Tag Archives: premature beats

AliveCor (Kardia) Has A Premature Beat Problem: How PVCs and PACs Confuse The Mobile ECG Device

The skeptical cardiologist has many patients who are successfully using their AliveCor/Kardia devices to monitor for episodes of atrial fibrillation (afib).

However, a significant number of patients who have had atrial fibrillation also have premature beats. Sometimes patients feel these premature beats as a skipping or irregularity of the heart beat. Such palpitations  can mimic the feeling patients get when they go into atrial fibrillation.

The ideal personal ECG monitor, therefore,  would be able to reliably differentiate afib from premature beats for such patients.

Premature Beats: PVCs and PACs

I’ve discussed premature ventricular contractions (PVCs) here and here.  Premature beats can also originate from the upper chambers of the heart or atria.

Such  premature atrial contractions (PACs) have generally been considered benign in the past but a recent study showed that frequent (>30 s per hour) PACs  or runs of >20 PACs in a row were associated with a doubling of stroke risk.

For patients who experience either PVCs or  PACs the AliveCor device is frequently inaccurate.

PACs Misdiagnosed As Atrial Fibrillation

Here is a panel of recordings made by a patient of mine who has had documented episodes of atrial flutter in the past and who monitors his heart rhythm with Alivecor regularly:

Of the ten recordings , four were identified as “possible atrial fibrillation.”

Unfortunately only one of the four “possible atrial fibrillation” recordings has any atrial fibrillation: this one has 7 beats of afib initially then changes to normal sinus rhythm (NSR).

The other 3 recordings identified by AliveCor as afib are actually normal sinus rhythm with premature beats.

The first 3 beats are NSR. Fourth beat is a premature beat

In addition, frequently for this patient AliveCor yields an “Unclassified” reading for NSR with PACs as in this ECG:

PVCs Misread As Atrial Fibrillation

I wrote about the first patient I identified in my office who had frequent PVCs which were misdiagnosed by AliveCor as afib here.

Since then, I’ve come across a handful of similar misdiagnoses.

One of my patients began experiences period palpitations 5 years after an ablation for atrial fibrillation. He obtained an AliveCor device to rec  ord his rhythm during episodes.

For this patient,, the AliveCor frequently diagnoses “possible atrial fibrillation” but  all of his episodes turn out not to be afib. In some cases he is having isolated PVCs:

The first 3 beats in the lower strip are NSR. The fourth beat (purpose circle) is a PVC. AliveCor interpreted this as afib

At other times he has periods of atrial bigeminy  which are also called afib by AliveCor. In this tracing he has atrial bigeminy and a PVC.

 

 

PVCs Read As Normal

Premature beats sometimes are interpreted by AliveCor as normal. A reader sent me a series of  recordings he had made when feeling his typical palpitations. all of which were called normal. Indeed, all of them but one showed NSR. However on the one below the cause of his palpitations can be seen: PVCs.

The NSR beats (blue arrows) followed at times by PVCs (red arrows))

I obtained the “Normal”  tracing below from a patient in my office with a biventricular pacemaker and frequent PVCs who had no symptoms.

Paced beats (blue arrows) PVCs (red arrows)

PVCs Read As Unclassified 

A woman who had undergone an ablation procedure to eliminate her very frequent PVCS began utilizing AliveCor to try to determine if she was having recurrent symptomatic PVCs. She became quite frustrated because AliveCor kept reading her heart rate at 42 BPM and giving her an unclassified reading.

AliveCor is always going to call rhythms (other than afib) unclassified when it counts a  heart rate less than 50 BPM or greater than 100 BPM.

In this patient’s case, every other beat was a PVC (red circles). Her PVCs are sufficiently early and with low voltage so the AliveCor algorithm cannot differentiate them from T Waves and only counts the normal sinus beats toward heart rate.

Accurate AliveCor Readings

I should point out that many of my patients get a very reliable assessment from their devices. These tracings from a woman with paroxysmal atrial fibrillation  are typical: all the Normal readings are truly normal and all the atrial fibrillation readings are truly atrial fibrillation with heart rates  above 100.

AliveCor’s Official Position on Premature Beats

The AliveCor manual states

The Normal Detector in the AliveECG app notifies you when a recording is “normal”.  This means that the heart rate is between 50 and 100 beats per minute, there are no or very few abnormal beats, and the shape, timing and duration of each beat is considered normal.

What qualifies as “very few” abnormal beats is not clear. The manual goes on to state that the AliveCor normal detector has been designed to be conservative with what it detects as normal.

What is clear is that premature beats  significantly confuse the AliveCor algorithm. Both PVCs and PACs can create a false positive diagnosis of atrial fibrillation when it is not present.

Consequently, if you have afib and premature beats you cannot be entirely confident that a reading of afib is truly afib. Strongly consider having the tracing reviewed by a cardiologist before concluding that you had afib.

On the other hand if you are experiencing palpitations and make a recording with Alivecor that comes back as normal do not assume that your heart rhythm was totally normal. While highly unlikely to be afib, your palpitations could still be due to PACs or PVCs.

If a patient of mine has an abnormal or questionable AliveCor recording it is currently a very simple process for me to review the recording online  through my AliveCor doctor dashboard. The recordings can also be emailed to me.

However, Kardia appears to be trying to move new AliveCor purchasers to a subscription or Premium service. In addition, Kardia keep giving me messages that “the doctor dashboard is going away.”

Coralively Yours,

-ACP

Are Your Palpitations Due to Benign PVCs?

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).

Premature Ventricular Contractions-Electrical Tissue Gone Rogue

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.

labeled-pvc
p waves represent depolarization and activation of the atria which are followed normally after120 to 200 milliseconds by the QRS complex which represents activation of the ventricles. The PVC (inside red circle) is wider and weirder and disrupts the regular interval between beats (green lines).

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

ECG from 70 year very vigrous man who had 20 thousand PVCs in 24 hours. Every third beat is a PVC (green arrow)
ECG from 70 year old very vigorous man who had 20 thousand PVCs in 24 hours. Every third beat is a PVC (green arrow PVC, blue arrow normal QRS.)This patient feels nothing with his frequent PVCs. He has had them probably lifelong and definitely for the last 10 years without any adverse consequences.

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.

lad-ccta
Images from Janet’s coronary CT angiogram showing the left anterior descending (LAD) coronary artery coming off the aorta. The LAD (and her other coronaries) were totally free of any plaque build-up.)

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.

Prematurely Yours,

-ACP