Characterization of left ventricular cavity flow, wall stress and energy loss by color doppler vector flow mapping in children and adolescents with cardiomyopathy

Abstract

Background: Vector flow mapping is an emerging echocardiographic method allowing for investigation of intracardiac blood flow mechanics, wall shear stress (WSS), and energy loss (EL). We hypothesized that alterations in EL and WSS will differ among subjects with hypertrophic (HCM), dilated (DCM) cardiomyopathy, and normal controls.

Methods: Echocardiograms were prospectively performed with the ProSound F75CV (Hitachi HealthCare., Tokyo, Japan) on all subjects. 2D color Doppler cine loop images were obtained from apical 5 and the apical long axis views and stored digitally. Measurements were averaged over three cardiac cycles using VFM software to derive flow patterns, WSS, and EL. Standard left ventricular (LV) systolic and diastolic functional parameters were also obtained.

Results: A total of 85 subjects, 22 with HCM (age 18 ± 9 yrs.), 18 DCM (age 18 ± 9 yrs.), and 45 age and gender matched controls were included in the study. Diastolic wall shear stress was found significantly different in HCM (0.004 ± 0.185 N/m²) compared with DCM (0.397 ± 0.301 N/m², P < 0.001), and controls (0.175 ± 0.255 N/m², P = 0.027). Furthermore, indexed systolic EL was found to be significantly elevated in HCM (13.91 ± 13.17 mW/m²/m³) compared with DCM (8.17 ± 9.77 mW/m²/m³, P < 0.001), but not controls (6.45 ± 7.47 mW/m²/m³).

Conclusion: Differences in abnormal ventricular mechanics observed in HCM and DCM are reflected in both EL and WSS, and are suggestive that changes in energetic parameters may represent novel indices of ventricular dysfunction.

Keywords: Diastolic function; Dilated cardiomyopathy; Echocardiography; Hypertrophic cardiomyopathy; Vector flow mapping.

Fig. 1

Representation of Vector Flow Mapping software utilized for determination of energy loss, global longitudinal strain, and wall shear stress. From left to right, energy loss (left) during the cardiac cycle determined utilizing vector flow mapping, global longitudinal strain, and wall shear stress from vector flow mapping were determined for all patients using the DAS-RS1, Hitachi HealthCare software. A representative trace of calculated energy loss over the cardiac cycle is shown on the right.

Fig. 2

Indexed total (left), systolic (middle), and diastolic (right) energy loss (EL) in Controls, HCM, and DCM. Significant differences between all groups were observed for indexed systolic energy loss (P < 0.0001).