important relationship among cognitive performance, HRV, and prefrontal neural function

These findings in total suggest an important relationship among cognitive performance, HRV, and prefrontal neural function that has important implications for both physical and mental health. Future studies are needed to determine exactly which executive functions are associated with individual differences in HRV in a wider range of situations and populations.
http://www.ncbi.nlm.nih.gov/pubmed/19424767

Low HRV is a risk factor for pathophysiology and psychopathology

The intimate connection between the brain and the heart was enunciated by Claude Bernard over 150 years ago. In our neurovisceral integration model we have tried to build on this pioneering work. In the present paper we further elaborate our model. Specifically we review recent neuroanatomical studies that implicate inhibitory GABAergic pathways from the prefrontal cortex to the amygdala and additional inhibitory pathways between the amygdala and the sympathetic and parasympathetic medullary output neurons that modulate heart rate and thus heart rate variability. We propose that the default response to uncertainty is the threat response and may be related to the well known negativity bias. We next review the evidence on the role of vagally mediated heart rate variability (HRV) in the regulation of physiological, affective, and cognitive processes. Low HRV is a risk factor for pathophysiology and psychopathology. Finally we review recent work on the genetics of HRV and suggest that low HRV may be an endophenotype for a broad range of dysfunctions.
http://www.ncbi.nlm.nih.gov/pubmed/18771686

Fundamentals of psychoneuroimmunology

The long-held concept that the nervous, endocrine and immune systems are separate entities has given way to a new understanding of human biology. Psychoneuroimmunology addresses the realisation that the neural, immune, and endocrine systems are inextricably linked and that the effects of each affect all-the systems work together as a complicated set of triggers and balances, an intertwining of the physiological and emotional states. Beginning with the fundamentals of immune and neuroendocrine function, Fundamentals of Psychoneuroimmunology explores the complexities of behavioural assessment, the basic types of immunity, the importance of immune cell redistribution in the response to challenges such as infection and stress, and the multifaceted roles of nerves, hormones and cytokines.
http://books.google.com/books/about/Fundamentals_of_psychoneuroimmunology.html?id=h0mEge8Oec8C

Sympathectomy should not be considered for such persons because of the risk of permanent worsening of erythromelalgia symptoms

The literature contains reports of remission with sympathectomy, but careful case selection is imperative before this procedure is performed.  Sympathectomy should be considered only for those whose erythromelalgia improves with blocks.  Conversely, if a sympathetic block causes worsening of a person's erythromelalgia, treatment should be discontinued.  Sympathectomy should not be considered for such persons because of the risk of permanent worsening of erythromelalgia symptoms.
Jay S. Cohen MD,
medicationsense.com/articles/2010/erythromelalgia0510.pdf