Effects of lisinopril on experimental ischemia in rats. Influence of infarct size.

OBJECTIVE - Angiotensin-converting enzyme inhibitors (ACEIs) have gained importance in preventing or attenuating the process of ventricular remodeling after myocardial infarction. The significance of infarct size in regard to the response to ACEIs, however, is controversial. This study aimed to analyze the effects of lisinopril on mortality rate, cardiac function, degree of cardiac hypertrophy and fibrosis in rats with different infarct sizes. METHODS - Lisinopril (20 mg/kg/day) dissolved in drinking water was administered to rats immediately after coronary artery occlusion. After being sacrificed, the infarcted animals were divided into two groups: one group of animals with small infarcts (< 40% of the left ventricle) and another group of animals with large infarcts (> 40% of the left ventricle). RESULTS - The mortality rate was 31.7% in treated rats and 47% in the untreated rats. There was no statistical difference between the groups with small and large infarcts in regard to myocardial concentration of hydroxyproline. In small infarcts, the treatment attenuated the heart dysfunction characterized by lower levels of blood pressure and lower values of the first derivative of pressure and of the negative derivative of pressure. The degree of hypertrophy was also attenuated in small infarcts. In regard to large infarcts, no differences between the groups were observed. CONCLUSION - Treatment with the ACEIs had no effect on mortality rate and on the amount of fibrosis. The protective effect of lisinopril on heart function and on the degree of hypertrophy could only be detected in small infarcts