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High doses of caffeine do not induce arrhythmias

Excess doses of caffeine did not increase the risk for cardiac arrhythmias among patients with heart failure, according to study findings published in JAMA Internal Medicine.

“The relationship between caffeine consumption and the triggering of arrhythmias has been explored for decades but remains controversial,” Priccila Zuchinali, ScD, from the Federal University of Rio Grande do Sul in Porto Alegre, Brazil, and colleagues wrote.

“Few studies have assessed the effect of high doses of caffeine in patients with heart failure due to left ventricular systolic dysfunction at high risk for ventricular arrhythmias,” they added.

Between March 5, 2013 and October 2, 2015, Zuchinali and colleagues performed a double blind, randomized crossover study at the heart failure and cardiac transplant clinic of a tertiary-care university hospital in Brazil to investigate whether high-dose caffeine ingestion influenced the occurrence of supraventricular and ventricular arrhythmias. They used continuous electrocardiographic monitoring to measure the number and percentage of ventricular and supraventricular premature beats.

Fifty-one patients (37 male; mean age, 60.6 years) with chronic heart failure, moderate-to-severe systolic dysfunction (left ventricular ejection fraction <45%) and New York Heart Association functional class I to III were included and studied at rest and during a symptom-limited exercise test. Of those, 31 (61%) had an implantable cardioverter-defibrillator device.

Patients were randomly assigned to caffeine or placebo. They consumed 100 mg of caffeine or lactose capsules mixed into 100 mL of decaffeinated coffee at 1-hour intervals for a total of 5 hours. Overall, participants consumed 500 mg of caffeine or placebo. This procedure was repeated after participants adhered to a no-caffeine diet for 7 days.

Continuous electrocardiographic monitoring revealed that patients in the caffeine and placebo groups did not differ significantly in the number of ventricular premature beats (185 vs. 239 beats, respectively) or supraventricular premature beats (six vs. six beats, respectively). In addition, there was no significant difference between groups in couplets, bigeminal cycles or nonsustained tachycardia.

Caffeine consumption also had no impact on ventricular and supraventricular premature beats, duration of exercise, estimated peak oxygen consumption and heart rate during an exercise test.

In addition, patients with higher levels of plasma caffeine concentration did not display an increased rate of ventricular premature beats compared with those with lower plasma levels or those in the placebo group (91 vs. 223 vs. 207 beats, respectively).

“The acute ingestion of high doses of caffeine did not induce arrhythmias in patients with chronic systolic [heart failure] at rest and during a symptom-limited physical exercise,” Zuchinali and colleagues concluded. “To date, there is no solid evidence to support the common recommendation to limit moderate caffeine consumption in patients at risk for arrhythmias.”

In an accompanying editorial, Jacob P. Kelly, MD, and Christopher B. Granger, MD, both of the Duke Clinical Research Institute at Duke University, note that the results of this study are not conclusive due to the short duration of caffeine exposure and the limited quantity of patients included in the study. Rather, they suggest that the study provides better evidence that “modest” ingestion of caffeine does not induce arrhythmias in high risk patients.

“However, the longer-term safety of moderate- and high-dose consumption of caffeine, including in popular energy drinks and in patients at high risk for arrhythmias, remains unknown,” Kelly and Granger conclude. “For the time being, it seems reasonable to reassure our patients that modest caffeine consumption appears to be safe, including for most patients with heart failure.” – by Alaina Tedesco

Disclosure: Zuchinali and colleagues report funding from CNPq (National Council for Scientific and Technological Development. Kelly and Granger do not report any relevant financial disclosures.