Duchenne explained Glossary of research terms Cardiomyopathy In Duchenne, the heart is damaged before symptoms appear. Cardiac fibrosis refers to an usual thickening of the heart valves due to a growth of fibroblasts in the cardiac muscle. Fibrosis impedes the ability of the tissue to properly function, making it a lot stiffer, contributing to the progression of heart failure. ACE inhibitors are used to widen blood vessels, increasing blood flow to the heart and thus reducing blood pressure. There has been evidence to suggest that ACE inhibitors can slow progression of myocardial fibrosis in muscular dystrophy patients. Beta blockers also act to reduce blood pressure, helping the heart muscle to relax.