We developed and examined a new method to evaluate the cooperation between sinoatrial node (SA node) and atrioventricular node (AV node) with a correlation diagram of R-R and P-R interval which we newly developed. Twenty healthy subjects were examined. Electrocardiograph was measured during supine rest, sitting rest, and submaximal exercise by an electrically braked cycle ergometer. One subject was selectively blocked autonomic nervous system (ANS) by pharmacological agents. The correlation diagram of R-R and P-R interval was plotted by beat-to-beat. We also evaluated both sympathetic nervous activity (SNS) and parasympathetic nervous activity (PNS) with spectral analysis of R-R interval variability during exercise. According to the correlation diagrams, both R-R interval and P-R interval decreased with progress of exercise intensity, and these showed nonlinearity. The correlation diagram for PNS blockade was overlapped on physiological response. PNS activities decreased to near zero at halfway of exercise by spectral analysis. SNS activities rapidly increased when PNS activities near zero. The correlation diagram was useful for evaluation of cooperation between SA and AV node because it reflected ANS activity. It is indicated that the cooperation between SA and AV node will be evaluated with the correlation diagram and spectral analysis together.
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