Speckle Tracking Imaging In Evaluation Of Mouse Models Of Regional Myocardial Dysfunction After Myocardial Infarction

BackgroundIschemic heart disease (IHD) is the leading cause of death worldwide. In vivo evaluation of cardiac dysfunction and fibrosis following myocardial infarction is crucial to prediction of prognosis. With the rise of transgenic technology, murine myocardial infarction (MI) models are increasingly used in medical research. Speckle tracking imaging (STI) can be used to measure strain and strain rate of global and regional myocardium. However, it is still unknown whether STI can be used to measure regional myocardial strain and strain rate in mouse models of myocardial infarction.ObjectiveTo investigate the value of two-dimensional speckle tracking imaging (STI) in assessing regional myocardial dysfunction following myocardial infarction and the correlation of chronic myocardial dysfunction and myocardial fibrosis in mouse models of myocardial infarction.Methods1. Mouse models of myocardial infarction.Acute myocardial dysfunction models:twenty-five C57/B6 mice were randomly divided into two groups:myocardial infarction (MI) group (n=15) and sham-operation (SO) group (n=10).Chronic myocardial dysfunction models:thirty C57/B6 mice were randomly divided into two groups:myocardial infarction (MI) group (n=20) and sham-operation (SO) group (n=10).2. Echocardiography examination and software analysis of strain and strain rate parameters. Echocardiography was respectively performed 3 days in acute myocardial dysfunction group and 4 weeks in chronic myocardial dysfunction group after surgery. High frame rate two dimensional images were recorded in the left ventricular short axis views at the papillary muscle level and analysised at EchoPac workstation. Peak radical strain (PRS) and peak radical strain rate (PRSR) of each segment were measured at systolic period.3. Masson stain and assessment of myocardial fibrosis.All mice were killed after echocardiography examination. Percent segmental fibrosis (PSF) was assessed from histological LV cross sections stained by Masson trichrome.Results1. Compared with those of SO group, LVIDd, LVIDs, LVVd and LWs of MI group increased significantly while FS and EF reduced in acute myocardial dysfunction models.2. PRS and PRSR decreased significantly in all segments of MI group, compared with those of SO group in acute myocardial dysfunction models.3. PRSR of anterosepetal, anterior and lateral segments in MI group decreased significantly than other segments in acute myocardial dysfunction models.4. PRS and PRSR decreased significantly in all segments of MI group, compared with those of SO group, especially in anterosepetal, anterior and lateral segments in chronic myocardial dysfunction models.5. PSF of anterosepetal, anterior, lateral and posterior segments in MI group increased significantly than those in SO group, and were negatively correlated with PRS and PRSR of these segments in chronic myocardial dysfunction models.Conclusion1. Two-dimensional strain imaging could accurately quantify regional myocardial function in a mouse model of acute myocardial infarction.2. Two-dimensional ultrasound STI could accurately quantify regional myocardial function in chronic myocardial dysfunction of mouse models following myocardial infarction. Segmental radial strain and strain rate, which were measured by STI, can be a non-invasive tool for monitoring myocardial fibrosis after myocardial infarction.