Injectable Microsphere Gel Progressively Improves Global Ventricular Function, Regional Contractile Strain, and Mitral Regurgitation After Myocardial Infarction

Background. There is continued need for therapies which reverse or abate the remodeling process after myocardial infarction (MI). In this study, we evaluate the longitudinal effects of calcium hydroxyapatite microsphere gel on regional strain, global ventricular function, and mitral regurgitation (MR) in a porcine MI model. Methods. Twenty-five Yorkshire swine were enrolled. Five were dedicated weight-matched controls. Twenty underwent posterolateral infarction by direct ligation of the circumflex artery and its branches. Infarcted animals were randomly divided into the following 4 groups: 1-week treatment; 1-week control; 4-week treatment; and 4-week control. After infarction, animals received either twenty 150 mL calcium hydroxyapatite gel or saline injections within the infarct. At their respective time points, echocardiograms, cardiac magnetic resonance imaging, and tissue were collected for evaluation of MR, regional and global left ventricular function, wall thickness, and collagen content. Results. Global and regional left ventricular functions were depressed in all infarcted subjects at 1 week compared with healthy controls. By 4-weeks post-infarction, global function had significantly improved in the calcium hydroxyapatite group compared with infarcted controls (ejection fraction 0.485 +/- 0.019 vs 0.38 +/- 0.017, p < 0.01). Similarly, regional borderzone radial contractile strain (16.3%+/- 1.5% vs 11.2%+/- 1.5%, p = 0.04), MRgrade (0.4 +/- 0.2 vs 1.2 +/- 0.2, p = 0.04), and infarct thickness (7.8 +/- 0.5mmvs 4.5 +/- 0.2mm, p < 0.01) were improved at this time point in the treatment group compared with infarct controls. Conclusions. Calcium hydroxyapatite injection after MI progressively improves global left ventricular function, borderzone function, and mitral regurgitation. Using novel biomaterials to augment infarct material properties is a viable alternative in the current management of heart failure. (C) 2015 by The Society of Thoracic Surgeons