Relationship between graft patency, postoperative work status, and symptomatic relief.

In 405 men under the age of 65 requiring coronary bypass, in whom 6 month postoperative arteriograms were performed, we compared graft patency to postoperative work status and recurrent symptoms. We divided the population into subgroups of patients with varying degrees of patency. When these subgroups were tested, no significant dependence was found between the degree of graft patency and the percentages of patients who were working after operation, unless certain subgroups were removed from the population. When relief of angina was examined in the same manner as the postoperative work, we found a significant dependence between the graft patency and the percentage of patients who reported either short or long-term relief of angina in all groups. Because the rate of rehabilitation was high, even in patients with occluded grafts, and because older patients were less likely to return to work than younger patients despite successful revascularization, we conclude that physician emphasis on work rehabilitation and patient age, as well as graft patency, are all important factors which influence postoperative work status.

Conditional probability of multiple coronary graft failure.

To assess the potential capability of using artery-specific factors to predict the success of coronary bypass grafting, we classified each graft according to the type of graft (mammary, single vein, or multiple skip vein), the degree of obstruction in the native coronary artery, and the size of the grafted artery. The mean patency rates for each category of graft were determined by performing early postoperative (mean 6.6 months) arteriograms in 354 patients. We found that mammary arteries gave the best results for every graft category. Skip vein grafts had a higher mean patency rate than single vein grafts for arteries with obstructions between 70% and 90% and lumina less than 2.0 mm in diameter. The results for vein and skip grafts were equivalent for the category with arteries greater than 2.0 mm and obstruction greater than 90%. Vein grafts produced better results than skip grafts for the remaining categories. Patients were classified into subgroups according to the number of actually observed graft failures. The probabilities that specific numbers of grafts would fail were calculated for each patient. These probabilities were based upon the observed patency rates for the category appropriate for each graft and the hypothesis that individual grafts within a patient fail independently. We observed an excess number of patients with no failures or multiple failures than would be expected according to the hypothesis of independent failure and category-specific patency rates. Conversely, there were fewer patients than expected who had single failures. Therefore, we postulate that there may also be global factors which influence early graft patency.

Efficacy of chest radiography in a respiratory intensive care unit. A prospective study.

A prospective study of chest radiographic examinations in a respiratory intensive care unit was conducted to determine the diagnostic and therapeutic efficacy of such examinations. Analysis of data from 1,354 x-ray films from 167 patients revealed a 34.5 percent incidence of new (or increased) abnormalities, or tube or catheter malposition. Changes in diagnostic approach or therapeutic measures, excluding catheter position adjustments, occurred after 28.5 percent of the examinations. Radiographic yield was higher when a change in clinical condition prompted the radiographic examination than when the examination was a routine morning study. Changes in the approach to patient management were also more likely (42.7 percent) following examinations that were prompted by a change in a patient's clinical status. Less than 6 percent of the radiographic films taken post-procedure demonstrated abnormalities potentially related to the procedure. We conclude that, in a respiratory intensive care unit: routine morning radiographic examination frequently demonstrates unexpected or changing abnormalities, many of which prompt changes in diagnosis or management radiographic evaluation of a change in a patient's clinical condition has a higher yield than routine examinations; and post-procedure radiographic examination uncommonly demonstrates complications related to the procedure, but frequently demonstrates abnormalities of tube or catheter placement.

Preexamination prediction of radiographic findings.

Computerized medical logic has been developed to calculate the patient-specific pretest likelihood of pleural fluid for radiographic examinations. This medical logic was determined by searching the computerized data base for clinical indicants which are found to differ between groups of patients with and without pleural fluid. By using a priori probabilities of pleural fluid and sequential application of Bayes' equation to revise the likelihood according to the presence of significant indicants, patient-specific likelihood were calculated. This medical logic was tested on a group of 591 patients with and without pleural fluid by radiographic evidence. The results indicated a sensitivity of 95% and a specificity of 81%.

Privacy, confidentiality, and electronic medical records.

The enhanced availability of health information in an electronic format is strategic for industry-wide efforts to improve the quality and reduce the cost of health care, yet it brings a concomitant concern of greater risk for loss of privacy among health care participants. The authors review the conflicting goals of accessibility and security for electronic medical records and discuss nontechnical and technical aspects that constitute a reasonable security solution. It is argued that with guiding policy and current technology, an electronic medical record may offer better security than a traditional paper record.

Knowledge-based approaches to the maintenance of a large controlled medical terminology.

OBJECTIVE: Develop a knowledge-based representation for a controlled terminology of clinical information to facilitate creation, maintenance, and use of the terminology. DESIGN: The Medical Entities Dictionary (MED) is a semantic network, based on the Unified Medical Language System (UMLS), with a directed acyclic graph to represent multiple hierarchies. Terms from four hospital systems (laboratory, electrocardiography, medical records coding, and pharmacy) were added as nodes in the network. Additional knowledge about terms, added as semantic links, was used to assist in integration, harmonization, and automated classification of disparate terminologies. RESULTS: The MED contains 32,767 terms and is in active clinical use. Automated classification was successfully applied to terms for laboratory specimens, laboratory tests, and medications. One benefit of the approach has been the automated inclusion of medications into multiple pharmacologic and allergenic classes that were not present in the pharmacy system. Another benefit has been the reduction of maintenance efforts by 90%. CONCLUSION: The MED is a hybrid of terminology and knowledge. It provides domain coverage, synonymy, consistency of views, explicit relationships, and multiple classification while preventing redundancy, ambiguity (homonymy) and misclassification.

Internet as clinical information system: application development using the World Wide Web.

Clinical computing application development at Columbia-Presbyterian Medical Center has been limited by the lack of a flexible programming environment that supports multiple client user platforms. The World Wide Web offers a potential solution, with its multifunction servers, multiplatform clients, and use of standard protocols for displaying information. The authors are now using the Web, coupled with their own local clinical data server and vocabulary server, to carry out rapid prototype development of clinical information systems. They have developed one such prototype system that can be run on most popular computing platforms from anywhere on the Internet. The Web paradigm allows easy integration of clinical information with other local and Internet-based information sources. The Web also simplifies many aspects of application design; for example, it includes facilities for the use of encryption to meet the authors' security and confidentiality requirements. The prototype currently runs on only the Web server in the Department of Medical Informatics at Columbia University, but it could be run on other Web servers that access the authors' clinical data and vocabulary servers. It could also be adapted to access clinical information from other systems with similar server capabilities. This approach may be adaptable for use in developing institution-independent standards for data and application sharing.

Computer-generated informational messages directed to physicians: effect on length of hospital stay.

OBJECTIVE: With the advent of hospital payment by diagnosis-related group (DRG), length of stay (LOS) has become a major issue in hospital efforts to control costs. Because the Columbia-Presbyterian Medical Center (CPMC) has had above-average LOSs for many DRGs, the authors tested the hypothesis that a computer-generated informational message directed to physicians would shorten LOS. DESIGN: Randomized clinical trial with the patient as the unit of randomization. SETTING AND STUDY POPULATION: From June 1991 to April 1993, at CPMC in New York, 7,109 patient admissions were randomly assigned to an intervention (informational message) group and 6,990 to a control (no message) group. INTERVENTION: A message giving the average LOS for the patient's admission or provisional DRG, as assigned by hospital utilization review, and the current LOS, in days, was included in the main menu for review of test results in the hospital's clinical information system, available at all nursing stations in the hospital. MAIN OUTCOME MEASURE: Hospital LOS. RESULTS: The median LOS for study patients was 7 days. After adjustment for covariates including age, sex, payor, patient care unit, and time trends, the mean LOS in the intervention group was 3.2% shorter than that in the control group (p = 0.022). CONCLUSION: Computer-generated patient-specific LOS information directed to physicians was associated with a reduction in hospital LOS.

The rehabilitation of coronary surgical patients.

Coronary revascularization has been reported to have failed to effectively rehabilitate working-age patients. This study of 565 patients demonstrates that motivation to return to work is strongly influences by age and educational level. Patients under age 55 are more likely to return to work than are patients over that age, but preoperative job classification does not influence rehabilitation. Although preoperative disability was associated with a slightly lower return-to-work rate (90%) than was the case with patients working preoperatively (97%) preoperative retirement was a strongly negative influence on rehabilitation. In this study, 80% of the patients worked to or beyond retirement age, and duration of work was not influenced by preoperative disability. The salary produced by those patients who were rehabilitated by surgery was four and a half times greater than the total cost of care and disability payments for the entire patient population. The factors which seemed to be the most important in effective rehabilitation were the psychological preparation of patients and their families and the attitude toward rehabilitation expressed by physicians and employers.

Coronary bypass surgery early after thrombolytic therapy for acute myocardial infarction.

The safety of coronary bypass operations after coronary reperfusion with streptokinase for acute myocardial infarction is not well documented. Therefore we studied 23 consecutive patients (mean age, 59.5 years; 22 men) undergoing bypass operations a median of 5 days (range, 1 to 23 days) after thrombolysis (streptokinase). The control group consisted of 169 concurrent patients of similar mean age (58.8 years) having bypass operations for standard indications. The preoperative angiographic ejection fraction was 68 +/- 14% in the control patients and 61 +/- 14% in the streptokinase group (p less than 0.05). The number of diseased vessels (70% stenosis or greater) averaged 2.6 in control and 2.3 in streptokinase patients. A previous myocardial infarction had occurred in 42% of the controls and all of the streptokinase patients. Aortic cross-clamp times did not differ between the two groups (80 +/- 35 minutes for the controls and 68 +/- 25 minutes for the streptokinase group). Cardiopulmonary bypass times were similar: 108 +/- 45 minutes in the controls versus 109 +/- 28 minutes in the streptokinase group. Grafts per patient averaged 3.7 +/- 1.5 for the controls versus 2.8 +/- 1.1 for the streptokinase patients (p less than 0.01). Difficult operative hemostasis was noted in 4% of both groups. Inotropic support was given postoperatively to 11% of the control and 13% of the streptokinase patients (p = not significant). Measured blood loss during the first 48 hours postoperatively was similar, averaging 809 ml in controls and 776 ml in the streptokinase group. Blood product replacement was also comparable: mean, 713 ml in the control group versus 759 ml in the streptokinase group.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of motion on quantitative vessel measurements.

Optimal visualization of moving structures such as the heart and coronary arteries using digital radiographic imaging systems is a difficult problem that can involve tradeoffs between temporal, spatial, and density resolution. The motion dependence of four angiographic measures of vessel dimensions is given and demonstrated experimentally. Although the densitometric cross-sectional area is shown to be independent of motion, densitometric thickness (contrast) decreases and the apparent width (distance between edges) and densitometric width both increase with motion. Knowledge of the velocity allows the apparent width but not the densitometric width to be corrected. It is also shown that current limitations which result in tradeoffs between kVp and x-ray pulse duration seriously compromise the advantages of using small focal spots in coronary artery imaging.

Revision of diagnostic logic using a clinical database.

Statistical pattern-recognition techniques have been frequently applied to the problem of medical diagnosis. Sequential Bayesian approaches are appealing because of the possibility of generating the underlying sensitivities, specificities, and prevalence statistics from the estimates of medical experts. The accuracy of these estimates and the consequences of inaccuracies carry implications for the future development of this type of system. In an effort to explore these subjects, the authors used statistics derived from a clinical database to revise the diagnostic logic in a Bayesian system for generating a differential diagnostic list. Substantial changes in estimated a priori probabilities, sensitivities, and specificities were made to correct for significant under- and overestimations of these values by a group of medical experts. The system based on the derived values appears to perform better than the original system. It is concluded that the statistics used in a Bayesian diagnostic system should be derived from a database representative of the patient population for which the system is designed.

Bringing HELP to the clinical laboratory--use of an expert system to provide automatic interpretation of laboratory data.

In domains where the types of data which are to be interpreted are relatively constrained (as in the case of specific laboratory test results), our modular data-driven approach can be very productive and well received by the clinical recipient of the data. The computer rarely surpasses the knowledge of an experts result from lack of communication, imperfect memory, oversight or multiple decision-makers caring for the same patient. In such cases, most of the alerts are immediately recognized as valid, so the need for elaborate explanations is not a high priority. On the other hand, a non-specialist is alerted to the need for additional investigation, tests or collaborative support, by the fact that a reminder or diagnosis that s/he had not previously considered, appears. In other words, for the expert, a data-driven system provides unceasing oversight in high-volume low-yielded situations where a small number of mistakes may uncommonly occur for reasons which are not related to the lack of knowledge of the provider. For the non-specialist the system suggests that the patient may have problems in a domain for which the physician needs additional support. In the present state of the art, we do not think that total reliance on the computer-contained knowledge is the ultimate source of this additional support; providing the awareness of the need may be the most important contribution. Once you know that you need help, it is usually obtainable. In a discussion about how computer systems have failed, Friedman and Gustafson made the following observation.(ABSTRACT TRUNCATED AT 250 WORDS)

Integrated Advanced Medical Information Systems (IAIMS): payoffs and problems.

IAIMS (Integrated Advanced Information Management Systems) is an initiative to improve the access to information needed to provide patient care, health-oriented education, biomedical research, and management of large medical center environments. This paper will review the goals, history, and accomplishments of the IAIMS initiative. Shortcomings and frustrations, lessons learned, and the future of such initiatives will also be discussed.

Building a comprehensive clinical information system from components. The approach at Intermountain Health Care.

OBJECTIVES: To discuss the advantages and disadvantages of an interfaced approach to clinical information systems architecture. METHODS: After many years of internally building almost all components of a hospital clinical information system (HELP) at Intermountain Health Care, we changed our architectural approach as we chose to encompass ambulatory as well as acute care. We now seek to interface applications from a variety of sources (including some that we build ourselves) to a clinical data repository that contains a longitudinal electronic patient record. RESULTS: We have a total of 820 instances of interfaces to 51 different applications. We process nearly 2 million transactions per day via our interface engine and feel that the reliability of the approach is acceptable. Interface costs constitute about four percent of our total information systems budget. The clinical database currently contains records for 1.45 m patients and the response time for a query is 0.19 sec. DISCUSSION: Based upon our experience with both integrated (monolithic) and interfaced approaches, we conclude that for those with the expertise and resources to do so, the interfaced approach offers an attractive alternative to systems provided by a single vendor. We expect the advantages of this approach to increase as the costs of interfaces are reduced in the future as standards for vocabulary and messaging become increasingly mature and functional.

Encoding a post-operative coronary artery bypass surgery care plan in the Arden Syntax.

The Arden Syntax for medical logic modules (Arden) was used to test the feasibility of encoding large, complex care plans. The critical portions of an existing paper-based care plan for the management of patients following coronary artery bypass graft (CABG) surgery were encoded in Arden and an X-windows user-interface was developed. The Arden Syntax proved adequate for encoding all of the necessary functions of the care plan. The limitations of the current Arden Syntax and possible additions to Arden are discussed.

Design and implementation of a multi-institution immunization registry.

One of every four children in the USA is underimmunized. Surveys of children in New York City have documented rates of appropriate immunization as low as 37% in certain populations in northern Manhattan. In response to this, government and private agencies have undertaken efforts to improve immunization rates. As part of one such multiinstitution effort in northern Manhattan, we have begun implementation of a computer-based immunization registry. Key features of this registry system include adaptation of legacy software in order to perform initial capture of data in electronic format; design of a user interface using a World Wide Web server that provides data review and capture functions with appropriate security; implementation of a registry database with links to the server, communication links between hospital registration systems, a Master Patient Index, community providers and the central registry; and integration of decision support in the form of Medical Logic Modules encoded in the Arden Syntax. We discuss our design of this multi-institution immunization registry and implementation efforts to date.

ASTM E31.15 on health knowledge representation: the Arden Syntax.

ASTM subcommittee E31.15 on Health Knowledge Representation was formed to promote standards for defining and sharing health knowledge bases. Its first standard, the Ardan Syntax, is focused on knowledge bases that can be represented as a set of independent modules called Medical Logic Modules (MLMs). The standard is in clinical use and has generated significant interest in industry and academics. The Extensions task group plans to extend the syntax where appropriate, to expand to other types of knowledge bases. The Validation/Verification task group is approaching the enormous problem of evaluating knowledge bases and the process of sharing them.

Dialogue. Privacy protection: paper or computer records? Confidentiality of healthcare records.

In summary, security concerns surrounding health data are justified, but solutions are surmountable with currently available technologies. Whether systems are paper or electronic, human factors such as errors, negligence and unethical activities can result in breaches of confidentiality, despite optimal implementations. Neither automated teller machines (ATMs) nor EMRs are free from instances of abuse, but policies and protocols for electronic systems can be implemented that may provide better security than analogous paper record systems.