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