Clinical Applications of Heart Rate Variability in Neurological Disorders

ABSTRACT

Heart rate variability (HRV) is a useful marker for predicting mortality and cardiovascular events in cardiac diseases. Various time- and frequency-domain parameters are used for assessing HRV. The time-domain measures include standard deviation of the NN intervals (SDNN), standard deviation of the average NN interval, root mean square of the successive differences SDNN index, NN50 count, and pNN50, while the power spectrum that is used the most widely in frequency-domain analyses is divided into low frequency (LF), high frequency (HF), LF norm, HF norm, and LF/HF. The HF band is modulated by the parasympathetic nervous system, while the LF band is modulated by both the sympathetic and parasympatheticnervous systems. Altered or reduced HRV parameters have been shown to be related to cardiovascular events in patients with various neurological disorders, such as parkinsonian syndromes, dementia, cerebrovascular disorder, and epilepsy. Furthermore, analyses of HRV have attempted to distinguish different diseases and evaluate the degree of disability. This article discusses the clinical use of HRV in the neurological field.