Regional myocardial function after myocardial infarction in mice: a follow-up study by strain rate imaging

New therapeutic strategies aim to reduce the extent of myocardial infarction (MI) to decrease long-term left ventricular (LV) remodeling. These innovations are often developed on murine models of MI and have led to the need for a sensitive tool allowing follow-up. The aim of this study was to investigate by strain rate (SR) imaging early and long-term alteration in regional LV function occurring after MI in mice.

Echocardiography was serially performed during a 4-month follow-up period in 3 groups of C57BL6 male mice: 7 normal, 5 sham operated, and 27 with left coronary artery ligation (the MI group). In addition to conventional measurements, SR was obtained from short-axis views in the anterior wall and posterior wall (PW). Triphenyltetrazolium chloride staining allowed the localization and measurement of the transmural extent of MI. A transmural MI was defined as an extension > 75% of the wall thickness.

In the MI group, LV ejection fractions significantly decreased, while LV dimensions and PW thicknesses increased from baseline to 4 months. On day 3, SR could differentiate transmural from nontransmural (1 +/- 1 vs 10 +/- 1 s(-1); P < .05) and noninfarcted myocardium (25 +/- 1 s(-1)). SR values did not significantly change between day 3 and month 4 and could still differentiate those segments at month 4. Wall thickening was not able to differentiate transmural from nontransmural infarcted segments at day 3 (16 +/- 3% vs 21 +/- 3%; P = NS) or at month 4.

In this murine model of MI, SR was able to predict the transmural extent of MI as early as 3 days after MI, then remained stable and still differentiated them at 4 months.