Reducing caffeine for treatment of arrhythmias - myth or evidence-based medicine?

Introduction

Cardiac arrhythmias are frequently encountered in isolation or associated with other conditions (eg. hyperthyroidism, sepsis, myocardial infarction, cardiac surgery). The term encompasses a range of disorders from benign premature atrial or ventricular complexes to malignant tachycardias such as ventricular tachycardia or fibrillation. In clinical practice, patients with a suspected or confirmed diagnosis of cardiac arrhythmia are often advised to limit their intake of caffeine, which can be an important source of enjoyment and have significant impact on their overall quality of life. Furthermore patients are exposed to news headlines such as “Teen dies from too much caffeine, coroner says.”⁽¹⁾ In this review, we will explore the association between caffeine intake and arrhythmias to evaluate whether providing such advice is truly justified.

Discussion

Caffeine is a methylxanthine compound related to theophylline that is able to stimulate the sympathetic nervous system through a variety of different mechanisms. Its effects include non-selective competitive antagonism of adenosine receptors that are responsible for cardiovascular regulation and increasing cytosolic calcium concentrations by blocking reuptake of calcium into the sarcoplasmic reticulum.⁽²⁾

The caffeine content in standard beverages is summarised in Table 1.^(3,4)

Table 1. Caffeine content in beverages

Previous studies have demonstrated that very high doses of caffeine in animals increased susceptibility to both supraventricular and ventricular arrhythmias.^(5–7)

However, the results from human trials are less convincing with many studies showing no increase in arrhythmia burden or symptoms despite high doses of caffeine.^(8–16) Some of these negative studies included patients with known arrhythmias^(12,14,16), reduced ejection fraction heart failure⁽⁸⁾ and recent myocardial infarction.⁽¹⁷⁾ One large epidemiological study did show increased incidence of ventricular premature beats with caffeine. However, it was performed almost 4 decades ago and the association was found only in patients who ingested very high doses of caffeine (≥9 cups of coffee per day).⁽¹⁸⁾ Studies demonstrating a lower risk of arrhythmias with caffeine are sparse. A recent study of 1,475 healthy patients found a lower incidence of atrial fibrillation with caffeine intake of >320mg per day.⁽¹⁹⁾ A summary of published trials can be found in Table 2.

Table 2. Studies evaluating the effects of caffeine on arrhythmias. AF = atrial fibrillation; VPB = ventricular premature beats; MI = myocardial infarction

The European Society of Cardiology (ESC)^(22,23) and American College of Cardiology/American Heart Association/Heart Rhythm Society (ACC/AHA/HRS)⁽²⁴⁾ guidelines for supraventricular and ventricular arrhythmias do suggest that patients should be advised to avoid stimulants such as caffeine. However, this is in the context of benign arrhythmias only, with no references provided.

With conflicting results from several studies, it is not surprising that physicians may choose to remain cautious and advise at-risk patients to reduce their caffeine intake. However, as with all clinical decisions, the patient’s views should be respected and any envisaged benefits should be balanced against potential impact to their quality of life. Additionally, it should be done in light of current available evidence that do not suggest an increased risk of arrhythmias with caffeine. However, there may remain a minority of patients who exhibit a clear relationship between arrhythmia onset and burden with caffeine intake. In such patients, it would seem appropriate to avoid caffeine.

Conclusion

Overall the evidence do not suggest that reducing or avoiding caffeine intake will reduce the risk of arrhythmias.

References

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