Changes in the basal-to-apical pressure drop estimated by blood speckle tracking reflect changes in left ventricular diastolic function

Introduction Blood speckle tracking (BST) is a imaging modality which includes a new method for noninvasive estimation of pressure differences. The magnitude of the early diastolic left ventricular (LV) basal-to-apical intra-ventricular pressure drop (IVPD) is in part determined by relaxation rate and restoring forces. Noninvasive estimation of the IVPD by BST may therefore be of clinical interest. Purpose We performed interventions to vary relaxation rate and restoring forces and investigated if estimated IVPD by BST corresponded with invasively measured IVPD and varied according to these changes in diastolic function. Methods Apical BST images of LV inflow were acquired using a GE Vivid E95 ultrasound scanner and the M5Sc probe in pigs (n=4, 50-58 kg) (Figure 1, top panel). Calibrated microtip pressure catheters were placed basally in the mitral inflow region and apically in the LV. LV volume was measured from implanted sonomicrometric crystals. Recordings were performed with respirator on during baseline, esmolol infusion and dobutamine infusion. Custom software was utilised to analyse the BST images and estimate IVPD (IVPD = apical – basal pressure). Relaxation rate was quantified as the exponential time-constant, tau, of isovolumic pressure decay. Changes in restoring forces were reflected by changes in end-systolic volume (ESV). Results Esmolol infusion significantly reduced noninvasive and invasive IVPD, and significantly reduced relaxation rate (i.e. higher tau) and restoring forces (i.e. higher ESV), while dobutamine infusion had opposite effects (p<0.001, Figure 1). Noninvasive IVPD correlated well with invasive IVPD (r=0.93) (Figure 2). Conclusions In this small sample size study, estimation of LV IVPD by BST corresponded well with invasively measured IVPD. Estimated IVPD captured the changes in diastolic function assessed as relaxation rate and restoring forces. This encourages further research to investigate its ability to detect impaired left ventricular relaxation and restoring forces, for which there are currently no established clinical markers.