Features and Prognosis of High-Gradient Aortic Stenosis

Sep 24, 2024
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Authors:
Ito S, Oh JK, Michelena HI, et al.
Citation:
High-Gradient Aortic Stenosis With Valve Area >1.0 cm2: The “Forgotten” Discordant Hemodynamic Phenotype. JACC Cardiovasc Imaging 2024;Sep 18:[Epublished].
Summary By:
Sarah Kohnstamm, MD, FACC

Quick Takes

  • This retrospective study evaluated the features and prognosis of patients with high-gradient (mean gradient >40 mm Hg, peak velocity >4.0 m/s) aortic stenosis (AS) with calculated aortic valve area (AVA) >1.0 cm2.
  • Patients in this high-gradient AS group with an AVA >1.0 cm2 had:
    1. Higher mortality rates than the expected mortality of the general population.
    2. Lower mortality rates when compared to the other AS profiles (high-gradient with a calculated AVA <1.0 cm2 and low-gradient with a calculated AVA <1.0 cm2).
    3. Better survival outcomes when undergoing an AVR compared to those not undergoing AVR.
  • Providers should not be falsely reassured by the presence of an AVA of 1.0 cm2 when patients have high gradients.

Study Questions:

What are the clinical features and prognosis of patients with high-gradient (HG) aortic stenosis (AS) with a calculated aortic valve area (AVA) of >1.0 cm2?

Methods:

This was a retrospective single-center study of 3,209 patients identified with native AS from an echocardiography database between 2010 and 2013. Patients with prior valve surgery, left ventricular outflow tract (LVOT) obstruction, ≥ moderate aortic or mitral regurgitation, or ≥ moderate mitral stenosis were excluded. Patients were classified according to AVA (cm2), peak velocity (m/s), and mean pressure gradient (MG) (mm Hg) and placed into the following four groups: (1) HG-AVA >1 (>1.0, ≥4, and ≥40); (2) HG-AVA ≤1 (≤1.0, ≥4, and ≥40); (3) LG-AVA ≤1 (low gradient) (≤1.0, <4, and <40); and (4) moderate AS = 1.0 < AVA ≤1.5, 3 ≤ peak velocity <4, and 20 ≤ MG <40.

Results:

The HG-AVA >1 group had 230 cases (7.2% of total cohort, and 14% of patients with HG AS) and compared to the other groups were younger (70.2 ± 12 years), more frequently male (85.7%), and had larger body surface areas (BSAs) (2.1 ± 0.2), LVOT diameters (2.43 ± 0.19), calculated stroke volumes (115 ± 19.3), fewer comorbidities, and a higher prevalence of bicuspid aortic valves (BAVs) (39.6%). Peak velocity and MG in the HG-AVA >1 group were lower than in the HG-AVA ≤1 group at 44.0 mm Hg and 4.3 m/s compared to 51 and 4.6 (p < 0.01 for all). During the median follow-up of 944 days (Q1-Q3: 27-2,212), there were 1,523 deaths total (47.5%). All-cause mortality was higher in the HG-AVA ≤1 group (hazard ratio [HR], 1.4; 95% confidence interval [CI], 1.1-1.7), the LG-AVA ≤1 group (HR, 2.8; 95% CI, 2.2-3.6), and moderate AS group (HR, 1.4; 95% CI, 1.1-1.7) when compared to the HG-AVA >1 group. After adjusting for age, comorbidities, presence of BAV, and LV ejection fraction, these differences were no longer significant. However, patients in the HG-AVA >1 group had higher mortality rates when compared to age- and sex-matched mortality of the general population. In the HG-AVA >1 group, 67.4% of patients underwent aortic valve replacement (AVR) and had better survival outcomes than those who did not undergo AVR (p < 0.001) after balancing the two groups.

Conclusions:

Patients with HG AS with calculated AVA >1.0 cm cm2 have:

  1. Higher mortality rates than the expected mortality of the general population.
  2. Lower mortality rates when compared to the other AS profiles (HG-AVA <1.0 cm2 and LG-AVA <1.0 cm2).
  3. Better survival outcomes when undergoing an AVR when compared to those not undergoing AVR after balancing the two groups.

Perspective:

Current echocardiographic guidelines to diagnose severe AS include a peak velocity ≥4 m/s and mean gradient ≥40 mm Hg. By applying the Continuity Equation (CE), these measurements will typically result in a calculated AVA of <1.0 cm2. However, discrepancies between calculated valve area and the hemodynamic parameters are common, can be difficult to reconcile, and lead to uncertainty as to the timing of an intervention. This study’s cohort found the incidence of this HG-AVA >1.0 cm2 group to be 7%, with comparatively younger patients, more men with larger BSAs/body mass indexes, and a much higher prevalence of BAVs (39.6%).

The authors do note several limitations of this retrospective single-center study, including the data predating the widespread use of TAVR and the lack of strain data to better assess LV systolic function. More importantly, the accuracy of the calculated AVA through the use of the CE relies greatly upon accurate LVOT diameter assessments. Small errors in this measurement get further magnified by squaring the value in the CE. The LVOT diameters were significantly larger in the HG-AVA >1.0 cm2 group (an average of 24 mm), which could track with the patients being predominantly male and having a larger BSA, but in turn, this also increases the calculated stroke volume and contributes to being considered a high-flow state. For future research, it would be interesting to see how the calculated AVA values in this HG-AVA >1.0 cm2 group correlate to actual measured AVAs (such as on computed tomography, cardiac magnetic resonance imaging [MRI], or 3D echocardiography) to ensure these calculated AVAs are real, and not just mathematical constructs.

Clinical Topics: Noninvasive Imaging, Valvular Heart Disease, Echocardiography/Ultrasound

Keywords: Aortic Valve Stenosis, Echocardiography, Heart Valve Diseases


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