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Published on: February 17, 2018
Decreased cardiac parasympathetic activity in chronic heart failure and its relation to left ventricular function
J Nolan1, A D Flapan, S Capewell
1University Department of Medicine, Royal Infirmary, Edinburgh.
Insights
Patients with chronic heart failure often have reduced cardiac parasympathetic activity, indicated by lower heart rate variability. This dysfunction correlates with impaired left ventricular function, potentially increasing arrhythmia risk.
Area of Science:
- Cardiology
- Autonomic Nervous System Research
Background:
- Sympathetic nervous system activity is well-studied in heart failure, but parasympathetic nervous system's role is less understood.
- Limited research exists on cardiac parasympathetic activity in chronic heart failure patients.
Purpose of the Study:
- Investigate cardiac parasympathetic activity in chronic heart failure.
- Examine the relationship between parasympathetic activity and left ventricular function.
Main Methods:
- Measured heart rate variability using 24-hour ambulatory electrocardiograms.
- Quantified parasympathetic activity by counting specific RR interval variations (counts).
Main Results:
- Most patients (60%) exhibited reduced cardiac parasympathetic activity compared to normal subjects.
- A significant positive correlation was found between total 24-hour RR counts and left ventricular ejection fraction (r=0.49, p<0.05).
Conclusions:
- Chronic heart failure patients often display diminished heart rate variability, signifying reduced cardiac parasympathetic activity.
- The extent of parasympathetic dysfunction is linked to the severity of left ventricular dysfunction.
- This parasympathetic impairment may contribute to ventricular arrhythmias and poor prognosis in heart failure.
Background:
Activation of the sympathetic nervous system has been extensively studied in patients with chronic heart failure, but the parasympathetic nervous system has received relatively little attention. The objective in this study was to investigate cardiac parasympathetic activity in chronic heart failure and to explore its relation to left ventricular function.
Methods:
Heart rate variability was measured from 24 hour ambulatory electrocardiograms by counting the number of times each RR interval exceeded the preceding RR interval by more than 50 ms (counts). This method provided a sensitive index of cardiac parasympathetic activity.
Results:
Mean (range) of counts were: waking 48 (1-275)/h, sleeping 62 (0-360)/h, and total 1310 (31-7278)/24 h. These were lower than expected, and in 26 (60%) of the 43 patients counts fell below the lower 95% confidence intervals (95% CI) for RR counts in normal subjects. A significant correlation between total 24 hour RR counts and left ventricular ejection fraction was present (r = 0.49, p less than 0.05).
Conclusions:
These results indicate that most patients with chronic heart failure have reduced heart rate variability and therefore reduced cardiac parasympathetic activity. The degree of parasympathetic dysfunction is related to the severity of left ventricular dysfunction. This may be relevant to the high incidence of ventricular arrhythmias and poor prognosis of patients with chronic heart failure.
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