The robustness of the flow-gradient classification of severe aortic stenosis

• Published in: JTCVS open 2023-12, Vol.16, p.177-188
• Main Authors: Velders, Bart J.J., Vriesendorp, Michiel D., Asch, Federico M., Moront, Michael G., Dagenais, Francois, Reardon, Michael J., Sabik III, Joseph F., Groenwold, Rolf H.H., Klautz, Robert J.M.
• Format: Article
• Language: English
• Subjects: Adult: Aortic Valve; flow-gradient classification; low flow; severe aortic stenosis; stroke volume
• ISSN: 2666-2736; 2666-2736
• DOI: 10.1016/j.xjon.2023.08.022

A flow-gradient classification is used to determine the indication for intervention for patients with severe aortic stenosis (AS) with discordant echocardiographic parameters. We investigated the agreement in flow-gradient classification by stroke volume (SV) measurement at the left ventricular outflow tract (LVOT) and at the left ventricle. Data were used from a prospective cohort study and patients with severe AS (aortic valve area index ≤0.6 cm2/m2) with preserved ejection fraction (>50%) were selected. SV was determined by an echocardiographic core laboratory at the LVOT and by subtracting the 2-dimensional left ventricle end-systolic from the end-diastolic volume (volumetric). Patients were stratified into 4 groups based on SV index (35 mL/m2) and mean gradient (40 mm Hg). The group composition was compared and the agreement between the SV measurements was investigated using regression, correlation, and limits of agreement. In addition, a systematic LVOT diameter overestimation of 1 mm was simulated to study flow-gradient reclassification. Of 1118 patients, 699 were eligible. The group composition changed considerably as agreement on flow state occurred in only 50% of the measurements. LVOT SV was on average 15.1 mL (95% limits of agreement −24.9:55.1 mL) greater than volumetric SV. When a systematic 1-mm LVOT diameter overestimation was introduced, the low-flow groups halved. There was poor agreement in the flow-gradient classification of severe AS as a result of large differences between LVOT and volumetric SV. Furthermore, this classification was sensitive to small measurement errors. These results stress that parameters beyond the flow-gradient classification should be considered to ensure accurate recommendations for intervention. [Display omitted]