Construction and Application of an Electronic ECG Management System

Transcription

1 Construction and Application of an Electronic ECG Management System Chia-Cheng Chiang Cathay General Hospital/Hsinchu Branch/Emergency Department National Chiao Tung University/Department of Electrical and Control Engineering Wen-Ching Tzeng* Chung Hua University/Department of Bioinformatics Han-Chin Cheng Chung Hua University/Department of Bioinformatics Wei Gong Memorial Hospital Chin-Teng Lin National Chiao-Tung University/Department of Electrical and Control Engineering Ya-Chu Yang Chung Hua University/Department of Bioinformatics Sheng-Fu Liang University System of Taiwan/Brain Research Center Soon-Bock Lim Ching Chyuan General Hospital/Emergency Department Abstract Background and Purpose: Electrocardiogram (ECG) is one of the most used non-invasive and low-cost diagnostic examinations in clinical practice. Most hospitals use plain paper for ECG recording and storage. In modern hospitals, medical data need to be digitized for efficient management. The primary objective of this study was to develop an electronic 12-lead ECG database management system for a local hospital. Methods: The system was developed by using PHP, MySQL, and Matlab for file transmission, format conversion, record storage, and signal analysis of SCP-ECG records. Computerized ECG data were collected in a local hospital since August Open-source formats (XML, SVG, PNG) were transformed for further application and representation of ECG. Results: (1) more than ten thousands complete ECG files were collected; (2) ECG files were transformed into FDA_XML, ecgml, SVG and PNG formats through the established server; (3) a disease-specific database was established; (4) physicians and researchers can review and analyze ECG via this database system. Conclusions: The established electronic ECG management system can provide effective ECG informatics services to aid diagnosis for clinical physicians and ECG signal processing for researchers. In the future, studies will be done on other medical signals such as holter ECG, exercise ECG, patient monitor, and phenocardiogram. The establishing of an inter-hospital medical signal database will also be investigated. Key word: Computerized, Database, ECG, SCP, XML * Corresponding author. 135

2 1. Introduction ECG is one of the most essential non-invasive diagnostic examination methods; it is a low cost procedure wich makes early diagnosis of heart-related diseases possible. It s the most common emergency cardiological examination used in healthcare. Currently, ECGs are mainly done on plain paper. The paper ECG has many disadvantages: poor maintenance, low availability, and inferior interoperability. To overcome these drawbacks and enhance usability of ECG, its digitization is necessary. Computerized ECG has been developed for decades. To facilitate the compatibility of the data of different electrocardiographs, the OpenECG project has been promoting SCP-ECG (Standard Communications Protocol for Computer-Assisted Electrocardiography) format for decades[1]. However, most ECG equipment manufacturers use proprietary protocols for data communication and storage. Some researchers have developed hard copy or scanning methods for converting paper ECGs into electronic format[2,3]. However, poor resolution and tedious manual processes have been the major impediment to their applicability. To facilitate the acquisition of raw ECG data and to promote the usage of open-source ECG formats, an SCP-compatible ECG decoding program was designed in a previous study[4]. This decoding program obtains SCP-related ECG data from clinical electrocardiographs and then transmits them to a web server. A web-based electronic ECG management system was developed and applied in a clinical environment over the past two years. 2. Materials and Methods 2.1 Materials SCP-compatible files were collected from the Emergency Department of the Wei-Gong Memorial Hospital in Miao-Li County in Taiwan. The collecting time was from August 2003 to July The ECG cart used in this study was a Philips/Agilent PageWriter M1770A Cardiograph with an Option #A05 storage package. The ECG records were transmitted to the local host by a RS232 cable. 2.2 ECG Database Management System (EMS) A three-tier architecture model, which has been an industry standard for decades and has been used in many studies[5,6], was applied for the system implementation. The database was based on MySQL and Windows OS with a web-based front-end interface. The ECG data were managed with a MySQL database management system (DBMS). Temporal data and ECG waveform data were stored in the Windows built-in file-directory system. Open source software was used for system implementation dependent upon maintenance cost, stability and efficiency. The backbone of this system was Apache, PHP and MySQL, all freeware but with satisfactory performance. The base of the system (first-tier) consisted of the MySQL DBMS and a file-directory system. The file-directory structure was modified to meet the needs of the MySQL database and the PHP scripts. On top of first-tier was the second-tier, which was implemented with Apache and PHP. This was the core component of the system. Apache was used as web server to facilitate communications between each sub-system. PHP was the preprocessor used for logic interpretation of web applications. Commands for each sub-system were interpreted and processed by PHP and then passed to the Apache server for web representation. Finally, web-browsers formed the third-tier for end-users (clients) via the Internet. Figure 1 illustrates the three-tier architecture of the web-based electronic ECG management system. Figure 1: The three-tier architecture of the web-based electronic ECG management system 2.3 Database schema The ECG database system is a relational database management system (RDBMS). As shown in Figure 2, seven tables were established under this schema. Figure 2: Schema of the ECG database system 136

3 2.4 File-Directory System For the flexibility and performance of the database system, only the index/indices to individual files is/were stored in the database. Large chunks of biomedical data were stored in separate files using an ASCII-based file format (.tx0,.tx1,.tx2). This file-directory system was built on the Windows operation system. Waveform data generated from 2.5 seconds standard 12-lead and 10 seconds long-lead rhythm were stored in filename.tx1 and filename.tx2, respectively. The path for each file was recorded in the database system. For further inter-hospital data exchange, the hospital and department codes were stored in the database. The decoded files (.tx0,.tx1,.tx2) and related files (such as.png,.xml,.svg, etc.) were stored in corresponding sub-directories. As shown in Figure 3, the file-directory system was organized in a tree structure. Figure 4: Information stored in the MySQL database. 3.2 Web Server Interface A user-friendly, easy-to-use web interface (WebECG) was developed[7]. Authorized end-users can log in the system and browse the database. Figure 5 shows the query function of the EMS system. Figure 5: Query function of the EMS system Figure 3: Tree structure of the file-directory system 2.5 Data format exchange ECG raw data were stored in EMS in the ASCII format. In order to meet the needs of clinical physicians and academic researchers, several open-source ECG formats, such as XML (FDA-XML or ecgml), SVG, and PNG, were used to exchange ECG information. 3 Results 3.1 ECG database More than ten thousand complete 12-lead ECG files were collected over the past two years. As shown in Figure 4, some useful information decoded from SCP file was stored in the MySQL database. There are two ways an end-user can query the database: (1) query by patient id; (2) query by date. Figure 6 shows the results of a query by a patient id. Figure 6: Results of a query by patient id (pid) 3.3 Data format exchange Four open-source ECG-related formats were generated by this system including FDA_XML, ecgml, SVG, and PNG Rendering ECG with XML An XML-related format has been recommended by the Food and Drug Administration (FDA) for annotated ECG waveform data since November 2001[8,9]. An FDA_XML format was developed using the HL7 Version 3 standard[10,11]. Figure 7 shows the FDA_XML document generated by this ECG management system. 137

4 Figure 7: FDA_XML document of an ECG shown in IE6.0 with MSXML4.0 plug-in An FDA_XML viewer downloaded from AMPS LLC website can be used to visualize the FDA_XML file[11,12]. Figure 8 shows the FDA_XML document of an ECG represented by the FDA_XML viewer Rendering ECG with SVG In order to represent ECG waveform data on the web, some graphic formats were used for viewing and transmitting. SVG and PNG are the most popular formats and have been recommended by World Wide Web Consortium (W3C)[14]. For this study PNG was chosen as the raster image output format and SVG as the scalable vector image output format. Comprehensive documentation and support of these two formats are available on the W3C website and Internet. A standalone SVG document was generated online by the system. Figure 10 shows the SVG document of an ECG represented by the Adobe SVG viewer using IE6.0 with Adobe viewer 3.0 plug-in[15]. Figure 10: SVG document of ECG represented by the Adobe SVG viewer using IE6.0 Figure 8: FDA_XML document of an ECG represented by the FDA_XML viewer An alternative XML format for ECG is ecgml, which was developed by Wang et al and had a simpler structure[13]. Figure 9 shows an ecgml document represented by the ecgml browser. A PNG file was also generated online by the system. Figure 11 shows the PNG graphic representation of an ECG using IE6.0. Almost all web browsers support the PNG format, including Netscape and Internet Explore. Authorized end-users can review the ECG records stored in the database worldwide via the PNG format. Figure 9: ecgml document represented by the ecgml browser Figure 11: PNG file representation of ECG using IE

5 3.3.3 Specific Disease Database During the past two years, three specific disease databases have been established from the clinical data: (1) Hyperkalemia: 67 records (2) Hypokalemia: 80 records (3) AMI: 98 records Every case was diagnosed and reviewed by clinical physicians to confirm the diagnosis. Related clinical data and laboratory examinations, such as electrolyte concentrations (sodium and potassium for hyper- or hypo-kalemia), and cardiac enzymes (CPK, MB, and Troponin-I for AMI), were collected from the results of laboratory tests. 4. Discussion A web-based electronic ECG management system, which offers multifaceted solutions for managing ECGs, such as stability, compatibility, accessibility, flexibility, user-friendly interface and easy-to-maintain properties, was developed. Open source freeware with good performance and stability, such as Apache, PHP and MySQL, were used to minimize maintenance cost. No all-purpose, efficient, user-friendly, and unified format for ECG data is available yet. The choice of format depends on the domain of researchers application[16]. The XML related format (including FDA_XML, ecgml, and SVG) is a well-formed format, since it is derived from Standard Generalized Markup Language (SGML) and verified by W3C. At present, it seems that the XML format is preferred for the ECG format. FDA_XML is well-defined by HL7 and recommended by FDA[8,9]. A viewer with multiple functions has been developed for FDA_XML format representation of an ECG[12]. However, the FDA_XML is designed for dealing with various biological signals, and it is not specifically tailored for ECG. Hence, not only is the format of the FDA_XML for ECG complex, but the vocabulary of FDA_XML does not conform to the traditional nomenclatures of the ECG. To overcome these drawbacks, ecgml was proposed in 2003[13]. Simplicity, flexibility and extensibility are major advantages of ecgml. A primitive ecgml browser with simple functions was developed. However, the applicability of the ecgml browser is limited, because only three leads can be seen in the browser at the same time, and the quality and precision are less than that of the FDA_XML viewer. SVG, an extension of XML file format, has been recommended by W3C[17] and widely used by many institutes for graphic representation of data in XML files. It does not only reserve all information of the raw ECG data but also provides an interactive function via a properly designed viewer. The powerful functionality offered by an SVG viewer makes it an attractive alternative of ECG format. Some ECG signal analysis modules, such as ECG characteristic points detection and RR wave detection, have been developed successfully in a previous study[4]. Until now, the developed modules have not been integrated into other components such as XML or SVG for further analysis. Since FDA_XML and ecgml both support annotation of an ECG waveform, the results of the signal analysis can be embedded in the XML-related ECG files. Integration of these analysis modules with other components enhances the functionality of the studied ECG management system. Although more then ten thousands ECG records have been stored in the database, only three disease-specific databases have been established. The process of disease database establishment is tedious and time-consuming because the collection of the clinical data is done mainly manually. The process can be accelerated, if this system can communicate with or be integrated into the Hospital Information System (HIS). In conclusion, the established electronic ECG management system can provide effective ECG informatics services such as online ECG pattern recognition to aid diagnosis for clinical physicians and ECG signal processing and analysis for researchers. The design and development of this web-based electronic system is an important component in providing better and more efficient online ECG data management. With the addition of signal analyzing modules, the system can serve as a diagnosis-aid for physicians and as an analysis platform for researchers. The format exchanging programs developed in this study can enhance the interoperability of ECG data. Other medical signals such as holter ECG, exercise ECG, patient monitor, and phenocardiogram could be studied in future. Other possible studies could include intra-hospital integration systems, for example communication with HIS, interaction with Picture Archiving and Communication System (PACS) and integration with Electronic Patient Record (EPR). Eventually, a country-wide inter-hospital medical signal database should be aimed at. Acknowledgements This project is granted by NSC (National Science Council, NSC E and NSC E ), Taiwan. Our gratitude is extended to Shih-Ming Shieh, M.D., the head of Wei-Gong Memorial Hospital, who generously assisted our research. Finally, we thank for the funding and support provided by Chung Hua University, Taiwan. 139

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