A subset of bicuspid aortic stenosis (AS) patients undergoing transcatheter aortic valve replacement (TAVR) may be at increased risk for progressive ascending aorta (AAo) dilation, according to a new exploratory analysis of 61 patients. The study identified 3 key factors associated with continuous AAo dilation: maximum transprosthetic gradient, transcatheter aortic valve (TAV) eccentricity at the leaflet outflow level and the raphe length–to–annulus mean diameter. While the sample size is relatively small, the findings should trigger larger studies into the link between transcatheter aortic valve structure and function with AAo dilation outcomes, the researchers said in a letter about the study, published online in JACC: Cardiovascular Interventions. The analysis was sparked by a need to elucidate the natural progression of AAo dilation in severe bicuspid AS patients with significant aortopathy undergoing TAVR, the letter’s authors, led by Yuheng Jia, MD, from Rigshospitalet in Denmark, noted. Bicuspid aortic valve (BAV) disease is a common cardiac pathology frequently associated with aortopathy, the authors noted, adding that in the patient population of focus, the dilated aorta is left untreated despite being linked with increased mortality. The 61 bicuspid AS patients included in the analysis underwent TAVR between 2008 and 2022 in one of 4 sites across Europe and China, using self-expanding (67%), balloon-expandable (30%) and mechanically expandable (3%) TAVs. They were narrowed down from a dataset on a total 969 patients, including only those with a maximum AAo diameter of ≥40mm and a post-implant computed tomography (CT) scan available beyond 1 year (median 2.9 years; interquartile range [IQR]: 1.6 - 3.7 years). In the study cohort, the maximum AAo diameter was 45.6 ± 3.9 mm. AAo dilatation was deemed to be either stable (<2 mm increase) or continuous ≥2 mm) after TAVR. The majority (85%) of patients maintained stable AAo dimensions during follow-up, however, continuous AAo dilation was noted in 15%, with an average maximum AAo diameter expansion rate of 1.4 mm/ year. The fastest expansion rate was 3.4 mm/ year, the authors noted, and 10 patients had a maximum AAo diameter above 50 mm at follow-up, though 7 of those were already above 50 mm pre-TAVR. The researchers conducted a stepwise logistic regression analysis to identify associated factors and independent predictors of continuous AAo dilatation after TAVR, screening 58 variables including clinical, procedural, CT and echocardiographic characteristics. Odds ratios (OR) for the 3 factors found through univariate logistic regression analysis to be associated with continuous AAo dilation (defined as P < 0.1) included; 1.30 for maximum transprosthetic gradient (95% confidence interval [CI]: 0.99-1.73; P = 0.058), 2.11 for TAV eccentricity at the leaflet outflow level (95% CI: 1.12-4.53; P = 0.031), and 4.09 for the raphe length–to–annulus mean diameter ratio (95% CI: 1.40-16.7; P = 0.022). In a multivariate analysis, the ratio of raphe length/aortic annulus mean diameter emerged as an independent predictor of continuous AAo dilatation (OR: 5.67; 95% CI: 1.50-35.3; P = 0.026). “These results indicate that a majority of BAV patients maintain stable AAo dimensions after TAVR. However, a subset of TAVR patients with certain anatomical and procedural characteristics may be at increased risk for progressive AAo dilatation,” said the researchers. Abnormal flow dynamics The researchers went on to speculate over potential explanations behind the associated variables identified in the study. BAV patients exhibit abnormal helical and eccentric AAo blood flow patterns, which result in increased aortic wall shear stress (WSS), they noted. “A recent cardiac magnetic resonance study further suggested that elevated regional WSS may contribute to a higher rate of continuous AAo dilatation,” they said. “Restoration of this flow pattern to a more central laminar flow by aortic valve replacement has been shown to result in a reduction in aortic WSS.” Bigger issue with expanded TAVR use Now that TAVR use is expanding to include younger populations, more patients with bicuspid AS and Aao dilation will be encountered, the authors added. The findings help to shed a “new light” on the issue, they said, and while further research is needed, the research underlines the importance of “a tailored assessment and and possibly influencing future procedural planning and postprocedural surveillance strategies.” Source: Jia Y, Khokhar AA, Piglrim T, et al. Research Letter: Ascending Aortic Growth Following TAVR in Bicuspid Aortopathy; A CT Follow-Up Study. JACC: Cardiovasc Interv 2024; DOI: 10.1016/j.jcin.2024.09.046. Image Credit: Дмитрий Симаков – stock.adobe.com