EXERCISE-INDUCED VASODILATION IN FOREARM CIRCULATION OF NORMAL SUBJECTS AND PATIENTS WITH CONGESTIVE-HEART-FAILURE - ROLE OF ENDOTHELIUM-DERIVED NITRIC-OXIDE

Objectives. This study was undertaken to investigate the role of endot helium-derived nitric oxide in the regulation of forearm blood flow du ring exercise in normal subjects and patients with congestive heart fa ilure. Background. Nitric oxide-mediated vasodilation in response to m uscarinic stimulation is impaired in the peripheral circulation of pat ients with congestive heart failure, Whether nitric oxide-mediated vas odilation during exercise is also impaired in patients with congestive heart failure is unknown. Methods. Forearm blood flows (ml/min per 10 0 ml) were determined during rhythmic hand grip exercise at 15%, 30% a nd 45% of maximal voluntary contraction by venous occlusion plethysmog raphy before and after regional inhibition of nitric oxide synthesis,v ith administration of L-N-G-monomethylarginine (L-NMMA) in the brachia l artery of 17 patients with congestive heart failure (mean age 49 yea rs, mean left ventricular ejection fraction 0.22) and 10 age-matched n ormal subjects. Results. Before administration of L-NMMA in the brachi al artery, forearm blood flows in patients with congestive heart failu re during rhythmic hand grip exercise at 15%, 30% and 45% of maximal v oluntary contraction were slightly but not significantly lower than th at of normal subjects ([mean +/- SE] 6.8 +/- 1.0, 8.5 +/- 1.0 and 12.9 +/- 1.7 ml/min per 100 ml, respectively, in patients with congestive heart failure vs, 6.6 +/- 1.2, 11.6 +/- 1.9 and 16.2 +/- 1.9 ml/min pe r 100 ml, respectively, in normal subjects, p = NS), After administrat ion of L-NMMA in the brachial artery, forearm blood flows in normal su bjects significantly decreased by 10% to 21% during hand grip exercise but did not change during exercise in patients with congestive heart failure. Conclusions. Regional inhibition of nitric oxide synthase wit h administration of L-NMMA in the brachial artery significantly decrea sed forearm blood flows during rhythmic hand grip exercise in normal s ubjects but not in patients with congestive heart failure, These findi ngs suggest that nitric oxide-mediated vasodilation during submaximal exercise is impaired in the forearm circulation of patients with conge stive heart failure.