Apple Watch gives clues to cardiac rhythm changes

Tuesday, 11 Feb 2020

Smart watches with a heart rate monitoring function have the potential to alert patients and their clinicians to cardiac rhythm changes, Victorian cardiologists say.

Dr Liam Toner and colleagues form the Department of Cardiology, Austin Hospital, Melbourne have reported the case of an elderly woman with atrial fibrillation whose Apple Watch made her aware of a spontaneous reversion to sinus rhythm when it displayed a sudden and persistent decrease in her heart rate.

The 80-year old patient had a history of paroxysmal atrial fibrillation and was undergoing routine ambulatory Holter monitoring at the time to assess the adequacy of ventricular rate control.

When returning the Holter monitor to the clinic she told her doctor that she had felt a sensation of her heart ‘doing a flip’ the previous evening, when she noticed her Apple Watch showed her heart rate drop suddenly from 99 bpm to 65 bpm.

Writing in BMJ Case Reports, Dr Toner said the conversion to sinus rhythm was confirmed when heart rate recordings from the Apple Watch were obtained via the Apple Health App and found to match readings taken on Holter monitoring the same time intervals over a 22-hour period. The median interval was 6 minutes and IQR of 5.75min).

Analysis showed that the average heart rate as measured by smart watch in AF prior to reversion was 94 bpm compared with 66 bpm after reversion to sinus rhythm.

Dr Toner said that the increasing popularity of smart watches among patients highlighted the potential usefulness of the heart rate function for chronotropic assessment and arrhythmia detection.

“This case highlights the advantage of incorporating continuous capture photoplethysmography with contemporary single-lead ECG technology to facilitate chronotropic and rhythm assessment of patients with atrial fibrillation,” the report authors said.

“Our key finding is that a sudden and persistent alteration in HR on a wearable device may be suggestive of a subclinical arrhythmia.”

“Sudden and persistent changes in heart rate as detected by smart watches should alert clinicians to the possibility of cardiac rhythm changes,” they concluded.

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