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WASHINGTON, Oct. 17 (Xinhua) -- Contrary to conventional thinking, drinking high doses of caffeine might not cause the heart to beat irregularly in heart failure patients, a small study said Monday.
The relationship between caffeine consumption and the triggering of arrhythmias, or irregular heartbeats, has been explored for decades but remains controversial, according to the study published online by the U.S. journal JAMA Internal Medicine.
Advice to reduce caffeine to high-risk patients is widely recommended in clinical practice, despite a lack of evidence of an arrhythmogenic effect of caffeine on these individuals, it said.
In the new study, Luis Rohde of the Federal University of Rio Grande do Sul in Brazil, and colleagues conducted a clinical trial to examine the short-term effect of high doses of caffeine in patients with heart failure at increased risk for arrhythmic events.
The study enrolled 51 patients with predominantly moderate-to-severe heart failure.
Half received decaffeinated coffee mixed with 500 milligrams of caffeine over a five-hour period, while the other half were given placebo lactose powder.
The study included a treadmill test one hour after the last ingestion to test the potential proarrhythmic effect of caffeine use during exercise at the highest blood caffeine concentration.
The researchers were surprised to find no association between caffeine ingestion and arrhythmic episodes, even during the physical stress of a treadmill test.
"We did not observe any indication of a potential increased risk of ventricular or supraventricular premature beats, couplets, or nonsustained tachycardia," they wrote in the paper.
"Our results challenge the intuitive notion that caffeine intake should be limited or prohibited in patients with heart disease and at risk for arrhythmia."
The researchers were quick to note that about 50 percent of their patients were habitual coffee drinkers and that this could influence the results because routine users may be less prone to the effects of the substance.
Although they believed this to be unlikely, they acknowledged they "cannot ensure that long-term and high-dose use of caffeine is not associated with a proarrhythmic effect in patients with HF (heart failure)," the researchers reported.
"In this sense, our findings should be interpreted with caution because of the small number of patients included and the relatively low prevalence of arrhythmias that was observed."
