Abstract
This study investigated the feasibility of using the values of tissue Doppler imaging (TDI)-derived myocardial velocity during isovolumic relaxation (VIR) and myocardial acceleration during isovolumic relaxation (ACC) obtained from the left ventricular (LV) free wall to evaluate LV relaxation in normal dogs. Seven dogs were anesthetized, and dobutamine or esmolol was infused at a rate of 5.0 and 10.0 μg/kg/min or 100 and 500 μg/kg/min, respectively, via a cephalic vein. The order of drug administration (dobutamine or esmolol) was assigned to each dog. Simultaneous pulsed-Doppler (PD) echocardiography, TDI and hemodynamic measurements were performed. Compared with the baseline values, dobutamine significantly increased dP/dt min, but significantly shortened tau (τ). Similarly, esmolol significantly decreased dP/dt min, but significantly prolonged τ. Compared with the baseline values, dobutamine significantly increased VIR and ACC, and esmolol significantly decreased VIR and ACC. Both dP/dt min and τ were significantly correlated with TDI-derived IVRT (r=-0.43 and 0.74), VIR (r=0.85 and -0.49) and ACC (r=0.84 and -0.52). These results indicate that the TDI-derived VIR and ACC values obtained from the LV free wall can potentially be used to assess LV relaxation in dogs.
