Background: Changes in autonomic regulation of the heart may be responsible for the occurrence of arrhythmias. Although a decrease in 24-hour heart rate variability is a strong predictor of subsequent arrhythmias in patients with heart disease, many questions remain unanswered concerning changes in heart rate and heart rate variability in the minutes or hours preceding an arrhythmia. The aim of our study was to analyze changes in heart rate and heart rate variability occurring during the 90 minutes preceding an arrhythmia, in patients with coronary heart disease and an implantable defibrillator.
Materials and methods: Thirty-eight patients, with a total of 93 episodes of ventricular arrhythmia, were included in the study. Heart rate and heart rate variability were measured in three 30-minute and five 2-minute periods preceding the arrhythmia. Heart rate variability was assessed using measurements of Poincaré plots.
Results: The results show a gradual increase in heart rate before the arrhythmia, from 73+/-13/min, to 75+/-14/min, and finally 78+/-15/min in the 90 minutes preceding the arrhythmia (P<0.05).
Conclusion: Measurements of Poincaré plots showed a significant increase in their length and no significant change in their width. These results suggest that sympathetic activation is the predominant change in autonomic nervous system before a ventricular arrhythmia in patients with coronary heart disease. This change may occur as early as one hour and a half before the arrhythmia.