Patch challenges Holter monitor for detecting arrhythmias

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 - ZIO patch
Source: iRhythm Technologies

Is the Holter monitor heading toward obsolescence? One study that compared a lightweight patch to Holter monitors for detecting arrhythmias declared the patch the victor and suggested the newer technology will oust this standard approach.

Conventional 24-hour Holter monitoring allows physicians to track patients with suspected arrhythmias in an outpatient ambulatory setting, but it has been criticized as being ineffective and costly. One way to amp up its effectiveness is to prolong the monitoring period, but some patients find the device to be intrusive and cumbersome.

Paddy M. Barrett, MB BCh, of the Scripps Translational Science Institute in La Jolla, Calif., and colleagues designed a prospective study to compare 24-hour Holter monitoring with the ZIO Patch (iRhythm Technologies). They published their results in the January issue of the American Journal of Medicine.

The adhesive patch is a single-lead, ambulatory electrocardiographic device that can be worn up to 14 days. It is waterproof and patients can self-apply it. The FDA granted it 510(k) clearance in 2012.  

The study enrolled 146 patients between April and July 2012 who had been referred to Scripps Green Hospital for evaluation of cardiac arrhythmias. Each patient was fitted with a patch and a 24-hour Holter monitor. The primary endpoint was the detection of arrhythmia events. A secondary endpoint compared arrhythmia events over a simultaneous 24-hour period.

Researchers also performed a survey that 143 patients completed. Of that group, more patients reported that the patch as comfortable and less interfering with daily activities compared with the Holter monitor. Eighty-one percent preferred to wear the patch.

A survey of 102 physicians found 90 percent reported achieving a definitive diagnosis with the patch vs. 64 percent with the Holter monitor.

Holter monitors detected 61 events vs. 96 for the patch. Both devices detected 60 events, and the patch detected another 36 events, primarily through prolonged monitoring. Eliminating supraventricular tachycardia, which the researchers considered less clinically relevant, the patch detected more events.

“Using the incremental diagnostic yield of an extended monitoring period as opposed to relying on data  acquisition during brief, often asymptomatic periods is critical, because even prolonged pauses of up to 9.7 seconds can be asymptomatic,” Barrett et al wrote.

When the analysis was restricted to 24 hours, the Holter monitor detected more events (61 vs. 50). Looking at events detected by one but not the other device, the Holter monitor detected 11 events and the patch two events. The Holter monitor also detected more events when supraventricular tachycardia was eliminated (27 vs. 24).

The median wear time for the patch was 11.1 days, which they proposed “is likely a sufficient diagnostic window to capture arrhythmia events, because the highest diagnostic yield for arrhythmia detection is usually the first 7 days of ambulatory ECG monitoring. Ambulatory ECG monitoring beyond 7 days often provides only an additional 3.9% of patients with a diagnosis.”

They described the Holter monitor’s better performance when the analysis was limited to 24 hours as “unexpected.” Through further analysis and review, they identified two of the 11 discrepancies as an algorithm misclassification and seven as a processing error. Adjustments and corrections were implemented as a consequence.

They also acknowledged that three-lead detection captures data such as broader QRS complexes but the patch proved equal for detecting atrial fibrillation and flutter; clinically meaningful events that were undetected in the first 24 hours were captured later.

“On the basis of these findings, novel, single-lead, prolonged-duration, low-profile devices may soon replace conventional Holter monitoring platforms for the detection of arrhythmia events in patients referred for ambulatory ECG monitoring,” they wrote.

iRhythm Technologies provided funding for the study.