While some arrhythmias (abnormal heart rhythms) may be harmless or even go unnoticed in patients, others can increase risk for sudden cardiac arrest.
Atrial fibrillation (AFib), the most common heart rhythm disorder, causes the heart to beat rapidly and skip beats, and if left untreated, can cause strokes.
A single cup of coffee contains about 95 mg of caffeine and acts as a stimulant to the central nervous system. Once in the body, caffeine blocks the effects of adenosine, a chemical that can facilitate AFib.
The authors analysed multiple population-based studies to determine an association between caffeine intake and its effects on atrial and ventricular arrhythmias.
These studies have consistently shown a decrease in AFib with an increase in caffeine ingestion, with one analysis of 228,465 participants showing AFib frequency decreasing by six percent in regular coffee drinkers, and a further analysis of 115,993 patients showing a 13 percent risk reduction.
Peter Kistler, director of electrophysiology at Alfred Hospital and Baker Heart and Diabetes Institute, and the review’s lead author, said: “There is a public perception, often based on anecdotal experience, that caffeine is a common acute trigger for heart rhythm problems.
"Our extensive review of the medical literature suggests this is not the case."
The authors also determined that caffeine has no effect on ventricular arrhythmias (VAs). Caffeine doses up to 500 mg daily (equivalent to six cups of coffee) did not increase the severity or rate of VAs.
A randomized study of 103 post-heart attack patients who received an average of 353 mg per day resulted in improved heart rate and no significant arrhythmias. Only two studies showed an increased risk for VAs, where patients ingested at least 10 cups and nine cups per day, respectively.
Dr Lucy Chambers, editor of Nutrition Bulletin, said: “Evidence indicates that moderate caffeine intake (about 5 cups of coffee per day) does not increase the occurrence of arrhythmia, but some people choose to avoid caffeine as they find it can trigger an episode, particularly at high doses.
“Having a healthy bodyweight and avoiding drinking alcohol to excess (limit intake to no more than 14 units per week) reduces the risk of developing arrhythmias.
“Other ways to improve your heart health include cutting down on saturated fat and replacing with unsaturated fats, having fish twice a week (one of which should be oily type), watching your salt intake, eating high fibre and wholegrain foods, giving up smoking and being physically active.”
The authors determined that energy drinks should be avoided by patients with pre-existing heart conditions. One energy drink can contain anywhere from 160 to 500 mg of concentrated caffeine. Three quarters of patients with pre-existing heart conditions who consumed two or more energy drinks per day reported palpitations within 24 hours.
Both large population studies and randomized control trials suggest caffeine intake of up to 300 mg per day may be safe for arrhythmic patients, according to the review. However, there may be individual differences in susceptibility to the effects of caffeine on the factors which trigger arrhythmias in some, and up to 25 percent of patients report coffee as an AFib trigger.