Background and objectives: The assumption of a circular shape of the left ventricular outflow tract in the continuity equation might lead to aortic valve area underestimation in 2-dimensional echocardiography. Our study evaluated whether continuity equation with ventricular outflow tract (LVOT) area evaluated by computed tomography (CT) is able to reclassify the degree of aortic valve stenosis compared to the traditional continuity equation calculation of aortic valve area and to assess the impact of a reclassification on patients outcome after TAVR.

Methods and results: 422 patients with indexed aortic valve area (AVAi) of <0.6 cm²/m² assessed by continuity equation and echocardiography (mean age 81 ±6 years, 51% female) were included. Patients were classified according to flow (stroke volume index; <35 or ≥35 mL/m2) and gradient (mean transaortic pressure gradient ≤40 or >40 mmHg) into four groups. Although CT-derived LVOT area was comparable among the four groups, the fusion AVAi was significantly larger in the low gradient groups. By using the CT derived AVAi, 68% (n = 85) of patients with normal flow – low gradient and 38% (n = 51) of patients with low flow– low gradient would have been reclassified into moderate AS. Reclassified patients showed significantly higher sST2 values at baseline and significantly higher NT-pro BNP values 6 months after TAVR.

Conclusion: The AVAi from a CT-based continuity equation calculation reclassifies a significant part of low gradient severe AS into moderate AS by providing the true cross-sectional LVOT area. Reclassified patients showed increased biomarkers of myocardial stress at baseline and also 6 months after TAVR.