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. 2014 Jun 15;174(2):368-75.
doi: 10.1016/j.ijcard.2014.04.157. Epub 2014 Apr 21.

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

Markus Amann  1 , Massimo Venturelli  2 , Stephen J Ives  3 , David E Morgan  4 , Benjamin Gmelch  4 , Melissa A H Witman  3 , H Jonathan Groot  3 , D Walter Wray  5 , Josef Stehlik  2 , Russell S Richardson  5
Affiliations

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

Markus Amann et al. Int J Cardiol. .

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.

Keywords: Autonomic control; Circulation; Exercise pressor reflex; Sensory neurons.

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Figures

Figure 1
Figure 1
Cardiac-related variables at rest and during exercise. The p-value indicates a significant main effect of fentanyl. *p<0.05, #not different from rest
Figure 2
Figure 2
Hemodynamic responses at rest and during the final minute of exercise. The p-value indicates the overall main effect of fentanyl. *p<0.05
Figure 3
Figure 3
Leg O2 supply and demand at rest and during the final minute of exercise. The p-value indicates the overall main effect of fentanyl. *p<0.05
Figure 4
Figure 4
Exercise-induced reduction in maximal quadriceps voluntary concentration force (MVC) in patients with HF. N=5; *P<0.01
See this image and copyright information in PMC

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