Zoll Itamar launches an Arrhythmia Detection algorithm for its WatchPAT devices.

By Sree Roy

When a sleep specialist faces a months-long backlog, it can feel overwhelming to also screen all sleep apnea patients for comorbidities, even potentially devastating ones like heart rhythm abnormalities. 

While the evidence pointing toward potential cardiac problems, such as atrial fibrillation (afib) and premature beats, is available in the raw data from sleep study pulse or electrocardiogram signals, busy physicians can miss the signs. Thankfully, as the links between sleep health and heart health increasingly become apparent, easier ways to triage potential heart problems in sleep apnea patients have entered the marketplace. 

“As sleep medicine gets more and more referrals from primary care, sleep specialists may be the first people to discover arrhythmias,” says cardiologist Ronald H. Wharton, MD, FACC, FASE, director of the hypertrophic cardiomyopathy program and co-director of the collaborative program in cardiovascular disease and sleep medicine at North Shore University Hospital in New York.

Key Takeaway: Sleep specialists could play a valuable role in identifying undiagnosed arrhythmias, but challenges such as time constraints mean they can miss heart rhythm flags.

Facilitating Cardio-Sleep Bidirectional Referrals

In Wharton’s experience, cardio-sleep referrals have long been one-way—that is, cardiologists refer patients to sleep medicine, but sleep specialists rarely refer to cardiology.

“It’s an unusual paradigm; we’re not trained to diagnose or treat [sleep apnea], but all the patients with sleep apnea are in our cardiology clinics,” he says. “I’m hoping as home sleep testing devices become more sophisticated that we start to see an uptick in referrals [from sleep], where they detect the arrhythmias before we do.”

Over the years, sleep specialist Mehran Farid, MD, medical director of Peninsula Sleep Center Inc in Burlingame, Calif, has noticed atrial fibrillation’s characteristic shape in the pulse rate graph of sleep studies and referred those patients for Holter monitoring and to cardiologists for treatment.

But, he adds, “Not all sleep studies are comprehensively reviewed by physicians….If you have to rely on your image recognition, not everyone does it or is familiar with that.”

Since April, Farid, who’s also an adjunct clinical associate professor at Stanford Sleep Medicine Center, was part of a pilot program for a new Arrhythmia Detection feature by ZOLL Itamar. The feature, which became widely available in November 2023, flags atrial fibrillation and premature beats on the company’s WatchPAT 200U, 300, and ONE home sleep test reports.

Farid says, “Once we have the data, we are ethically responsible to look at it. Therefore, WatchPAT makes it easier because they do some of the work for you.”

Wharton says the sleep team he works with also recently had the Arrhythmia Detection feature enabled on its WatchPAT devices. “We’d like to see sleep medicine become more of an equal partner in the bidirectional flow between us and them now that this technology is becoming available,” Wharton says.

Key Takeaway: Cardiologists say they refer patients to sleep medicine but don’t get many referrals from sleep medicine. Sleep specialists and cardiologists hope that ZOLL Itamar’s new Arrhythmia Detection feature will facilitate more cardiology referrals from sleep medicine.

What Can WatchPAT Arrhythmia Detection Help With?

The US Food and Drug Administration (FDA) recently gave ZOLL Itamar’s Arrhythmia Detection feature clearance to identify/detect atrial fibrillation events and premature beats (but not to diagnose them) as supplemental information to WatchPAT home sleep studies.

It doesn’t replace cardiac event/Holter monitoring or similar diagnostic procedures, and there’s no change in the device’s intended use: The WatchPAT is a home sleep apnea device for diagnosing sleep-related breathing disorders.

What it does mean: Potential atrial fibrillation events and premature beats are notated in WatchPAT sleep study reports. 

A green “AFIB” label marks the beginning, middle, and end of potential atrial fibrillation events. A “PB” label designates likely premature beats. And a table presents the duration of the events. “It’s much easier to see,” Farid says.

Lauren Kinney-Kruse, ZOLL Itamar’s senior marketing manager – cardiology, says, “It’s estimated that by the year 2030, in the United States, 12.1 million patients will be diagnosed with afib.1 A recently published study found that nearly one in 10 patients with obstructive sleep apnea have undiagnosed atrial fibrillation, leaving them vulnerable.”2

She shares the takeaways from a retrospective study the company submitted to the FDA about the Arrhythmia Detection algorithm. It compared automatic analysis by the algorithm versus manual scoring of electrocardiogram data from a sleep study.


  • WP 200U 
  • 84 subjects with a broad range of comorbidities
    • 41 patients with heart failure
    • 17 had afib


  • The sensitivity and specificity of the WatchPAT to detect afib segments (of at least 60 seconds) were 0.77 and 0.99, respectively.
  • The correlation between the WatchPAT-derived detection of premature beats (events/min) to that of the PSG was 0.98.

Since the novel algorithm can reasonably detect afib events and premature beats, it should be used as “flag raising” to indicate if further clinical investigation is needed, Kinney-Kruse says, which typically means referral for 24-hour Holter monitoring.

Sleep specialists have access to the raw data. Because the patient must be asleep for the algorithm’s accuracy (it needs stable peripheral arterial tone), short events in particular deserve review.

The new algorithm is now being enabled practice by practice. “Once training is complete at the practice, it’s turned on from the information technology side,” Kinney-Kruse says.

Key Takeaway: WatchPAT Arrhythmia Detection can identify atrial fibrillation events and premature beats, flagging patients for whom further testing is recommended.

Next Step: Getting Sleep Patients to Cardiologists

Once sleep specialists identify a sleep apnea patient with potential cardiac comorbidities, some choose to immediately refer to cardiology, while others first opt to order a diagnostic cardiac test, such as a Holter monitor, then only refer the patient to a cardiologist if the arrhythmia is confirmed.

For sleep practices affiliated with larger health systems, flagging patients for cardiac referrals has the added advantage of keeping people within that healthcare ecosystem. “It provides a number of touches of how they stay within the ecosystem of that hospital,” says ZOLL Itamar’s Kinney-Kruse. “That’s one thing we’re really proud of.”

Though many patients with atrial fibrillation are eventually treated by electrophysiologists, any general cardiologist can take care of the initial management of afib, says cardiologist Wharton. “Just find someone with whom you have a good rapport and refer.”

Electrophysiologist Dale Yoo, MD, who practices at Heart Rhythm Specialists PLLC in Dallas, Texas, says, “Arrhythmia Detection cements ZOLL Itamar’s journey to excellence at the intersection of heart health and sleep medicine by empowering providers to visualize arrhythmia threats to the body during one of the most vulnerable moments…while we sleep. With Arrhythmia Detection, providers will be able to expose life-threatening arrhythmias and manage them appropriately to lower the risk of stroke and heart failure.”

Key Takeaway: A general cardiologist can handle initial referrals from sleep medicine. If you have a cardiologist within your health system, your patients will benefit from having an additional touchpoint.


1. Colilla S, Crow A, Petkun W, et al. Estimates of current and future incidence and prevalence of atrial fibrillation in the US adult population. Am J Cardiol. 2013 Oct 15;112(8):1142-7.

2. Højager A, Schoos MM, Tingsgaard PK, et al. Prevalence of silent atrial fibrillation and cardiovascular disease in patients with obstructive sleep apnea. Sleep Med. 2022;100:534-41.

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