The skeptical cardiologist has had several of his readers submit stories and tracings of AliveCor Mobile ECG recordings which yield unclassified or unreadable recordings. In some cases this is due to excess noise but a lot of these tracings suffer from low voltage: the height of the tracing is very small.
John, a skepcard reader, is typical.
Recently, he noted his heart was racing and made an AliveCor recording which came back interpreted by the app as normal
Three hours later he made a second recording which has drastically lower voltage: the only deflections visible are tiny QRS complexes, the p waves have disappeared. I think this is also normal sinus rhythm but because p waves can’t be seen this came back uninterpretable and if there were any irregularity AliveCor would have called it atrial fibrillation:
John has a theory on the cause of some of his low voltage recordings which I shall reveal in a subsequent post after testing it.
In the meantime, if any readers have suggestions as to causes of low voltage recordings or have noted similar issues please comment below or send recordings and observations to DRP@theskepticalcardiologist.com.
In a previous post, the skeptical cardiologist pontificated on the causes and evaluation of the most common cause of palpitations: premature ventricular contractions or PVCs.
The vast majority of these common extra beats turn out to be benign (meaning not causing death, heart attack or stroke), and most patients with sufficient reassurance of this benignity (often accompanied by significant caffeine reduction), do well. These people usually continue to notice the beats either randomly, or with stress, but they recognize exactly what is going on and are able to say to themselves “there go my benign PVCs again,” and aren’t worried or bothered.
A small percentage of patients that I diagnose with palpitations due to benign PVCs continue to have symptoms.
Part of my initial evaluation involves checking potassium, magnesium, kidney function, and thyroid levels.
Potassium Supplementation For PVCs
Low potassium levels (hypookalemia) have been clearly associated with an increase in ventricular ectopy. Patients who take diuretics like hydrochlorothiazide (HCTZ, often used for high blood pressure) or furosemide (Lasix, often used for leg swelling or heart failure), are at high risk for hypokalemia with potassium levels less than 3.5 meQ/L.
Hypokalemia can also develop if you are vomiting, having diarrhea, or sweating excessively. There are lots of other infrequent causes including excess licorice consumption. The body regulates potassium levels closely, due to its importance in the electrical activities involved in cardiac, muscular and neurological function.
The normal range of potassium (K) is considered to be 3.5 to 5 meq/L , however, I have found that PVCs are more frequent when the potassium is less than 4.
Most of my symptomatic PVC patients with potassium less than 4 find significant improvement with potassium supplementation. I usually give them a prescription for potassium chloride (KCl) 10-20 meq daily to accomplish raising the level to >4.
An alternative to potassium supplements is ramping up how much potassium you consume in your diet. Most patients I talk to about low K immediately assume they should eat more bananas, but lots of fresh fruit and vegetables contain as much or more K than bananas.
The charts to the right show that a medium tomato contains as much K as a medium banana with a third of the calories. Avocados are a great source of K and contain lots of healthy fat. Yogurt (and I recommend full fat yogurt, of course) is a great source as well.
If you have kidney disease you are much more likely to develop hyperkalemia, or high K, and you want to avoid these high K foods. Potassium infusions are used as part of a “lethal injection” in executions because extreme hyperkalemia causes the heart to stop beating. (In fact, Arkansas is hurrying to execute 8 men between April 17 and 27 utilizing KCl. According to deathpenaltyinformation.org: “The hurried schedule appears to be an attempt to use the state’s current supply of eight doses of midazolam, which will expire at the end of April. Arkansas does not currently have a supply of potassium chloride, the killing drug specified in its execution protocol, but believes it can obtain supplies of that drug prior to the scheduled execution dates”)
Lifestyle, Stress and PVCs
It’s probably time I revealed that I have PVCs. I feel them as a sense that something has shifted inside my chest briefly, like my breath has been interrupted, like my heart has hiccoughed. If I didn’t know about PVCs and hadn’t made the diagnosis very quickly by hooking myself up to an ECG monitor in my office, I know I would have become very anxious about it.
I know exactly what causes them: stress and anxiety. And this is the case for many patients. Stress activates our sympathetic nervous system, causing the release of hormones from the adrenal gland that prepare us for “fight or flight.” These hormones stimulate the heart to beat faster and harder and often trigger PVCs.
I rarely get PVCs these days, as the major source of stress in my personal life has gone away. This is also a typical story my patient’s relate: troubling palpitations seem to melt away when they retire or change to less stressful occupations, or as they recover from depression/anxiety/grief related to death of loved ones, divorce or illness.
You can’t always control external stresses, but several factors in your lifestyle are key to managing how those stresses activate your sympathetic nervous system and trigger troubling PVCs.
Dr. Mandrola lists as Steps 5-8 (Steps 1-4 are reassurance) for PVC treatment his “four legs of the table of health”:
: good food, good exercise, good sleep and good attitude. Cutting back on caffeine and alcohol, looking critically at the dose of exercise, going to bed on time, and smiling are all great strategies for PVCs.
Of these four table legs, I consider regular aerobic exercise the most important, and modifiable factor for PVC reduction. Aerobic exercise improves mood and increases the parasympathetic (the calming component of the autonomic nervous system) activity, while lowering the output of the sympathetic nervous system.
The three factors that I find essential to handling the demanding and stressful job of being a cardiologist: restful sleep, regular, aerobic exercise and lots of love from my eternal fiancee (who also has occasional PVCs!)
Beyond sleep and exercise there is a plethora of techniques that purport to help individuals deal with stress: yoga, meditation, and progressive muscular relaxation, among them.
Apps touting methods for relaxation abound these days. My new Apple Watch is constantly advising me to engage in a breathing exercise for a minute at a time. I don’t find any of these techniques helpful for me (I haven’t found a good way to shut my brain down without falling asleep), but they may work for you.
Magnesium, Snake Oil and PVCs
Patients will find that the internet is rife with stories of how this supplement or vitamin or herb dramatically cures PVCs. You can be assured that a sales pitch accompanies these claims and that the snake oil being promoted has not been proven effective or safe. Because symptomatic PVCs like most benign, common and troubling conditions (lower back pain, fatigue, and nonspecific GI troubles come to mind), are closely related to mood and wax and wain spontaneously; the placebo effect proves powerful. In such conditions, snake oil and charlatans thrive.
Magnesium is enthusiastically hyped on the internet for all manner of cardiovascular problems including PVCs. Even Dr. Mandrola, who I respect quite a lot as an EP doc who promotes lifestyle change and who is definitely not a quack, lists his step 10 for PVCs (apologetically) as follows:
Step 10 (a): Please don’t beat me up on this one. Some patients report benefit from magnesium supplementation. I have found it helpful in my case of atrial premature beats. Let me repeat, I am not promoting supplements. Healthy patients with benign arrhythmia might try taking magnesium, especially at night. Don’t take magnesium if you have kidney disease. And if you take too much, watch out for diarrhea.
Most of the internet’s top quacks, however, greedily market and glowingly swear by magnesium. A Google search for magnesium cardiovascular disease yields 833,000 entries and the first page is a Who’s Who of quackery, including Dr Mercola (strong candidate for America’s greatest quack), Dr. Sinatra (see here, currently in the semifinals for America’s greatest quack cardiologist), NaturalNews and Life Extension (see here). This totally unsupported and dangerous blather from the Weston Price Foundation is often repeated and is typical:
(magnesium) Deficiency is related to atherosclerosis, hypertension, strokes and heart attacks. Deficiency symptoms include insomnia, muscle cramps, kidney stones, osteoporosis, fear, anxiety, and confusion. Low magnesium levels are found in more than 25 percent of people with diabetes. But magnesium shines brightest in cardiovascular health. It alone can fulfill the role of many common cardiac medications: magnesium inhibits blood clots (like aspirin), thins the blood (like Coumadin), blocks calcium uptake (like calcium channel-blocking durgs such as Procardia) and relaxes blood vessels (like ACE inhibitors such as Vasotec) (Pelton, 2001).
Magnesium levels are very important to monitor in hospitalized and critically ill patients, especially those receiving diuretics and medications that can effect cardiac electrical activity.
However, for individuals with normal diets and palpitations due to PVCs, there is scant evidence that it plays a significant role in cardiovascular health.
The MAGICA study looked at supplementation with both magnesium and potassium (in the active treatment group, daily oral dosing consisted of 2 mg of magnesium-dl-hydrogenaspartate (6 mmol magnesium) and 2 mg of potassium-dl-hydrogenaspartate (12 mmol potassium) daily. The dose was chosen to increase the recommended minimal daily dietary intake of magnesium (12 to 15 mmol) and potassium (20 to 30 mmol) by ∼50% in addition to usual diet ) in 307 patients with more than 720 PVCs per hour and normal baseline K and Mg levels.
The patients receiving magnesium/potassium supplements showed a decrease of 17% in frequency of PVCs but no improvement in symptoms.
A 2012 study in a Brazilian journal evaluated magnesium pidolate (MgP) in 60 patients with both PVCs and premature atrial contractions (PACs). The dose of MgP was 3.0 g/day for 30 days, equivalent to 260 mg of Mg elemental.
93% of patients receiving MgP experienced improved symptoms compared to only 13% of patients recieiving placebo. Both PVC and PAC frequency was reduced in those receiving MGP, whereas they increased by 50% in those receiving placebo.
This small study has never been reproduced, and the main results table makes little sense. It would not have been published in a reputable American cardiology journal and cannot be relied on to support magnesium for most patients with benign PVCs or PACs.
Drug or Ablation Treatment of PVCs: Usually Not Needed
A small percentage of my patients require treatment with beta-blockers which reduces the effects of the sympathetic nervous system on the heart. Very rarely, I will use anti-arrhythmic drugs. And every once in a while, very frequent PVCs resulting in cardiomyopathy require an ablation.
However, the vast majority of patients with benign PVCs, in my experience, feel drastically better with a simple non-pharmacological approach consisting of 4 factors:
Reassurance that the PVCS are benign
Caffeine (or other stimulant) reduction
Lifestyle adjustment with regular aerobic exercise
The skeptical cardiologist has often sung the praises of the AliveCor Mobile ECG for home and office heart rhythm monitoring (see here and here.) However, there is a significant rate of failure of the device to accurately identify atrial fibrillation. I’ve seen numerous cases where the device read afib as “unclassified” and normal sinus rhythm (usually with PVCs or PACs) called afib both in my office and with my patient’s home monitors.
In such cases it is easy for me to review my patient’s recordings and clarify the rhythm for them.
For those individuals who do not have a cardiologist available to review the recordings, AliveCor offers a service which gives an option of having either a cardiac technician or cardiologist review the tracing. The “cardiac technician assessment” costs $9 and response time is one hour. The “Clinical Analysis and Report by a U.S. Board Certified Cardiologist” costs $19 with 24 hour response time.
Obviously, I have no need for this service but I’ve had several readers provide me with their anecdotal experiences with it and it hasn’t been good.
One reader who has a familial form of hypertrophic cardiomyopathy utilizes his AliveCor device to monitor for PVCs. One day he made the following recording which AliveCor could not classify:
He then requested a technician read which was interpreted as “atrial fibrillation sustained.”
He then had requested the cardiologist reading which came back as Normal Sinus Rhythm.
Finally, he again requested the technician read and got the correct reading this time which is normal sinus rhythm with PACs
When my reader protested to Kardia customer service about this marked inconsistency: three different readings in a 24 hour period, a Kardia customer service rep responded :
I was able to review this with our Chief Medical Officer who advised that the recording shows Sinus Rhythm with PACs. The Compumed report seldom provides identification of PACs and PVCs as most cardiologists believe they are not significant findings. The sustained AFib finding was incorrect, so I have refunded the $5 fee you had paid.
Please let us know if you have any other questions.
As I pointed out in my post on palpitations, most PVCS are benign but some are not and patients with palpitation would like to know if they are having PVCS and/or PACs when they feel palpitations.
More importantly, the misdiagnosis of afib when the rhythm is NSR with PACs or PVCs can lead to extreme anxiety.
Heres a recording
I made in my office this morning on a patient with cardiomyopathy and a defibrillator.
This is very clearly NSR with PVCs yet AliveCor diagnosed it as “possible atrial fibrillation.”
The AliveCor algorithm is not alone in making frequent errors in the diagnosis of atrial fibrillation.
The vast majority of ECGs performed in the US come with an interpretation provided by a computerized algorithm and medical personnel rely on this interpretation until it can be verified or corrected by an overreading cardiologist.
One study demonstrated that computerized ECG interpration (ECG-C) is correct only 54% of the time when dealing with a rhythm other than sinus rhythm
Another study found that 19% of ECG-C misinterpreted normal rhythm as atrial fibrillation. Failure of the physician ordering the ECG to correct the inaccurate interpretation resulted in change in management and initiation of inappropriate treatment, including antiarrhytmic medications and anticoagulation, in 10% of patients. Additional unnecessary diagnostic testing was performed based on the misinterpreted ECGs in 24% of patients.
When lives or peace of mind are at risk you want your ECG interpreted by a cardiologist.
I would like to take this opportunity to personally issue a challenge to IBM’s Watson.
Hey, Watson, I bet $1,000 I can Interpret cardiac rhythm from an ECG with more accuracy than you can!
If you feel your heart flip-flopping, then you are experiencing palpitations: a sensation that the heart is racing, fluttering, pounding, skipping beats or beating irregularly.
Often, this common symptom is due to an abnormal heart rhythm or arrhythmia.
The arrhythmias that cause palpitations range from common and benign to rare and lethal, and since most individuals cannot easily sort out whether they have a dangerous or a benign problem, they often end up getting cardiac testing or cardiology consultation.
The most common cause of palpitations, in my experience, is the premature ventricular contraction, or PVC (less commonly known as the ventricular ectopic beat or VEB).
The PVC occurs when the ventricles of the heart (the muscular chambers responsible for pumping blood out to the body) are activated prematurely.
This video shows the normal sequence of electrical and subsequent mechanical activation of the chambers of the heart.
To get an efficient contraction, the electrical signal and contraction begins in the upper chambers, the atria, and then proceeds through special electrical fibers to activate the left and right ventricles.
Sometimes this normal sequence is disrupted because a rogue cell in one of the ventricles becomes electrically activated prior to getting orders from above. In this situation, the electrical signal spreads out from the rogue cell and the ventricles contract out of sequence or prematurely.
This results in a Premature Ventricle Contraction.
I recorded the above AliveCor tracing in my office on a patient who suffers palpitations due to PVCs (we’ll call her Janet).
The wider, earlier beat (circled in red) in the sequence is the PVC. The prematurity of the PVC means that the heart has not had the appropriate time to fill up properly. As a result, the PVC beat pumps very little blood and may not even be felt in the peripheral pulse. Patients with a lot of PVCs, say ocurring every other beat in what is termed a bigeminal pattern, often record an abnormally slow heart rate because only one-half of the heart’s contractions are being counted.
While recording this, every time Janet felt one of her typical “flip-flops,” we could see that she had a corresponding PVC and the cause of her symptoms was made clear.
There is a pause after the PVC because the normal pacemaker of the heart up in the right atrium (the sinus node) is reset by electrical impulses triggered by the PVC.. The beat after the PVC is more forceful due to a more prolonged time for the ventricles to fill and Consequently, most patients feel this pause after the PVC rather than the PVC itself,
PVCs are common and most often benign. I have patients who have
thousands of them in a 24-hour period and feel nothing. On the other hand, some of my patients suffer disabling palpitations from very infrequent PVCs. From an electrical or physiologic standpoint, there seems to be neither rhyme nor reason to why some patients are exquisitely sensitive to premature beats.
How Do I Know If My PVCs Are Benign?
My patient, Janet, is a great example of how PVCs can present and how inappropriate or inaccurate heart tests done to evaluate PVCs can lead to anxiety and unnecessary and dangerous subsequent testing.
A year ago, Janet began experiencing a sensation of fluttering in her chest that appeared to be random. Her general practitioner noted an irregular pulse and obtained an ECG, which showed PVCS. He ordered two cardiac tests for evaluation of the palpitations: a Holter monitor and a stress echo.
A Holter monitor consists of a device the size of a cell phone connected to two sensors or electrodes that are stuck to the skin of the chest area. The electrical activity of the heart is recorded for 24 or 48 hours, and a technician then scans the entire recording looking for arrhythmias while trying to correlate any symptoms the patient recorded with arrhythmias. The Holter allows us to quantitate the PVCs and calculate the total number of PVCs occurring either singly or strung together as couplets (two in a row), or triplets (three in a row.)
Janet’s Holter monitor showed that over 24 hours her heart beat around 100,000 times with around 2500 PVCs during the recording. Unfortunately, the report did not mention symptoms, so it was not possible to tell from the Holter if the PVCs were the cause of her palpitations.
A stress echocardiogram combines ultrasound imaging of the heart before and after exercise with a standard treadmill ECG. It is a very reasonable test to order in a patient with palpitations and PVCs, as it allows us to assess for any significant problems with the heart muscle, valves or blood supply and to see if any more dangerous rhythms like ventricular tachycardia occur with exercise. If it is normal, we can state with high certainty that the PVCs are benign.
Benign, in this context, means the patient is not at increased risk of stroke, heart attack, or death due to the PVCs.
In the right hands, a stress echocardiogram is superior to a stress nuclear test for these kinds of assessments for three reasons:
-Reduced rate of false positives (test is called abnormal, but the coronary arteries have no significant blockages)
-No radiation involved (which adds to costs and cancer risk)
-The echocardiogram allows assessment of the entire anatomy of the heart, thus detecting any thickening (hypertrophy), enlargement or weakness of the heart muscle, that would mean the PVCs are potentially dangerous.
Unfortunately, my patient’s stress echo (done at another medical center) was botched and read as showing evidence for a blockage when there was none. An invasive and potentially life-threatening procedure, a cardiac catheterization was recommended. Similar to the situation I’ve pointed out with the performance and interpretation of echocardiograms (see here), there is no guarantee that your stress echo will be performed or interpreted by someone who actually knows what they are doing. So, although the stress echo in published studies or in the hands of someone who is truly expert in interpretation, has a low yield of false positives, in clinical practice the situation is not always the same.
Given that Janet was very active without any symptoms, she balked at getting the catheterization and came to me for a second opinion. I felt the stress echo was a false positive and did not feel the catheterization was warranted. We discussed alternatives, and because Janet needed more reassurance of the normality of her heart (partially because her father had died suddenly in his sixties) and thus the benignity of her palpitations/PVCs, she underwent a coronary CT angiogram instead. This noninvasive exam (which involves IV contrast administration, and is different from a coronary calcium scan), showed that her coronary arteries were totally normal.
Benign PVCs-Treatment Options
Once we have demonstrated that the heart is structurally normal, reassurance is often the only treatment that is needed. Now that the patient understands exactly what is going on with the heart and that it is common and not dangerous, they are less likely to become anxious when the PVCs come on.
PVCS can create a vicious cycle because the anxiety they provoke can cause an increase in neurohormonal factors (catecholamines/adrenalin) that may increase heart rate , make the heart beat stronger and increase the frequency of the PVCs.
Some patients, find their PVCs are triggered by caffeine (tea, soda, coffee, chocolate) or stress, and reducing or eliminating those triggers helps greatly. Others, like Janet, have already eliminated caffeine, and are not under significant stress.
Since I’m already over a thousand words in this post, I’ll discuss treatment options for these patients with benign PVCs who continue to have troubling symptoms after reassurance and caffeine reduction in a subsequent post.