Dobutamine echocardiography impact on managing low-gradient aortic stenosis and solving the issue with inconclusive studies

Background Guidelines advocate the use of dobutamine echocardiography (DSE) in low-gradient aortic stenosis (LGAS: AVA<1cm² with AVMG<40mmHg) with reduced left ventricular ejection fraction (LVEF <50%) for determining AS severity and deciding on subsequent patient management. However, a significant proportion of patients have inconclusive DSE (indeterminate AS). Purpose We aimed to assess the impact of DSE on the management of patients with LGAS and reduced LVEF as well as the application of transaortic flow-based criteria for severe AS to improve the diagnostic yield of DSE. Finally, we aimed to review the impact of aortic valve intervention in those with indeterminate AS. Methods Accordingly, a retrospective analysis of 287 patients with LGAS and reduced LVEF (<50%) who underwent DSE was performed. We used the conventional criteria for classification of AS severity following DSE: severe AS when AVA <1cm² with AVMG ≥40mmHg, moderate AS when AVA ≥1cm², and indeterminate AS when AVA <1cm² and AVMG <40mmHg during stress. Furthermore, we assessed the proposed new criteria for AS classification: AVA <1cm² at normalised FR ≥210ml/s and projected AVA <1cm² at FR of 250ml/s. We also assessed the impact of afterload on the different AS groups by means of valvular resistance (valve disease related afterload) and arterial impedance (vascular disease related afterload). Results Following DSE 84 (29%) patients had severe AS, 81 (28%) moderate AS, and 122 (43%) indeterminate AS. Over the median follow-up of 12.0 (IQR= 5-33) months more patients with severe AS (73%) underwent aortic valve intervention compared with moderate (40%) and indeterminate AS (44%) (p< 0.001). In terms of afterload, the valvular resistance was significantly higher in patients with severe AS compared to indeterminate AS (p<0.001), but arterial impedance was higher in indeterminate AS amongst all 3 groups (p=0.02). Use of the proposed combined criteria for severe AS (AVA <1cm² at FR ≥210ml/s or projected AVA) in the indeterminate AS group improved the proportion of diagnostic tests from 57% to 90%, increased detection of severe AS from 29% to 61%, and reduced indeterminate AS to 9%. Aortic valve intervention was beneficial in the reclassified severe AS patients (HR 0.50, 95%CI 0.27-0.92, p=0.03) (Fig.1A), but not in the remaining indeterminate AS patients (HR 0.77, 95%CI 0.22-2.75, p=0.69) (Fig.1B). The benefit of aortic valve intervention was larger in the conventionally diagnosed severe AS patients compared to the reclassified severe AS patients (HR 2.88, 95%CI 1.34-6.21, p=0.007) (Fig.1C). Conclusions Clinicians managed LGAS patients according to DSE-determined AS severity. Application of the proposed combined criteria for severe AS reduced the number of non-diagnostic DSE and increased the detection of severe AS. In the reclassified severe AS patients aortic valve intervention can be beneficial, but not in those who remained indeterminate AS.