CHANGES IN AUTONOMIC NERVOUS ACTIVITY DURING COLONOSCOPY USING SPECTRAL ANALYSIS OF HEART RATE VARIABILITY

Background: Cardiac events are known to occur during colonoscopic procedures. In order to clarify the changes in autonomic nervous activity during colonoscopy, the circulatory dynamics were examined by spectrum analysis and by observing 1/f fluctuations of heart rate. Methods: The study group consisted of 39 subjects who underwent total colonoscopy (the TC group) and 46 subjects who underwent sigmoid colonoscopy (the SC group). Autonomic nervous function was assessed by analyzing the spectral analysis and 1/f fluctuation of the heart rate. Results: In the TC group, high-frequency spectral power (HF power; 0.15–0.40 Hz), which reflects parasympathetic activity, was decreased during the early stages of the examination compared with that before endoscopy, and it significantly decreased during the late stages of the examination. There were no significant changes in the SC group. However, low-frequency power (LF power; 0.04–0.15 Hz) and the LF/HF ratio both increased during the examination in both groups, suggesting increased sympathetic tone. The 1/f fluctuations were analyzed as the averaged regression lines and as that which related the log amplitude to the log frequency of spectra. The slopes of the regression line of 1/f fluctuations in the TC and SC groups had a tendency to approach zero during the colonoscopic procedure. Conclusion: These results indicate that the endoscopic procedure is stressful for patients. Total colonoscopy may more readily cause changes in the circulatory dynamics than does sigmoid colonoscopy. Increased blood pressure, arrhythmia and ST depression were also observed. These findings suggest that changes in autonomic nervous activity during colonoscopic procedure may cause cardiac accidents such as the appearance of fatal arrhythmia and acute myocardial infarction.