Patients and methods: The single-center observational study included 105 patients (55 females, 50 males; mean age: 78.8±6.7 years; range, 70 to 92 years) who underwent TAVI between October 2019 and September 2023. Comprehensive preprocedural evaluations were conducted, including echocardiography and computed tomography. Evolut R self-expandable supra-annular valves were used in the procedures.

Results: Hypertension (85.7%) and atrial fibrillation (78.2%) were the most common comorbidities, and 14.3% of patients exhibited moderate aortic regurgitation before TAVI. The mean aortic angle was 46.8±10.6° before the procedure. In receiver operating characteristic analysis, the aortic angle affecting aortic regurgitation after TAVI was determined as 49.5°. After TAVI, significant reductions in pulmonary artery pressures and aortic regurgitation prevalence were observed. Aortic regurgitation decreased in 38.1% of patients, remained unchanged in 47.6% of patients, and increased in 14.3% of patients. A weak linear relationship (R2=0.011) was observed between aortic insufficiency and the aortic angle.

Conclusion: The study showed that an aortic angle of 49.5° can be used to predict aortic regurgitation after TAVI. However, a weak linear correlation was detected between the aortic angle and aortic regurgitation.

Epidemiologically, AS represents a prevalent valvular heart disease, particularly in aging populations. Its prevalence escalates with age, and it is estimated that around 2 to 9% of individuals over 65 years exhibit some degree of AS.[4-6] As life expectancy rises, AS incidence is expected to surge, necessitating effective treatment strategies.[7]

Transcatheter aortic valve implantation (TAVI) involves inserting a prosthetic valve via catheter-based techniques, often through the femoral artery, and positioning it within the native aortic valve. This minimally invasive procedure allows for shorter recovery times and reduced complications.[8] Transcatheter aortic valve implantation utilization has increased due to technological advancements and acceptance as a viable AS treatment.[9,10]

While TAVI has revolutionized AS management, complications include vascular issues, bleeding, stroke, conduction abnormalities, and aortic regurgitation (AR).[11,12] Factors influencing AR after TAVI include anatomical considerations, valve sizing, and procedural techniques.[13,14] Moderate to severe AR can lead to heart failure and increased morbidity.[15]

Research into aortic valve anatomy and its impact on TAVI outcomes is evolving, with studies exploring aortic annulus dimensions, calcification, and angles.[16] The aortic angle, measured by computed tomography, refers to the angle between the horizontal and aortic annular planes in the coronal section. A greater angle may indicate higher risk for complications.[17,18]

This study aimed to investigate the correlation between the aortic angle and AR following TAVI in patients without advanced annular calcification, using self-expandable supra-annular valves, and offer insights into a specific TAVI subset, potentially refining prognostic information for this cohort.

Demographic data, comorbidities, and baseline characteristics were collected from electronic medical records. Preprocedural evaluations encompassed echocardiography, computed tomography, and the documentation of various cardiac parameters and anatomical measurements. All TAVI procedures were performed by experienced interventional cardiologists using the Medtronic Evolut R system self-expandable supra-annular valve (Medtronic, Minneapolis, MN, USA) Valve sizing (26, 29, or 34 mm) was determined based on individual patient anatomy. Pre- and postdilatation techniques were applied as clinically indicated.

Patients underwent meticulous predischarge assessments, including echocardiography and measurement of cardiac parameters. Followup evaluations aimed to compare pre-TAVI and post-TAVI values, assessing changes in left ventricular function, aortic gradients, pulmonary artery pressures, and the presence of aortic insufficiency.

The primary outcome was the impact of the aortic angle on AR. Secondary outcomes were the exploration of clinical and demographic factors that may influence variations in the aortic angle.

Statistical analysis
Statistical analysis was performed using IBM SPSS version 25.0 software (IBM Corp., Armonk, NY, USA). Descriptive statistics were used to summarize patient characteristics and baseline measurements. Continuous variables were presented as mean ± standard deviation (SD) or median with interquartile range (IQR). Paired t-tests or nonparametric tests were utilized to compare pre- and postprocedural values. Spearman correlation analyses were conducted to explore associations between variables. Receiver operating characteristic (ROC) analysis was employed to determine cutoff values for aortic angles affecting AR. A p-value <0.05 was considered statistically significant.

In the preprocedural echocardiographic assessments, the mean left ventricular ejection fraction (EF) was 48.1±14.1, the mean systolic pulmonary artery pressure was 43.8±10.3 mmHg, and the mean aortic gradient was 42.8±10.3 mmHg. Notably, 15 (14.3%) patients exhibited moderate to severe AR. The most common valve disease that was more than mild was mitral regurgitation (42.8%; Table 1).

Table 1: Clinical and demographic characteristics

In the preprocedural computed tomography evaluations, the mean left ventricular outflow tract diameter was 24.6±2.2, the mean aortic annulus diameter was 24.2±1.4, the mean left main coronary height was 14.4±3.0, and the mean right coronary height was 18.2±3.2. The sinus of Valsalva diameter, encompassing all three sinuses, yielded a mean measurement of 30.3±2.0. Notably, one-third of the patients exhibited moderate leaflet calcification. The degree of leaflet calcification was assessed using computed tomography, with mild calcification defined as scattered, thin calcifications covering less than 10% of the leaflet area, moderate calcification characterized by thicker calcifications covering 10 to 30% of the leaflet area, and severe calcification involving extensive, dense calcifications covering more than 30% of the leaflet area. Furthermore, the mean aortic angle was 46.8±10.6° (Table 1).

Evolut R self-expandable supra-annular 26-mm valves were used in 19%, 29-mm valves were used in 62%, and 34-mm valves were used in 19%. Predilatation was applied to 47.6% of the patients, and postdilatation was applied to 52.4%. A permanent pacemaker was needed after the procedure in 10 (9.5%) patients, and moderate AR was observed in 10 (9.5%) patients (Table 1).

The study compared pre-TAVI and predischarge echocardiographic parameters. As anticipated, a significant reduction was evident in the mean and peak aortic gradients before discharge (mean postprocedural gradient: 7.5±4.3 mmHg; peak aortic gradient: 14.9±7.7 mmHg; p<0.001). There was no significant difference between the mean EF (48.1±14.1%), left ventricular end-diastolic diameter (LVEDD; 47±11.5 mm), and left ventricular end-systolic diameter (LVESD; 32.8±6.5 mm) before TAVI and the mean EF (49.8±12.3%), LVEDD (48.6±5.3 mm), and LVESD (31.3±6.1 mm) before discharge. A significant decrease was noted in the systolic pulmonary artery pressure before discharge compared to preoperative levels (preoperative: 43.8±10.3; predischarge: 39.6±8.7; p=0.046). Additionally, the prevalence of moderate or higher AR decreased after valve implantation (preoperative: 14.3%; post-TAVI: 11.4%; p=0.033; Table 2).

Table 2: Comparison of preoperative and postoperative echocardiographic measurements

Patient characteristics affecting the aortic angle were evaluated with Spearman correlation analysis. A positive correlation was observed between interventricular septum thickness, ascending aorta diameter, and aortic angle (p=0.036 and p=0.004, respectively). A negative correlation was observed between EF, left ventricular outflow tract diameter, aortic annulus diameter, noncoronary cuspid sinus Valsalva diameter, sinus Valsalva height, right coronary artery height, and aortic angle (p=0.047, p=0.002, p=0.001, p=0.001, p=0.021, and p=0.001, respectively; Table 3).

Table 3: Clinical characteristics affecting the aortic angle

A ROC analysis was performed to determine the cutoff value for the aortic angle affecting the AR after TAVI (before postdilatation). An aortic angle of 49.5° was determined as the cutoff value for the development of AR after TAVI, with 56% sensitivity and 50% specificity (area under the curve: 0.653; Figure 1).

Figure 1: ROC analysis of the effect of the aortic angle on AR after TAVI.
AUC: Area under the curve; ROC: Receiver operating characteristic; AR: Aortic regurgitation; TAVI: Transcatheter aortic valve implantation; SE: Standard error; CI: Confidence interval.

Moderate AR was observed in 12 patients after TAVI (before postdilatation). Of the patients who developed moderate AR before postdilatation, the aortic angle was above 49.5° in 10 (Figure 2).

Figure 2: The graphical representation of the AR observed in patients according to the cutoff value of the aortic angle determined according to ROC analysis with a column chart.
AR: Aortic regurgitation; ROC: Receiver operating characteristic.

The change in AR after TAVI (before discharge) compared to before TAVI was examined in all patients. At least one-degree decrease in AR was observed in 40 (38.1%) patients, the same level was observed in 50 (47.6%) patients, and an increase in AR was observed in 15 (14.3%) patients (Figure 3).

Figure 3: The graphical representation of the change in AR in the echocardiography performed after TAVI (before discharge) compared to before TAVI with a bar graph.
TAVI: Transcatheter aortic valve implantation; AR: Aortic regurgitation.

When post-TAVI (before postdilatation) AR was divided into none, mild, and moderate, a weak linear relationship was detected between AR and the aortic angle (R2=0.011; Figure 4).

Figure 4: The graphical representation of the linear relationship between aortic insufficiency and the aortic angle after TAVI (before postdilation) with a scatter plot graph.
TAVI: Transcatheter aortic valve implantation; AR: Aortic regurgitation.

In line with our investigation, Roule et al.[19] demonstrated an association between increased angulation between the ascending aorta and the left ventricle long axis and higher rates of AR after TAVI, independent of other potential correlations. Conversely, conflicting findings emerged from other studies. One study suggested that an aortic angle ≥48° did not impact procedural success or in-hospital outcomes and recommended against considering it when determining valve selection.[20] Another study indicated that the aortic angle influenced procedural success in balloon-expandable valves but had no effect on self-expandable valves.[21]

Our study aligns with prior research, confirming the significance of the aortic angle in predicting AR following TAVI. The identified cutoff angle of 49.5° holds merit in assessing risk and forecasting outcomes for TAVI patients. Notably, our study reveals a correlation between higher aortic angles and the development of moderate AR after TAVI, albeit with a weak linear relationship. These insights underscore the importance of thorough preprocedural evaluations, emphasizing the necessity of meticulous assessment of aortic anatomy to anticipate and manage post-TAVI complications effectively.

Our investigation into patient characteristics influencing the aortic angle revealed potential predictors for post-TAVI outcomes. Positive correlations with interventricular septum thickness and ascending aorta diameter, alongside negative correlations with parameters such as EF, left ventricular outflow tract diameter, aortic annulus diameter, and sinus of Valsalva dimensions, provide nuanced insights into anatomical factors influencing the aortic angle. These correlations offer the potential for risk stratification and personalized approaches in TAVI procedures.

Although there is a lack of studies investigating specific associations between the aortic angle and interventricular septal hypertrophy, the study by Yoshitani et al.[22] indicated that surgical aortic valve replacement was more effective in improving functional impairment in the presence of interventricular septal hypertrophy in AS patients compared to TAVR. Additionally, sharper angulation of the aortic arch has been linked to late AR after arterial switch surgery for ascending aortic dilatation and transposition of the great arteries.[23] This highlights the diverse impact of aortic geometry on various cardiac conditions.

A decrease in left ventricular EF can remodel the left ventricle, resulting in a leftward shift and a flatter appearance at the apex. This alteration in shape helps elucidate the negative relationship between an increased aortic angle and EF.

Our study's focus on patients without advanced annular calcification, utilizing Evolut R self-expandable supra-annular valves, characterizes a distinct subset of TAVI patients. This focused approach provides unique insights into this subset, potentially facilitating more refined prognostic assessments for this subgroup.

The observed improvements in aortic gradients, pulmonary artery pressures, and the reduction in moderate or higher AR after TAVI underscore the procedure’s efficacy in managing valvular pathologies.[24] These improvements highlight the clinical benefits and success of TAVI in relieving symptomatic burden among patients with severe AS.

Our study aimed to identify the primary risk factors contributing to aortic insufficiency following TAVI procedures, with a particular focus on the aortic angle. One of the significant findings was the association between an increased aortic angle and a higher incidence of aortic insufficiency. To ensure a more accurate assessment of this relationship, patients with bicuspid aortic valves were excluded from our study. This exclusion was critical in eliminating a well-known confounding factor that could independently affect the outcomes. We acknowledge that aortic insufficiency is multifactorial, and other potential risk factors such as leaflet calcification extent, annular dimensions, bicuspid aortic valves, and overall valve morphology could play crucial roles. Our findings emphasize the need for future studies to incorporate a broader evaluation of these additional risk factors. A comprehensive analysis that includes various anatomical and procedural factors will provide a more holistic understanding of the determinants of aortic insufficiency after TAVI.

This study had several limitations that warrant consideration. The study's single-center observational design and limited sample size might constrain the generalizability of the findings. Additionally, potential confounders not accounted for in the analysis, incomplete medical records, and retrospective data collection could introduce bias due to missing information. While correlations were established, determining causation necessitates further prospective investigations encompassing comprehensive multifactorial analyses.

In conclusion, this study highlights the pivotal role of the aortic angle in predicting AR after TAVI, establishing a crucial threshold at 49.5°. Investigating correlations between the aortic angle and patient characteristics revealed potential predictors for post-TAVI outcomes, offering avenues for further exploration. The observed improvements in aortic gradients, pulmonary artery pressures, and decreased prevalence of moderate or higher AR after TAVI underscore the procedure's efficacy in managing valvular pathologies. While a weak linear correlation between AR and the aortic angle was noted, the study emphasizes the significance of meticulous preprocedural assessments for predicting and managing complications.

Data Sharing Statement: The data that support the findings of this study are available from the corresponding author upon reasonable request.

Author Contributions: Conceived of the presented idea: T.O., F.P. Developed the theory and performed the computations: F.P.; Verified the analytical methods: B.Y.; Supervised the findings of this work: T.O., B.Y. All authors discussed the results and contributed to the final manuscript.

Conflict of Interest: The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

Funding: The authors received no financial support for the research and/or authorship of this article.

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