Einthoven and precordial lead accuracy of smartwatch-acquired electrocardiographs : A review of the literature

Introduction
This review aims to summarise the literature regarding the ability of commercial smartwatch products to produce an electrocardiograph of diagnostic quality for interpreting Einthoven and precordial leads.

Methods
PubMed, Embase, MEDLINE Complete, Web of Science, and Scopus were systematically searched. Articles were screened by a sole investigator against the inclusion criteria – first by title, then abstract, then full text. The reference lists of included articles were also screened. The inclusion criteria were: discussion of smartwatch-acquired tracing of Einthoven or precordial lead accuracy, and demonstrating sufficient rigor when undergoing critical appraisal using the Joanna Briggs Institute evaluation tools. A synopsis of results was provided in a summary of information table.

Results
Twelve articles were identified for inclusion, nine of which had physician (cardiology or emergency specialty) evaluation of tracings, one of which had statistical comparison of wave duration and amplitude, and two of which were expert commentary. Only evaluations of Apple Watch products were discovered during the literature search. All leads in all studies were considered suitable for interpretation, with no clinically significant differences. Four studies found that 100% of patients were able to accurately use a smartwatch as an electrocardiogram after a brief tutorial.

Conclusion
The current early evidence, based largely on visual evaluations by cardiologists during the previous year, suggests that electrocardiograph abnormality recorded by this technology is sufficiently precise to be presumed accurate until proven otherwise.