What is the clinical evidence from this study?

Study design: Cohort. Population: Low-Gradient Aortic Stenosis (n=221). Intervention: Dobutamine stress echocardiography (DSE) vs. Cardiac Computer Tomography (C-CT) Aortic Valve Calcification (AVC) score. Primary outcome: Diagnostic accuracy (AUC) of DSE mean gradient for severe AS (AUC 0.90, p=0.0007).

March 1, 2023Open Access

Dobutamine Stress Echocardiography in Low-Gradient Aortic Stenosis

Key Result

Dobutamine stress echocardiography demonstrated significant diagnostic heterogeneity for severe aortic stenosis depending on LVEF, with the highest accuracy (AUC 0.90) in patients with LVEF <35%.

Study Design

Type

Cohort (n=221)

Blinding

Single-blind

Multicenter

Yes

Structured PICO

Does dobutamine stress echocardiography accurately diagnose severe aortic stenosis compared to C-CT in patients with low-gradient AS across different LVEF ranges?

Population

221 adults (aged ≥18 years) with low-gradient aortic stenosis (aortic mean-gradient <40 mmHg, AVA <1.0 cm2) and stroke volume index ≤35 mL/m2, stratified by LVEF (<35%, 35-50%, >50%). Multinational (Canada, Denmark).

Intervention

Dobutamine stress echocardiography (DSE) initiated at 5 µg/kg/min and increased every 3 min to a maximal dosage of 20 µg/kg/min.

Comparator

Cardiac Computed Tomography (C-CT) derived Aortic Valve Calcification (AVC) score as the reference standard for severe AS (≥2000 AU for men, ≥1200 AU for women).

Outcome

Diagnostic accuracy of DSE (mean gradient, Vmax, AVA) for severe AS compared to C-CT AVC score, and safety/feasibility of DSE.surrogate

DSE is safe but its diagnostic accuracy for severe low-gradient aortic stenosis is highly dependent on LVEF, performing best in patients with LVEF <35% and poorly in those with LVEF ≥35%.

Main Result

Effect estimate: AUC 0.90

Absolute Event Rate: 0.9% vs 0.65%

p-value: p=0.0007

Limitations

AVC does not quantify fibrotic tissue, which might play an important role in the development of low-gradient AS or in bicuspid valves.
Current AVC thresholds are derived from patients with concordant AS and have not been validated in low-gradient AS patients.
Reproducibility of AVC may be challenging.

Abstract

Abstract Background Dobutamine stress echocardiography (DSE) is recommended by guidelines to distinguish between true-severe and pseudo-severe aortic stenosis (AS) in patients with low-gradients and left ventricular ejection fraction (LVEF) 50%. Methods Patients with aortic mean gradient 50%. Severe AS was defined as AVC score ≥2000 AU among men, and ≥1200 AU for women on C-CT. Results Two hundred twenty-one patients were included in the study. Seventy-eight (35%) presented with LVEF 50%. DSE was performed without adverse symptoms or significant arrhythmias in 215 (96%) patients and stroke volume increased uniformly with no significant differences between groups (p=0.28). Mean gradient and V max during DSE showed significantly diagnostic heterogeneity between LVEF groups, being most precise when LVEF 50%, and leads to similar increase in stroke volume as in patients with LVEF <50%. The diagnostic accuracy of DSE, compared to AVC as the reference for severe AS, depends on LVEF with highest accuracy in patients with LVEF <35%. Suggested reference thresholds for DSE may not be the most accurate for AS severity, when compared to AVC. What are the clinical implications? Based on our study, we suggest that DSE should primarily be used for determining AS severity in patients with LVEF <35%.

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