Non-invasive determination of left ventricular workload in patients with aortic stenosis using magnetic resonance imaging and Doppler echocardiography.
Early detection and accurate estimation of aortic stenosis (AS) severity are the most important predictors of successful long-term outcomes in patients. Current clinical parameters used for evaluation of the AS severity have several limitations including flow dependency. Estimation of AS severity is specifically challenging in patients with low-flow and low transvalvular pressure gradient conditions. A proper diagnosis in these patients needs a comprehensive evaluation of the left ventricle (LV) hemodynamic loads. This study has two objectives: (1) developing a lumped-parameter model to describe the ventricular-valvular-arterial interaction and to estimate the LV stroke work (SW); (2) introducing and validating a new index, the normalized stroke work (N-SW), to assess the global hemodynamic load imposed on the LV. N-SW represents the global hemodynamic load that the LV faces for each unit volume of blood ejected. The model uses a limited number of parameters which all can be measured non-invasively using current clinical imaging modalities. The model was first validated by comparing its calculated flow waveforms with the ones measured using Cardiovascular Magnetic Resonance (CMR) in 49 patients and 8 controls. A very good correlation and concordance were found throughout the cycle (median root mean square: 12.21 mL/s) and between the peak values (r = 0.98; SEE = 0.001, p<0.001). The model was then used to determine SW using the parameters measured with transthoracic Doppler-echocardiography (TTE) and CMR. N-SW showed very good correlations with a previously-validated index of global hemodynamic load, the valvular arterial impedance ([Formula: see text]), using data from both imaging modalities (TTE: r = 0.82, SEE = 0.01, p<0.001; CMR: r = 0.74, SEE = 0.01, p<0.001). Furthermore, unlike , N-SW was almost independent from variations in the flow rate. This study suggests that considering N-SW may provide incremental diagnostic and prognostic information, beyond what standard indices of stenosis severity and provide, particularly in patients with low LV outflow.
Laboratory of Biorheology and Medical Ultrasonics, University of Montreal Hospital Research Center (CRCHUM), Montréal, Québec, Canada ; Laboratory of Cardiovascular Fluid Dynamics, Mechanical and Industrial Engineering, Concordia University, Montréal, Québec, Canada.
Zahra
Z
Keshavarz-Motamed
Department of Radiology, Northwestern University, Chicago, Illinois, United States of America ; Québec Heart and Lung Institute, Laval University, Québec, Québec, Canada.
Julio
J
Garcia
Laboratory of Cardiovascular Fluid Dynamics, Mechanical and Industrial Engineering, Concordia University, Montréal, Québec, Canada.
Emmanuel
E
Gaillard
Québec Heart and Lung Institute, Laval University, Québec, Québec, Canada.
Romain
R
Capoulade
Québec Heart and Lung Institute, Laval University, Québec, Québec, Canada.
Florent
F
Le Ven
Laboratory of Biorheology and Medical Ultrasonics, University of Montreal Hospital Research Center (CRCHUM), Montréal, Québec, Canada ; Department of Radiology, Radio-Oncology and Nuclear Medicine and Institute of Biomedical Engineering, University of Montreal, Montréal, Québec, Canada.
Guy
G
Cloutier
Laboratory of Cardiovascular Fluid Dynamics, Mechanical and Industrial Engineering, Concordia University, Montréal, Québec, Canada.
Lyes
L
Kadem
Québec Heart and Lung Institute, Laval University, Québec, Québec, Canada.
Philippe
P
Pibarot
D000328:Adult; D001024:Aortic Valve Stenosis / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D001783:Blood Flow Velocity / Q000502:physiology; D003198:Computer Simulation; D015150:Echocardiography, Doppler; D017097:Electric Impedance; D005260:Female; D006351:Heart Valves / Q000000981:diagnostic imaging / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D015203:Reproducibility of Results; D013318:Stroke Volume / Q000502:physiology; D016277:Ventricular Function, Left / Q000502:physiology*