4D flow MRI left atrial kinetic energy in hypertrophic cardiomyopathy is associated with mitral regurgitation and left ventricular outflow tract obstruction

To noninvasively assess left atrial (LA) kinetic energy (KE) in hypertrophic cardiomyopathy (HCM) patients using 4D flow MRI and evaluate coupling associations with mitral regurgitation (MR) and left ventricular outflow tract (LVOT) obstruction. Twenty-nine retrospectively identified patients with HCM underwent 4D flow MRI. MRI-estimated peak LVOT pressure gradient (∆P_MRI) was used to classify patients into non-obstructive and obstructive HCM. Time-resolved volumetric LA kinetic energy (KE_LA) was computed throughout systole. Average systolic (KE_LA-avg) and peak systolic (KE_LA-peak) KE_LA were compared between non-obstructive and obstructive HCM groups, and associations to MR severity and LVOT ∆P_MRI were tested.The study included 15 patients with non-obstructive HCM (58.6 [45.9, 65.2] years, 7 females) and 14 patients with obstructive HCM (51.9 [47.6, 62.6] years, 6 females). Obstructive HCM patients demonstrated significantly elevated instantaneous KE_LA over all systolic time-points compared to non-obstructive HCM (P < 0.05). Obstructive HCM patients also demonstrated higher KE_LA-avg (14.8 [10.6, 20.4] J/m³ vs. 33.4 [23.9, 61.3] J/m³, P < 0.001) and KE_LA-peak (22.1 [15.9, 28.7] J/m³ vs. 57.2 [44.5, 121.4] J/m³, P < 0.001) than non-obstructive HCM. MR severity was significantly correlated with KE_LA-avg (rho = 0.81, P < 0.001) and KE_LA-peak (rho = 0.79, P < 0.001). LVOT ∆P_MRI was strongly correlated with KE_LA metrics in obstructive HCM (KE_LA-avg: rho = 0.86, P < 0.001; KE_LA-peak: rho = 0.85, P < 0.001).In HCM patients, left atrial kinetic energy, by 4D flow MRI, is associated with MR severity and the degree of LVOT obstruction.