Heart smart latte

Coffee drinkers with heart issues can breathe a sigh of relief. A new study shows coffee is safe for people at risk of arrhythmias, even if they have heart failure and are wearing a pacemaker.

It seems intuitive that caffeine intake should be limited or prohibited in patients with heart disease. No-one wants to die with a latte in their hand. On the other hand, for a coffee drinker, the idea of facing a lifetime of coffee-free mornings might seem more unpalatable than risking sudden death.

The beautiful news from this well-designed study from Brazil (where they know their coffee) is that this risk is non-existent after all. The heart keeps ticking along just fine, even as the morning fog clears.

The background

Evidence prior to this study had not shown that coffee was risky, but nor was there proof it was safe. Animal studies had produced some rhythm disturbances (ventricular premature beats) at high caffeine doses, but most human studies were of low quality (no placebo), and dated from the 1980s, back when Australians liked their coffee instant.

With definitive evidence lacking, many physicians and guidelines erred on the side of caution, recommending little or no coffee intake for patients at increased risk of rhythm disturbance. However, because caffeine is the most widely consumed sympathetic nervous stimulant in the world, this apparently innocuous recommendation had a notable impact on ‘pleasurable life-years lost’* calculations.

The study

This randomised, double-blinded study published in JAMA Internal Medicine recruited 51 participants from a heart failure clinic, with moderate-to-severe left ventricular dysfunction, 60% of whom had a pacemaker.

Subjects drank five cups of decaffeinated coffee, stirring in a powder containing either 100mg of caffeine or placebo. They had continuous ECG heart monitoring throughout, both at rest and during a treadmill stress test. A week later, they repeated the process, but with the caffeine and placebo ‘crossed over’.

The 100mg of caffeine would be considered a strong coffee. No mention was made of the coffee quality, but it is understood no baristas were harmed during the study.

The results

There were no detected differences in any type of arrhythmia, either at rest or on the treadmill. Blood testing confirmed the expected differences in caffeine levels, but interestingly, the average heart rate was indistinguishable between the two groups.

Although the study was fairly small, it was of high quality, and had enough power to detect any trend towards rhythm problems if coffee was actually causative. This adds a lot more weight to the statement that coffee is a safe beverage for people with heart failure.

Let’s drink to that.

*The PLYL calculation is a fantasy invented by the author.

This article was first published in Medical Observer, Oct 2016