High frame rate speckle tracking echocardiography to assess left ventricular repolarization and factors determining left ventricular mechanical dispersion

Left ventricular (LV) repolarization and mechanical dispersion (LVMDr) have a proven prognostic value. High frame rate (HFR) echocardiography can detect subtle timing differences in local myocardial deformation, such as the onset of local lengthening. We tested the feasibility of mapping LV repolarization and investigated the effect of fibrosis and changes in loading conditions on LVMDr using HFR speckle tracking echocardiography (STE). 25 healthy volunteers (HV), 20 patients with left bundle branch block (LBBB) and 14 acutely decompensated heart failure (HF) patients were included. Data from the latter were acquired before and after diuretic administration, to account for volume loading changes. Subjects were scanned with a HFR ultrasound scanner and the 3 standard apical views were acquired. In each view, a manually placed contour was tracked during the cardiac cycle by a 2D HFR STE algorithm and was then divided according to the standard 16 segment LV segmentation model. Segmental strain rate (SR) curves were computed and used to measure the time interval between the onset of the QRS complex on the ECG and the segmental repolarization onset, i.e. first negative to positive zero crossing in the SR curve after ejection phase. LVMDr was defined as the standard deviation of the segmental contraction duration (i.e. the time to repolarization onset) of all segments. LVMDr and total repolarization time significantly differed among all patient groups except between the HV and the HF patients pre discharge, showing the effect of fibrosis and of volume load on LVMDr. In conclusion, HFR STE could be used for mapping LV repolarization and estimating LVMDr and render these biomarkers more easily accessible in clinical practice.