Left ventriculotomy of the heart: tissue repair and localization of collagen types I, II, III, IV, V, VI and fibronectin.

The reparative process following left ventriculotomy was investigated immunohistochemically using anti-type I, II, III, IV, V and VI collagen antibodies, and anti-fibronectin antibody. Wound healing began with proliferation of young fibroblasts positive for type I, III and V collagens at the wound margin; vascular granulation tissue then grew into the injured myocardium followed by deposition of fibrous components immunoreactive with type I and III. At 30 days after operation when almost the entire thickness of the myocardium at the wound was replaced by fibrosing granulation tissue, a small cluster of adipocytes appeared around capillaries at the wound margin. The granulation tissue was gradually replaced by the adipose tissue with establishment of a fibrous union at the subendocardium by 90 days. In addition to type I and III collagens, type VI collagen was detected in a fine fibrillary pattern along thick collagen fibre bundles in the fibrous tissue and around the adipocytes. Fibronectin was distributed diffusely in the granulation tissue and gradually decreased with increase of the fibrous components. These results indicate that the ventriculotomy was finally repaired in the form of a fibrous scar, particularly in the endocardium. There was marked infiltration of adipose tissue in the damaged myocardium. Presumably type VI collagen, as well as type I and type III collagens, plays an important role in wound union.