An analysis of the circadian rhythmicity of atrial and ventricular rates in complete heart block.
A 19 year old female human subject with complete heart block was put at complete bed rest for 63 hours during which a Lead II EKG was monitored at half hour intervals. Atrial and ventricular rates demonstrated cyclic activity with peaks during the day and troughs during the night. A correlation coefficient of plus 0.85 and a slope of plus 1.0 from a linear regression between atrial and ventricular rates demonstrated a close parallel. Calculation of the crosscovariances confirmed the observed cyclic activity with a period of 24 hours and phase angle of zero degrees between the two chambers. The data may be explained by one or all of the following mechanisms: (1) both chambers are subject to the same internal milieu, (2) autonomic nervous system discharge and associated reflexes may integrate relative changes in rate, (3) direct mechanical or electrotonic forces may result in alteration of rates in direct proportion to the magnitude of the dominant chamber, (4) program which operates independent of external factors. The question remains for direct experimental data to demonstrate whether the observed phenomenon is an intrinsic biologic rhythm within the heart or in its control system.
D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology; D002940:Circadian Rhythm; D004562:Electrocardiography; D005260:Female; D006325:Heart Atria / Q000503:physiopathology; D006327:Heart Block / Q000503:physiopathology*; D006339:Heart Rate; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D012849:Sinoatrial Node / Q000503:physiopathology