High Frequency Speckle Tracking Echocardiography in the Assessment of Left Ventricular Function after Murine Myocardial Infarction

Objectives: To assess the feasibility and accuracy of high frequency speckle tracking echocardiography (STE) in a murine model of myocardial infarction (MI). Background: STE is used clinically to quantify global and regional cardiac function but its application in mice is challenging because of the small cardiac size and rapid heart rates. Methods: A high frequency micro-ultrasound system with STE (Visualsonics Vevo 2100) was compared against magnetic resonance imaging (MRI) for the assessment of global left ventricular (LV) size and function after murine MI. Animals subjected to coronary ligation (n=46) or sham ligation (n=27) were studied 4 weeks postoperatively. Regional and global deformation were also assessed. Results: STE-derived LV ejection fraction (EF) and mass correlated well with MRI indices (r=0.93, 0.77 respectively, p<0.001), as did STE-derived mass with post-mortem values (r=0.80, p<0.001). Higher STE derived volumes correlated positively with MRI-derived infarct size (p<0.01). Global strain parameters were significantly reduced after MI (all p<0.0011) and strongly correlated with LV mass and MRI-derived infarct size as promising surrogates for the extent of remodeling and infarction respectively (both p<0.05). Regional strain analyses showed that radial strain and strain rate were relatively preserved in anterior basal segments after MI compared to more apical segments (P<0.0001); however, longitudinal strain and strain rate were significantly impaired both basally and distally (P<0.0001). Strain-derived parameters of dyssynchrony were significantly increased in the MI group (p<0.01). Analysis time for STE was 210±45 seconds with acceptable inter- and intra-observer variability. Conclusion: High frequency STE enables quantitative assessment of regional and global function in the remodeling murine LV after MI.