We evaluated the feasibility and accuracy of four-dimensional preclinical ultrasound (4D-US) and speckle-tracking imaging (STI) for monitoring changes in function post reperfused myocardial infarction (MI).
Methods Seventeen female mice (age = 10–12 wk) underwent ligation of the left anterior descending coronary artery. Cardiac MRI (Varian 9.4T) and echocardiographic images (Visualsonics 3100) were acquired at 2weeks (n=6) or8weeks (n=11) post-surgery. Ejection fraction was calculated and then compared between 4D-US, MRI, M-mode and Simpson’s multi slice at each time point. Eight healthy mice and seventeen MI mice were used for STI strain analysis.
Results All ultrasound methods calculated ejection fractions that correlated with MRI. However, 4D-US provided the strongest agreement, outperforming M-mode and Simpson’s multi slice (4D-US: R2= 0.81, M-mode: R2= 0.55, Simpson’s: R2= 0.73) (table 1). STI-derived measures of global strain were significantly lower in the MI group in all dimensions (P < 0.005). (Figure 1 A) For regional strain analysis, circumferential strain values in MI were significantly lower in antero-lateral and septal regions compared with control mice (P < 0.001). (Figure 1 B). The longitudinal strain and radial strain were decreased in all segments of MI hearts compared with control mice except for one basal segment (P < 0.001) (figure 2 A-B). These reductions in regional contractility reflect the territory of the occluded coronary artery.
Conclusion This study demonstrates that 4D-US performs well against MRI and better than M-mode and Simpson’s multi slice for left ventricle function analysis after MI. STI offers global and regional assessment of myocardium deformation in MI models and can be used to evaluate global and regional functional improvement from experimental treatments for MI.
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