Di Vanna Andrea, Braga Ana Maria F W, Laterza Mateus C, Ueno Linda M, Rondon Maria Urbana P B, Barretto Antonio C P, Middlekauff Holly R, Negrão Carlos E
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.
Am J Physiol Heart Circ Physiol. 2007 Jul;293(1):H846-52. doi: 10.1152/ajpheart.00156.2007. Epub 2007 Apr 13.
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.
心力衰竭（HF）患者交感神经活动的化学反射控制被夸大。然而，HF患者化学感受器激活期间增强的交感神经活动对血管的影响尚不清楚。我们检验了这样一个假设：HF患者在周围和中枢化学反射刺激期间肌肉血流反应会减弱。研究了16例HF患者（49±3岁，纽约心脏协会心功能II-III级）和11例年龄匹配的正常对照者。通过吸入10%氧气和90%氮气3分钟来评估周围化学反射控制。通过吸入7%二氧化碳和93%氧气3分钟来评估中枢化学反射控制。通过微神经ography直接评估肌肉交感神经活动（MSNA）。通过静脉阻塞体积描记法评估前臂血流量。HF患者的基线MSNA显著更高（33±3次/分钟对20±2次/分钟，P = 0.001）。两组之间的前臂血管传导率（FVC）没有差异。在低氧期间，HF患者MSNA的增加显著大于正常对照者（9.0±1.6次/分钟对0.8±2.0次/分钟，P = 0.001）。HF患者FVC的增加显著更低（0.00±0.10对0.76±0.25单位，P = 0.001）。在高碳酸血症期间，HF患者的MSNA反应显著大于正常对照者（13.9±3.2次/分钟对2.1±1.9次/分钟，P = 0.001）。HF患者的FVC反应显著更低（-0.29±0.10对0.37±0.18单位，P = 0.001）。总之，HF患者在周围和中枢化学感受器刺激期间肌肉血管舒张减弱。这种血管反应似乎至少部分可以由低氧和高碳酸血症期间MSNA反应的夸大来解释。
