Longitudinal follow-up of cardiac structure and functional changes in an infarct mouse model using retrospectively gated micro-computed tomography.

Objectives: Mouse models of myocardial infarction are valuable in studying the effect of genetic modifications on structural and functional remodeling of the heart. Our group recently developed a method for acquiring three-dimensional images of the beating mouse heart using micro-computed tomography (micro-CT) and retrospective gating. In this study, we evaluated cardiac function in sham and infarcted mice longitudinally, using this novel technique.

Materials And Methods: Thirteen mice (7 sham-operated, 6 infarcted; male, C57BL/6) were imaged at baseline and at weeks 1, 2, 3, and 4 postligation of the left anterior descending coronary artery. Animals were anesthetized with 1.5% isoflurane; mechanical ventilation was not used. Contrast between blood and tissue was provided by an iodinated blood-pool contrast agent (0.01 mL/g Fenestra VC). The cardiac and respiratory waveforms were recorded during the 50-second scan time, to enable retrospective gating. Once scanning was completed on week 4 postsurgery, hemodynamic measurements were performed using a Millar pressure conductance catheter.

Results: There were significant differences in systolic and diastolic volumes, and ejection fraction, between sham and myocardial infarction groups (P < 0.0001). A comparison of ejection fraction derived from both CT and hemodynamic measurements was not significantly different (P > 0.1).

Conclusions: We have demonstrated the first use of dynamic micro-CT for monitoring cardiac remodeling, resulting from myocardial infarction, over time. The fast scan times (<1 minute) and ability to track individual animals over an entire study make this quantitative noninvasive technique a promising tool for in vivo studies of cardiac disease in mouse models.