Recording of Bipolar Multichannel ECGs by a Smartwatch: Modern ECG Diagnostic 100 Years after Einthoven

Abstract

Aims: Feasibility study of accurate three lead ECG recording (Einthoven I, II and III) using an Apple Watch Series 4. Methods: In 50 healthy subjects (18 male; age: 40 ± 12 years) without known cardiac disorders, a 12-lead ECG and three bipolar ECGs, corresponding to Einthoven leads I, II and III were recorded using an Apple Watch Series 4. Einthoven I was recorded with the watch on the left wrist and the right index finger on the crown, Einthoven II with the watch on the left lower abdomen and the right index finger on the crown, Eindhoven III with the watch on the left lower abdomen and the left index finger on the crown. Four experienced cardiologists were independently asked to assign the watch ECGs to Einthoven leads from 12-lead ECG for each subject. Results: All watch ECGs showed an adequate signal quality with 134 ECGs of good (89%) and 16 of moderate signal quality (11%). Ninety-one percent of all watch ECGs were assigned correctly to corresponding leads from 12-lead ECG. Thirty-nine subjects (78%) were assigned correctly by all cardiologists. All assignment errors occurred in patients with similar morphologies and amplitudes in at least two of the three recorded leads. Erroneous assignment of all watch ECGs to leads from standard ECG occurred in no patient. Conclusion: Recording of Einthoven leads I-III by a smartwatch is accurate and highly comparable to standard ECG. This might contribute to an earlier detection of cardiac disorders, which are associated with repolarization abnormalities or arrhythmias.

Feasibility and Reliability of SmartWatch to Obtain 3-Lead Electrocardiogram Recordings

“…As an interesting finding, the mean age of our included patients was 63.6 ± 14.0 years, which reflects an older age in comparison to other studies [ 14 , 15 ]. This is important because one might think that it would be very difficult for the elderly to record ECG with a smartwatch, but our experience showed that the elderly without motor or mental problems could undertake this task confidently after a very short training.…”

“…Although we are not the first group who reported the utility and description of this technique, our study has confirmed its validity in a relatively large sample. Our previous understanding regarding the smartwatch ECGs were limited to the findings of several case reports and case series [ 7 , 27 , 28 , 29 , 30 ], and three studies on around 50–100 patients [ 13 , 14 , 15 ].…”

“…The current method that we used in this study to record a 3-lead ECG was previously described by Samol et al [ 14 ] and Cobos-Gil [ 12 ]. In a study by Samol et al, 50 healthy individuals were enrolled and the similarity of 3-lead ECG recordings by an Apple Watch Series 4, encompassing Einthoven’s leads I to III, was compared to the same leads obtained by a standard ECG set [ 14 ]. This group of researchers further assessed their method of obtaining ECG with a smartwatch in a larger study of 100 patients [ 13 ] and another study of 50 healthy individuals [ 15 ].…”

“…Our systematic search of the Pubmed database with the following search terms “Apple Watch”, “Smartwatch”, “Electrocardiogram”, and “ECG” in August 2020 result in 79 records. However, the feasibility of recording a 3-lead ECG with the Apple Watch Series 4 was reported in only one case report of two patients with myocardial infarction [ 7 ], a technical report [ 12 ], and three observational studies from a same group of investigators [ 13 , 14 , 15 ]. The other available studies were related to the other capabilities of smart wearables, ranging from screening and diagnostic to treatment functions, using other technologies, namely photoplethysmography (PPG) [ 4 , 5 , 16 , 17 , 18 , 19 , 20 , 21 ].…”

“…Additionally, the possibility of generating 3-lead ECGs with smartwatches is yet to be confirmed in a large study with other study groups. In addition, a few studies have verified the ability of handheld ECG recorders to record different ECG leads [ 14 , 15 ], but the need for additional wires and adhesive ECG tabs have limited their use in practice.…”