Utility and Accuracy of Online Schematics That Illustrate ECG Electrode Positions

The 12-lead Electrocardiogram (ECG) is one of the most widely used diagnostic tests for assessing patients. It is routinely used to determine the cardiac state of person’s heart. Nevertheless, 12-lead ECG acquisition requires precise placement of 6 chest electrodes and 4 limb electrodes. It has been reported that 36% of electrodes are misplaced and that an electrode misplacement can cause a misdiagnosis and result in inefficient therapy. And given students and clinicians often use Internet resources to assist in the recording of clinical procedures; we decided to assess the veracity of Google images. In particular, we assessed those online images that could potentially be used by clinicians to guide the positioning of ECG electrodes.Objective: To determine the utility and accuracy of online images that illustrate ECG electrode positionsMethods:Common search criteria was defined as “ECG electrode positions”. The top 42 relevant images that illustrate ECG electrode placement were scrapped from Google images in the web browser. Six expert delegates from the International Society of Computerised Electrocardiolgy (San Jose, California) independently reviewed and assessed each of the images. Using a rating scale (where 1 is negative and 10 is positive), each expert rated the usefulness and the accuracy of electrode positions as illustrated in each of the schematics. They were also asked to identify which electrodes were wrongly positioned in each image.Results:Fleiss' generalized kappa coefficient indicates a slight agreement between how experts rated the usefulness (Pa = 0.2) and the accuracy (Pa = 0.17) of each image respectively. Out of the 10-point rating scale, the images were on average rated 4.07 (SD=1.89) for accuracy and 4.02 (SD=1.94) for usefulness. The ratings given for usefulness and accuracy did have a strong correlation as expected (r > 0.9 [Pearson’s correlation coefficient]). The most useful image according to the experts was rated as 7.2 (SD=1.72). This image can be found online [tinyurl.com/ns9xofp] and is returned as the fourth item as a result of the Google image-ranking algorithm. However the most useful image was not rated as the most accurate image. In terms of electrode positioning, the most accurate image according to the experts was rated as 7.2 (SD=2.48). And this image can also be found online [tinyurl.com/pc57vyb] and is returned as the 28th item as a result of the Google image-ranking algorithm.Conclusions:All experts in this study agree that the quality of these web-based images that illustrate ECG acquisition is poor. Neither the accuracy of electrode positions or the utility of the schematics are suitable to guide clinicians in the accurate recording of the 12-lead ECG. Clinicians should be careful with regards to which web-based image they decide to use as an adjunct in clinical practice.