By Peter Galvin, MD
Coffee is one of the most commonly consumed beverages in the world, yet little is known about its acute health effects. There has always been an assumed relationship between (caffeinated) coffee consumption and cardiac ectopy. The word ectopy refers to “extra” heartbeats. A normal human heart beats at a set rate with the same time interval between each beat. That set interval is required because the heart’s internal pacemaker (the SA node) must electrically reset itself before the next beat can be generated. This resetting process is called repolarization and can be traced on an EKG. When an “extra” or premature beat occurs before the next regularly scheduled beat, that scheduled beat does not occur because the heart does not have enough time to reset or repolarize. Therefore, the time interval between the premature beat and the next regular beat is longer than normal, causing the heart to overfill with blood, making that next regular beat stronger than normal. This stronger beat is often felt by the individual in the form of a thump or flutter. Premature beats can either have an atrial source (PAC, or premature atrial contraction) or ventricular (PVC, or premature ventricular contraction). It has long been thought that PACs may be a predictor or risk factor for atrial fibrillation, and PVCs for heart failure.
In many observational studies, coffee consumption has been associated with lower rates of diabetes and (early) death, a finding that is often attributed to the possibility that caffeine stimulates increased physical activity. Coffee may also suppress effective sleep, but objective measurements of this relationship in natural environments (i.e., not in a sleep lab) are scarce. Recently, results of the CRAVE (Coffee and Real-time Atrial and Ventricular Ectopy) trial, done at the UCSF Medical School, were published. Participants were randomized into two groups – one that consumed caffeinated coffee, and one that avoided it. All participants wore continuous recording EKG patches (Zio XT Patch or iRhythm) for the duration of the study. The study results found that among the healthy adult volunteers the consumption of caffeinated coffee did not result in more daily PACs. Daily coffee consumption was associated, however, with increased recorded daily steps taken, fewer minutes of sleep per night, and more daily PVCs (among those who consumed more than one cup of coffee per day).
Cardiac ectopy is a nearly universal human phenomenon, and, as mentioned above, PACs are a predictor of atrial fibrillation and PVCs heart failure. Studies, including this one, have shown that coffee drinkers have a lower risk of developing atrial fibrillation than non-coffee drinkers, a finding that has been attributed to the anti-inflammatory and antivagal (vagus nerve) effects of coffee, as evidence supports the roles of both inflammation and vagal tone as harbingers of atrial arrythmias. Also, as other studies have shown, consumption of more than one cup of coffee per day is linked to increased rates of PVCs, a fact that has yet to be fully explained. Finally, study after study has shown that coffee drinkers have lower rates of diabetes and live longer, facts also not yet fully understood. So, it’s a safe bet that one cup of coffee per day will have a beneficial effect on most people.
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