Heart rate variability in stroke population and normals: a comparison using spectral analysis

Frequency-domain spectral analysis was used to examine the effect of the parasympathetic division of the autonomic nervous system on heart rare in normal healthy subjects and stroke patients. Stroke survivors are at increased risk for cardiac events such as myocardial infarction and sudden death. Evidence suggests that decrease in heart rate variability (HRV) is a risk factor for arrhythmias and sudden death. Data were analyzed from normal healthy subjects and stroke patients during rest, paced breathing, progressive exercise and recovery periods, which caused changes in the autonomic regulation of heart rate. After analysis data were compared to see changes in the parasympathetic function in normal subjects and stroke patients. One significant peak (respiration peak) in the heart rate variability spectrum was examined by this technique. The area of the peak at the respiration frequency showed parasympathetic changes. During rest the parasympathetic activity was found to be high. Paced breathing increased the respiration frequency peak and during progressive exercise. The parasympathetic activity was found to decrease. Stroke patients were found to have significantly lower parasympathetic input to HRV at rest, during paced breathing and during exercise. The use of this technique enables one to explore and examine the autonomic contributions to heart rate regulation and also other physiological and environmental conditions where the input to the autonomic nervous system changes significantly.>