Discordant impairment of multidirectional myocardial deformation in rats with doxorubicin induced cardiomyopathy

Background: In doxorubicin-induced cardiomyopathy (DIC), the sequence of decrease in multidirectional myocardial deformation has not been clearly elucidated. Objectives: We investigated the sequence of myocardial deformations in rat DIC, using two-dimensional speckle tracking echocardiography (2DSTE). Methods: Twenty rats were treated with doxorubicin (1.25 mg/kg × 16 times, intraperitoneal) for 4 weeks and compared with nine control rats. Myocardial strain analysis with 2DSTE, as well as conventional echocardiography, was obtained. Results: Compared with baseline, longitudinal strain/strain rate (LS/LSr) decreased at week 2 (-15.7 ± 1.5 to -14.1 ± 1.4%, P = 0.01 for LS; -4.4 ± 0.7 to -3.9 ± 0.5 per second, P = 0.009 for LSr). Left ventricular ejection fraction (LVEF) and circumferential strain (CS) decreased at week 4 (80.3 ± 3.2 to 78.1 ± 3.3%, P = 0.031 for LVEF; -18.6 ± 1.9 to -15.0 ± 3.4%, P = 0.019 for CS). Circumferential strain rate (CSr) decreased at week 6 (-5.5 ± 0.8 to -4.6 ± 1.0 per second, P = 0.008). Radial strain/strain rate (RS/RSr) decreased at week 8 (54.8 ± 9.4 to 43.7 ± 10.6%, P = 0.005 for RS; 8.0 ± 1.1 to 7.0 ± 1.1 per second, P = 0.005 for RSr), while there was no significant change in LS/LSr, LVEF, CS/CSr, or RS/RSr in the control group. LVEF had the highest correlation with LS (r =-0.607, P = 0.000) and the lowest correlation with RSr (r = 0.357, P = 0.000). Conclusions: In DIC of rat hearts, LS/LSr decreased first, and then LVEF, CS, CSr, RS/RSr subsequently decreased. LS/LSr is considered to be a more sensitive predictor than LVEF in progressive rat DIC, and RS/RSr was preserved until the last stage. (Echocardiography 2012;29:720-728)