Angiotensin I converting enzyme inhibitors and cardiac remodeling.

Angiotensin I converting enzyme (ACE) inhibitors are widely used in the treatment of heart failure. It is not known whether the beneficial effects of ACE inhibition are only due to a reduction in pre- and afterload or whether ACE inhibition also has direct effects on cardiac remodeling processes after myocardial infarction. In addition, the effects of differential timing of the treatment are not known. The left coronary artery was ligated in rats to induce a myocardial infarction. Control rats received no treatment. Captopril was given via s.c. placed minipumps (500 micrograms/kg.h) in the first 3 weeks or in the third and fourth week after induction of the myocardial infarction. The structural changes of the heart were investigated. Early after ligation the left ventricle was dilated in association with a marked, but transient DNA synthesis in the remaining left ventricle; the amount of collagen also increased. Early captopril treatment blocked this response, while late treatment had no effects. We suggest that the negative effects of early captopril treatment are due to an interference with the normal adaptive responses of the heart to the loss of muscle, probably through interactions at the cellular level.