Quantitative Analysis of Left Ventricular Flow Dynamics in Hypertrophic Cardiomyopathy using vector flow mapping: Comparison with hypertensive LV hypertrophy

Background Hypertrophic cardiomyopathy (HCM) and secondary hypertensive LV hypertrophy (H-LVH) differ in pathophysiology. However, the differences and mechanisms of their blood flow fields have not been well studied. This study aimed to assess energy loss (EL), circulation, vortex area, vorticity and intraventricular velocity gradient between these two hypertrophy types. Methods Vector flow mapping (VFM) echocardiography was performed in 35 healthy participants, 25 HCM patients, and 24 H-LVH patients. Circulation, vortex area and vorticity during atrial filling (A-filling), isovolumic contraction (IVC) and ejection period were measured, as well as intraventricular velocity gradient during the E-filling period and average energy loss (EL-ave) during one cardiac cycle for each period. Measurements were averaged over three cardiac cycles. Results The “absent E-filling vortex ring” phenomenon was found in 8 HCM cases (32%), with significantly increased EL-ave during the A-filling period and relatively reduced diastolic intraventricular velocity gradient between the base and the apex (Vbp) compared with patients with normal E-filling vortex ring. EL-ave during the E-filling period was weaker in HCM than in the control and H-LVH groups. From A-filling to ejection, EL-ave was obviously increased in the HCM and H-LVH groups compared to the control group. Multivariable analyses revealed that EL-ave during the E-filling period in the HCM and H-LVH groups was affected by different heart structure-related factors and had a good diagnostic efficiency in differentiating HCM from H-LVH. Conclusion Differences in abnormal hemodynamics observed between HCM and H-LVH are reflected in both VFM-derived parameters, especially non-physiological vortices and early filling EL, which is closely related to special morphology. EL during E-filling as a novel parameter may be may be useful in differentiating HCM from hypertensive LVH.