Concepts of Bicuspid Aortic Valve Repair: A Review

Multiscale structure and function of the aortic valve apparatus

Whereas studying the aortic valve in isolation has facilitated the development of life-saving procedures and technologies, the dynamic interplay of the aortic valve and its surrounding structures is vital to preserving their function across the wide range of conditions encountered in an active lifestyle. Our view is that these structures should be viewed as an integrated functional unit, here referred to as the aortic valve apparatus (AVA). The coupling of the aortic valve and root, left ventricular outflow tract, and blood circulation is crucial for AVA's functions: unidirectional flow out of the left ventricle, coronary perfusion, reservoir function, and support of left ventricular function. In this review, we explore the multiscale biological and physical phenomena that underlie the simultaneous fulfillment of these functions. A brief overview of the tools used to investigate the AVA, such as medical imaging modalities, experimental methods, and computational modeling, specifically fluid-structure interaction (FSI) simulations, is included. Some pathologies affecting the AVA are explored, and insights are provided on treatments and interventions that aim to maintain quality of life. The concepts explained in this article support the idea of AVA being an integrated functional unit and help identify unanswered research questions. Incorporating phenomena through the molecular, micro, meso, and whole tissue scales is crucial for understanding the sophisticated normal functions and diseases of the AVA.

Prolapse repair for aortic regurgitation in tricuspid aortic valves

OBJECTIVE

Cusp prolapse is an important cause of aortic regurgitation (AR) in tricuspid aortic valves (TAVs) and can be caused by myxomatous degeneration or cusp fenestration. Long-term data for prolapse repair in TAVs are scarce. We analyzed the results of aortic valve repair in patients with TAV morphology and AR caused by prolapse and compared the results for cusp fenestration and myxomatous degeneration.

METHODS

Between October 2000 and December 2020, 237 patients (221 male; 15-83 years) underwent TAV repair for cusp prolapse. Prolapse was associated with fenestrations in 94 (group I) and myxomatous degeneration in 143 patients (group II). Fenestrations were closed using a pericardial patch (n = 75) or suture (n = 19). In myxomatous degeneration, prolapse was corrected by free margin plication (n = 132) or triangular resection (n = 11). Follow-up was 97% complete (cumulatively 1531, mean 6.5, median 5.8 years). Cardiac comorbidities were present in 111 patients (46.8%), and more frequent in group II (P = .003).

RESULTS

Ten-year survival was better in group I (I: 84.5%; II: 72.4%; P = .037), and patients without cardiac comorbidities (89.2% vs 67.0%; P = .002). Ten-year freedom from reoperation (P = .778), moderate or greater AR (P = .070), and valve-related complications (P = .977) were similar in both groups. AR at discharge was the only significant predictor for reoperation (P = .042). The type of annuloplasty did not affect repair durability.

CONCLUSIONS

Repair of cusp prolapse in TAVs with preserved root dimensions can be performed with acceptable durability, even in the presence of fenestrations.

Long-term outcome of bicuspid aortic valve repair using figure-of-8 hitch-up stitches

Objective

To maximize successful repair of bicuspid aortic valves by adding figure-of-8 hitch-up stitches at commissures.

Methods

From 2000 to 2022, bicuspid aortic valve repair was performed on 1112 patients at Cleveland Clinic, with 367 patients receiving figure-of-8 hitch-up stitches along with classical techniques, including Cabrol suture, cusp plication, raphe resection, and valve-sparing root replacement. Operative outcomes, repair durability, and survival were assessed in the figure-of-8 hitch-up stitches cohort, and outcomes were compared among 195 balancing-score-matched patient pairs who underwent bicuspid aortic valve repair with and without figure-of-8 hitch-up stitches.

Results

Patients who underwent bicuspid aortic valve repair with figure-of-8 stitches had an operative mortality of 0.3% (1 of 367) and in-hospital reoperation for aortic valve dysfunction of 1.1% (4 of 367). At 10 years, prevalence of severe aortic regurgitation was 8.6%, mean gradient 24 mm Hg, freedom from aortic valve reoperation 75%, and survival 98%. In matched cohorts, operative mortality was similar (0.51% vs 0%; P > .9) as were morbidities, including in-hospital reoperation due to aortic valve dysfunction (1.0% vs 1.5%; P > .9). Comparable long-term outcomes were observed at 10 years (prevalence of severe aortic regurgitation of 8.7% vs 5.0% [P = .11], mean gradient 18 vs 17 mm Hg [P = .40]; freedom from aortic valve reoperation 80% vs 81% [P = .73]; and survival 99.5% vs 94.6% [P = .18]).

Conclusions

Figure-of-8 hitch-up stitch is a safe bicuspid aortic valve repair technique. It increases the likelihood of a successful repair without increasing risk of cusp tear and achieves satisfactory long-term survival and durability when added to classical repair techniques.

Surgical outcomes among children with bicuspid aortic valve: 17 years of experience in a single center. First report in Mexico

PURPOSE

To evaluate the clinical and surgical outcomes among children with bicuspid aortic valve who underwent cardiac surgery.

METHODS

This observational and retrospective study included patients with a diagnosis of bicuspid aortic valve who underwent cardiac surgery between January 1, 2003, and March 31, 2020. Demographic characteristics and perioperative conditions were described.

RESULTS

One hundred and sixteen patients were included, with a mean age of 12.4 ± 4.2 years; 63.2% were male. The most frequent diagnosis was congenital aortic stenosis (23.5%), followed by connective tissue disorders (16%). Mechanical aortic prostheses were used in 87.7% of cases, with a mean size of 21 ± 2.6 mm. The main factors associated with mortality were valve prosthesis dysfunction (odds ratio [OR]: 12.44; 95% confidence interval [CI]: 1.05-147.48; p = .04) and reoperation (OR: 24.29; 95% CI: 1.03-570.08; p = .04). The overall survival was 87.9%, with better outcomes among those who did not undergo reoperation (Log Rank, p = .01).

CONCLUSIONS

Outcomes after aortic valve replacement in children with bicuspid aortic valve are excellent in the short and long term, regardless of using mechanical or biological prostheses.

Validating In Silico and In Vitro Patient-Specific Structural and Flow Models with Transcatheter Bicuspid Aortic Valve Replacement Procedure

INTRODUCTION

Bicuspid aortic valve (BAV) is the most common congenital cardiac malformation, which had been treated off-label by transcatheter aortic valve replacement (TAVR) procedure for several years, until its recent approval by the Food and Drug Administration (FDA) and Conformité Européenne (CE) to treat BAVs. Post-TAVR complications tend to get exacerbated in BAV patients due to their inherent aortic root pathologies. Globally, due to the paucity of randomized clinical trials, clinicians still favor surgical AVR as the primary treatment option for BAV patients. While this warrants longer term studies of TAVR outcomes in BAV patient cohorts, in vitro experiments and in silico computational modeling can be used to guide the surgical community in assessing the feasibility of TAVR in BAV patients. Our goal is to combine these techniques in order to create a modeling framework for optimizing pre-procedural planning and minimize post-procedural complications.

MATERIALS AND METHODS

Patient-specific in silico models and 3D printed replicas of 3 BAV patients with different degrees of post-TAVR paravalvular leakage (PVL) were created. Patient-specific TAVR device deployment was modeled in silico and in vitro-following the clinical procedures performed in these patients. Computational fluid dynamics simulations and in vitro flow studies were performed in order to obtain the degrees of PVL in these models.

RESULTS

PVL degree and locations were consistent with the clinical data. Cross-validation comparing the stent deformation and the flow parameters between the in silico and the in vitro models demonstrated good agreement.

CONCLUSION

The current framework illustrates the potential of using simulations and 3D printed models for pre-TAVR planning and assessing post-TAVR complications in BAV patients.

Fifteen-year experience with the Tirone David procedure in bicuspid aortic valve: A safe option

BACKGROUND

We evaluated short and midterm outcomes with use of aortic valve-sparing root replacement to treat bicuspid aortic valves (BAVs).

METHODS

From December 2007 to January 2022, all patients with BAVs who underwent aortic root replacement using Tirone's procedure were included. This study based on department database information for retrospective and follow-up data.

RESULTS

Among 51 adults undergoing aortic root replacement using Tirone's procedure, the mean age was 47.4 ± 12.5 years, and most were men (92.2%). Three presented with a dysmorphic syndrome and one had Marfan's syndrome. All patients were alive at 30 days, and as of January 2022, 45 were alive, two were lost to follow-up, and there were four noncardiac deaths. Two patients had infectious endocarditis and needed a Bentall's procedure. One patient had a double biologic valve replacement in the context of severe mitral insufficiency with moderate aortic stenosis at 4.5 years postprocedure. Echocardiographic follow-up showed a left ventricular ejection fraction of 63 ± 7% (n = 36), V_max 2 ± 0.6 m/s (n = 17), and a mean gradient of 9.4 ± 5.4 mmHg (n = 27). No patients had grade 3 or 4 aortic regurgitation, one patient had grade 2, and four had grade 1.

CONCLUSION

Tirone's procedure is an option for BAV surgery, with good safety and outcomes, especially in younger patients.

Understanding the Aortic Root Using Computed Tomographic Assessment: A Potential Pathway to Improved Customized Surgical Repair

There is continued interest in surgical repair of both the congenitally malformed aortic valve, and the valve with acquired dysfunction. Aortic valvar repair based on a geometric approach has demonstrated improved durability and outcomes. Such an approach requires a thorough comprehension of the complex 3-dimensional anatomy of both the normal and congenitally malformed aortic root. In this review, we provide an understanding of this anatomy based on the features that can accurately be revealed by contrast-enhanced computed tomographic imaging. We highlight the complimentary role that such imaging, with multiplanar reformatting and 3-dimensional reconstructions, can play in selection of patients, and subsequent presurgical planning for valvar repair. The technique compliments other established techniques for perioperative imaging, with echocardiography maintaining its central role in assessment, and enhances direct surgical evaluation. This additive morphological and functional information holds the potential for improving selection of patients, surgical planning, subsequent surgical repair, and hopefully the subsequent outcomes.

Commissural repositioning in bicuspid aortic valve repair: an in vitro acute model to explore and explain different results

OBJECTIVES

Commissural orientation <160° is a recognized risk factor for bicuspid aortic valve repair failure. Based on this observation, repairing this subtype of aortic valve by reorienting the 2 commissures at 180° has recently been proposed.

METHODS

Nine porcine hearts with aortic annulus diameters of 25 mm were selected. A pathological model of a Sievers 1 bicuspid aortic valve was obtained by suturing the coaptation line between the left and right leaflets. Each heart underwent reimplantation procedures both in the native (120°) and the reoriented (180°) configuration. After the operation, each sample was tested on a pulse duplicator at rest (heart rate 60 beats per min) and with mild exercise (heart rate 90 beats per min) conditions.

RESULTS

No statistically significant difference was noted in mean and peak transvalvular aortic gradients between the 2 configurations at rest (18.6 ± 5 vs 17.5 ± 4 for the mean aortic gradient; 42.8 ± 12.7 vs 36.3 ± 5.8 for the peak aortic gradient) but the group with the 120°-oriented commissures had significantly higher mean transaortic gradients compared to the group with the 180°-oriented commissures at initial exercise stress conditions (30.1 ± 9.1 vs 24.9 ± 3.8; p value 0.002).

CONCLUSIONS

The 180° commissural reorientation of the asymmetrical bicuspid aortic valve does not improve the transvalvular aortic gradient in an acute model at rest conditions, but it could do so under stress situations. Even if it is surgically more complex and time-consuming, this approach could be a good strategy to improve long-term results, particularly in young patients.

Root Reimplantation and Aortic Annuloplasty With External Ring in Bicuspid Aortic Valve: An Anatomical Comparison

Aortic annuloplasty has demonstrated to be a protective factor in valve-sparing root replacement and aortic valve repair. Both reimplantation for aortic root aneurysms and external ring annuloplasty for isolated aortic regurgitation have demonstrated good long-term results. The aim of this anatomical study is to compare aortic reimplantation with Valsalva graft with aortic external ring annuloplasty in bicuspid aortic valves, analyzing their morphological features with CT scan. We selected 56 patients with bicuspid aortic valve who underwent reimplantation procedure with Valsalva graft or external ring annuloplasty; after propensity-matching, 2 homogeneous groups of 10 patients each were obtained. Through multiplanar ECG-gated CT-Scan reconstructions, pre- and postoperative, aortic annular, and valve geometrical characteristics were compared (diameters, perimeter, area and ellipticity index for the annulus; effective height, coaptation length and commissural height for the valve). Aortic root volume was also analyzed. Postoperative comparison of the two groups showed similar geometric features of the aortic annulus in terms of major and minor diameters, perimeter, area and ellipticity index. Analysis of valve's parameters showed similar results in terms of effective height and coaptation length (respectively 10.9 ± 2.1 mm and 7.5 ± 1.9 mm in External Ring group and 10.1 ± 2.0 mm and 7.6 ± 1.6 mm in the Reimplantation group). Both techniques achieve an efficient annuloplasty with similar anatomical results on bicuspid the aortic valves. The stability of these results needs to be confirmed by long-term clinical and echocardiographic follow-up.

Valve Sparing Root Replacement versus Bio-Bentall: Inverse Propensity Weighting of 796 Patients

BACKGROUND

This large cohort, single center study aims to compare the 10-year survival and freedom from aortic valve reintervention between valve sparing root replacement (VSRR) and bioprosthetic Bentall (bio-Bentall).

METHODS

All patients undergoing elective VSRR or bio-Bentall for aortic root aneurysm between March 2005 through October 2019 were retrospectively reviewed (n=796 [VSRR = 360]). Inverse probability of treatment weighting (IPTW) balanced clinical variables between groups. Mean follow-up was 58.0 +/- 45.4 (range 0-167) months.

RESULTS

After IPTW adjustment, 10-year survival did not differ between groups (VSRR: 87.0% vs bio-Bentall: 92.7%, p=0.780). Cumulative incidence of aortic valve reintervention was 5.9% for VSRR (95% CI, 2.9%-10.4%) and 10.6% for bio-Bentall (95% CI, 6.2%-16.4%, p=0.798). Fine and Gray computing risk regression model identified age at surgery (sHR 0.97, 95% CI, 0.95-0.99, p=0.015), body surface area (sHR 6.21, 95% CI, 1.97-19.59, p=0.002) and bicuspid aortic valve (sHR 2.15, 95% CI, 1.04-4.44, p =0.038) as independently associated with aortic valve reintervention. For patients ≤50-year-old, cumulative incidence of aortic valve reintervention was 16.2% for VSRR (95% CI, 7.0%-28.8%) and 17.8% for bio-Bentall (95% CI, 6.9%-32.8%)(p=0.363).

CONCLUSIONS

VSRR and bio-Bentall show similar excellent survival and freedom from aortic reintervention rates up to 10 years; however, a durable valve solution for young patients with bicuspid aortic valve remains a challenge.

Understanding TAVR device expansion as it relates to morphology of the bicuspid aortic valve: A simulation study

The bicuspid aortic valve (BAV) is a common and heterogeneous congenital heart abnormality that is often complicated by aortic stenosis. Although initially developed for tricuspid aortic valves (TAV), transcatheter aortic valve replacement (TAVR) devices are increasingly applied to the treatment of BAV stenosis. It is known that patient-device relationship between TAVR and BAV are not equivalent to those observed in TAV but the nature of these differences are not well understood. We sought to better understand the patient-device relationships between TAVR devices and the two most common morphologies of BAV. We performed finite element simulation of TAVR deployment into three cases of idealized aortic anatomies (TAV, Sievers 0 BAV, Sievers 1 BAV), derived from patient-specific measurements. Valve leaflet von Mises stress at the aortic commissures differed by valve configuration over a ten-fold range (TAV: 0.55 MPa, Sievers 0: 6.64 MPa, and Sievers 1: 4.19 MPa). First principle stress on the aortic wall was greater in Sievers 1 (0.316 MPa) and Sievers 0 BAV (0.137 MPa) compared to TAV (0.056 MPa). TAVR placement in Sievers 1 BAV demonstrated significant device asymmetric alignment, with 1.09 mm of displacement between the center of the device measured at the annulus and at the leaflet free edge. This orifice displacement was marginal in TAV (0.33 mm) and even lower in Sievers 0 BAV (0.23 mm). BAV TAVR, depending on the subtype involved, may encounter disparate combinations of device under expansion and asymmetry compared to TAV deployment. Understanding the impacts of BAV morphology on patient-device relationships can help improve device selection, patient eligibility, and the overall safety of TAVR in BAV.

Relationship between indexed aortic area and aortic diameter in bicuspid aortic valve aortopathy: A retrospective cohort study

BACKGROUND

Aortic dissection is a life-threatening complication of bicuspid aortic valve (BAV)-associated aortopathy. In these populations, whilst prophylactic replacement of proximal thoracic aortic aneurysms (TAAs) is generally recommended at threshold diameters ≥5.5 cm, dissection may occur in smaller aortas. An alternative size-based parameter, the cross-sectional aortic area/patient height ratio (indexed aortic area, IAA), correlates with increased dissection risk at abnormal values > 10 cm2/m. We sought to assess the utility of the IAA in identifying at-risk BAV-associated TAAs with abnormal IAA, albeit with sub-threshold aortic diameter.

MATERIALS AND METHODS

We retrospectively identified 69 patients with BAV-associated TAAs who underwent surgical repair between 2010 and 2016. Aortic diameter was measured on pre-operative imaging, and IAA calculated, at the mid-sinus of Valsalva, sino-tubular junction and mid-ascending aorta for each patient. We determined proportions of aneurysms with IAA >10 cm2/m, median IAAs corresponding to aortic diameters <4.0 cm, 4.0-4.5 cm, 4.5-5.0 cm, 5.0-5.5 cm and >5.5 cm, and median aortic diameters corresponding to an abnormal IAA.

RESULTS

50.9%, 12.5% and 64.6% of aneurysms at the sinus of Valsalva, sino-tubular junction and mid-ascending aorta, respectively, had an abnormal IAA. 51.9% and 88.9% of patients with aortic diameter 4.5-5.0 cm and 5.0-5.5 cm, respectively, had an abnormal IAA. In aneurysms with abnormal IAA involving the sinus of Valsalva, sino-tubular junction, and mid-ascending aorta, median aortic diameters were 4.98 cm, 5.04 cm and 5.11 cm, respectively. Overall, 57/72 (79.2%) at-risk aneurysms with IAA >10 cm2/m had diameters smaller than the 5.5 cm guideline cut-off for surgical intervention.

CONCLUSION

Significant proportions of BAV-associated TAAs are at increased risk of aortic dissection attending an IAA >10 cm2/m, whilst not fulfilling the size criteria indicating aortic surgery in contemporary guidelines. Further analysis of IAA in larger BAV cohorts is necessary to clarify its role in patient selection and optimal timing for prophylactic aortic replacement.

Transcatheter Aortic Valve Implantation Current Indications and Future Directions

Degenerative heart valve disease is associated with significant morbidity and mortality and healthcare expenditures. Transcatheter heart valve repair and replacement has introduced a fundamental change in the therapeutic management and transcatheter aortic valve replacement (TAVR) has gained substantial popularity. Favorable results from randomized trials and large real world registries lead to TAVR being considered a standard procedure with high rates of procedural success and low rates of peri-procedural complications. This article aims to review the past evolution, summarize the available evidence, discuss current indications and limitations and venture a glimpse into the future of percutaneous interventions for aortic valve disease.