Sodium/
hydrogen exchange (NHE) inhibitors show promise as potential therapeutic agents for the treatment of
heart failure, but it is not known whether they can reverse the maladaptive remodeling that results in
heart failure. We sought to determine the effect of the NHE-1-specific inhibitor
EMD-87580 (EMD) on
heart failure produced by
myocardial infarction in the rat and to assess whether up to 4 wk of
treatment delay results in beneficial effects. Male Sprague-Dawley rats were subjected to coronary artery
ligation (or a
sham procedure) and followed for up to 3 mo, at which time
hypertrophy and hemodynamics were determined. EMD was provided in the diet, and treatment commenced immediately or 2-4 wk after
ligation. EMD significantly reduced hemodynamic abnormalities, including the elevation in left ventricular end-diastolic pressure, and diminished the loss of systolic function with all treatment protocols. Left ventricular dilatation and
hypertrophy, as assessed by heart weight, cell size, and
atrial natriuretic peptide (
ANP) expression, were similarly reversed to
sham or near-
sham levels. In addition, the increased plasma
ANP and pro-
ANP values were reversed to levels not significantly different from
sham. Surprisingly, virtually all beneficial effects were identical with all treatment protocols. These effects were observed in the absence of
infarct size reduction or blood pressure-lowering effects. Our results suggest that NHE-1 inhibition attenuates and reverses postinfarction remodeling and
heart failure with a
treatment delay of up to 4 wk after
infarction. The effect is independent of
infarct size or afterload reduction, indicating a direct effect on the myocardium.