A Web Application for Visualising and Interrogating the 12-lead Ecg

Introduction The ten-second 12-lead electrocardiogram (ECG) is the most commonly used tool for non-invasive cardiac assessment. Although many paper based methods in healthcare have been made redundant, the 12-lead ECG continues to be printed on standard graph paper. The reliance on paper as a medium to visualise the ECG means that collaboration and the sharing of data is not as straightforward. The limited resolution of the printed ECG has also, in the past, made it difficult to accurately measure intervals and amplitudes. These drawbacks provide rationale for research into alternative computer based interfaces that are more usable and intuitive to clinical staff. Methods In this study a multi-disciplinary team of experts involving ECG researchers, engineers and multimedia designers developed a Web based 12-lead ECG viewer. This viewer was developed using an iterative design approach as feedback was sought from potential users. The authors envisaged the Web to be a suitable platform for visualising the ECG since it would allow clinicians to share and remotely read ECGs independent of their geographical location. This viewer was developed using the Adobe Flash technology. This technology is a vector-based platform, which can be exploited to maintain the quality of the ECG waveforms when they are scaled. As a result, clinicians can view the ECG on multiple levels of detail and accurately measure intervals and amplitudes. This is a novel feature, as the ECG is commonly represented using raster graphics where the scalar traces distort when scaled. The developed viewer supports any 12-lead ECG that has been formatted using the Health Level Seven Annotated ECG (HL7 aECG) storage format. The HL7 aECG format is arguably the first ECG storage format that was developed using the eXtensible Markup Language (XML). HL7 aECG was chosen as the primary format since it is an interoperable open standard. Although the viewer is based on the Web, actual 12-lead ECG files can be loaded from local storage. This leaves fewer security risks, as the patient’s file is not uploaded to a server. Once the file has been loaded, the 12 leads are drawn onto a standard ECG grid using vector graphics. The user can switch the layout of the 12 leads from 1 column by 12 rows (1x12) to 4 columns by 3 rows plus 1 rhythm strip (4x3+1) using a drop down box. This is important, as different formats are often preferred in different clinical settings. The viewer supports drag and zoom functionality, allowing users to interrogate the ECG at a higher resolution. The viewer also provides interactive callipers for measuring intervals and amplitudes. The most elaborate feature of the viewer is the facility to define beat markers in a novel way. With this feature, the user can superimpose all 12 leads and use the mouse to drag vertical lines to fiducial points such as the QRS onset. The novelty being that whilst dragging these lines, the region of interest is scaled to a larger resolution, allowing for more accurate beat markers. Results and Conclusions The viewer has been tested to run on different operating systems (MAC and Windows XP) and in different Web browsers (Safari, Firefox, Internet Explorer). To insure interoperability and standard compliance the viewer has been tested by visualising a range of different HL7 aECG files. Further work will involve a usability study where clinicians will be asked to attempt a set of tasks whilst thinking out loud. This will identify the usability problems, which will help improve clinical interfaces. []