Managing Fatigue in the Syncope Unit

Julia L. Newton


Europace. 2012;14(12):1696-1699. 

In This Article

So why Might Autonomic Dysfunction Lead to Fatigue?

It has been suggested that autonomic dysfunction occurring in association with fatigue-associated diseases is a phenomena of deconditioning. Our studies would strongly suggest that this is unlikely to be the whole story as consistently there is no association between the presence and severity of autonomic dysfunction either measured subjectively, or objectively, and length of disease. Studies performed using state-of-the-art magnetic resonance imaging spectroscopy of skeletal muscle have confirmed the presence of significant abnormalities of acid metabolism in patients with CFS and fatigue-associated diseases.[26,27] These studies suggest on baseline and repeat exercise that patients with fatigue accumulate significant amounts of acid within their muscles. The degree to which individuals have the ability to remove this acid during and after exercise significantly associates with the severity of autonomic dysfunction.[26,27] The mechanisms of this abnormality are as yet undetermined but we would suggest that they may indicate a deficiency in transporters in cell membranes, the regulation of which may be controlled by the autonomic nervous system, or alternatively, may relate to an abnormality in the blood flow response to exercise directly related to autonomic modulation of the calibre of downstream blood vessels.

Another alternative explanation as to why those with autonomic dysfunction experience fatigue is that the subjects have an abnormality of cardiac function. Studies performed using impedance cardiography and magnetic resonance imaging (both spectroscopy and cardiac tagging) suggest that patients with CFS and the fatigue-associated disease primary biliary cirrhosis may well have a sub-clinical cardiomyopathy which could potentially lead to problems with blood pressure modulation and as a consequence, neurally mediated hypotension.[28,29]