Quantitative assessment of regional myocardial function in mice by tissue Doppler imaging - Comparison with hemodynamics and sonomicrometry

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 vendo 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.