The Value of Self-Experimentation: Monitoring Caffeine Effects On PVC Frequency With Zio and Kardia

Palpitatons due to premature beats, either ventricular contractions (PVCs) or atrial contractions (PACs) can be extremely vexing even when we know they are benign. For many individuals, these extrasystoles come in waves that are seemingly random and inexplicable. This unpredictability can add to the anxiety they create.

A reader recently shared his attempt to sort out the influence of caffeine consumption on the frequency of his symptomatic PVCs but encounters one of the many “variables” that confound his attempt at biohacking. I’ve added my editorial/educational comments in parenthesis in mauve.

I discovered that I had SEV’s (PACs) and PVCs about six months ago by using the 6-lead Kardia device.  I can watch the trace live in real-time, feel the PVC and then see it on the trace (easy to see with the 6 lead version) about a second after I actually feel it.  I went to an electrophysiologist and he offered me the option of monitoring with a Zio patch for two weeks.

I followed the incidence of PVC’S with my Kardia in parallel with the patch. The results matched up well.

(Both Alivecor’s single and 6 lead mobile ECG devices in combination with its new Advanced Determinations AI algorithm can identify PVCs and PACs in your heart rhythm. I discuss the different ambulatory monitoring devices available here. Zio was the original 2-week patch-type monitor of which there are now numerous different brands. In my experience, these patch long-term monitors have greatly improved the process of continuous monitoring for arrhythmias for patients and physicians. We place them on the patient in the office at the end of our visit and patients mail them back to us when completed. When I started at Saint Louis University we utilized the Preventice type patch monitor. More recently, I have found the CAM patch from Bardy to offer excellent results. The CAM is “p-wave centric” which theoretically improves the accuracy of atrial fibrillation detection.)

The CAM patch from Bardy. It is attached centrally to the sternum whereas the Zio patch is attached over the left precordial area.

I have an imperfect experiment to share.  See the attached log from the Zio report. Some years ago I cut over to decaf coffee, but I actually drink a lot of it; two large mugs in the morning which turns out to be 6 official measure cups (3 scoops of Petes decaf). My guess is that its 30-50 mg caffeine in total.

For the first week of the Zio I kept up my decaf coffee habit and then on the second week (03/08/2021) I cut out all the decaf. As you can see from the data the second week had a dramatic decrease in PVC’S. I resumed the decaf drinking the morning of 3-11-2021, but did not see an immediate return of the PVC’s until 3 days later.

The results are pretty dramatic. I might have failed to mention that the experiment was conducted during lent, when I traditionally abstain from all alcohol. So it was not a variable in the experiment. 

 However, the experiment is imperfect because a second variable was changed in the second week.  I got sick of using the Kardia all the time and sick of worrying about this whole situation and pretty much forgot about it.  I suspect that measuring the PVCs with the Kardia actually causes them to be worse because I am tensed up while measuring. Other scientists might understand why I call this a Heisenberg problem.

So were the decreased PVCs in week 2 due to the reduced caffeine or the reduced stress due to an attitude adjustment?

For reference, I am 66 years old, extremely active (2 jobs), I exercise 5 days a week (you can see the 1 hour elevated heart rate in the report). Oh, and my mother recently told me that she and every single one of her 5 siblings have Afib and are on Coumadin. So I am highly motivated to make whatever lifestyle adjustments need to defer what may be an inevitable fate due to my genes.

Caffeine and Extrasystoles

A recent observational study looked at the frequency of extrasystoles in relation to habitual caffeine consumption. The introduction to that paper nicely lays out our current understanding of that relationship:

Patients often associate the symptoms of premature cardiac contractions with emotional stress, physical activity, dietary factors, and caffeine or other stimulant use.11 Though there is little data to support the role of behavioral modifications or trigger avoidance in reducing or preventing premature cardiac contractions, clinicians often instruct patients with any arrhythmia to avoid caffeine intake. The American College of Cardiology/American Heart Association guidelines on the management of supraventricular arrhythmias state that if a patient’s history is consistent with premature extra beats, one should review and eliminate potential exacerbating factors, such as caffeine, alcohol, and nicotine. Prominent online medical resources for clinicians, such as UpToDate and Medscape, feature similar recommendations for the management of premature beats.While none of these sources explicitly refer to the acute versus chronic effects of caffeine on ectopy, they focus on general avoidance in order to avoid triggering arrhythmias. Caffeine is of particular interest because of its known sympathomimetic effects, leading to increased plasma norepinephrine and epinephrine levels and, as a result, possibly increasing ectopy.

The study found no relationship between the frequency of PVCs or PACs by 24 hour Holter monitoring versus level of coffee, tea or chocolate consumption.

The Value of Quantification in Self-Experimentation with PVCs

Despite the absence of a demonstrable relationship between the frequency of extra-systoles and habitual caffeine consumption in the general population, I am convinced that PVCs in certain individuals (including myself) are triggered by higher levels of caffeine. Such a relationship is revealed by the type of self-experimentation performed by my reader.

These so-called “n of 1” or bio-hacking studies when combined with an accurate and precise way of measuring the outcome of interest (like a patch monitor for PVC frequency) yield insights into idiosyncratic or individual responses to chemicals, foods, and medications that don’t show up in large population studies.

When self-experimenting it is important to be aware of all the variables that might be influencing the measured outcome. My reader was able to maintain zero alcohol intake during the two weeks of his Zio recording. Presumably, his dietary intake and exercise program remained constant. Hopefully his sleep patterns and quality remained constant although this is quite difficult to control.

But one parameter for all creatures that cannot be controlled is our sympathetic autonomic nervous system response to psychological stressors. For many of my patients, the simple act of measuring their blood pressure activates the sympathetic nervous system, thereby causing a BP spike. For some, seeing their PVCs on an ECG recording might similarly induce stress.

Idiosyncratically Yours,



22 thoughts on “The Value of Self-Experimentation: Monitoring Caffeine Effects On PVC Frequency With Zio and Kardia”

  1. I also have thousands of PACs daily. I had an ablation 4 years ago for PVCs which corrected that issue. It is so odd to me that now I have the same amount of PACs as I had PVCs then when I never had PACs before. Makes me wonder if the ablation could have caused it? I don’t really see how but it’s just strange to me.

    I do wonder if sometimes we spend so much time and energy trying to get rid of them and focusing on them that it keeps them going. Who knows. It’s a miserable way to live though.

  2. I think that good cardio-pulmonary fitness is a very important factor in reducing the risk of any sort of arrhythmia.
    I think that fitness is the most important in the age group that tends toward arrhythmias.
    The more maturity advantaged you are (old!), the more muscle you lose with inactivity (sarcopenia) and the more difficult it then is to get the muscle back.
    This last year and a half has been very challenging. There’ve been many worries seemingly more serious than losing fitness, so many of us were distracted and lost it.
    Then, when you try to do things that you always used to do, you can’t do them without the strain of overdoing taking a cardiovascular-pulmonary toll.
    Me, I got episodes of tachycardia and various sorts of ectopy.
    Now, well into a carefully managed outdoor working season, I’m in much better shape than I was in March.
    No arrhythmias.
    That may be due to better conditioning or avoiding tea (see above) or both. Sun, fresh air, lots of green. It’s all good.

  3. Dr. P: I, like leanlulu, experience the most frequent and longest occurrence of PACs while lying on my left side, generally waking me from my sleep as my sleep cycle ends at morning? I’m glad to know that I’m having a shared experience.

  4. As human beings we want to know why? Why this? Why that? Dr. why am I having PVCs? We are desperate to blame it on something. Coffee is a handy thing.
    I have gone through similar self examination for my episodic PVCs. I will go months without having any problem and then for several days to weeks will have as bad as bigemini. Ultimately I don’t think quitting helped and currently having resumed 2 to 4 cups per day, I am not having any.
    Your audience seems to be remarkably homogeneous 60+ years, active physically more than several days a week, Self examiners.

    • I also used to go months at a time without any pvc’s, over a 20 year span. But in the last year they have been coming more frequently and now are everyday. Yep, they are a real pain in the butt(or heart…ba da dum tss). So yeah that gets your attention real fast, and yeah I am on a quest to try and figure out why, and at least try to minimize them, they now interfere with life and that doesn’t sit right with me. So yes I am a self examiner, and will continue to be. I’m sure not gonna leave it up to a doctor who sees 20 patients a day.

  5. Kind of off topic

    But, why refer to PVCs/PACs (aka SVEs) as “benign”?

    This 63 year old lifetime cardio exerciser finds that, during cardio, if I feel a SVE I immediately notice on my Polar HRM that my HR jumps up by ~10bpm. And, if I don’t slow down my cardio workout, the SVE will trigger afib and/or aflutter (according to Zios that I have worn several times).

    So, why “benign”?

    • They are benign in that they don’t directly result in death, stroke, heart attack although they can cause significant symptoms.
      In your case it would be hard to sort out whether the SVE triggered afib or whether the same process (increased sympathetic outflow due to exercise) that triggers the SVE is also triggering the afib/flutter.

  6. I have always consumed a lot of caffeine, mainly from coffee. I drink about a zillion cups a day! Years ago I developed sporadic atrial fib and I underwent two cardiofversions. I quit alcohol and reduced caffeine but it didn’t seem to make a difference. Later I went into atrial flutter that required an ablation procedure. I was OK for a period of time, but then I developed frequent bouts of atrial fib. I finally went through a five hour ablation procedure by Dr. Silver at Lahey in Boston. That was six years ago and I haven’t had any further episodes and I am not aware of any PVCs. I am back to drinking my zillion cups of coffee a day, likely because at the age of 72 I still practice medicine and I am Mr. Mom for a wonderful 7-year-old daughter!

  7. Interestingly the days I have worse SVEs is on the same day as I have my aspirin. I take it every other day but it doesn’t always occur. I also drink a single shot black coffee daily but the randomness is so confusing. I do wonder whether it’s actually a delayed response . Today was one of the bad days , made worse as I was working in the garden bending down and crushing my stomach which was delicate ,gas filled and making lots of noises. Again when my stomach is like this the SVEs are worse. All very strange and is so annoying that I can’t figure the cause.

  8. N of 2:

    Granted fully that some people suffer PVCs as a result of coffee intake, I do not.
    N 1: My wife is bothered. “Flip-flops” result for her after any coffee, but not after tea.

    N 2: I’d been bothered in recent months with PVCs and PACs. I’d never been bothered before as a result of my one to two cups of coffee in the morning. However, my wife and I have been indulging in strong black Irish tea at tea-time.
    Now, strong it was, but still less caffein-strong than coffee/espresso.
    Ah but, there’s more than that to tea. Theophylline is present in enough quantity, perhaps, to effect rhythm in those sensitive to it. It’s a beta adrenergic agonist. Adrenaline is a known trigger of PVCs. A real problem for arrhythmia prone asthmatics.

    I quit tea.
    My PVCs went away in a few days.
    I’ve not re-challenged myself with tea yet. Reluctant to go back there.

    Self-experimentally yours,

    • That is fascinating. Tea has less caffeine per cup than coffee but does contain the sympathomimetics theophylline and theobromine.
      I have suffered from asthma since early childhood. The major medication I was given as a child was Tedral which contained theophylline (a bronchodilator), ephedrine (a sympathomimetic) and phenobarbital (a sedative included to calm the victim…i mean patient after receiving the stimulatory effects of the first two drugs). This was nasty stuff.
      Interestingly, theophylline is used in cardiology these days to reverse the chemical that we give (regadenoson or lexiscan) in conjunction with nuclear perfusion imaging because it
      “Like other methylated xanthine derivatives, theophylline is both a

      competitive nonselective phosphodiesterase inhibitor,[21] which raises intracellular cAMP, activates PKA, inhibits TNF-alpha[22][23] and inhibits leukotriene[24] synthesis, and reduces inflammation and innate immunity[24]
      nonselective adenosine receptor antagonist,[25] antagonizing A1, A2, and A3 receptors almost equally, which explains many of its cardiac effects”

      Doses in tea are quite low but there may be another chemical in your tea (?L-theanine) that is triggering the extrasystoles.
      Inquiring minds want to know. Will the PVCs return when you go back to drinking tea.
      Another hypothesis-it is the timing of the beverage consumption that is important.

      • Timing:
        I started out by replacing my late afternoon tea with a second dark roast coffee – the same coffee I’d had every morning for several years. Same time.
        PVCs ended.
        I’ve since replaced the tea-time coffee with decaf, not wanting to flirt with risk. Been fine with that too.
        Another timing fact is that my “flip-flops” usually were the worst while relaxing in the evening.
        I’ll re-challenge with tea after I’ve been free of arrhythmias for a month or so.

        Branching out – I’ve been reading about ivabradine. It seems to help recuperating COVID patients that suffer POTS (postiional orthostatic TACHYCARDIA syndrome). It is not negatively inotropic, unlike other meds that slow heart rate. It doesn’t seem to change BP and it actually improves cardiac perfusion.
        Why not try it for PVCs, PACs, and even short runs of tachycardia? TGTBT?

        • An abstract presented at 2020 ACC meetings tested ivabradine in 2 patients with PVCs and found it worsened them
          Idiopathic premature ventricular contractions in the setting of a structurally normal heart are often difficult to control pharmacologically. Hyperpolarization-activated cyclic nucleotide gated (HCN) channels are key determinant of cardiac automaticity in the atrium, and have now been demonstrated to be expressed in the ventricle. We hypothesized that selective HCN channel blockade with ivabradine may suppress the abnormal automaticity leading to idiopathic PVC production.


          Two patients with structurally normal hearts and symptomatic idiopathic PVCs refractory to all available medical therapy with beta blockers, calcium channel blockers and anti-arrhythmic agents. The patients were advised to undergo catheter ablation but refused.


          After obtaining informed consent, ivabradine was initiated at 5mg bid and titrated to 7.5 mg bid based on baseline heart rate. PVC burden was measured using 24-hour holter monitoring at baseline and then 2-3 weeks after initiation of ivabradine. Two consecutive male patients (age 43±13 years) received ivabradine. In the first patient the 24-hour PVC burden increased from 25,000 to 35,000 beats. In the second patient, the 24-hour PVC burden increased from 3000 to 69,000 beats. The medication was immediately discontinued with no adverse effects. Both patients continued to be highly symptomatic and ultimately agreed to ablation. The focus was found in the right coronary cusp (patient 1) and right ventricular outflow tract (patient 2).

          • My own heart is not so healthy, having required four ablations.
            I think part of my problem is the instantaneous resting heart rate increase from the high fifties to the mid seventies after my cryo for AF. The phenomenon has been described and documented, but I’ve not found a cogent explanation.
            It seems to me that now, when I’m taxed enough to increase HR with physical work, it simply gets too high too quickly – with ectopics to follow. Hence the ivabradine idea.
            Being in better physical shape seems to help avoid getting too fast. Maybe that’s enough.

  9. Wow, that is really a helpful article, thank you to whomever wrote it. As an amateur biohacker myself, I appreciate the well thought out test he performed…test…monitor….measure….everything!

    I recently tried “grounding” or “earthing” as a remedy for my PVCs. I spent at least 45 minutes, sometimes and hour or two hitting golf balls and retrieving them in an open field with bare feet, and had my feet on an "grounding mat" inside my house that plugs into the wall socket for grounding. I was so hopeful, I had a few days without experiencing any, I thought...yes...I found the answer, only to be disappointed one morning when they came back with a vengeance. I still practice grounding, but its back to the drawing board to getting rid of them.

    I know theres no known cure, but Im determined to find a way to minimize them.

    I`m 60 yrs old and passed the stressed test with flying colors, normal CIMT, all other test looked good except a little high on the cholesterol (215 ish) and a 321 calcium score which freaked me out.

    I have been eating clean for many years, go to the gym at least 4 days a week, have one 8 oz. decaf coffee every morning and no alcohol.
    I tried tracking everything I put in my mouth for possible triggers, nothing consistently did it, this thing is so baffling.

    I wore a heart monitor for a week, no concerns, I averaged 400 pvcs a day, I know thats not very high, but it sure seems like I feel every one.

    Oh well, I will keep on experimenting.

    Thank you Dr. Peasrson for this website, it has been extremely helpful to me in my quest to keep my heart healthy.

    • Hmmm. I must say that the theory behind earthing as a health promoter is on extremely shaky scientific basis…”When you take off your shoes and walk barefoot on the earth outside, the earth’s electrons flow into you. The same thing happens when you touch Earthing products inside your home”

      • No doubt it is, sounded pretty mystical to me, but what the heck, it was a free experiment. Im willing to "try" anything, thats what biohacking is, trying, testing and measuring.

        • Agree. So many potential positive effects of wandering through a field hitting golf balls and retrieving them…bonding with nature, fresh air, sunshine, warmth (or cold).
          The grounding matt, however, I’m going to go out on a limb and cry BS! Any improved outcomes related to placebo effect.

  10. For me, consumption of too much of a particular Trader Joe’s chocolate bar generates palpitations. “Too much” is maybe 30 grams a day. I mostly don’t eat it anymore, but just had a square, for science. My wife thinks it may be mold rather than caffeine that triggers the palpitations because I can eat other chocolate without issues. All of it is the super dark variety.


Please leave your comments. The skeptical cardiologist loves feedback. He reads all and replies to all that warrant a reply.