Targeted myocardial microinjections of a biocomposite material reduces infarct expansion in pigs

Background. Left ventricular (LV) remodeling after myocardial infarction (MI) commonly causes infarct expansion (IE). This study sought to interrupt IE through microinjections of a biocompatible composite material into the post-MI myocardium. Methods. MI was created in 21 pigs (coronary ligation). Radiopaque markers (2-mm diameter) were placed for IE (fluoroscopy). Pigs were randomized for microinjections (25 injections; 2- x 2-cm array; 200 mu L/injection) at 7 days post-MI of a fibrin-alginate composite (Fib-Alg; fibrinogen, fibronectin, factor XIII, gelatin-grafted alginate, thrombin; n = 11) or saline (n = 10). Results. At 7 days after injection (14 days post-MI), LV posterior wall thickness was higher in the Fib-Alg group than in the saline group (1.07 +/- 0.11 vs 0.69 +/- 0.07 cm, respectively, p = 0.002). At 28 days post-MI, the area within the markers (IE) increased from baseline (1 cm(2)) in the saline (1.71 +/- 0.13 cm(2), p = 0.010) and Fib-Alg groups (1.44 +/- 0.23 cm(2), p < 0.001). However, the change in IE at 21 and 28 days post-MI was reduced in the Fib-Alg group (p = 0.043 and p = 0.019). Total collagen content within the MI region was similar in the saline and Fib-Alg groups (12.8 +/- 1.7 and 11.6 +/- 1.5 mu g/mg, respectively, p = NS). However, extractable collagen, indicative of solubility, was lower in the Fib-Alg group than the saline group (59.1 +/- 3.5 vs 71.0 +/- 6.1 mu g/mL, p = 0.020). Conclusions. Targeted myocardial microinjection of the biocomposite attenuated the post-MI decrease in LV wall thickness and infarct expansion. Thus, intraoperative microinjections of biocompatible material may provide a novel approach for interrupting post-MI LV remodeling.