Myocardial remodeling after discrete radiofrequency injury: effects of tissue inhibitor of matrix metalloproteinase-1 gene deletion

Discrete myocardial lesions created through the delivery of radiofrequency (RF) energy can expand; however, the mechanisms have not been established. Matrix metalloproteinases (MMPs) play an important role in myocardial remodeling, and MMP activity can be regulated by the tissue inhibitors of the metalloproteinases (TIMPs). This study examined the role of TIMP-1 in postinjury myocardial remodeling. Lesions were created on the left ventricular (LV) epicardium of wild-type (WT, 8–12 wk, 129SVE) and age-matched TIMP-1 gene-deficient (timp-1–/–) mice through the delivery of RF current (80°C, 30 s). Heart mass, LV scar volumes, and collagen content were measured at 1 h and 3, 7, and 28 days postinjury (n = 10 each). Age-matched, nonablated mice were used as reference controls (n = 5). Heart mass indexed to tibial length increased in WT and timp-1–/– mice but was greater in the timp-1–/– mice by 7 days. Scar volumes increased in a time-dependent manner in both groups but were higher in the timp-1–/– mice than t...