Today, there is a tremendous amount of information that can be found on your wrist. From never missing a phone call to caller ID to screen the calls you would like to miss. You can have calendar reminders, text, email, exercise tracking, and more. With an Apple Watch, you can even remind yourself to take a one-minute break throughout the day. Today the new feature that applies to us in the EP field is the ability to actually record an ECG! But… how reliable is it?
Atrial and atrial flutter (AF, collectively) are the most common types of cardiac arrhythmia and affect over five million people in the United States. Recent studies have suggested that ~700,000 people in the United States may have previously undiagnosed AF [1]. For the price of $384, early detection or additional monitoring may be available at the user’s fingertips.
A 30 second ECG may be recorded using a photoplethysmography that detects heart rate utilizing optical properties of vascular tissue with LEDs. This single lead is similar to Lead I, although Leads II and III may be recorded by placing the watch on your ankle [2]. There is even a way to record tracings similar to the precordial leads (https://annals.org/aim). So, what does this recording look like? Here is a screenshot of the recording I just acquired on myself.
The user may scroll through the ECG or view a PDF of the entire 30-second strip which can then be sent to your physician. It displayed my heart rate, the absence of atrial fibrillation, and if I felt symptoms, I would be able to enter them as well. It will classify a rhythm as sinus rhythm, bradycardia, tachycardia, atrial fibrillation, or inconclusive.
Below, is an example comparing the ECG tracing on patients with an Apple Watch vs. telemetry.
Next, is an example of a 16-year-old patient that recorded her rapid heart rate and symptoms. This is the PDF printout that was able to be presented to the physician. The patient underwent an EP study for this short RP tachycardia, AVNRT was induced and successfully ablated.
This should not replace a medical consultation and a physician should be contacted if you are experiencing any symptoms such as fatigue, palpitations, shortness of breath, or dizziness. Also, immediately contact 911 if you experience chest pain or other signs of a heart attack.
There are potential problems with this new technology including false-positive and/or false-negative readings. For example, if a patient is in atrial fibrillation but might not consult a doctor about symptoms because they feel falsely reassured by the absence of any alert from their watch.
In 2019, Apple sold an estimated 30.7 million Apple Watches around the world. This was 36% higher than the 22.5 million watches Apple sold in 2018. The company is doing more watch business than the entire Swiss watch industry, which sold 21.1 million watches last year [3].
The Apple Watch is definitely a handy tool to stay more active in your healthcare. However, my favorite function of the apple watch is still the ability to locate my phone that I absent-mindedly leave around the house. 😉
[1] D.R. Seshadri et al., “Accuracy of the Apple Watch 4 to Measure Heart Rate in Patients With Atrial Fibrillation,” in IEEE Journal of Translational Engineering in Health and Medicine, vo. 8, pp. 1-4, 2020, Art no. 2700204
[2] H. Siddeek et al., “AVNRT captured by Apple Watch Series 4: Can the Apple watch be used as an event monitor?” in Wiley Journal. December 2019. Retrieved April 2020. DOI: 10.1111/anec.12742.
This week’s EP question:
This is often observed during RF ablation of the slow pathway for AVNRT.
1. A wave with no H or V following
2. Stretching of the PR Interval
3. Accelerated Junctional Rhythm
4. Slow Junctional Rhythm
Answer
Slow Junctional Rhythm
Thermal injury to the area of the slow pathway will present with a slow junctional rhythm whereas injury to the fast pathway will elicit an accelerated junctional rhythm or complete heart block. A junctional rhythm is observed in the following electrogram. Notice the His signal followed by the atrial and ventricular activation with a VA interval <60 ms.
