Speckle-tracking echocardiography correctly identifies segmental left ventricular dysfunction induced by scarring in a rat model of myocardial infarction

Speckle-tracking echocardiography (STE) uses a two-dimensional echocardiographic image to estimate two orthogonal strain components. The aim of this study was to assess sensitivity of circumferential (S_circ) and radial (S_rad) strains to infarct-induced left ventricular (LV) remodeling and scarring of the LV in a rat. To assess the relationship among S_circ, S_rad, and scar size, two-dimensional echocardiographic LV short-axis images (12 MHz transducer, Vivid 7 echo machine) were collected in 34 Lewis rats 4 to 10 wk after ligation of the left anterior descending artery. Percent segmental fibrosis was assessed from histological LV cross sections stained by Masson trichrome. Ten normal rats served as echocardiographic controls. S_circ and S_rad were assessed by STE. Histological data showed consistent scarring of anterior and lateral segments with variable extension to posterior and inferior segments. Both S _circ and S_rad significantly decreased after myocardial infarction (P < 0.0001 for both). As anticipated, S_circ and S _rad were lowest in the infarcted segments. Multiple linear regression showed that segmental S_circ were similarly dependent on segmental fibrosis and end-systolic diameter (P < 0.0001 for both), whereas segmental S_rad measurements were more dependent on end-systolic diameter (P < 0.0001) than on percent fibrosis (P < 0.002). STE correctly identifies segmental LV dysfunction induced by scarring that follows myocardial infarction in rats.