Group III/IV muscle afferents impair limb blood in patients with chronic heart failure

• Published in: International journal of cardiology 2014-06, Vol.174 (2), p.368-375
• Main Authors: Amann, Markus, Venturelli, Massimo, Ives, Stephen J, Morgan, David E, Gmelch, Benjamin, Witman, Melissa A.H, Jonathan Groot, H, Walter Wray, D, Stehlik, Josef, Richardson, Russell S
• Format: Article
• Language: English
• Subjects: Aged; Autonomic control; Biological and medical sciences; Cardiology. Vascular system; Cardiovascular; Chronic Disease; Circulation; Exercise; Exercise pressor reflex; Heart; Heart Failure - physiopathology; Heart failure, cardiogenic pulmonary edema, cardiac enlargement; Humans; Leg; Male; Medical sciences; Middle Aged; Muscle Fatigue; Muscle, Skeletal - blood supply; Muscle, Skeletal - innervation; Muscle, Skeletal - physiopathology; Neurons, Afferent - physiology; Regional Blood Flow; Sensory neurons
• ISSN: 0167-5273; 1874-1754
• DOI: 10.1016/j.ijcard.2014.04.157

Abstract 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 μ-opioid receptor-sensitive muscle afferents. Results Cardiac-output ( Q ) and femoral blood-flow ( QL ) 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, QL 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.