Study objective: The aim was to test the hypothesis that endothelium dependent vasomotor control is impaired in heart failure.
Design and subjects: The haemodynamic effects of NG-nitro-L-arginine (NNA), an inhibitor of nitric oxide synthesis, were studied in five dogs with and without pacing induced heart failure.
Main results: In healthy dogs, NNA increased total peripheral resistance and arterial pressure, decreasing cardiac output and heart rate. These effects were partially reversed by L-arginine. In dogs with heart failure, NNA did not change any haemodynamic variable. However, L-arginine decreased total peripheral resistance.
Conclusions: These findings support a physiological role for endothelium derived nitric oxide in control of vascular resistance and are in agreement with the hypothesis that endothelium dependent vasomotion may be impaired in heart failure.