Veterans health information systems and technology architecture
The Veterans Health Information Systems and Technology Architecture (VistA) is an enterprise-wide information system built around an electronic health record, used throughout the United States Department of Veterans Affairs (VA) medical system, known as the Veterans Health Administration (VHA).  By 2001, the VHA was the largest single medical system in the United States, providing care to 4 million veterans, employing 180,000 medical personnel and operating 163 hospitals, over 800 clinics and 135 nursing homes.  By 2008, VA was providing electronic health records capability for over 8.9 Million active patients. VistA is thereby one of the most widely used EHRs in the world.

# Features
The Department of Veterans Affairs (VA) has had automated data processing systems within its medical facilities since before 1985,  beginning with the Decentralized Hospital Computer Program (DHCP) information system, including extensive clinical and administrative capabilities. In 1995, DHCP was enshrined as a recipient of the Computerworld Smithsonian Award for best use of Information Technology in Medicine.
VistA supports both ambulatory and inpatient care, and includes several significant enhancements to the original DHCP system. The most significant is a graphical user interface known as the Computerized Patient Record System (CPRS) for clinicians released in 1997. In addition, VistA now includes computerized order entry, bar code medication administration, electronic prescribing and clinical guidelines.
CPRS provides a client-server interface for health care providers to review and update a patients electronic medical record. This includes the ability to place orders, including medications, special procedures, x-rays, patient care nursing orders, diets, and laboratory tests. CPRS is flexible enough to be implemented in a wide variety of settings for a broad spectrum of health care workers and provides a consistent, event-driven, Windows-style interface.
For its development of VistA, the Department of Veterans Affairs (VA) / Veterans Health Administration (VHA) was named the recipient of the prestigious Innovations in American Government Award presented by the Ash Institute of the John F. Kennedy School of Government at Harvard University in July, 2006.
The adoption of VistA has allowed the VA to achieve a pharmacy prescription accuracy rate of 99.997%, and the VA outperforms most public sector hospitals on a variety of criteria, enabled by the implementation of VistA.
The VistA system is public domain software, available through the Freedom Of Information Act directly from the VA website, or through a growing network of distributors. The VistA Software Alliance is a non-profit trade organization that both promotes the widespread adoption of versions of VistA for provider environments.
VistA was developed using the M or MUMPS language/database. The VA currently runs a majority of VistA systems on InterSystems Cache. VistA can also run on GT.M, an open source database engine for Linux and Unix computers. Although initially separate releases, publicly available VistA distributions are now often bundled with the database in an integrated package. This has considerably eased installation.

# VistA Imaging
The Veterans Administration has also developed VistA Imaging, a coordinated system for communicating with PACS (radiology imaging) systems and for integrating others types of image-based information, such as EKGs, pathology slides, and scanned documents, into the VistA electronic medical records system. This type of integration of information into a medical record is critical to efficient utilization.
VistA Imaging has been made freely available in the public domain for private/public hospital use through the Freedom of Information Act. It is available through the Department of Veteran's Affairs software request office.
It can be used independently or integrated into the VistA electronic health record system (as is done in VA health facilities).

# Role in development of a national healthcare network
The VistA electronic healthcare record has been widely credited for reforming the VA healthcare system, improving safety and efficiency substantially. The remarkable results have spurred a national impetus to adopt electronic medical records similar to VistA nationwide.
VistA Web collectively describes a set of protocols that in 2007 was being developed and used by the VHA to transfer data (from VistA) between hospitals and clinics within the pilot project. This is the first effort to view a single patient record so that VistA becomes truly interoperable among the 128 sites running VistA today.
BHIE enables real-time sharing of electronic health information between DoD and VA for shared patients of allergy, outpatient pharmacy, demographic, laboratory, and radiology data. This became a priority during the Second Iraq War, when a concern for the transition of healthcare for soldiers as they transferred from active military status to veteran status became a national focus of attention.
Clinical Data Repository/ Health Data Repository or CHDR supports interoperability between DoDs Clinical Data Repository (CDR) & VAs Health Data Repository (HDR). Represents the development of interoperability between the DoD Clinical Data Repository (CDR) and Health VA Data Repository (HDR). It leverages DoD AHLTA experiences and lessons learned and provides the cornerstone for interoperability between electronic health records for DoD and VA
The first phase will include bidirectional real time exchange of computable pharmacy, allergy, demographic and laboratory data. In Phase 2 additional Drug  Drug interaction checking and Drug  Drug Allergy interaction checking will be added.
As of March 2007, Completed deployment at El Paso, Augusta, Pensacola, Puget Sound, Chicago, San Diego, and Las Vegas.
The combination of VistA and the interoperable projects listed above in the VA/DoD systems will continue to expand to meet the objectives of President Bush's statements that all citizens will have an electronic record by 2014.
The VHA has also started a pilot project, known as HealtheVet (HeV) that is the next generation of VistA. Preliminary plans have begun for the vision of HeV that evolve around moving away from the MUMPS and Delphi coding and towards more state of the art programming languages and enhanced functionality.
MyHealtheVet is another initiative that allows veterans to access, and create a copy of, their health records online. A national release of the project is underway. This will allow veterans to port their health records to institutions outside the VA health system or keep a personal copy of their health records, a Personal Health Record (PHR).
Because of the success of these programs, a national move to standardize healthcare data transmission across the country was started. Text based information exchange is standardized using a protocol called HL7  (Health Level 7), which is approved by the American National Standards Institute. DICOM is an international image communications protocol standard. VistA is compliant with both.
VistA has been interfaced with commercial off-the-shelf products. Standards and protocols used by VA are consistent with current industry standards and includine: HL7, DICOM, and other protocols.

# Usage in non-governmental hospitals
Under the Freedom of Information Act (FOIA), the VistA system, the CPRS interface (a CPOE), and unlimited ongoing updates (500-600 patches per year) are provided as public domain (but not free and open source) software.
This was done by the US government in an effort to make VistA available as a low cost electronic medical record system (EMR / EHR) for non-governmental hospitals and other healthcare entities.
It has been adopted by companies such as OHUM,Blue Cliff, DSS, Inc., and Medsphere, to a variety of environments, from individual practices to clinics to hospitals, to regional healthcare co-ordination between far-flung islands. In addition, VistA has been adopted within similar provider environments worldwide. Universities, such as UC Davis and Texas Tech implemented these systems.
VistA as other EMR/EHR systems can be interfaced with other healthcare databases not initially used by the VA system, including billing software, lab databases, and images databases (radiology, for example).

# Supporters of VistA
There have been many champions of VistA as the electronic healthcare record system for a universal healthcare plan. VistA can act as a standalone system, allowing self-contained management and retention of healthcare data within an institution. Combined with BHIE (or other data exchange protocol) is can be part of a peer-to-peer model of universal healthcare. It is also scalable to be used as a centralized system (allowing regional or even national centralization of healthcare records). It is, therefore, the electronic records system most adapatable to a variety of healthcare models.
In addition to the unwavering support of congressional representatives such as Congressman Sonny Montgomery of Mississippi, numerous IT specialists, physicians, and other healthcare professionals have donated significant amounts of time in adapting the VistA system for use in non-governmental healthcare settings.
The ranking member of the House Veterans Affairs Committees Oversight and Investigation Subcommittee, Rep. Ginny Brown-Waite of Florida, recommended that the Department of Defense (DOD) adopt VAs VistA system following accusations of inefficiencies in the DOD healthcare system. The DOD hospitals use Armed Forces Health Longitudinal Technology Application (AHLTA) which has not been as successful as VistA and has not been widely adapted to non-military environments, as VistA has.
In November 2005, the U.S. Senate passed the Wired for Health Care Quality Act, introduced by Sen. Enzi of Wyoming with 38 co-sponsors, that would require the government to use the VAs technology standards as a basis for national standards allowing all health care providers to communicate with each other as part of a nationwide health information exchange. The legislation would also authorize $280 million in grants, which would help persuade reluctant providers to invest in the new technology. There has been no action on the bill since December 2005. Two similar House bills were introduced in late 2005 and early 2006; no action has been taken on either of them, either.