How to avoid the pitfalls of underdiagnosing severe aortic stenosis (sAS)

The characterisation of aortic stenosis (AS) severity remains an ongoing challenge in clinical practice. Patients with discordant echocardiographic indices are commonly described in reports as having less than sAS despite meeting the criteria for sAS. Understanding the limitations of echocardiographic and adopting a step-by-step integrative approach to confirm AS severity can help meet the challenge.1-3

Severity of stenosis and concordant/discordant indices1

In patients with concordant indices (peak jet velocity [Vmax] ≥4 m/s and aortic valve area [AVA] ≤1 cm² ), there is little ambiguity about the severity of AS and when aortic valve replacement (AVR) is indicated. However, discordant indices (Vmax <4 m/s and AVA ≤1 cm² ) raises uncertainty about the actual severity of the stenosis and thus about the therapeutic management.1

A retrospective analysis was performed at a single academic medical centre on all echocardiograms with an AVA ≤1.2 cm² and Vmax ≥3 m/s from 1 December 2014 through 30 October 2017.1
Evaluating echocardiography reports from 807 patients found that:1
  • 40.0% of patients had concordant indices and 35.8% had discordant indices of AS
    • Patients with discordant indices were more commonly female (54.0% vs 44.3%) compared with those with concordant indices
    • 303 (93.8%) patients with concordant indices were reported as sAS
    • 123 (42.6%) patients with discordant indices were reported as sAS
      • 45 (49.5%) patients with discordant indices and a preserved ejection fraction ≥50% and a stroke volume index <35 mL/m² were reported as sAS
The relationships of recorded severity with AVA and Vmax1

Adapted from Raddatz MA et al. Open Heart 2020.

Given the potential benefit of AVR in patients with AVA ≤1 cm² , regardless of Vmax, it is important to avoid the underestimation of AS severity. As it could influence clinical management decisions and lead to fewer and later referrals.1

AS assessment: Echocardiography and the integrated, stepwise approach2,3

A large challenge in AS assessment, as we have seen, is in patients demonstrating discordant indices, also referred to as ‘low-gradient AS’.

 

Keys to overcoming this challenge are excluding measurement errors and the utilisation of complementary diagnostic modalities alongside echocardiography.²

 

Most common measurement errors:

Velocity

Failure to image from non-apical windows may result in underestimation of peak velocities – a multiwindow approach to imaging is therefore recommended. Optimising the signal by decreasing gain, increasing wall filter, adjusting baseline, curve and scale can also help2,3

Left ventricular outflow tract (LVOT) diameter 

Underestimation of the LVOT diameter contributes significantly to discordant AS parameters. It is recommended to measure at or just below the level of the aortic annulus using the mid-systolic image that bisects the LVOT in its largest dimension. In the presence of LVOT ectopic calcification, use the plane that bisects the largest diameter but excludes the calcification from the measurement2

Complementary diagnostic modalities:

  • Advanced echocardiography including transoephageal echocardiography (TOE) and 3D transthoracic echocardiography (TTE)3
    • Confirmation of LVOT measurements
    • Confirmation of stroke volume (SV) measurements
  • Dobutamine stress echocardiography3
    • To distinguish between pseudo severe and sAS in patients with discordant indices and an impaired (<50%) left ventricular ejection fraction (LVEF)
  • Multislice computed tomography3
    • For aortic valve calcium (AVC) scoring in patients with discordant indices and preserved LVEF (≥50%) to assess the likelihood of severe AS. A calcium score of ≥2000 for men and ≥1200 for women signify that severe AS is likely
In patients with discordant grading a step-by-step integrative approach that includes several imaging modalities and parameters should be considered to confirm AS severity and the need for AVR.²

Assessing the severity of AS is challenging but is crucial in optimising treatment timing.

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References

  • 1Raddatz MA, et al. Open Heart. 2020;7(2):e001331.
  • 2Delgado V, et al. JACC Cardiovasc Imaging. 2019;12(2):267–282.
  • 3Baumgartner H, et al. Eur Heart J Cardiovasc Imaging 2017;18(3):254–275.

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