the mitral?

In My Fair Lady, Professor Henry Higgins asks ‘Why can't a woman be more like a man?’, lamenting whether innate differences between the genders should make life and the charge of rehabilitation so difficult. Many valve repair surgeons regard the aortic and mitral valves similarly; for decades, reproducible and durable aortic valve repair has proved more elusive than mitral repair, and repair of the aortic valve a difficult nut to crack. But there is renewed interest and considerable progress on this front. Better understanding of the form and function of the aortic valve and the aortic root complex, in part a spin-off of the pioneering work of Sir Magdi Yacoub and Tirone David in valve sparing aortic root replacement for aneurysm disease [ 1 , 2 ], has empowered a new generation of surgeons to revisit the challenge of repairing regurgitant aortic valves and to develop principles of repair that can be articulated, taught and replicated.

One of the principles of successful repair (both aortic and mitral) is the correction of annular dilatation and restoration of optimal annular and valvular geometry, with a view towards stabilization of the annulus and maintenance of physiological cusp coaptation. This seems particularly so in bicuspid aortic valves as shown by the superior long-term results of aortic valve repair reported by El-Khoury [ 3 ] and Schäfers [ 4 ] when the aortic annulus and root are stabilized.

The aortic annulus and root can be stabilized using several different techniques: by complete replacement of the root by prosthetic material (The David and Yacoub procedures), by reinforcement of the root by external supporting prostheses (The Florida sleeve [ 5 ] and the personalized external aortic root support, or PEARS procedure [ 6 ]), by internal or external suture annuloplasty and by internal or external prosthetic annular rings. The report by Mazzitelli in this issue of the journal [ 7 ] updates the experience with one such internal annuloplasty ring, the HAART 300 Device, among 65 patients at 8 centres in Europe and North America; all patients had moderate-to-severe aortic regurgitation. This article is an update and expansion of the experience reported in 2014, when there were only 16 initial patients at four centres with follow-up ranging from 7 to 15 months [ 8 ]. The current study generated similar outcomes out to a mean of 2 years of follow-up: no operative or hospital deaths, no major complications, and no valve-related events, though 7 patients (10%) required aortic valve replacement, which the authors ascribe to ‘surgical technique.’ Most of the failures appeared to result from the limitations of leaflet repair and lack of an ideal leaflet substitute or patch material. The HAART 300 ring served its function well, which was to create and stabilize a favourable root geometry.

But is this the best method to stabilize the aortic valve's environment? Proponents will assert this is the only prosthesis that by design respects physiological geometry and preserves normal root compliance, and that its implantation is fairly straightforward. On the other hand, critics will warn of the possible hazards of a prosthetic ring in close proximity to the relatively thin and delicate aortic leaflets, the less attractive strategy of stabilizing a dilating structure by internal rather than external stabilization, and that the outcomes of aortic valve repair may depend more on the techniques to reconstruct leaflets than the method of annular stabilization. Significant progress in aortic valve repair may ultimately depend more on concomitant advances in biomaterials than novel designs of annuloplasty rings.

In this respect, Professor Higgins was right … the aortic valve is distinctly different from the regurgitant mitral, and there will be new lessons to be learned and shared. But we must get over it and get on with it.

This is an exciting space to watch.

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