Thickening of the infarcted wall by collagen injection improves left ventricular function in rats

OBJECTIVES We determined whether collagen implantation could thicken the infarcted left ventricular (LV) wall and improve LV function. BACKGROUND We hypothesized that thickening the infarcted wall by using collagen might result in some benefits that are similar to what previously had been reported when the infarcted wall was thickened with cells. METHODS Fischer rats with one-week-old myocardial infarcts were injected with collagen or saline (100 mu l) into the scar (n = 12 each group). Six weeks later, LV angiograms, hemodynamics, and regional myocardial blood flow were assessed. The hearts, were processed for measurements of postmortem LV volume and histology. RESULTS Collagen injection significantly increased scar thickness (719 +/- 26 mu m) compared with the saline-treated group (440 +/- 34 mu m, p = 2.6 X 10(6)). By LV angiography, stroke volume was significantly larger in the collagen-treated group (163 +/- mu l) than in the saline-treated group (129 +/- 6 mu l, p = 0.005), and LV ejection fraction was also greater in the collagen-treated group (48.4 +/- 1.8 %) than in the saline-treated group (40.7 +/- 1.0 %, p = 0.002). Analysis of regional wall motion demonstrated paradoxical systolic bulging in 5 of 10 saline-treated rats that averaged 20.3 +/- 2.6 % of the LV diastolic circumference, but in none of the 11 collagen-treated rats (P = 0.012). The LV end-diastolic and end-systolic volumes were 319 +/- 12 mu l and 190 +/- 7 mu l in the saline-treated group, respectively. There was a trend for larger LV end-diastolic volumes (343 23 mu l), but smaller end-systolic volumes (180 16 mu l) in the collagen-treated group. CONCLUSIONS This study shows that collagen injection thickens an infarct scar and improves LV stroke volume and ejection fraction, and prevents paradoxical systolic bulging after myocardial infarction. (c) 2005 by the American College of Cardiology Foundation.