Single-Lead ECG Recordings Including Einthoven and Wilson Leads by a Smartwatch: A New Era of Patient Directed Early ECG Differential Diagnosis of Cardiac Diseases?

Abstract

Background: Smartwatches that are able to record a bipolar ECG and Einthoven leads were recently described. Nevertheless, for detection of ischemia or other cardiac diseases more leads are required, especially Wilson’s chest leads. Objectives: Feasibility study of six single-lead smartwatch (Apple Watch Series 4) ECG recordings including Einthoven (I, II, III) and Wilson-like pseudo-unipolar chest leads (Wr, Wm, Wl). Methods: In 50 healthy subjects (16 males; age: 36 ± 11 years, mean ± SD) without known cardiac disorders, a standard 12-lead ECG and a six single-lead ECG using an Apple Watch Series 4 were performed under resting conditions. Recording of Einthoven I was performed with the watch on the left wrist and the right index finger on the crown, Einthoven II was recorded with the watch on the left lower abdomen and the right index finger on the crown, Einthoven III was recorded with the watch on the left lower abdomen and the left index finger on the crown. Wilson-like chest leads were recorded corresponding to the locations of V1 (Wr), V4 (Wm) and V6 (Wl) in the standard 12-lead ECG. Wr was recorded in the fourth intercostal space right parasternal, Wm was recorded in the fifth intercostal space on the midclavicular line, and Wl was recorded in the fifth intercostal space in left midaxillary line. For all Wilson-like chest lead recordings, the smartwatch was placed on the described three locations on the chest, the right index finger was placed on the crown and the left hand encompassed the right wrist. Both hands and forearms also had contact to the chest. Three experienced cardiologists were independently asked to allocate three bipolar limb smartwatch ECGs to Einthoven I–III leads, and three smartwatch Wilson-like chest ECGs (Wr, Wm, Wl) to V1, V4 and V6 in the standard 12-lead ECG for each subject. Results: All 300 smartwatch ECGs showed a signal quality useable for diagnostics with 281 ECGs of good signal quality (143 limb lead ECGs (95%), 138 chest lead ECGs (92%). Nineteen ECGs had a moderate signal quality (7 limb lead ECGs (5%), 12 chest lead ECGs (8%)). One-hundred percent of all Einthoven and 92% of all Wilson-like smartwatch ECGs were allocated correctly to corresponding leads from 12-lead ECG. Forty-six subjects (92%) were assigned correctly by all cardiologists. Allocation errors were due to similar morphologies and amplitudes in at least two of the three recorded Wilson-like leads. Despite recording with a bipolar smartwatch device, morphology of all six leads was identical to standard 12-lead ECG. In two patients with acute anterior myocardial infarction, all three cardiologists recognized the ST-elevations in Wilson-like leads and assumed an occluded left anterior descending coronary artery correctly. Conclusion: Consecutive recording of six single-lead ECGs including Einthoven and Wilson-like leads by a smartwatch is feasible with good ECG signal quality. Thus, this simulated six-lead smartwatch ECG may be useable for the detection of cardiac diseases necessitating more than one ECG lead li...

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 ].…”

“…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 ]. Both of these two studies highlighted that the quality of 3-lead ECGs obtained by an Apple Watch Series 4 was adequate in more than ≈90% of the recordings, and Apple Watch ECGs were quite similar to standard ECG recordings.…”

“…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.…”