Left ventricular vortex formation in preterm infants assessed by blood speckle imaging.

Abstract

A vortex is a rotational fluid structure formed by shearing of fluid layers. It forms during diastole in the left ventricle (LV) and helps redirect flow to the LV outflow tract for ejection, optimizing energy conservation. The aim of this study was to demonstrate the feasibility of detecting and analyzing LV vortices using a new ultrasound technique known as blood speckle imaging (BSI). Conventional and BSI parameters were acquired in preterm infants referred for echocardiography. BSI feasibility and reliability were explored using highest frequency settings and optimized Nyquist limits. Vortex area was determined by tracing the outer vortex ring at maximum area. Peak vortex formation time (PVFT) was determined at time of maximum vortex area relative to the R-wave, and vortex duration from frame-by-frame analysis of first appearance to vortex degradation. Left ventricle vortices were detected in 49 of the 50 preterm infants (weight 500-2020g) with excellent intra- and inter-observer reliability. Mean vortex area indexed to LV area was 0.19 (0.08). Peak vortex formation time was at 87 (7)% of the cardiac cycle, and vortex duration lasted 13 (4)% of the cardiac cycle. Vortex area correlated positively with LV length, end-diastolic dimension, end-diastolic volume, mitral annular (R +0.42, +0.50, +0.47, +0.50, all P<0.01), and transmitral Vti (R +0.37, P<0.01). PVFT correlated negatively with E, EA, and Ee' (R -0.42, -0.47, -0.47, all P<0.01). Left ventricle vortex formation can be analyzed with two-dimensional BSI and has the potential to complement existing parameters of cardiac health.