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Dobutamine Stress Echocardiography for Management of Low-Flow, Low-Gradient Aortic Stenosis
Mohamed-Salah Annabi1, Eden Touboul1, Abdellaziz Dahou1
1Institut Universitaire de Cardiologie et de Pneumologie, Université Laval, Québec, Canada.
Insights
Current guidelines for severe aortic stenosis (AS) lack validation in low-flow, low-gradient AS. Projected aortic valve area (AVAProj) better predicts mortality than standard dobutamine stress echocardiography criteria in these patients.
Area of Science:
- Cardiology
- Echocardiography
- Valvular Heart Disease
Background:
- Current American College of Cardiology/American Heart Association guidelines define true-severe aortic stenosis (AS) using mean gradient (MG) ≥40 mm Hg and aortic valve area (AVA) ≤1 cm² during dobutamine stress echocardiography (DSE).
- These criteria have not been validated, particularly in patients with low-flow, low-gradient AS (LF-LG AS).
Purpose of the Study:
- To assess the validity of DSE criteria for identifying true-severe AS in patients with LF-LG AS.
- To evaluate the predictive value of these criteria for mortality in LF-LG AS patients.
Main Methods:
- 186 patients with low ejection fraction LF-LG AS underwent DSE, measuring MG, AVA, and projected AVA (AVAProj).
- AS severity was independently confirmed by valve macroscopic evaluation, CT-measured aortic valve calcium, or both.
- Mortality was assessed in a subset of conservatively managed patients.
Main Results:
- AVAProj ≤1 cm² correctly classified AS severity in 70% of patients, outperforming standard MG and AVA criteria.
- Standard DSE criteria (MG ≥40 mm Hg or AVA ≤1 cm²) had limited accuracy (47-60%) in classifying AS severity.
- In conservatively managed patients, AVAProj ≤1 cm² strongly predicted mortality (HR: 3.65; P=.0003), unlike standard MG and AVA.
Conclusions:
- DSE criteria for true-severe AS have limited value in low LVEF LF-LG AS patients.
- AVAProj is superior to standard DSE parameters in distinguishing true-severe from pseudo-severe AS.
- AVAProj is a strong predictor of mortality in LF-LG AS patients managed conservatively.
Background:
In the American College of Cardiology/American Heart Association guidelines, patients are considered to have true-severe stenosis when the mean gradient (MG) is ≥40 mm Hg with an aortic valve area (AVA) ≤1 cm2 during dobutamine stress echocardiography (DSE). However, these criteria have not been previously validated.
Objectives:
The aim of this study was to assess the value of these criteria to predict the presence of true-severe AS and the occurrence of death in patients with low-flow, low-gradient aortic stenosis (LF-LG AS).
Methods:
One hundred eighty-six patients with low left ventricular ejection fraction (LVEF) LF-LG AS were prospectively recruited and underwent DSE, with measurement of the MG, AVA, and the projected AVA (AVAProj), which is an estimate of the AVA at a standardized normal flow rate. Severity of AS was independently corroborated by macroscopic evaluation of the valve at the time of valve replacement in 54 patients, by measurement of the aortic valve calcium by computed tomography in 25 patients, and by both methods in 8 patients. According to these assessments, 50 of 87 (57%) patients in the study cohort had true-severe stenosis.
Results:
Peak stress MG ≥40 mm Hg, peak stress AVA ≤1 cm2, and the combination of peak stress MG ≥40 mm Hg and peak stress AVA ≤1 cm2 correctly classified AS severity in 48%, 60%, and 47% of patients, respectively, whereas AVAProj ≤1 cm2 was better than all the previous markers (p < 0.007), with 70% correct classification. Among the subset of 88 patients managed conservatively (47% of the cohort), 52 died during a follow-up of 2.8 ± 2.5 years. After adjustment for age, sex, functional capacity, chronic kidney failure, and peak stress LVEF, peak stress MG and AVA were not predictors of mortality in this subset. In contrast, AVAProj ≤1 cm2 was a strong predictor of mortality under medical management (hazard ratio: 3.65; p = 0.0003).
Conclusions:
In patients with low LVEF LF-LG AS, the DSE criteria of a peak stress MG ≥40 mm Hg, or the composite of a peak stress MG ≥40 mm Hg and a peak stress AVA ≤1 cm2 proposed in the guidelines to identify true-severe AS and recommend valve replacement, have limited value to predict actual stenosis severity and outcomes. In contrast, AVAProj better distinguishes true-severe AS from pseudo-severe AS and is strongly associated with mortality in patients under conservative management. (Multicenter Prospective Study of Low-Flow Low-Gradient Aortic Stenosis [TOPAS]; NCT01835028).
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