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“.
Learn more about the EKG signal, see Steve’s article: “Understanding the EKG (ECG) Signal“.
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.
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.
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Last updated: Tuesday, April 14, 2015
17. “I care for my mom who has A-Fib. She is 94 and sees a doctor on a regular basis. She gets A-Fib attacks maybe once every two weeks and usually in the morning. But I work full time. Is there a heart rate monitor my mom can wear that would alert me when her heart rate is over a certain number? That way I can be alerted even when I’m at work.”
Yes, MyPulse by Smart Monitors, Inc. has a solution for you. This is a practical alternative to the expense of a medical monitoring service if you are just interested in simple heart rate data. Most consumer heart rate monitors rely on a chest strap which transmits heart rate data to a wristwatch. The MyPulse Long Range Monitor has a small Repeater device carried by the person wearing the chest strap. The Repeater transmits the data to a Receiver which is connected to a PC/notebook via a USB port. The MyPulse application runs on a PC and provides a graphic display of real time heart rate data.
The software can be configured to provide alerts via email or text message to multiple recipients if a preset heartbeat limit is exceeded.
(Thanks Julie Skarbeck for this important question and to Ed Webb for doing the research and writing about the Smart Monitor.)
By Steve S. Ryan, PhD
If your arrhythmia is intermittent, your doctor may have you wear a mobile type of heart rhythm monitor to capture the electrical activity of your heart. As a general rule, in order to make a diagnosis of an arrhythmia, some form of electrocardiographic recording (i.e., EKG,) must be made at the time the arrhythmia is occurring.
If an arrhythmia becomes persistent and is present day-in and day-out, as often is the case for A-Fib, the diagnosis is quite easy with a routine EKG done in the physician’s office.
The challenge is when an arrhythmia occurs intermittently (on and off) or is self-limiting. In this case, an EKG performed in between A-Fib episodes can be completely normal. To circumvent this problem, one would go to the next level of evaluation with a long-term monitor.
Long-term monitors basically are EKG recorders that patients can take with them (ambulatory). They fall into two major categories: continuous recording (Holter) and intermittent recording (Event).
The Holter Monitor
A Holter Monitor (named after Dr. Norman Holter, go figure) records continuously the EKG of a patient, usually for 24 – 48 hours. More modern Holter units record onto digital flash memory devices. The data are uploaded into a computer where software analyzes the input, counting ECG complexes, calculating summary statistics such as average heart rate, minimum and maximum heart rate, and finding candidate areas in the recording worthy of further study.
The advantage of a Holter is that every single heartbeat during that day is recorded and can be analyzed. The disadvantage is that if an arrhythmia did not happen on that particular day, the Holter data would not be useful.
The Event Monitor
An Event Monitor, on the other hand, is a long-term monitor that can be used for up to 30 days or longer. The advantage is that the longer the recording period, the better chance of “catching” an intermittent arrhythmia. The disadvantage is that an Event Monitor must be activated by the patient and downloaded telephonically, a task that requires a certain amount of manual dexterity and may be difficult for some patients.
Some event monitors are patient activated when having an episode and save the last several minutes of data; others detect the irregular heart rate and automatically record the data.
Number of Electrodes
The number and position of electrodes varies by model, but most Holter monitors employ between three and eight, whereas the Event Monitors typically use two. Both the Holter and Event monitors record electrical signals from the heart via a series of electrodes attached to the chest. The Loop (event) monitor is not attached to the patient but is instead pressed to the chest by the patient when experiencing an A-Fib episode.
Implantable ambulatory event monitors
Implantable event monitors are also available for those instances where individuals experience such infrequent symptoms that extended monitoring is needed.
These devices are inserted just under the skin in the chest area during an outpatient surgical procedure. The device may remain implanted for over one year.
Implantable loop recorders have the ability to record events either automatically (auto activated) or by manual activation (self-activated).
Real Time Remote Cardiac Recording
An example of the newer monitoring technologies is the Ambulatory Cardiac Telemetry (ACT), a wireless cardiac telemetry system. This event monitor is designed for remote arrhythmia monitoring in any location.
A small transmitter worn on the patient sends the ECG data to a portable handheld device where it is analyzed. If an arrhythmia is identified, the data is automatically transmitted to a Monitoring Center for immediate review. Integrated into a state-of-the-art mobile phone, the ACT provides next generation cardiac arrhythmia monitoring. What’s interesting is the transmitter is a dongle type device worn around the neck with leads placed on the chest. You carry or have available what, in essence, is a mobile phone (it’s actually more than a phone). It is small and not cumbersome.
No patient input is required. Data collected from the monitors is transmitted to the monitoring center via a cellular network, the internet, or over the phone (based on model). Data from the monitors is not intended to be used directly by the patient but rather by the monitoring center and your cardiologist.
Next-Generation: the ‘Smart Band-Aid’ Zio Patch
The ‘Smart Band-Aid’ provides the next-generation ambulatory cardiac monitoring service with beat-to-beat, real time analysis, automatic arrhythmia detection and wireless ECG transmission.
The sensors in the Band-Aid can be modified to monitor a number of different tasks as they can also provide a comprehensive suite of post-symptom, looping, and auto trigger event monitors as part of its turn-key cardiac event monitoring service.
Last updated: Thursday, September 3, 2015