Assessment of Early Diastolic Intraventricular Pressure Difference in Children by Blood Speckle-Tracking Echocardiography

BACKGROUND

The lack of reliable echocardiographic techniques to assess diastolic function in children is a major clinical limitation. Our aim was to develop and validate the intraventricular pressure difference (IVPD) calculation using blood speckle-tracking (BST) and investigate the method's potential role in the assessment of diastolic function in children.

METHODS

Blood speckle-tracking allows two-dimensional angle-independent blood flow velocity estimation. Blood speckle-tracking images of left ventricular (LV) inflow from the apical 4-chamber view in 138 controls, 10 patients with dilated cardiomyopathies (DCMs), and 21 patients with hypertrophic cardiomyopathies (HCMs) <18 years of age were analyzed to study LV IVPD during early diastole. Reproducibility of the IVPD analysis was assessed, IVPD estimates from BST and color M mode were compared, and the validity of the BST-based IVPD calculations was tested in a computer flow model.

RESULTS

Mean IVPD was significantly higher in controls (-2.28 ± 0.62 mm Hg) compared with in DCM (-1.21 ± 0.39 mm Hg, P < .001) and HCM (-1.57 ± 0.47 mm Hg, P < .001) patients. Feasibility was 88.3% in controls, 80% in DCM patients, and 90.4% in HCM patients. The peak relative negative pressure occurred earlier at the apex than at the base and preceded the peak E-wave LV filling velocity, indicating that it represents diastolic suction. Intraclass correlation coefficients for intra- and interobserver variability were 0.908 and 0.702, respectively. There was a nonsignificant mean difference of 0.15 mm Hg between IVPD from BST and color M mode. Estimation from two-dimensional velocities revealed a difference in peak IVPD of 0.12 mm Hg (6.6%) when simulated in a three-dimensional fluid mechanics model.

CONCLUSIONS

Intraventricular pressure difference calculation from BST is highly feasible and provides information on diastolic suction and early filling in children with heart disease. Intraventricular pressure difference was significantly reduced in children with DCM and HCM compared with controls, indicating reduced early diastolic suction in these patient groups.

Blood Speckle-Tracking Based on High-Frame Rate Ultrasound Imaging in Pediatric Cardiology

BACKGROUND

Flow properties play an important role in cardiac function, remodeling, and morphogenesis but cannot be displayed in detail with today's echocardiographic techniques. The authors hypothesized that blood speckle-tracking (BST) could visualize and quantify flow patterns. The aim of this study was to determine the feasibility, accuracy, and potential clinical applications of BST in pediatric cardiology.

METHODS

BST is based on high-frame rate ultrasound, using a combination of plane-wave imaging and parallel receive beamforming. Pattern-matching techniques are used to quantify blood speckle motion. Accuracy of BST velocity measurements was validated using a rotating phantom and by comparing BST-derived inflow velocities with pulsed-wave Doppler obtained in the left ventricles of healthy control subjects. To test clinical feasibility, 102 subjects (21 weeks to 11.5 years of age) were prospectively enrolled, including healthy fetuses (n = 4), healthy control subjects (n = 51), and patients with different cardiac diseases (n = 47).

RESULTS

The phantom data showed a good correlation (r = 0.95, with a tracking quality threshold of 0.4) between estimated BST velocities and reference velocities down to a depth of 8 cm. There was a good correlation (r = 0.76) between left ventricular inflow velocity measured using BST and pulsed-wave Doppler. BST displayed lower velocities (mean ± SD, 0.59 ± 0.14 vs 0.82 ± 0.21 m/sec for pulsed-wave Doppler). However, the velocity amplitude in BST increases with reduced smoothing. The clinical feasibility of BST was high, as flow patterns in the area of interest could be visualized in all but one case (>99%).

CONCLUSIONS

BST is highly feasible in fetal and pediatric echocardiography and provides a novel approach for visualizing blood flow patterns. BST provides accurate velocity measurements down to 8 cm, but compared with pulsed-wave Doppler, BST displays lower velocities. Studying blood flow properties may provide novel insights into the pathophysiology of pediatric heart disease and could become an important diagnostic tool.