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Doctors & patients are saying about 'Beat Your A-Fib'...

"If I had [your book] 10 years ago, it would have saved me 8 years of hell.”

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Pierre Jaïs, M.D. Professor of Cardiology, Haut-Lévêque Hospital, Bordeaux, France

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Dr. Wilber Su,
Cavanaugh Heart Center, Phoenix, AZ

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Rome, Italy

"Within the pages of Beat Your A-Fib, Dr. Steve Ryan, PhD, provides a comprehensive guide for persons seeking to find a cure for their Atrial Fibrillation."

Walter Kerwin, MD, Cedars-Sinai Medical Center, Los Angeles, CA

DIY Heart Rate Monitors: How They Work For A-Fib Patients (Part II)

Go to: DIY Heart Rate Monitors

by Steve S. Ryan, PhD

A-Fib patients sometimes use consumer ‘DIY” Heart Rate Monitors (HRM) when exercising or performing physically demanding activities (For specific models and options, see our article, DIY Heart Rate Monitors & Handheld ECG Monitors Part I.)

How Do DIY Heart Rate Monitors Work?

Basic HRMs use a chest strap to pick up the electrical signals from the heart. However, due to the inherent design of the chest strap, the accuracy is somewhat limited and is no replacement for the signals recorded by a Holter or Event Monitor.

A HRM keeps track of your heart’s R-R interval or the time between R peaks. Without getting too technical, the R peak on a generic ECG waveform (see the diagram) corresponds to the ventricle beat (depolarization) and has the largest amplitude (height) of the complete waveform.

When the amplitude (picked up as a voltage differential) exceeds a certain threshold, a “beat” is picked up by the chest strap and transmitted wirelessly to the HRM. It is the time between these R peak “beats” that is used by the HRM to determine instantaneous heart rate. It is only going to pick up episodes of arrhythmia as are manifested in ventricle beats (the R on the waveform).

Learn more about the EKG signal, see Steve’s article: “Understanding the EKG (ECG) Signal“.

So if your arrhythmia manifests itself in funky R activity (higher than normal rate) you will see a corresponding readout on the HRM. In this same light, an irregular or unevenly spaced R peaks will not be picked up by the HRM.

This is one of the fundamental differences in how data is recorded by HRMs (R-R interval) versus Holter/Event Monitors (actual waveform).

In fact, this is what Polar has to say:

“Polar products are not designed to detect arrhythmia or irregular rhythms and will interpret them as noise or interference. The computer in the wrist unit will make error corrections, so that arrhythmia beats are not included in the averaged beats per minute. The blinking heart symbol in the face of the unit, however, will continue to show all heart beats received.

In most cases the Polar products will work fine for persons with arrhythmia.”

Graphic example PC interface capability of a Polar PC program.

HRM Recording Capability

Most HRMs provide some internal storage recording capability. While lower cost HRMs simply record low, high and average heart rate, upper end models allow you to download heart rate data to your PC.

App-enabled smartphones are changing how this data is viewed, collected and saved for future review.

How To Setup and Use an HRM

On most of the HRMs, you can set a heart rate zone, and the watch monitor (or app-enabled smartphone) will record how long you stayed in that zone.

You could then program a high heart rate zone which you might only enter if you were in A-Fib. That way you could record how long you stayed in A-Fib and what your max heart rate was. This data could be reviewed on the watch monitor (or app-enabled smartphone) without having to download it to a PC.

On HRMs with PC interface capability, you can view data in a graphic form (on some watches/smartphones you can view the graphic data but with lower resolution.) This analyses could tell you when you were at a higher heart rate—A-Fib—and how long you stayed there. Of course these kinds of features require some PC skills, but typically the programs are pretty user friendly. (See the above graphic example of a Polar PC program).

For more, see our article, DIY Heart Rate Monitors & Handheld ECG Monitors.

Shop Amazon.com for Steve’s Top Picks: DIY Heart Rate Monitors for A-Fib Patients.

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