- Autonomic Dysfunction in Stroke

Stroke is the third leading cause of mortality and one of the leading causes of adult disability in the United States and Canada (American Heart Association, 2010; Heart and Stroke Canada, 2010). The two main types of stroke are ischemic and hemorrhagic. Ischemic stroke, which accounts for about 80% of all strokes (Heart and Stroke, 2010), occurs when a thrombus or an embolus blocks blood ¬ow to a part of the brain for a suf­cient amount of time to cause permanent damage. Hemorrhagic stroke occurs when a vessel ruptures and the increased pressure caused by the leaking ¬uid damages the brain. The speci­c disability and dysfunction resulting from a stroke depend on the areas affected by the infarct or hemorrhage. While the cardiovascular autonomic network remains incompletely understood, baroreceptor unloading (i.e., lower body negative pressure to reduce baroreceptor afferent information) has been shown to increase the activation of the right superior posterior insula and left cerebellar hemisphere and to decrease the activation of the bilateral anterior insula, right anterior cingulated amygdala, midbrain and mediodorsal thalamus (Kimmerly et al., 2005). The middle cerebral artery (MCA) supplies the insular cortex and other important parts of the autonomic network; therefore, stroke involving the MCA can have dramatic effects on autonomic cardiovascular control. This chapter discusses the changes in heart rate CONTENTS 20.1 Introduction ........................................................................................................................ 397 20.2 Heart Rate Variability in Stroke ....................................................................................... 398 20.3 Autonomic Indices and Stroke Prognosis ......................................................................400 20.4 Factors Affecting Studies Involving Stroke ................................................................... 401 20.4.1 Time Post-Event and Lesion Location ................................................................. 401 20.4.2 Stroke Location and Laterality .............................................................................402 20.4.3 Arterial Stiffness ....................................................................................................403 20.4.4 Comorbidities .........................................................................................................403 20.5 Pharmacologic Interventions ...........................................................................................404 20.6 Lifestyle Interventions ......................................................................................................405 20.7 Limitations and Future Considerations .........................................................................406 20.8 Summary and Conclusions ..............................................................................................406 Acknowledgment ........................................................................................................................ 407 Abbreviations .............................................................................................................................. 407 References ..................................................................................................................................... 407