A Glimpse Into the Future of Aortic Valve Repair: Learning to Fly!

The introduction of any novel cardio-thoracic surgery approach is always a stepwise process, in which subsequent historical phases can be identified: an initial phase characterized by the adoption of new techniques by a few centers only and a subsequent era of worldwide spreading and gradual confirmation as a daily practice. Looking back, this is what happened for mitral valve repair, for example. ¹ During the inception and pioneering phase, clinical research focused on the technical details, aiming at the standardization of the methods and definition of the criteria guiding procedural choices. Today, mitral valve repair is considered the first choice for degenerative mitral regurgitation surgical treatment ² and the clinical research on this topic has obviously moved to other objectives, including new techniques, application in particular clinical scenarios, translation into minimally invasive, robotic, and transcatheter settings ³ : the third phase can be defined as “pushing the limits.”

Along this paradigmatic path for the progressive implementation of an innovative surgical concept into daily clinical practice, where is aortic valve repair at, today? Original research coming from those few centers that introduced and pioneered it has led to important improvements in the understanding of the anatomy and function of the normal aortic valve, the pathogenetic mechanisms of aortic regurgitation (AR), the factors favoring a good outcome of the repair and those that proved prognostically adverse. Some of the authors of the 3-year “flight”/report of the AVIATOR project, published in this first issue of the Journal of the Heart Valve Society, ⁴ have been among the heroes of that phase. Is aortic valve repair now ready to enter its second era, that is, the phase of increasing popularity and introduction in common practice? The above report, ⁴ on top of a number of previous publications,^5,6 suggests an affirmative answer. The use of inverse probability weighting is aimed to provide a fair comparison between repair and replacement, not biased by the differences in patients’ characteristics influencing the choice of the technique. The advantage of repair here demonstrated, in terms of incidence of the composite endpoint, is, therefore, to be considered intrinsic to the repair approach, regardless of the patient's characteristics and type of disease (at least for those variables included in Supplemental Table S1). Previous recent propensity-adjusted comparisons from experienced centers; however, selecting only root procedures (Bentall operation vs valve-sparing root replacement), had shown lower rates of reintervention at 10-year follow-up with the conservative approach ⁵ or no difference in terms of reintervention, but superiority of valve-sparing in terms of thromboembolism, bleeding, and endocarditis. ⁶

Thus, the time is ripe for changing the aims of clinical research in this field: the next step is to define in a more granular way indication criteria and principles to guide technical choices. To this purpose, the investigative contribution not only of pioneering centers, but also and especially of less experienced centers, will be fundamental, providing the maybe unadjusted but surely “real-world” results of well-defined approaches in carefully selected patient groups. ⁷ In the AVIATOR study, ⁴ the presence of a bicuspid aortic valve (BAV) was significantly associated with the choice of repair rather than replacement: this suggests a predominant contribution of the most expert centers to the registry data. Less experienced centers have usually tended to consider BAV as a relative deterrent factor for repair, so far.^7–9

This year, new guidelines for the management of aortic diseases have been issued^8,9: regarding the aortic root they present some substantial points of innovation, including differentiated threshold diameters for surgical indication according to the phenotype of aorta dilatation. The root phenotype dilatation has been recognized as a marker of more severe aortopathy both for BAV and tricuspid aortic valve patients, therefore earlier elective surgery is suggested (ie at a diameter of ≥50 mm, as a Class II recommendation for tricuspid, Class I for BAV) than for the ascending phenotype dilatations.^8,9 An earlier intervention for root replacement implies that more often than in the past the aortic valve can be suitable for repair. Earlier surgery is historically indicated in hereditary aortopathies, and in the AVIATOR 3-year report these were significantly more represented in the repair/sparing group than in the replacement one. ⁴ How will less experienced centers cope with this foreseeable increasing need to address a normally functioning aortic valve (or a valve showing good quantity and quality of tissue) in the context of root replacement? To avoid the undue replacement of those valves, will the patients be referred to other centers, more experienced in aortic valve repair techniques? Or will collaborations be sought with expert surgeons, to learn the due principles and techniques and start new local aortic valve repair/sparing programs? Both options could also be combined together, thus enhancing the spreading of the repair procedures more widely, while maintaining the general standard of outcomes: what's of utmost importance is now to start leveling out the differences among centers wherever applicable.

Moreover, there is growing evidence that when operated on with earlier indications than recommended with Class I, patients with AR show significantly better long-term outcomes^2,10: if, following this evidence, the next guidelines for aortic valve diseases will include stronger recommendations for earlier indications, the above-portended need for a more widespread readiness to spare or repair aortic valves will come up even more.

After that general feasibility of aortic valve repair has been exhaustively demonstrated in the past and evidence of superior mid-term outcomes compared to replacement surgery is now available, the goal for the future is achieving worldwide diffusion of this surgical practice.