Assessment of infarct size and myocardial function in mice using transesophageal echocardiography

Because transthoracic echocardiography (TTE) has significant limitations in assessing changes consequent to myocardial infarction (MI) in mice, we studied two novel methods to characterize such infarcts.

Large MIs were produced by proximal left coronary artery ligation, and small MIs by distal left coronary artery ligation. Serum cardiac troponin I levels were measured 24 hours postoperatively. At 2 weeks, mice underwent transesophageal echocardiography (TEE) and TTE. Infarct sizes were determined histologically.

Surviving mice were classified according to infarct size. TEE identified all histologically proven large infarcts, and 4 of 5 small infarcts. TTE identified 4 of 5 large infarcts, but only 1 of 5 small infarcts. TEE-derived fractional area change, but not TTE-estimated left ventricular fractional shortening, was significantly different among large, small, and sham infarcts. Cardiac troponin I showed excellent correlation with infarct size and mortality.

Cardiac troponin I was found to predict infarct size and mortality, whereas TEE proved superior to TTE in determining infarct size and/or myocardial function in a murine MI model. These tools should provide more accurate assessments in preclinical studies of ischemic cardiomyopathy.