Dynamic Behavior of Heart Rate in Ischemic Stroke

Abstract

Background and Purpose-Traditional spectral and nonspectral methods have shown that heart rate (HR) variability is reduced after stroke. Some patients with poor outcome, however, show randomlike, complex patterns of HR behavior that traditional analysis techniques are unable to quantify. Therefore, we designed the present study to evaluate the complexity and correlation properties of HR dynamics after stroke by using new analysis methods based on nonlinear dynamics and fractals ("chaos theory"). Methods-In addition to the traditional spectral components of HR variability, we measured instantaneous beat-to-beat variability and long-term continuous variability analyzed from Poincaré plots, fractal correlation properties, and approximate entropy of R-R interval dynamics from 24-hour ambulatory ECG recordings in 30 healthy control subjects, 31 hemispheric stroke patients, and 15 brain stem stroke patients (8 medullary, 7 pontine) in the acute phase of stroke and 6 months after stroke. Results-In the acute phase, the traditional spectral components of HR variability and the long-term continuous variability from Poincaré plots were impaired (PϽ0.01) in patients with hemispheric and medullary brain stem stroke, but not in patients with pontine brain stem stroke, in comparison with control subjects. At 6 months after stroke, measures of HR variability in hemispheric stroke patients were still lower (PϽ0.05) than those of the control subjects. Various complexity and fractal measures of HR variability were similar in patients and control subjects. The conventional frequency domain measures of HR variability as well as the Poincaré measures showed strong correlations (Pearson correlation coefficient, rϭ0.68 to rϭ0.90) with each other but only weak correlations (rϭ0.09 to rϭ0.56) with the complexity and fractal measures of HR variability. Conclusions-Hemispheric and medullary brain stem infarctions seem to damage the cardiovascular autonomic regulatory system and appear as abnormalities in the magnitude of HR variability. These abnormalities can be more easily detected with the use of analysis methods of HR variability, which are based on moment statistics, than by methods based on nonlinear dynamics. Abnormal HR variability may be involved in prognostically unfavorable cardiac complications and other known manifestations of autonomic failure associated with stroke.

Comprehensive Overview of Nursing and Interdisciplinary Care of the Acute Ischemic Stroke Patient

“…162 Right hemispheric infarcts have been associated with a higher incidence of arrhythmias, possibly due to sympathetic and parasympathetic nervous system dysfunction. 163 Atrial fibrillation, often paroxysmal, is commonly first detected only after it has caused cardioembolic stroke. If cardiac output is compromised, arrhythmias may further aggravate an already compromised cerebral blood flow.…”

Head and Neck Cooling Decreases Tympanic and Skin Temperature, But Significantly Increases Blood Pressure

“…The cooling-induced cardiovagal activation with slowing of HR may have beneficial effects in patients with cerebral lesions caused by stroke, traumatic brain injury, or epilepsy, ie, in patients with the abovementioned shifts of autonomic balance toward predominant sympathetic outflow. 23,[25][26][27][28] This increase in cardiovagal outflow with subsequent HR slowing may be mediated by direct, cold-induced stimulation of the trigeminal brain stem reflex and of parasympathetic efferent pathways, as described with cold face stimulation; 16,17 or, it might be secondary to the cold-evoked increase in sympathetic activity and BP elevation, 16 ie, to baroreflex activation. 16 On cooling onset, BPsys increased immediately and prominently, by an average of 6.2Ϯ10.5 mm Hg, and continued to rise to values that were more than 15 mm Hg higher after 120 minutes cooling than at baseline.…”

“…33 As mentioned above, older persons, 22 and especially acute stroke patients, show even more pronounced sympathetic responses to activating stimuli. [23][24][25]28 Therefore, head and neck cooling might not be indicated in stroke patients unless there is stringent pharmacological BP control or buffering of sympathetic stimulation by pain-relieving and sedating medication. Yet, sedating medication negatively reduces the ability to judge the patient's clinical status and to monitor any disease deterioration.…”

Fractal behaviour of pathological heart rate variability dynamics

“…Impaired cardiovascular autonomic regulation has been described in stroke patients with abnormalities hypothesized to be mediated by the central nervous system as a result of the cerebrovascular event, whereas the mechanism of this phenomenon is not fully understood [13,14].…”