Blunted muscle vasodilatation during chemoreceptor stimulation in patients with heart failure

• Published in: American Journal of Physiology: Cell Physiology 2007-07, Vol.293 (1), p.H846-H852
• Main Authors: Di Vanna, Andrea, Braga, Ana Maria FW, Laterza, Mateus C, Ueno, Linda M, Rondon, Maria Urbana PB, Barretto, Antonio CP, Middlekauff, Holly R, Negrao, Carlos E
• Format: Article
• Language: English
• ISSN: 0363-6143; 1522-1563

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 plus or minus 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 sub(2) and 90% N sub(2) for 3 min. The central chemoreflex control was evaluated by inhalation of 7% CO sub(2) and 93% O sub(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 plus or minus 3 vs. 20 plus or minus 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 plus or minus 1.6 vs. 0.8 plus or minus 2.0 bursts/min, P = 0.001). The increase in FVC was significantly lower in HF patients (0.00 plus or minus 0.10 vs. 0.76 plus or minus 0.25 units, P = 0.001). During hypercapnia, MSNA responses were significantly greater in HF patients than in normal controls (13.9 plus or minus 3.2 vs. 2.1 plus or minus 1.9 bursts/min, P = 0.001). FVC responses were significantly lower in HF patients (-0.29 plus or minus 0.10 vs. 0.37 plus or minus 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.