Effects of combined inhibition of the Na+-H+ exchanger and angiotensin-converting enzyme in rats with congestive heart failure after myocardial infarction

1 We investigated the single vs the combined long-term inhibition of Na+-H+ exchanger-1 (NHE-1) and ACE in rats with congestive heart failure induced by myocardial infarction (MI). 2 Rats with MI were randomized to receive either placebo, cariporide ( 3000 p. p. m. via chow), ramipril ( 1mgkg(-1)day(-1) via drinking water) or their combination for 18 weeks starting on day 3 after surgery. 3 Cardiac morphology and function was assessed by echocardiography and by means of a 2.0F conductance catheter to determine left ventricular ( LV) pressure volume relationships. 4 MI for 18 weeks resulted in an increase in LV end-diastolic diameter ( LVDed) in the placebo-treated group when compared to sham ( placebo: 1.1 +/- 0.04 cm; sham: 0.86 +/- 0.01; P<0.05). Combined inhibition of NHE-1 and ACE, but not the monotherapies, significantly reduced LVDed ( 1.02 +/- 0.02 cm). 5 Preload recruitable stroke work ( PRSW), dp/dt(max) (parameter of systolic function) and enddiastolic pressure volume relationship ( EDPVR, diastolic function) were significantly impaired in placebo-treated MI group ( PRSW: 39 +/- 7 mmHg; dp/dt(max): 5185 +/- 363mmHgs(-1); EDPVR: 0.042 +/- 0.001mmHg mu l(-1); all P<0.05). Cariporide treatment significantly improved PRSW ( 64 +/- 7 mmHg), dp/dt(max) ( 8077 +/- 525mmHg s(-)1) and EDPVR ( 0.026 +/- 0.014mmHg mu l(-1)), and reduced cardiac hypertrophy in rats with MI. Combined inhibition of NHE-1 and ACE had even a more pronounced effect on PRSW ( 72 +/- 5mmHg) and EDPVR ( 0.026 +/- 0.014mmHg mu l(-1)), as well as cardiac hypertrophy that, however, did not reach statistical significance compared to cariporide treatment alone. 6 The NHE-1 inhibitor cariporide significantly improved LV remodeling and function in rats with congestive heart failure induced by MI. The effect of cariporide was comparable or tended to be stronger ( e. g. systolic function) compared to ramipril. Combined treatment with cariporide and ramipril tended to be more effective on LV remodeling in rats with heart failure than the single treatments. Thus, inhibition of the NHE-1 may be a promising novel therapeutic approach for the treatment of congestive heart failure.