Patient Directed Recording of a Bipolar Three-Lead Electrocardiogram using a Smartwatch with ECG Function

This protocol enables subjects owning a smartwatch with ECG function to record three bipolar signal lead ECGs comparable to Einthoven leads one to three from a standard ECG. This technique may help to detect cardiac arrhythmias or myocardial ischemia. Subjects could help a doctor identify ECG abnormalities immediately after onset of symptoms.

This method can principally be applied to all bipolar ECG recording devices and smartwatches with ECG function, except for the protocol for sending PDF to the doctor, which is specific to the device app. It is important that the subject is able to generate a good skin contact, especially during recording of leads two and three. It may be difficult to record Einthoven leads two and three because the watch has to be placed in the lower abdominal of the individual.

Therefore a resting position is mandatory. Demonstrating the procedure will be Sven Kaese, a colleague from our department. To record a standard ECG, use a common ECG device and adjust the paper running speed to 50 millimeters per second.

Perform the recording after a five minute resting period in a supine position. Place the right and left arm electrodes near the shoulders and the right and left leg electrodes near the ankles. Then place the V1 and V2 electrodes in the fourth intercostal space at the right and left parasternal lines respectively.

Place the V4 electrode in the fifth intercostal space at the midclavicular line and the V3 electrode between the V2 and V4.Then place the V5 electrode in the fifth intercostal space at the anterior axillary line and the V6 electrode at the mid axillary line. Once all electrodes are in place, record a standard 12 lead ECG with the ECG device. Record the smartwatch ECG immediately after recording the standard ECG.

Enable the application for ECG recording, which will record a 30 second ECG after proper skin contact with the smartwatch. Record Einthoven one by placing the back of the smartwatch on left wrist and the right index finger on the crown. Then, record Einthoven two by placing it on the left lower abdomen and the right index finger on the crown.

Finally, record Einthoven three in the same position, but with the left index finger on the crown. Ensure that the right and left index finger do not contact the skin of the wrist of lower abdomen and that the subject does not move during the recording. Use the Send PDF to Your Doctor function to create a PDF document of every smartwatch ECG lead.

Then print the digital ECG on paper for comparison with the standard ECG. Classify all smartwatch ECGs as moderate quality if at least three consecutive QRS complexes show noise free signal quality and there are no artifacts in the isoelectric lines between complexes. If this is true for 10 QRS complexes, classify the ECG as good quality.

Then, perform statistical analysis on the ECGs. The smartwatch recording protocol was tested on 100 healthy subjects, all of whom managed the ECG recording procedure after a short tutorial. Of the total recorded ECGs, 92%were of good signal quality and 8%of moderate signal quality.

Despite different writing speeds of the standard and smartwatch ECG curves, the morphologies of the three channels were clearly identical. Three blinded cardiologists were asked to assign the smartwatch ECGs to the corresponding Einthoven leads in each subject and all three correctly assigned the ECGs from 89 participants. All assignment errors were made in the ECGs with good signal quality, but the errors occurred in statistically older subjects.

When attempting this procedure, the most important thing is to perform recordings under resting conditions to obtain best ECG signal quality. Chest lead ECG recordings may also be recorded with mobile device to give additional informations of the interior wall of the left ventricle. This technique may enable widespread of diagnostic potential in an outpatient setting for cardiac disorders.