期刊
INTERNATIONAL JOURNAL OF CARDIOLOGY
卷 174, 期 2, 页码 368-375出版社
ELSEVIER IRELAND LTD
DOI: 10.1016/j.ijcard.2014.04.157
关键词
Circulation; Exercise pressor reflex; Sensory neurons; Autonomic control
资金
- US National Heart, Lung, and Blood Institute [HL-116579, HL-103786, HL-09183]
- VA Merit Grant [E6910R]
Objective: To better understand the hemodynamic and autonomic reflex abnormalities in heart-failure patients (HF), we investigated the influence of group III/IV muscle afferents on their cardiovascular response to rhythmic exercise. Methods: Nine HF-patients (NYHA class-II, mean left ventricular ejection-fraction: 27 +/- 3%) performed single leg knee-extensor exercise (25/50/80% peak-workload) under control conditions and with lumbar intrathecal fentanyl impairing mu-opioid receptor-sensitive muscle afferents. Results: Cardiac-output (Q) and femoral blood-flow (Q(L)) were determined, and arterial/venous blood samples collected at each workload. Exercise-induced fatigue was estimated via pre/post-exercise changes in quadriceps strength. There were no hemodynamic differences between conditions at rest. During exercise, Q was 8-13% lower with Fentanyl-blockade, secondary to significant reductions in stroke volume and heart rate. Lower norepinephrine spillover during exercise with Fentanyl revealed an attenuated sympathetic outflow that likely contributed to the 25% increase in leg vascular conductance (p < 0.05). Despite a concomitant 4% reduction in blood pressure, Q(L) was 10-14% higher and end-exercise fatigue attenuated by 30% with Fentanyl-blockade (p < 0.05). Conclusion/practice/implications: Although group III/IV muscle afferents play a critical role for central hemodynamics in HF-patients, it also appears that these sensory neurons cause excessive sympatho-excitation impairing QL which likely contributes to the exercise intolerance in this population. (C) 2014 Elsevier Ireland Ltd. All rights reserved.
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