HF Patients Steady as Rock With Short-Term High-Dose Caffeine

Patrice Wendling

October 17, 2016

PORTO ALEGRE, BRAZIL — Consuming high doses of caffeine did not increase arrhythmias in people with chronic systolic heart failure (HF), even during a treadmill test, in a small randomized controlled trial[1].

There was no significant association between intake of 500 mg of caffeine over a 5-hour period and ventricular premature beats (VPBs) or supraventricular premature beats (SVPBs).

"Our results challenge the intuitive notion that caffeine intake should be limited or prohibited in patients with heart disease and at risk for arrhythmia," lead author Dr Priccila Zuchinali (Federal University of Rio Grande do Sul, Porto Alegre, Brazil) and colleagues reported in the study, published October 17, 2016 in the JAMA Internal Medicine.

They noted that animal studies have suggested an increased risk of developing ventricular fibrillation in animals that received caffeine, but this was probably the result of receiving very high doses of caffeine (up to 35 mg/kg) not regularly consumed by humans. A brewed eight-ounce cup of coffee typically contains 95 to 200 mg of caffeine.

Few studies have actually assessed the effect of high doses of caffeine in patients with HF. A recent meta-analysis[2] conducted by the investigators found no significant effect of caffeine on the occurrence of VPBs in humans, but she noted that some of the studies were decades old and had poor methodologic quality.

Commenting to heartwire from Medscape, Dr Thomas Whayne Jr (Gill Heart Institute, University of Kentucky, Lexington) said unless there is a genetic abnormality, coffee does not appear to increase coronary artery events and decreases adult-onset diabetes mellitus.

"The major clinical implication is that we can reassure our patients that moderate, fully caffeinated coffee intake is fine if enjoyed, unless bothersome arrhythmias or bothersome symptoms are associated. In addition, hospitals should offer caffeinated coffee to cardiovascular patients able to ingest it, in moderate levels, instead of prohibiting it for cardiovascular patients as in the past," he added.

To more robustly evaluate the effects of caffeine, 51 patients (74% male, mean age 60.6 years) with HF due to LV systolic dysfunction (mean ejection fraction 29%) were randomly assigned to a 7-day washout period with no caffeine intake before consuming five doses of 100-mL decaffeinated coffee mixed with caffeine or lactose powder at 1-hour intervals. Continuous ECG monitoring began 1 hour after the first coffee, with a treadmill test performed 5 hours later.

Three-fourth of patients (67%) had nonischemic HF, 61% had an ICD, 25% had a prior MI, 13% had chronic atrial fibrillation, and 45% had hypertension.

Most patients were in NYHA functional class 1 to 2 and receiving standard HF treatment including an ACE inhibitor or angiotensin II receptor blocker (ARB) in 97% and a beta-blocker in 98%.

The median plasma caffeine concentration was 9480 μg/L (4882 μmol/L) in the caffeine group and 0 μg/L in the placebo group.

During the continuous ECG monitoring, there were no significant differences between patients drinking caffeinated coffee or placebo in VPBs (185 beats vs 239 beats; P=0.47) or SVPBs (six vs six beats; P=0.44). Their mean heart rates were also indistinguishable (70 vs 70 bpm; P=0.40).

Subgroup analyses revealed no differences in VPBs or SVPBs in patients with an ICD, ischemic etiology, taking amiodarone and digoxin, or in those who were habitual coffee drinkers.

There were no between-group differences in VBPs or SVPBs during the treadmill test.

"Although we did not observe an improvement in exercise performance, it has been suggested that caffeine in doses from 4 to 9 mg/kg can also induce analgesia, reduce fatigue sensations, and improve neuromuscular function, all of which could prolong time to fatigue during muscular exercise," the authors noted.

The major limitation of the study identified by Whayne and the investigators was the extremely short-term use of caffeine.

In an accompanying editorial[3] Drs Jacob P Kelly and Christopher Granger (Duke Clinical Research Institute, Durham, NC) write that the study findings are "reassuring" in the context of epidemiologic data suggesting safety in broader populations but add that the short-term caffeine exposure and small sample size "preclude any reliable information on clinical outcomes."

They note, for example, that the upper bound of the 95% confidence interval for zero episodes of sustained and/or life-threatening arrhythmias out of 25 patients is approximately 12%, "which is hardly comforting."

Kelly and Granger conclude that "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.

"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."

The study was supported by a research grant from the Brazilian government's National Council for Scientific and Technological Development. The authors report they are "habitual coffee drinkers" but have no other disclosures. Whayne, Kelly, and Granger reported no relevant financial relationships.

Follow Patrice Wendling on Twitter: @pwendl. For more from theheart.org, follow us on Twitter and Facebook.

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