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Caffeine Enhances Heart Rate Variability in Middle-Aged Healthy, But Not Heart Failure Subjects
Catherine F Notarius1, John S Floras1
1Division of Cardiology, University Health Network and Mount Sinai Hospital, University of Toronto , Toronto, ON, Canada .
Insights
Caffeine boosts heart rate variability (HRV) and reduces sympathetic nerve activity in healthy individuals but does not benefit patients with chronic heart failure (CHF). This suggests caffeine may not be a viable therapeutic option for improving HRV in CHF patients.
Area of Science:
- Cardiology
- Autonomic Nervous System Research
- Pharmacology
Background:
- Diminished heart rate variability (HRV) is a key predictor of poor prognosis in chronic heart failure (CHF).
- Caffeine has previously demonstrated an ability to increase HRV in healthy young individuals.
- The potential for caffeine to benefit CHF patients by improving HRV warrants investigation.
Purpose of the Study:
- To investigate the effects of intravenous caffeine infusion on HRV in patients with CHF and age-matched healthy controls.
- To assess whether caffeine administration alters autonomic modulation of heart rate and sympathetic nerve activity.
Main Methods:
- A double-blind, randomized design was employed, administering either saline or caffeine (4 mg/kg) intravenously to 11 CHF patients and 10 healthy controls on separate days.
- Heart rate variability (HRV) was assessed using fast Fourier Transform analysis to determine total spectral power, high-frequency (HF), and low-frequency (LF) components.
- Muscle sympathetic nerve activity (MSNA) was directly measured via microneurography from the peroneal nerve.
Main Results:
- In healthy controls, caffeine significantly reduced heart rate and sympathetic nerve traffic while increasing the HF/total power ratio.
- Patients with CHF exhibited lower baseline LF power and LF/HF ratio compared to controls.
- Caffeine administration had no significant effect on any measured HRV parameters in the CHF group.
Conclusions:
- Caffeine enhances cardiac vagal modulation and decreases muscle sympathetic nerve activity in healthy middle-aged adults.
- These beneficial effects of caffeine on HRV and sympathetic activity were not observed in patients with chronic heart failure.
- Caffeine does not appear to improve HRV or reduce sympathetic nerve activity in individuals with CHF.
Background:
In chronic heart failure (CHF) due to left ventricular dysfunction, diminished heart rate variability (HRV) is an independent predictor of poor prognosis. Caffeine has been shown to increase HRV in young healthy subjects. Such an increase may be of potential benefit to patients with CHF.
Objective:
We hypothesized that intravenous infusion of caffeine would increase HRV in CHF, and in age-matched healthy control subjects.
Methods:
On two separate days, 11 patients (1F) with CHF (age=51.3±4.6 years; left ventricular ejection fraction=18.6±2.7%; mean±standard error) and 10 healthy control subjects (age=48.0±4.0) according to a double-blind randomization design, received either saline or caffeine (4 mg/kg) infusion. We assessed HRV over 7 minutes of supine rest (fast Fourier Transform analysis) to determine total spectral power as well as its high-frequency (HF) (0.15-0.50 Hz) and low-frequency (LF) (0.05-0.15 Hz) components, and recorded muscle sympathetic nerve activity (MSNA) directly from the peroneal nerve (microneurography).
Results:
In healthy control subjects, compared with saline, caffeine reduced both heart rate and sympathetic nerve traffic (p≤0.003) and increased the ratio of HF/total power (p≤0.05). Baseline LF power and the ratio LF/HF were significantly lower in CHF compared with controls (p=0.02), but caffeine had no effect on any element of HRV.
Conclusions:
Caffeine increases cardiac vagal heart rate modulation and reduces MSNA in middle-aged healthy subjects, but not in those with CHF.
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