Autonomic nervous system activity during myocardial ischemia in man estimated by power spectral analysis of heart period variability

Abstract

Ambulatory patients with coronary artery disease exhibit a nearly universal increase in heart rate during episodes of ST depression. 1 The cause of the increase in heart rate presumably represents an increase in sympathetic nervous activity, a decrease in parasympathetic nervous activity, or both. The purpose of this investigation was to determine the cause of increased heart rate during ambulatory ischemic episodes using power spectral analysis of normal RR intervals. An increase in sympathetic nervous activity causes an increase in low frequency power and an increase in the low to high frequency ratio. A decrease in parasympathetic nervous activity causes a decrease in both low and high frequency power, that is, no change or a decrease in the low to high frequency ratio.