Intraventricular Pressure Difference by Blood Speckle Tracking - Invasive Validation and Clinical Application
Authors: Sørensen Kristian , Fadnes Solveig , Mawad Wadi , Henry Matthew , Flade Hans Martin , Østvik Andreas , Myklebust Tor Åge , Kirkeby-Garstad Idar , Løvstakken Lasse , Mertens Luc , Nyrnes Siri Ann 
Published: August 2024

Background

Early diastolic relaxation creates an intraventricular pressure difference (IVPD) and resulting diastolic suction. Non-invasive estimation by echocardiographic techniques would allow to clinically evaluate this IVPD as an important component of ventricular filling. Recently, Blood Speckle Tracking (BST) echocardiography was introduced, allowing two-dimensional assessment of ventricular flow dynamics. Mitral inflow BST data can be used to estimate IVPD. The aims of the current study were to evaluate the accuracy of BST-based IVPD estimation compared to invasive pressure measurements in an in vivo animal model, and to clinically apply the method by comparing IVPD in children with univentricular hearts (UVH) and healthy controls.

Methods

The accuracy of BST-based IVPD-estimates was assessed in an open-chest porcine model, comparing BST-based IVPD with simultaneous repeated invasive pressure measurements in six pigs using micromanometer catheters. BST-based IVPD assessment was performed in 120 healthy controls and 44 patients with UVH < 18 years of age. Total IVPD (from base to apex) and apical IVPD (from the apical 2/3 of the ventricle) during early diastolic filling of the systemic ventricle was compared between patients with UVH and healthy controls.

Results

The validation in pigs included 103 measurements, demonstrating a mean difference of - 0.01mmHg (p=0.33) and high correlation (r = 0.95, p-value < 0.001) between IVPD from BST (-1.31 ± 0.28 mmHg) and invasive measurements (-1.30 ± 0.31 mmHg). In the pediatric patients, age range 2 days-17.76 years, feasibility was 96% in controls and 88.6% in UVH patients. Total and apical IVPD were significantly higher in controls compared to UVH (-1.82 vs -0.88 mmHg and -0.63 vs -0.33 mmHg, p < 0.001).

Variability was low with intraclass correlation coefficients of 0.99/0.96 (interobserver) and 0.98/0.99 (intraobserver) for total and apical IVPD respectively.

Conclusions

BST echocardiography provides accurate estimation of early diastolic IVPD. When clinically applied in children, we found high feasibility and reproducibility. IVPD was significantly lower in children with UVH compared to controls suggesting lower diastolic suction which can impact overall filling dynamics.

Clinical perspective

What is new

Blood speckle tracking echocardiography provides non-invasive estimation of intraventricular pressure difference in early diastole using two-dimensional blood flow velocities

Intraventricular pressure difference based on blood speckle tracking is highly feasible, accurate and reproducible

Blood speckle tracking demonstrates significantly reduced intraventricular pressure difference in early diastole in children with univentricular hearts indicating impaired relaxation and suction in these patients

What are the clinical implications

Intraventricular pressure difference based on blood speckle tracking is a novel and potential sensitive echocardiographic parameter to describe early diastolic ventricular relaxation and diastolic function in children with univentricular hearts

Blood speckle tracking could improve assessment of diastolic function in children with congenital heart disease

Non-invasive estimation of intraventricular pressure difference based on blood speckle tracking could improve assessment of diastolic function both in children and adults with heart disease