Personal ECG devices like Apple Watch and KardiaMobile are wonderful for most people at recording a single-lead ECG and determining cardiac rhythm. With both devices, however, it is not uncommon to get an inconclusive (Apple’s term) or unclassified (AliveCor’s term) reading at times.
I’ve discussed some fixes for KardiaMobile here. Often recordings can be drastically improved by moistening the skin contacting the two electrodes, thereby improving the conductance of the electrical signal. Minimizing movement helps many cases. But for some, this is the norm no matter how elaborately fingers are lubricated or how aggressively motion is eliminated.
A reader emailed me with his very frustrating case which typifies this problem:
“Not sure if you can help me but I wanted to reach out based on a post I saw from you online. I have advanced CAD (CT scan calcium score of 2,300) and purchased an Apple Watch 5 about a year ago to be able to monitor my heart rate and do ECGs. I am unable to get a consistent Sinus Rhythm even though I know I have a normal ECG.
“In fact the display when I am taking an ECG is all over the map – many times it looks like a three-year-old coloring with a crayon. I have worked with Apple support, they sent a new watch but the same issues. I then was asked to submit my data file to engineering after I replicated the issue, and that was done in February. Now when I call support they basically tell me ‘don’t call us we will call you’ and the standard answer is ‘engineering is still looking into it.’
“I am convinced there is something with me physiologically that prevents the watch from doing consistent ECGs with me. I believe Apple engineering knows there is a deficiency and no solution so just ignoring it. I am not sure what recourse I have other than to try and find others with similar issues and go down a class action lawsuit rat hole. I was curious though if you had come across this issue in the past and/or you know of groups that might be organizing to pursue some type of action from Apple.”
I asked him to send me examples of his inconclusive Apple Watch (AW) ECGs, and it was clear that this individual (we’ll call him Don) suffered from what I term “Low Lead I Voltage Syndrome.”
Here’s a typical recording for him. Note that the squiggles that correspond to electrical activation of the ventricles (the QRS complexes) can be barely be discriminated from the background noise of the tracing. Understandably, the AW algorithm can make neither heads nor tales of such a scribble. Even the Skeptical Cardiologist, who prides himself on interpreting the most difficult of single-lead ECG rhythms, cannot be sure this is normal.
A very large percentage of Don’s overall recordings were inconclusive, but all of them demonstrated this problem with extremely low amplitude (or voltage) of the standard lead I AW tracing.
We have seen this same problem with KardiaMobile single-lead ECG recordings and have discussed the cure. It was not fixed by moistening or lubricating either the back of the wrist of the right fingertip.
I instructed Don to try making a recording with the AW on his left knee, preferably a flat, non-hairy portion, as opposed to his wrist. I told him that sometimes the heart is vertically oriented in the chest (often seen in thin individuals) and the leg works better.
This is where the AW ended up for Don: back of AW on top of the left knee and tip of right index finger then touches the crown to activate ECG recording.
From this spot, Don’s ECG recordings were dramatically improved and never inconclusive. The amplitude of the QRS complexes increased from 2 to 16 mm!
I’m going to call this manner of recording the “Albert maneuver” as AliveCor’s David Albert, MD, first showed it to me.
My reader was right — there was something about him that was different. Not wrong and not his physiology or cardiac rhythm. Just a normal variation in his anatomy which led to a vertically-oriented heart.
Don informed me that he was thin: “6 foot 3 inches and 165 pounds soaking wet” to be precise.
If you’re getting great recordings with high amplitude QRS complexes and AW or Kardia is still reading inconclusive or unclassified, then you likely are having frequent premature atrial contractions or premature ventricular contractions, something KardiaMobile plans to address with its soon-to-be-released AI V2 algorithm.
Apple engineering presumably consists of the brightest minds in the industry. It’s surprising that they don’t know about the “Low Lead I Voltage Syndrome” and its curative Albert maneuver. They could save many AW wearers from experiencing the dreaded “inconclusive” categorization and cut down on Apple support costs.
For more discussion on reducing unclassified single-lead ECG recordings from KardiaMobile and the advantages of lead II, see my prior post here.
Anthony C. Pearson, MD, is a noninvasive cardiologist and professor of medicine at St. Louis University School of Medicine. He blogs on nutrition, cardiac testing, quackery, and other things worthy of skepticism at The Skeptical Cardiologist, where a version of this post first appeared.