ECG monitors superior for detecting AF in patients with cryptogenic stroke

Issue: September 2014

The future of detecting atrial fibrillation in patients with cryptogenic stroke may come in the form of new technology.

Recent data published in The New England Journal of Medicine demonstrated that two ECG monitors were superior to 24-hour Holter monitoring for the detection of AF in this patient population. The studies have prompted discussion surrounding whether 24-hour Holter monitoring is no longer acceptable for the detection of AF in patients with cryptogenic stroke and, if that is the case, which of the newer monitoring technologies are appropriate for which patients.

Hooman
Kamel

In the EMBRACE trial, the ER910AF cardiac event monitor (Braemar), a 30-day event-triggered loop recorder worn around the chest, improved AF detection as compared with 24-hour Holter monitoring in patients with a recent cryptogenic stroke or transient ischemic attack. In the CRYSTAL AF trial, the Reveal XT insertable cardiac monitor (Medtronic) was superior to 24-hour Holter monitoring for AF detection in patients with cryptogenic stroke.

In a commentary published with the studies in NEJM, Hooman Kamel, MD, from the department of neurology and the Feil Family Brain and Mind Research Institute at Weill Cornell Medical College, New York, said the recent study results “indicate that prolonged monitoring of heart rhythm should now become part of the standard care of patients with cryptogenic stroke.”

Findings of superiority

The EMBRACE study included 572 patients aged 55 years and older. The patients had no known history of AF, but had a cryptogenic ischemic stroke or TIA within the previous 6 months. The patients were randomly assigned to the ER910AF monitor or the 24-hour Holter.

The primary outcome, newly detected AF lasting ≥30 seconds within 90 days, occurred in 16.1% of patients in the ER910AF group vs. 3.2% in the Holter group (absolute difference, 12.9%; 95% CI, 8-17.6; number needed to screen=8). At 90 days, oral anticoagulation was prescribed for 18.6% of patients in the ER910AF group vs. 11.1% in the Holter group (absolute difference, 7.5%; 95% CI, 1.6-13.3).

The CRYSTAL AF study evaluated 441 patients aged 40 years and older with cryptogenic stroke and no evidence of AF during 24 hours of ECG monitoring. Patients were randomly assigned within 90 days of the index event to the Reveal XT monitor or the 24-hour Holter.

According to the results, which were previously presented at the International Stroke Conference, at 6 months, AF was detected in 8.9% of patients in the Reveal XT group vs. 1.4% of patients in the Holter group (HR=6.4; 95% CI, 1.9-21.7). At 12 months, AF was detected in 12.4% of patients in the Reveal XT group vs. 2% of patients in the Holter group (HR=7.3; 95% CI, 2.6-20.8). As in the EMBRACE study, patients in the ECG group were more likely than those in the Holter group to be switched to an oral anticoagulant.

Implications considered

While the proportion of patients with cryptogenic stroke with undetected AF is unknown, these studies indicate that it is not small and, therefore, clinical practice should be changed, according to experts interviewed by Cardiology Today.

Smit
Vasaiwala

“More neurologists and cardiologists may move toward continuous monitoring of AF” as a result of the studies, Smit Vasaiwala, MD, cardiac electrophysiologist at Loyola University Health System and assistant professor of cardiology at Loyola University Chicago Stritch School of Medicine, said in an interview. “I believe 24 hours is too short of a time for monitoring. What needs to be determined is whether improved detection of AF will result in better outcomes in terms of stroke prevention and mortality benefit.”

Jonathan P. Piccini, MD, MHSc, FACC, FAHA, FHRS, associate professor of medicine at Duke University Medical Center and Duke Clinical Research Institute, told Cardiology Today that an important finding of the studies is that “better detection leads to more treatment (anticoagulation). However, further study is needed to confirm improved outcomes.”

Technology choices

The technologies studied are just two of many options, and cardiologists now need to determine which to use in which patients with cryptogenic stroke, should they deem traditional Holter monitors no longer acceptable.

Jonathan P.
Piccini

“The field of cardiac monitoring technology is rapidly expanding,” Piccini said. “Implanted monitors are becoming easier to implant. Similarly, there are a lot of innovations in noninvasive monitoring including technologies like outpatient telemetry, intermittent rhythm monitoring with smartphone-enabled technologies, and more advanced patch Holter monitors like the Zio XT Patch (iRhythm). The main questions that need to be answered for these technologies are: No. 1, do they lead to improved outcomes, the ultimate goal of monitoring, and, No. 2, are they cost-effective compared to current technologies?”

Vasaiwala told Cardiology Today that “having a discussion with the patient regarding the pluses and minuses of [internal and external monitors] is reasonable when deciding what modality is ultimately chosen.” He noted that “some of the wearable monitors have [the] capability … to automatically detect AF” and that “the implantable monitors provide a longer time period for detection and are generally better tolerated by the patients.”

In his NEJM commentary, Kamel noted that the ER910AF and Reveal XT monitors identified AF “that would not have otherwise declared itself.” Therefore, he wrote, “most patients with cryptogenic stroke or [TIA] should undergo at least several weeks of rhythm monitoring. Relatively inexpensive external loop recorders, such as those used in the EMBRACE trial, will probably be cost-effective; the value of more expensive implantable loop recorders is less clear.”

In addition, Piccini said, one thing to keep in mind is that the technologies are not perfect. “Even implantable monitors have a reasonably high false positive rate,” he said, noting that one study found it could be as high as 15%. – by Erik Swain

Gladstone DJ. N Engl J Med. 2014;370:2467-2477.

Hindricks G. Circ Arrhythm Electrophysiol. 2010;3:141-147.

Kamel H. N Engl J Med. 2014;370:2532-2533.

Sanna T. N Engl J Med. 2014;370:2478-2486.

Jonathan P. Piccini, MD, MHSc, FACC, FAHA, FHRS, can be reached at Duke Clinical Research Institute, Duke University Medical Center, PO Box 17969, Durham, NC 27705.

Smit Vasaiwala, MD, can be reached at the Loyola University Center for Heart and Vascular Medicine, 2160 S. 1st Ave., Maywood, IL 60153.

Disclosures: Kamel reports no relevant financial disclosures. Piccini reports receiving research grants from Johnson & Johnson and consulting for Medtronic. Vasaiwala reports consulting for Medtronic.