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High-Dose Caffeine and Arrhythmias in Heart Failure Patients
Study Questions:
What is the effect of high-dose caffeine on the frequency of supraventricular and ventricular arrhythmias, at rest and during a symptom-limited exercise test?
Methods:
This was a double-blinded randomized clinical trial with a crossover design of patients with chronic heart failure with left ventricular ejection fraction <45% and New York Heart Association functional class I-III. Patients consumed caffeine (100 mg) or lactose capsules, in addition to five doses of 100 ml decaffeinated coffee at 1-hour intervals, for a total of 500 mg of caffeine or placebo during a 5-hour protocol. After a 1-week washout period, the protocol was repeated. The number and percentage of ventricular and supraventricular premature beats was assessed by continuous electrocardiographic monitoring.
Results:
A total of 51 patients (74% male; mean age 60.6 years) had a mean left ventricular ejection fraction of 29%. No significant differences between the caffeine and placebo groups were observed in the number of ventricular (185 vs. 239 beats, p = 0.47) and supraventricular premature beats (6 vs. 6 beats, p = 0.44), as well as in couplets, bigeminal cycles, or nonsustained tachycardia. Exercise test–derived variables, such as ventricular and supraventricular premature beats, duration of exercise, estimated peak oxygen consumption, and heart rate, were not affected by caffeine ingestion. There was no increase in ventricular premature beats (91 vs. 223 vs. 207 beats, respectively) in patients with higher levels of plasma caffeine concentration compared with lower plasma levels (p = 0.91) or with the placebo group (p = 0.74).
Conclusions:
Acute ingestion of high doses of caffeine does not induce arrhythmias in patients with systolic heart failure and at high risk for ventricular arrhythmias.
Perspective:
Caffeine is known to stimulate the sympathetic nervous system through a variety of pathways, most important of which is adenosine receptor antagonism. While older studies suggested that very high doses of caffeine may induce ventricular ectopy or sustained ventricular arrhythmia, studies involving human subjects have shown conflicting results. The present study, while not definitive evidence, strongly suggests that patients at highest risk for ventricular arrhythmia, 98% of whom are on beta-blockers, do not experience increased atrial or ventricular ectopy. Of note, 20% of the patients in the study were taking amiodarone. In that sense, the study cohort was a reflection of the real-world heart failure population.
Keywords: Arrhythmias, Cardiac, Caffeine, Electrocardiography, Exercise Test, Geriatrics, Heart Conduction System, Heart Failure, Systolic, Heart Failure, Heart Rate, Oxygen Consumption, Secondary Prevention, Stroke Volume, Sympathetic Nervous System, Tachycardia, Ventricular Premature Complexes
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