Hemodynamic forces using 4D flow MRI: an independent biomarker of cardiac function in heart failure with left ventricular dyssynchrony?

Aims Heart failure patients with LV dyssynchrony often do not respond to cardiac resynchronization therapy (CRT), indicating that the pathophysiology is insufficiently understood. Intracardiac hemodynamic forces computed from 4D flow MRI have been proposed as a new measure of cardiac function. We therefore aimed to investigate how hemodynamic forces are altered in LV dyssynchrony. Methods 31 patients with heart failure and LV dyssynchrony and 39 controls underwent cardiac magnetic resonance imaging with acquisition of 4D flow. Hemodynamic forces were computed using the Navier-Stokes equations and integrated over the manually delineated LV volume. The ratio between transverse (lateral-septal and inferior-anterior) and longitudinal (apical-basal) forces was calculated for systole and diastole separately and compared with QRS duration, aortic valve opening delay, global longitudinal strain and ejection fraction. Results Patients exhibited hemodynamic force patterns which were significantly altered compared to controls, including loss of longitudinal forces in diastole (force ratio, controls vs patients: 0.32 vs 0.90, p<0.0001), and increased transverse force magnitudes. Systolic force ratio was correlated with global longitudinal strain and EF (p<0.01). Diastolic force ratio separated patients from controls (AUC=0.98, p<0.0001) but was not correlated to other dyssynchrony measures (p>0.05 for all). Conclusion Hemodynamic forces by 4D flow represents a new approach to quantification of left ventricular dyssynchrony. Diastolic force patterns separate healthy from diseased ventricles. Different force patterns in patients indicates possible use of force analysis for risk stratification and CRT implantation guidance.