This Week in Cardiology on Medscape - Heart Rate Monitors

[EngMac]

Wearable HR Monitor Accuracy

Canadian authors from Toronto and Calgary (first author Ryan Quinn) have a short but important research letter in the Journal of the American College of Cardiology (JACC) regarding the accuracy of wearable HR monitors in sinus rhythm (SR) and atrial fibrillation (AF).

This should be one of the foundational principles in cardiology, so I hesitate even giving a sentence to it, but when you measure a pulse in the periphery of the body — usually the wrist — during AF with higher rates, there is likely to be what’s called a pulse deficit.

Meaning, when you feel a pulse, you are measuring the arterial pulse wave that stems from cardiac contraction. In SR and at reasonable rates, it’s a great surrogate for HR. Because one pulse equals one QRS or heartbeat.

In AF, there is an irregularly irregular rhythm, and when there are two tightly coupled heart beats, the second one may not generate a good pulse in the periphery.

Yet, wrist smartwatches that output HR’s are common. Fitness trackers most often rely on photoplethysmography (PPG) technology to calculate HR; in other words, a pulse in the wrist.

• The research team, led by Paul Dorian, wondered how the PPG monitors compared with a standard ECG during exercise.

• They studied patients who were scheduled for routine treadmill tests; 81 patients had device HRs compared with the ECG. They studied six different wearable HR monitors.

• It wasn’t good for the fitness trackers.

• At rest, the mean of absolute differences between the ECG-measured HR and the device-displayed rate were 4.6 ± 8.4 beats/min in SR and 7.0 ± 11.8 beats/min in AF.

• At peak exercise, these differences were substantially larger: 13.8 ± 18.9 beats/min in SR and 28.7 ± 23.7 beats/min in AF (P < 0.01).

• As for correlation, this too was bad. At rest, the correlation coefficient was 0.931 for and 0.504 for AF.

• During exercise, the correlation coefficient was 0.726 for SR and 0.301 for AF. As the HR measured by ECG increases, the device-detected HR becomes less accurate, especially for subjects in AF and during exercise.

• Comments by Dr. John Mandrola. This is nice work. It’s a modest experiment, but the systematic nature allows us to confirm what we all suspected: That watch-based HRs during AF are not reliable enough to act on.

• If your patient with AF brings you one of those graphs from a fitness app that shows good HR control, it would be wise to confirm this with a proper ECG tracing.

•

[jeanjeannie50]

I have known for years that the pulse in my wrist doesn't always match the rate my heart is actually beating. Paramedics were quite interested when they came to me and noticed this anomaly. Hence my reluctance to purchase any type of wrist monitor. I also wonder if finger or arm monitors aren't accurate for me either. I'm sure they may be fine for some members here.

I bought myself a stethoscope on the recommendation of a nurse member on this forum who was a volunteer in the US called Grandma. Do any members remember her from way back?

Jean