Archiving and exchange of digital ECGs: A review of existing data formats

Digital ECG is today a common practice but a universal format for its storage and exchange has never been widely implemented. The reason is linked on one side to the need of the manufacturing industry to (rightly) protect intellectual propriety and technology, but on the other to an inadequate effort of the research community to sufficiently enforce the use of digital ECG data. To some degree, and at least from a practical point of view, the problem is also linked to other factors, such as the need in some instances to protect patient-sensitive information, and whether digital exchanged data should also include annotations and measurements from an algorithm or by human intervention. As a result, after more than 30 years it is still common that the full ECG acquired information is not preserved, but only partially stored or saved as a PDF report. Paradoxically, the modern era of hospital information technology and the advent and large diffusion of electronic health record systems did not bring expected improvements: the process of digital ECG retrieval and management remains extremely complicated and cumbersome. The ultimate risk is that the ECG may end up being considered "just" an image rather than a voltage-versus-time signal as it has always been. A critical review of the most commonly used formats for digital ECG will be given, focusing in particular to those linked with DICOM, HL7 and SCP-ECG standards, and highlighting the respective advantages and limitations with special emphasis to the needs typically encountered by the research community. The goal is to provide a snapshot of the present, and to discuss mid- and long-term potential directions and changes, emphasizing what digital ECG organizations could do to "save" ECG information and facilitate its widespread exchange.