Cardiac Hypertrophy and Salt Status in Chronic Myocardial Infarction in the Rat

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Abstract
The effects of salt restriction and the ACE inhibitor enalapril were compared in a model of chronic myocardial infarction in the rat. Total exchangeable sodium was measured by an isotopic dilution technique to quantitate the effects of the low salt diet and ACE inhibitor on body sodium and extracellular fluid. Rats with infarction developed a marked increase in cardiac weight (4.29 .+-. 0.18 mg/g body weight) compared with control rats (3.64 .+-. 0.08 mg/g, p < 0.01). There was hypertrophy of both left and right ventricles. Salt restricted rats with infarction developed identical cardiomegaly (4.30 .+-. 0.11 mg/g), although total exchangeable body sodium fell by 10% (p < 0.001). In contrast, rats with infarction receiving enalapril developed significantly less cardiomegaly (3.97 .+-. 0.10 mg/g) while body sodium remained unchanged. Rats with infarction has a significant increase in lung weight which was not changed by salt restriction but which was abolished by enalapril. These results suggest that salt restriction does not prevent the progression of cardiomegaly in chronic left heart failure. In contrast our results confirm the ability of ACE inhibitors to prevent progressive cardiomegaly and left heart failure without affecting long-term changes in sodium balance.