Clinical implications of the biomechanics of bicuspid aortic valve and bicuspid aortopathy

Quantitative in silico analysis for patient-specific annuloplasty in bicuspid aortic valve regurgitation

Bicuspid aortic valve (BAV) patients are more predisposed to aortic regurgitation. Annuloplasty is a crucial therapeutic intervention, however, determining its ideal size remains a clinical challenge. This study aims to quantify the effects of varying annuloplasty sizes on treating BAV regurgitation, providing optimal size range for effective treatment while avoiding complications. Annuloplasty was simulated on a patient-specific BAV model using 19-27 mm diameter Hegar dilators to reduce the basal ring and elastic ring sutures to constrain it. Finite element simulation was performed to simulate BAV motion, followed by computational fluid dynamics simulation to obtain hemodynamic parameters at peak systole. Results show that as the basal ring size decreased, the leaflet coaptation area increased, accompanied by a reduction in maximum principal stress at the coaptation zone. However, the reduction in annuloplasty size significantly elevated the peak systolic flow velocity within the sinus, particularly near the basal ring, leading to a higher wall shear stress in the adjacent region. Moreover, an excessively small basal ring diameter induced a sharp increase in transvalvular pressure gradient. These findings suggest that the small-sized annuloplasty enhances BAV function and durability, whereas excessive ring reduction may aggravate mechanical burden on the aortic root, potentially resulting in long-term complications such as tissue damage and stenosis. Thus, these factors establish critical upper and lower limits for optimal annuloplasty sizing.

Ascending Aortic Progression After Isolated Aortic Valve Replacement Among Patients with Bicuspid and Tricuspid Aortic Valves

OBJECTIVES

The aims of the present study were to compare the long-term outcomes for ascending aortic dilatation and adverse aortic events after isolated aortic valve replacement between patients with bicuspid aortic valve (BAV) and tricuspid aortic valve ( TAV).

METHODS

This retrospective study included 310 patients who had undergone isolated aortic valve replacement with an ascending aorta diameter ≤ 45 mm between January 2010 and September 2021. The patients were divided into BAV group (n=90) and TAV group (n=220). The differences in the dilation rate of the ascending aorta and long-term outcomes were analyzed.

RESULTS

Overall survival was 89 ± 4% in the BAV group vs. 75 ± 6% in the TAV group at 10 years postoperatively (P=0.007), yet this difference disappeared after adjusting exclusively for age (P=0.343). The mean annual growth rate of the ascending aorta was similar between the two groups during follow-up (0.5 ± 0.6 mm/year vs. 0.4 ± 0.5 mm/year; P=0.498). Ten-year freedom from adverse aortic events was 98.1% in the BAV group vs. 95.0% in the TAV group (P=0.636). Multivariable analysis revealed preoperative ascending aorta diameter to be a significant predictor of adverse aortic events (hazard ratio: 1.76; 95% confidence interval: 1.33 to 2.38; P<0.001).

CONCLUSION

Our study revealed that the long-term survival and the risks of adverse aortic events between BAV and TAV patients were similar after isolated aortic valve replacement. BAV was not a risk factor of adverse aortic events.

Aortic Valve Engineering Advancements: Precision Tuning with Laser Sintering Additive Manufacturing of TPU/TPE Submillimeter Membranes

Synthetic biomaterials play a crucial role in developing tissue-engineered heart valves (TEHVs) due to their versatile mechanical properties. Achieving the right balance between mechanical strength and manufacturability is essential. Thermoplastic polyurethanes (TPUs) and elastomers (TPEs) garner significant attention for TEHV applications due to their notable stability, fatigue resistance, and customizable properties such as shear strength and elasticity. This study explores the additive manufacturing technique of selective laser sintering (SLS) for TPUs and TPEs to optimize process parameters to balance flexibility and strength, mimicking aortic valve tissue properties. Additionally, it aims to assess the feasibility of printing aortic valve models with submillimeter membranes. The results demonstrate that the SLS-TPU/TPE technique can produce micrometric valve structures with soft shape memory properties, resembling aortic tissue in strength, flexibility, and fineness. These models show promise for surgical training and manipulation, display intriguing echogenicity properties, and can potentially be personalized to shape biocompatible valve substitutes.

Bicuspid aortic valve and its ascending aortopathy

PURPOSE OF REVIEW

To synthesize and critically assess recent clinical and research advancements in pediatric bicuspid aortic valve (BAV) and its associated aortopathy.

RECENT FINDINGS

In pediatric patients with BAV, progressive aortic dilation (i.e. bicuspid aortopathy) is commonly present and associated with increased risk for aortic aneurysm, dissection, and surgery in adulthood. Ongoing research explores the cause, incidence, and progression of bicuspid aortopathy to promote earlier diagnosis and improve preventive management. Recent findings include: high familial incidence and need for improved familial screening; safety of recreational physical activity in most affected children; potential for medical management to slow aortic growth; feasibility of pediatric registries to evaluate longitudinal outcomes; and potential genetic and hemodynamic biomarkers for disease risk stratification.

SUMMARY

Pediatric bicuspid aortopathy is an important area for investigation and preventive management to improve long-term cardiovascular outcomes. Recent literature promotes familial screening, recreational exercise, medical prophylaxis, registry-based longitudinal evaluation, and continued scientific inquiry.

Aortic Dilatation in Pediatric Patients with Bicuspid Aortic Valve: How the Choice of Nomograms May Change Prevalence

BACKGROUND

Aortic dilation (AoD) is commonly reported in patients with bicuspid aortic valve (BAV) and has been related to flow abnormalities and genetic predisposition. AoD-related complications are reported to be extremely rare in children. Conversely, an overestimate of AoD related to body size may lead to excess diagnoses and negatively impact quality of life and an active lifestyle. In the present study, we compared the diagnosis performance of the newly introduced Q-score (based on a machine-learning algorithm) versus the traditional Z-score in a large consecutive pediatric cohort with BAV.

MATERIALS AND METHODS

Prevalence and progression of AoD were evaluated in 281 pediatric patients ages > 5 and < 18 years at first observation, 249 of whom had isolated BAV and 32 had BAV associated with aortic coarctation (CoA-BAV). An additional group of 24 pediatric patients with isolated CoA was considered. Measurements were made at the level of the aortic annulus, Valsalva sinuses, sinotubular aorta, and proximal ascending aorta. Both Z-scores using traditional nomograms and the new Q-score were calculated at baseline and at followup (mean 4.5 years).

RESULTS

A dilation of the proximal ascending aorta was suggested by traditional nomograms (Z-score > 2) in 31.2% of patients with isolated BAV and 18.5% with CoA-BAV at baseline and in 40.7% and 33.3%, respectively, at followup. No significant dilation was found in patients with isolated CoA. Using the new Q-score calculator, ascending aorta dilation was detected in 15.4% of patients with BAV and 18.5% with CoA-BAV at baseline and in 15.8% and 3.7%, respectively, at followup. AoD was significantly related to the presence and degree of aortic stenosis (AS) but not to aortic regurgitation (AR). No AoD-related complications occurred during the followup.

CONCLUSIONS

Our data confirm the presence of ascending aorta dilation in a consistent subgroup of pediatric patients with isolated BAV, with progression during followup, while AoD was less common when CoA was associated with BAV. A positive correlation was found with the prevalence and degree of AS, but not with AR. Finally, the nomograms used may significantly influence the prevalence of AoD, especially in children, with a possible overestimation by traditional nomograms. This concept requires prospective validation in long-term followup.

Bicuspid aortic valve associated aortopathy: 2022 guideline update

PURPOSE OF REVIEW

Bicuspid aortic valve (BAV) disease is observed in 1-2% of the general population. In addition to valve-related complications (such as aortic stenosis and aortic regurgitation), individuals with BAV often develop dilatation of the proximal aorta (aortic root and ascending aorta), a condition termed BAV aortopathy. The development of BAV aortopathy can occur independent of valvular alterations and can lead to aneurysm formation, aortic dissection or aortic rupture. This review aims to update the clinician with an approach to BAV aortopathy decision making in keeping with the 2022 American College of Cardiology (ACC)/American Heart Association (AHA) Guideline recommendations.

RECENT FINDINGS

The ACC/AHA 2022 guidelines provide a contemporary and comprehensive approach to the diagnosis and treatment of aortic pathologies. We review the thresholds for replacement of the aortic root and/or ascending aorta along with the strength and level of evidence recommendations. We also review the various Class 2A and 2B recommendations for earlier intervention, which emphasize the importance of experienced surgeons, and multidisciplinary aortic teams (MATs).

SUMMARY

BAV aortopathy is a common and heterogenous clinical problem. The decision making around timing of intervention requires a personalized approach that is based on the aortic dimensions, valve function, rate of growth, family history, patient factors, and surgical experience within MATs.

The Role of Genetic Testing in Patients with Heritable Thoracic Aortic Diseases

Heritable thoracic aortic disease (HTAD) is a term used to define a large group of disorders characterized by the occurrence of aortic events, mainly represented by aneurysm or dissection. These events generally involve the ascending aorta, although the involvement of other districts of the aorta or peripheral vessels may occur. HTAD can be classified as non-syndromic if the disorder is limited to the aorta, and syndromic when associated with extra-aortic features. About 20-25% of patients with non-syndromic HTAD exhibit a family history of aortic disease. Thus, a careful clinical evaluation of the proband and the first-degree family members is required to differentiate familial and sporadic cases. Genetic testing is essential since it allows confirmation of the etiological diagnosis of HTAD (particularly in patients with a significant family history) and may guide family screening. In addition, genetic diagnosis significantly impacts patients' management since the different conditions significantly differ with respect to natural history and treatment strategies. The prognosis in all HTADs is determined by the progressive dilation of the aorta, potentially leading to acute aortic events, such as dissection or rupture. Moreover, the prognosis varies according to the underlying genetic mutations. This review aims to describe the clinical characteristics and natural history of the most common HTADs, with particular emphasis on the role of genetic testing in risk stratification and management.