Prognostic impact of echocardiographic mean transvalvular gradients in patients with aortic stenosis and low flow undergoing transcatheter aortic valve implantation. - Fischer-Rasokat U; Renker M; Liebetrau C; Weferling M; Rolf A; Doss M; Hamm CW; Kim WK (Catheterization and cardiovascular interventions : official journal of the Society for Cardiac Angiography & Interventions, 2021)