Quantitative Assessment of Regional Myocardial Function in Mice by Tissue Doppler Imaging

Abstract

Background— Tissue Doppler imaging (TDI) is a novel echocardiographic method to quantify regional myocardial function. The objective of this study was to assess whether myocardial velocities and strain rate (SR) could be obtained by TDI in mice and whether these indices accurately quantified alterations in left ventricular (LV) systolic function. Methods and Results— TDI was performed in 10 healthy mice to measure endocardial (v endo ) and epicardial systolic velocities and SR. In further experiments, TDI indices were compared with dP/dt max and with sonomicrometer-derived regional velocities, at rest and after administration of dobutamine or esmolol. TDI indices were also studied serially in 8 mice before and 4 and 7 hours after endotoxin challenge. Myocardial velocities and SR were obtained in all mice with low measurement variability. TDI indices increased with administration of dobutamine (v endo from 2.2±0.3 to 3.8±0.2 cm/s [ P <0.01]; SR from 12±2 to 20±2 s −1 [ P <0.05]) and decreased with administration of esmolol (v endo 1.4±0.2 cm/s [ P <0.05]; SR 6±1 s −1 [ P <0.01]). Both indices correlated strongly with dP/dt max ( r 2 =0.79 for SR and r 2 = 0.69 for v endo ; both P <0.0001). SR and shortening fraction were predictors of dP/dt max even after adjustment for the confounding effect of the other variables. V endo correlated closely with sonomicrometer-measured velocity ( r 2 =0.71, P <0.0005). After endotoxin challenge, decreases in both v endo and SR were detected before decreases in shortening fraction became manifest. Conclusions— Myocardial velocities and SR can be measured noninvasively in mice with the use of TDI. Both indices are sensitive markers for quantifying LV global and regional function in mice.