EDITORIAL COMMENT
Repair of the Congenitally Bicuspid Regurgitant Aortic ValveA Strategic Advance*
Jeffrey S. Borer, MD, FACC* and
Leonard N. Girardi, MD
The Howard Gilman Institute for Valvular Heart Diseases, Cardiovascular Pathophysiology Unit, and the Department of Cardiothoracic Surgery, Weill Cornell Medical College, New York, New York.
* Reprint requests and correspondence: Dr. Jeffrey S. Borer, 47 East 88th Street, New York, New York 10128. (Email: canadad45{at}aol.com).
Key Words: aortic regurgitation • bicuspid aortic valve • valve surgery • aortic root
Bicuspid aortic valve (BAV) is a common congenital abnormality, affecting 1% to 2% of live births and found in approximately 4,000,000 persons in the U.S. (1). BAV results in severe aortic regurgitation (AR) in almost 20% of those affected (2); it is the primary cause of AR among persons age <65 years. When AR is severe and consequent symptoms or specific asymptomatic left ventricular or ascending aortic alterations develop (3), the generally accepted response is valve replacement with or without replacement/repair of some portion of the ascending aorta. Surgery for BAV commonly is required during the fourth through sixth decades of life. Long-term survival after surgery for AR now is reasonably favorable (4–6), limited primarily by pre-operative myocardial function rather than by limitations imposed by surgery (7). Nonetheless, aortic valve replacement is a suboptimal solution for patients with AR from BAV: the operated patient faces a prolonged interval of substantial risk for pathological bleeding if the prosthesis is an anticoagulation-requiring mechanical device (despite relative freedom from reoperation [6]), or late prosthesis failure and reoperation if a nonanticoagulation-requiring bioprosthesis is employed (6), even if allografting is selected (8). When corrected for age at operation, cardiac function and comorbidities, late survival (and thromboembolism risk) is similar with bioprosthetic and anticoagulated mechanical valves (5,6). Various valve repair procedures (tailored to the specific characteristics of congenitally deformed valves) long have provided alternatives (9). While repairs have been highly successful and reasonably durable for congenital mitral leaflet prolapse (10), BAV repairs generally have failed earlier than bioprostheses (11), rendering current approaches of questionable utility. One reason may be the relatively unforgiving mechanical demands of BAV architecture and tissue quality, mandating refinements in surgical techniques; another may be inadequate criteria to identify valves likely to be durably repaired with current techniques. In this issue of the Journal, Pettersson et al. (12) propose a new solution to the latter problem. These authors prospectively employed a description system using intracardiac quantitative echocardiography (variably supplemented by pre-operative computerized tomographic and magnetic resonance imaging) to characterize deformed valves by cusp pathology (redundancy, restriction, cusp height to indicate likely adequacy of coaptatation, mobility/pliability, thickness, integrity), commissure variations (fusion, splaying, attachment site, and alignment), and root morphology (septal hypertrophy, septal integrity, annular size, sinus and sinotubular junction dimensions, and ascending aorta dimension). Decisions about reparability of any valve component were based on the surgeon's subjective interpretation of these data; each reparable echocardiographic characteristic was corrected with a maneuver specific for that finding. After repair, intraoperative echocardiographic characteristics were identified that most closely tracked with surgical success/failure (defined by valve function and need for reoperation) during an average 2-year follow-up.
Others have reported objective criteria for appropriate selection of valves for repair (including cusp or commissural thickening and cusp calcification [13]) or for selecting repair technique (e.g., effective cusp height [14]). The study of Pettersson et al. (12) adds importantly to these earlier efforts, first, by employing a particularly comprehensive and systematic approach. Secondly, these authors include a measure of tissue quality, a "tissue normality index" of cusp pliability, and of residual transvalvular gradient, together with anatomic descriptors (including a new morphologic "coaptation deficiency index"). Indeed, deficient tissue quality probably was involved in the 4 early repair failures, though not clearly predicted by the echocardiographic measures used in this small series.
Although Pettersson et al. (12) used their system to evaluate appropriateness of repair and to select technical maneuvers to be used during the procedure, the study was undertaken primarily to identify intraoperative measures and surgical responses most closely associated with successful repair. As such, its conclusions inherently are limited by its small size, few adverse events, and relatively short follow-up. More importantly, the study is descriptive and observational; its design does not permit assessment of the relative utility of selection criteria based on the objective measurements. Indeed, precise criteria employed to eliminate repair as an option, or judged sufficient to require a specific technical repair maneuver, are not defined, limiting application of these data by other surgeons and suggesting dependence on subjective judgment. In addition, though root characteristics did not importantly predict outcome, this may have resulted, in part, from patient selection, suggesting the need for further assessment of the contribution of root pathology to selection of repair techniques and their success. Alternatively, the authors' relatively low threshold for associated root surgery (aortic dimension of 40 mm, rather than the generally accepted 45 mm [3]) may have precluded problems that otherwise might have arisen. Finally, more information relating pre-operative to intraoperative echocardiographic findings would have been useful: pre-operative identification of poor candidates for repair could beneficially inform discussions with patients.
Randomized trials of surgical strategies, required for optimal evaluation of the approach of Pettersson et al. (12), are highly desirable, but very difficult in practice. Moreover, given the biological variability among valves and tissues, some individual judgment always will be needed. However, judgment might be usefully guided by comprehensive tissue characterization (composition, cell/molecular biology), as inferable from results with authors' tissue normality index, though this index, itself, was not optimally predictive; authors missed a useful opportunity to characterize tissue from surgical wastes (shaved cusps, resected raphe) or from root biopsies, and so on. Recent observations concerning the potential importance of deficiencies of microfibrillar proteins (2) and of endothelial nitric oxide synthase expression (15) in the pathogenesis of BAV suggest that comprehensive tissue characterization may contribute importantly to optimizing approaches to BAV surgery.
Limitations notwithstanding, Pettersson et al. (12) have provided a valuable contribution. Their data support systematic segmental characterization of valve and outflow tract morphology for technical decisions during BAV surgery and, preliminarily, suggest that patients with coaptation or pliability deficiencies probably should not undergo BAV repair. Further data are needed to define appropriate application, and ultimate utility, of this strategy.
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Footnotes
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* Editorials published in the Journal of the American College of Cardiology reflect the views of the authors and do not necessarily represent the views of JACC or the American College of Cardiology. 
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References
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