Smartphone ECG Can Spot AF in Acute Stroke, Add to Holter Data

Marlene Busko

October 19, 2018

MONTREAL — A miniature electrocardiogram (ECG) device combined with a smartphone spotted more cases of atrial fibrillation (AF) than were later detected by Holter monitoring in a trial of 294 patients hospitalized for stroke or transient ischemic attack (TIA).

In the SPOT-AF trial, stroke-unit nurses used the US Food and Drug Association (FDA)–approved Kardia Mobile (AliveCor) device to obtain ECG readings from patients when they were routinely measuring pulse and blood pressure during a median hospital stay of about 4 days.

The device consists of two electrodes in a smartphone cover. The patient places one finger of each hand on the device, which then displays an ECG on a smartphone.

The device detected AF in 8.5% of the stroke patients in hospital. By contrast, Holter monitoring, which was generally carried out within the next 3 months, detected AF in 2.7% of patients. Physicians could then decide on treatment on the basis of local practice.

The smartphone ECG is not meant to replace Holter monitoring, Bernard Yan, MD, Royal Melbourne Hospital, Australia, cautioned. He presented the results here at the 11th World Stroke Congress (WSC) 2018.

"We now believe that the smartphone is not an alternative," he said, "but is complementary to the local practice.

"If you have the patient earmarked for Holter monitoring," he continued, "there's no harm in also adding on the smartphone detection during the inpatient stay, because it might change your [treatment strategy]."

The device is "complementary," he clarified totheheart.org | Medscape Cardiology, because the guidelines stipulate that AF can be detected using Holter monitoring and implanted cardiac monitoring.

However, "this study adds a bit more weight to the fact that if you really want to pick up AF, you want to do it early, " he said.

Similarly, session comoderator Prof Patrik Michel, MD, CHUV, Lausanne, Switzerland, told Medscape Medical News that this device, used early on after a stroke or TIA in the hospital setting, is probably a complementary device that does not replace other guideline-recommended long-term monitoring, such as prolonged Holter monitoring or use of other wearable or implanted devices, "so it would just be one other option to detect intermittent AF after strokes — an add-on device.

"The latest data show that it is important to diagnose AF before starting any anticoagulation," he noted. These devices or techniques are needed to be sure the patient does have AF."

"All the trials that put patients on anticoagulation blindly without knowing if they have AF have failed so far, so it is really worth investing time, money, and energy into the search of covert AF.

"But again, this method is only one of several methods, and it's probably not going to be a gold standard; it would be an add-on while the patient is still in the hospital," Yan said.

More AF in the "Hot Period"

AF accounts for about 29% of all ischemic strokes, but paroxysmal AF is very hard to detect, Yan noted. After a stroke or TIA, a single ECG would probably pick up 2% of cases of AF; 24-hour Holter monitoring would detect about 6% of cases, he said.

The CRYSTAL AF trial reported that a long-term implantable device detected about 12% of cases of AF.

There may be problems with reimbursement with use of these long-term implantable cardiac monitoring devices, Yan added. In addition, adherence may be poor; in a study of 17,000 patients, only 30% completed 24-hour monitoring.

Therefore, smartphone technology might provide more information. There are now about eight or nine apps for ECG measurements, including products from Applied Biomedical Systems, Omron, and Zenicor.

Of these, as previously reported, the FDA approved the AliveCor device to measure ECG. More recently it approved the Apple Watch Series 4 for the same purpose.

In the SEARCH-AF study of 1000 outpatients, the AliveCor device had a sensitivity 98% and specificity 91% for detecting AF.

However, "all of these apps and smartphone devices were tested in patients who have not had a stroke," Yan noted. "It is possible that in the 'hot period,' that is, the first month or so, we could pick up more of these AF if we use a smart device."

In FIND-AF, about two thirds of the cases of AF were detected in the first 10 days. In CRYSTAL-AF, about half of the cases were detected in the first 42 days.

The current study, SPOT-AF, compared the proportion of cases of paroxysmal AF detected by the AliveCor heart monitor device with standard 24-hour Holter monitoring in a pragmatic international cohort of patients who had experienced acute ischemic stroke or TIA.

The researchers hypothesized that AF detection by Kardia Mobile monitoring is comparable to that of standard Holter monitoring.

"The decision to start a DOAC [direct oral anticoagulant] or warfarin was entirely at the discretion of the treating physician," Yan noted.

In this real-world study, 1079 patients were recruited, but only 294 patients underwent Holter monitoring. The median age of the patients was 68 years, the median CHADSVASC score was 4, and 46% were women.

The device picked up physician-confirmed AF in 25 of 294 patients (8.5%). Of these 25 patients, DOAC was initiated for 11 (44%).

Of these 25 patients, Holter monitoring detected AF in only seven patients.

"Most of the Holters were applied after the patient was discharged from hospital, so we don't have concurrent AliveCor vs Holter comparison," Yan conceded.

Holter monitoring detected AF in eight of the 294 patients (2.7%). For seven of these eight patients, AF was detected by smartphone.

"I think we are seeing more and more patients carrying smart devices — so having more data and more evidence helps everybody, or at least adds a bit of clarity," said Yan.

The study was funded by Boehringer Ingelheim and the Neurosciences Foundation. Dr Yan has received speaker's honoraria from Stryker, Bayer, Boehringer Ingelheim, and Pfizer. He holds a patent for a microrobotic catheter and is cofounder of Neuroglide (a microrobotic catheter).

For more from theheart.org | Medscape Cardiology, follow us on Twitter and Facebook.

World Stroke Congress (WSC) 2018. Presented October 17, 2018.

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