A novel functional index, aortic-valve-coefficient, for assessing aortic-stenosis in patients undergoing TAVR: A prospective-pilot study.

Background: Evaluating the severity of aortic stenosis (AS) can be challenging, particularly in patients with low-gradient (LG, Δp < 40 mmHg) AS.

Objective: This study aims to improve the accuracy of assessing severity of AS using a novel functional index- Aortic Valve Coefficient (AVC). The AVC is defined as ratio of mean transvalvular pressure-drop (Δp) to the proximal dynamic pressure (1/2 × blood density × V_LVOT²; V_LVOT: left ventricular outflow tract peak velocity).

Hypothesis: AVC, developed from fundamental fluid dynamic principles, is a better index for accessing AS severity as it incorporates square of V_LVOT and downstream pressure recovery.

Methods: This pilot prospective study enrolled 47 patients undergoing TAVR for AS. Using cardiac-catheterization-measured Δp and echocardiography-Doppler-derived V_LVOT, AVC was evaluated. Pre- and post-TAVR pressure-velocity measurements were obtained, resulting in a dataset with 78 data points, including 32 data points specifically linked to LG AS. Linear regression analysis was performed to correlate AVC with Δp, V_LVOT and aortic-valve-area. Welch 2-sample t-test was carried out to compare the means of AVC against aortic-valve-area.

Results: Moderate correlation (r = 0.85) was observed between AVC and aortic-valve-area indicating AVC could be a prospective index. However, correlation decreased (r = 0.75) in LG AS patients, indicating increased discordancy. Comparing AVC and aortic-valve-area in LG AS patients with left ventricular ejection fraction (LVEF) < 50 % and LVEF ≥50 %, t-test showed that AVC values are significantly different (p < 0.05) as compared to aortic-valve-area (p = 0.48).

Conclusion: AVC, a novel index, has the potential to improve assessment of AS severity and clinical decision making for treating patients with AS.

Condensed abstract: Complex hemodynamics, such as paradoxical "low-flow low-gradient (LG)" Aortic stenosis (AS) can be difficult to diagnose. Currently, mean transvalvular pressure-drop and flow-derived aortic-valve-area assess AS severity. Aortic valve coefficient (AVC) is a novel index which combines both pressure-drop and flow measurements to assess the severity of AS. A total of 47 patients (72 data points) were studied undergoing TAVR. In LG AS patients, t-test comparing left ventricular ejection fraction (LVEF) < 50 % and LVEF ≥50 % showed that AVC are significantly different (p < 0.05) as compared to aortic-valve-area (p = 0.48). Therefore, AVC could be a better index.