January 7th, 2014
Is It Time to Sunset the Holter Monitor?
CardioExchange’s John Ryan interviews Paddy M. Barrett about his research group’s study, published in the American Journal of Medicine, comparing 24-hour Holter monitoring with the Zio Patch 14-day single-lead ECG device.
One hundred forty-six patients who had been referred for evaluation of cardiac arrhythmias underwent simultaneous ambulatory ECG recording with a conventional 24-hour Holter monitor and with the single-lead Zio Patch 14-day adhesive patch monitor. Over the total wear time of both devices, the adhesive patch monitor detected significantly more arrhythmia events than the Holter monitor did (96 vs. 61). During the initial, simultaneous 24-hour monitoring period for the two devices, the Zio Patch monitor detected significantly fewer events than the Holter monitor (52 vs. 61). The maker of Zio Patch partly funded the study.
Ryan: Why did you compare a 24-hour device (Holter monitor) with a 14-day device (Zio Patch)? Did that affect your results?
Barrett: The most commonly used platform for detecting cardiac arrhythmias is the Holter monitor, which (with some modifications) has been used since the 1960s. Typically, Holter monitoring is conducted for 24 hours, as in our study. With the explosion in novel biosensors, we felt that a direct comparison of the Holter monitor, as it is traditionally used, with a novel 14-day patch sensor was a valuable question to answer in assessing incremental benefits in arrhythmia detection.
Ryan: Why do you think the Zio device missed some events in the first 24 hours? If a patient agrees to only 24 hours of monitoring, can Zio be recommended for this purpose, given the evidence to date?
Barrett: We believe the Zio Patch can be used for any duration up to at least 14 days. A crucial factor, of course, is the potential frequency of arrhythmias in the monitored patients, some of whom will be asymptomatic (the longer the monitoring period, the better).
The primary reason that Zio Patch did not detect some arrhythmia events in the first 24 hours was that our study defined events by very short episodes, often only four sequential beats. The Zio Patch detected these, but because the raw data were initially screened by an iRhythm physician who prepared the report, some of those very short episodes were not included in the report. iRhythm now populates all arrhythmia events to the report.
Ryan: What was the rate of allergic reactions in the study? Will chest hair, adiposity and emphysema interfere with detection of events?
Barrett: Allergic reactions were very infrequent. This has been a major area of focus in this area, as high rates of skin allergy in patients have been documented for historical devices. Even up to 14 days, we had very few skin reactions. A small section of chest hair was shaved to apply the device, but we did not find that additional adiposity or larger lung volumes impeded arrhythmia detection.
Ryan: When can providers start prescribing the Zio device — and how?
Barrett: The Zio Patch is available right now and can be prescribed in two ways. First, the physician can purchase a stock and apply the device in the office; the patient returns the device to iRhythm by mail for analysis and generation of a report, which is made available to the ordering physician. Second, the physician can have the device independently mailed to the patient, who then self-applies it.
Ryan: Is it realistic that the Zio device will replace the Holter monitor any time in the foreseeable future?
Barrett: Absolutely — this device and others like it will replace the Holter monitor. Using a device the size of a VHS cassette with multiple wires and stickers is just not a suitable method for detecting arrhythmia events when novel biosensor platforms exist (and will evolve even further). It is not a technology of the future; it is a technology of today.
Given Dr. Barrett’s analysis, what do you think the future of arrhythmia-detection devices like Zio Patch will be?