Blunted muscle vasodilatation during chemoreceptor stimulation in patients with heart failure.
Chemoreflex control of sympathetic nerve activity is exaggerated in heart failure (HF) patients. However, the vascular implications of the augmented sympathetic activity during chemoreceptor activation in patients with HF are unknown. We tested the hypothesis that the muscle blood flow responses during peripheral and central chemoreflex stimulation would be blunted in patients with HF. Sixteen patients with HF (49 +/- 3 years old, Functional Class II-III, New York Heart Association) and 11 age-paired normal controls were studied. The peripheral chemoreflex control was evaluated by inhalation of 10% O(2) and 90% N(2) for 3 min. The central chemoreflex control was evaluated by inhalation of 7% CO(2) and 93% O(2) for 3 min. Muscle sympathetic nerve activity (MSNA) was directly evaluated by microneurography. Forearm blood flow was evaluated by venous occlusion plethysmography. Baseline MSNA were significantly greater in HF patients (33 +/- 3 vs. 20 +/- 2 bursts/min, P = 0.001). Forearm vascular conductance (FVC) was not different between the groups. During hypoxia, the increase in MSNA was significantly greater in HF patients than in normal controls (9.0 +/- 1.6 vs. 0.8 +/- 2.0 bursts/min, P = 0.001). The increase in FVC was significantly lower in HF patients (0.00 +/- 0.10 vs. 0.76 +/- 0.25 units, P = 0.001). During hypercapnia, MSNA responses were significantly greater in HF patients than in normal controls (13.9 +/- 3.2 vs. 2.1 +/- 1.9 bursts/min, P = 0.001). FVC responses were significantly lower in HF patients (-0.29 +/- 0.10 vs. 0.37 +/- 0.18 units, P = 0.001). In conclusion, muscle vasodilatation during peripheral and central chemoreceptor stimulation is blunted in HF patients. This vascular response seems to be explained, at least in part, by the exaggerated MSNA responses during hypoxia and hypercapnia.
Di Vanna
Andrea
A
Instituto do Coração (InCor Unidade de Reabilitação Cardiovascular e Fisiologia do Exercício, Av. Dr. Enéas de Carvalho Aguiar, 44 Cerqueira César, CEP 05403-000, São Paulo (SP), Brazil.
Braga
Ana Maria F W
AM
Laterza
Mateus C
MC
Ueno
Linda M
LM
Rondon
Maria Urbana P B
MU
Barretto
Antonio C P
AC
Middlekauff
Holly R
HR
Negrão
Carlos E
CE
D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity; D002303:Cardiac Output, Low / Q000503:physiopathology*; D002628:Chemoreceptor Cells; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply / Q000294:innervation* / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D014664:Vasodilation