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Biomedical subjects

J H van Bemmel

Publications and source records attributed to J H van Bemmel.

At least 19 recordsLinked to original sources
PubMed2001

Assessment of decision support for blood test ordering in primary care. a randomized trial.

BACKGROUND: Different methods for changing blood test-ordering behavior in primary care have been proven effective. However, randomized trials comparing these methods are lacking. OBJECTIVE: To compare the effect of two versions of BloodLink, a computer-based clinical decision support system, on blood test ordering among general practitioners. DESIGN: Randomized trial. SETTING: 44 practices of general practitioners in the region of Delft, the Netherlands. PARTICIPANTS: 60 general practitioners in 44 practices who used computer-based patient records in their practices. INTERVENTION: After stratification by solo practices and group practices, practices were randomly assigned to use BloodLink-Restricted, which initially displays a reduced list of tests, or BloodLink-Guideline, which is based on the guidelines of the Dutch College of General Practitioners. MEASUREMENTS: Average number of blood tests ordered per order form per practice. RESULTS: General practitioners who used BloodLink-Guideline requested 20% fewer tests on average than did practitioners who used BloodLink-Restricted (mean [+/-SD], 5.5 +/- 0.9 tests vs. 6.9 +/- 1.6 tests, respectively; P = 0.003, Mann-Whitney test). CONCLUSIONS: Decision support based on guidelines is more effective in changing blood test-ordering behavior than is decision support based on initially displaying a limited number of tests. Guideline-driven decision support systems can be effective in reducing the number of laboratory tests ordered by primary care practitioners.

Decision Support Techniques↗
PubMed2001

Employment of intra-individual variability to improve computerized ECG interpretation.

One of the reasons for the limited practical utility of computer programs for interpretation of electrocardiograms (ECGs) is their susceptibility to intra-individual variability. Two of the most prominent sources of intra-individual variability in ECGs, electrode placement variations and respiration, were studied for their effects on computerized ECG interpretation. Previous research has shown that the effects of intra-individual variability on computerized ECG interpretation depend largely on the individual ECG. To enable the assessment of chest electrode position variations for individual standard 12- lead ECGs, ECGs resulting from simulations of such position variations were interpreted. Variability due to respiration was assessed by interpreting all individual ECG beats instead of an averaged beat. In this paper two methods are presented that employ information about the intra-individual variability in individual ECGs. The first method provides an estimate of the reliability of the interpretation, the second attempts to improve the interpretation itself. In the first method we quantified the variation in interpretation caused by the two sources of intra-individual variability with the use of a stability index, a high index value indicating a low variation in interpretation. This index was subsequently studied using two sets of ECGs. For the first set a â clinical' reference interpretation was obtained from discharge letters. For the second set three cardiologists provided a â cardiologists' reference. The performance of subgroups of ECGs having stability indices higher than a particular value was computed. It appeared that for the â cardiologists' reference, the interpretations of ECGs with a high stability index were more often correct. No effect was found for the â clinical' reference. In the second method we attempted to improve the original interpretation by combining the alternative interpretations into a new interpretation. This was done by taking the median or the average of the quantified alternatives. These combined interpretations proved to perform better than the original interpretation when a cardiologist's interpretation was taken as a reference. This paper shows that intra-individual ECG variability can be used to improve original interpretations. This can be done without having to record multiple ECGs, provided that a model is available to simulate intra-individual variability. The presented methods do not depend on the classification algorithm that is used. They can be used both during classifier design to correct imperfections, and in routine use of the classifier to produce more representative classifications.

Decision Trees↗
PubMed1999

Both decreased and increased heart rate variability on the standard 10-second electrocardiogram predict cardiac mortality in the elderly: the Rotterdam Study.

Decreased heart rate variability has been associated with an adverse prognosis in patients after myocardial infarction. Studies carried out in the population at large show contradictory results. The authors examined the association between heart rate variability on a standard 10-second electrocardiogram and cardiac and all-cause mortality in the Rotterdam Study, a population-based cohort study of men and women aged > or =55 years, using data collected between 1990 and 1996 (mean follow-up = 4 years). Heart rate variability, taken as the standard deviation of normal R-R intervals (SDNN), was computed by means of the Modular ECG Analysis System. After exclusion of subjects with arrhythmia and those with fewer than six normal R-R intervals, the study population consisted of 2,088 men and 3,184 women. Cox's proportional hazards model was used to examine the age- and sex-adjusted risk for cardiac, noncardiac, and total mortality in relation to quartiles of SDNN, using the third quartile of SDNN as the reference category. Subjects in the lowest quartile of SDNN relative to those in the third quartile had an 80 percent age- and sex-adjusted increased risk for cardiac mortality (hazard ratio = 1.8; 95% confidence interval: 1.0, 3.2). Interestingly, for subjects in the highest quartile of SDNN, an even more pronounced risk for cardiac mortality was present (hazard ratio = 2.3; 95% confidence interval: 1.3, 4.0). Additional adjustment for possible confounders did not materially change the risk estimates. The authors conclude that heart rate variability measured on the standard 10-second electrocardiogram can be used to identify older men and women with an increased risk for cardiac mortality. In the elderly, increased heart rate variability is an even stronger indicator of cardiac mortality than decreased heart rate variability. Further studies are needed to confirm these findings and to elucidate their physiologic meaning.

Aged↗
PubMed1999

QT dispersion as an attribute of T-loop morphology.

BACKGROUND: The suggestion that increased QT dispersion (QTD) is due to increased differences in local action potential durations within the myocardium is wanting. An alternative explanation was sought by relating QTD to vectorcardiographic T-loop morphology. METHODS AND RESULTS: The T loop is characterized by its amplitude and width (defined as the spatial angle between the mean vectors of the first and second halves of the loop). We reasoned that small, wide ("pathological") T loops produce larger QTD than large, narrow ("normal") loops. To quantify the relationship between QTD and T-loop morphology, we used a program for automated analysis of ECGs and a database of 1220 standard simultaneous 12-lead ECGs. For each ECG, QT durations, QTD, and T-loop parameters were computed. T-loop amplitude and width were dichotomized, with 250 microV (small versus large amplitudes) and 30 degrees (narrow versus wide loops) taken as thresholds. Over all 1220 ECGs, QTDs were smallest for large, narrow T loops (54.2+/-27.1 ms) and largest for small, wide loops (69. 5+/-33.5 ms; P<0.001). CONCLUSIONS: QTD is an attribute of T-loop morphology, as expressed by T-loop amplitude and width.

Action Potentials↗
PubMed1999

Prolonged QT interval predicts cardiac and all-cause mortality in the elderly. The Rotterdam Study.

AIMS: To examine the association between heart-rate corrected QT prolongation and cardiac and all-cause mortality in the population-based Rotterdam Study among men and women aged 55 years or older and to compare the prognostic value of the QT interval, using different formulas to correct for heart rate. METHODS AND RESULTS: After exclusion of participants with arrhythmias or bundle branch block on the ECG, the study population consisted of 2083 men and 3158 women. The QT interval was computed by the Modular ECG Analysis System (MEANS). Data were analysed using Cox' proportional hazards model. Participants in the highest quartile of the heart-rate corrected QT interval had about a 70% age- and sex-adjusted increased risk for both all-cause mortality (hazard ratio (HR) 1.8; 95% CI:1.3-2.4) and cardiac mortality (HR 1.7; 95% CI:1.0-2.7) compared to those in the lowest quartile. In women, the increased risk associated with prolonged QT for cardiac death was more pronounced than in men. These risk estimates did not change after adjustment for potential confounders, including history of myocardial infarction, hypertension and diabetes mellitus. CONCLUSION: A prolonged heart-rate corrected QT interval is an independent predictor for cardiac and all-cause mortality in older men and women. The risk associated with prolonged QT is hardly affected by the heart-rate correction formula used.

Age Distribution↗
PubMed1999

ORCA: the versatile CPR.

The introduction of computer-based patient records (CPRs) that fully replace paper records proves especially difficult in specialized care, despite the potential advantages of CPRs for patient care and research. Improved data legibility, availability, sharing of records, and decision support may directly benefit patient care. Barriers to the introduction of CPR applications at institutions may be caused by lack of infrastructure, or by financial or organizational issues. To have clinicians interactively enter data at the point of care is still a big challenge. This paper presents an overview of ORCA (Open Record of CAre): a generic CPR, designed for integration with existing systems, presentation of multi-media patient data, and the collection of structured data, directly by clinicians. ORCA can easily be tailored to the needs of a variety of medical specialists without the need for changes to its data model, functionality, or interface. The paper describes the essence of the architecture of ORCA and the user benefits with emphasis on the support of structured data entry.

Medical Records Systems, Computerized↗
PubMed1999

Postmarketing surveillance based on electronic patient records: the IPCI project.

Researchers claim that data in electronic patient records can be used for a variety of purposes including individual patient care, management, and resource planning for scientific research. Our objective in the project Integrated Primary Care Information (IPCI) was to assess whether the electronic patient records of Dutch general practitioners contain sufficient data to perform studies in the area of postmarketing surveillance studies. We determined the data requirements for postmarketing surveillance studies, implemented additional software in the electronic patient records of the general practitioner, developed an organization to monitor the use of data, and performed validation studies to test the quality of the data. Analysis of the data requirements showed that additional software had to be installed to collect data that is not recorded in routine practice. To avoid having to obtain informed consent from each enrolled patient, we developed IPCI as a semianonymous system: both patients and participating general practitioners are anonymous for the researchers. Under specific circumstances, the researcher can contact indirectly (through a trusted third party) the physician that made the data available. Only the treating general practitioner is able to decode the identity of his patients. A Board of Supervisors predominantly consisting of participating general practitioners monitors the use of data. Validation studies show the data can be used for postmarketing surveillance. With additional software to collect data not normally recorded in routine practice, data from electronic patient record of general practitioners can be used for postmarketing surveillance.

Family Practice↗
PubMed1998

T axis as an indicator of risk of cardiac events in elderly people.

BACKGROUND: The T axis was postulated to be a general marker of repolarisation abnormality, indicative of subclinical myocardial damage. The aim of this investigation was to assess the prognostic importance of the T axis for fatal and non-fatal cardiac events, in a prospective cohort study of men and women aged 55 years and older. METHODS: 2352 men and 3429 women from the population-based Rotterdam Study took part in the study. Electrocardiograms were done, and T axes were categorised as normal, borderline, or abnormal. Data were analysed with Cox's proportional-hazards models; adjustment for age and sex was done where appropriate. FINDINGS: During 3-6 (mean 4) years of follow-up of the 5781 participants, 165 (2.9%) fatal and 192 (3.3%) non-fatal cardiac events occurred. Participants with an abnormal T axis (n=609) had an increased risk of cardiac death (hazard ratio 3.9 [95% CI 2.8-5.6]), sudden cardiac death (4.4 [2.6-7.4]), non-fatal cardiac events (2.7 [1.9-3.9]), and combined fatal or non-fatal cardiac events (3.2 [2.5-4.1]); p<0.001 for each. Additional adjustment for established cardiovascular risk factors resulted in lower, but still significant risk for all endpoints. The risk associated with an abnormal T axis was higher than those for any other cardiovascular risk factor. Additional subgroup analyses indicated that the risk of cardiac death was not substantially modified by age, sex, or history of myocardial infarction. INTERPRETATION: The T axis is a strong and independent risk indicator of fatal and non-fatal cardiac events in the elderly.

Aged↗
PubMed1998

QTc dispersion predicts cardiac mortality in the elderly: the Rotterdam Study.

BACKGROUND: Increased QTc dispersion has been associated with an increased risk for ventricular arrhythmias and cardiac death in selected patient populations. We examined the association between computerized QTc-dispersion measurements and mortality in a prospective analysis of the population-based Rotterdam Study among men and women aged > or = 55 years. METHODS AND RESULTS: QTc dispersion was computed with the use of the Modular ECG Analysis System as the difference between the maximum and minimum QTc intervals in 12 and 8 leads (ie, the 6 precordial leads, the shortest extremity lead, and the median of the 5 other extremity leads). After exclusion of those without a digitally stored ECG, the population consisted of 2358 men and 3454 women. During the 3 to 6.5 years (mean, 4 years) of follow-up, 568 subjects (9.8%) died. The degree of QTc dispersion was categorized into tertiles. Data were analyzed using the Cox proportional hazards model, with adjustment for age. For QTc dispersion in 8 leads, those in the highest tertile relative to the lowest tertile had a twofold risk for cardiac death (hazard ratio, 2.5; 95% confidence interval [CI], 1.6 to 4.0) and sudden cardiac death (hazard ratio, 1.9; 95% CI, 1.0 to 3.7) and a 40% increased risk for total mortality (hazard ratio, 1.4; 95% CI, 1.2 to 1.8). Additional adjustment for potential confounders, including history of myocardial infarction, hypertension, and overall QTc, did not materially change the risk estimates. Hazard ratios for QTc dispersion in 12 leads were comparable to those found for QTc dispersion in 8 leads. CONCLUSIONS: QTc dispersion is an important predictor of cardiac mortality in older men and women.

Age Factors↗
PubMed1998

Reproducibility of computerized ECG measurements and coding in a nonhospitalized elderly population.

The standard 12-lead electrocardiogram (ECG) is used in many epidemiologic studies to diagnose and predict cardiovascular disease. In view of this, knowledge about the reproducibility of ECG measurements and coding is essential. Minute-to-minute, day-to-day, and year-to-year variability of ECG measurements, composite scores, and Minnesota Code classification were assessed by use of a computer program, in 101 nonhospitalized elderly men and women. Interval ECG measurements were more reproducible than amplitude measurements. The best reproducibility was found for the overall QTc interval (coefficient of variation 3.1%, 4.0%, and 5.2% for the minute-to-minute, day-to-day, and year-to-year groups, respectively) and the poorest was found for the Cardiac Infarction Injury Score (coefficient of variation 67.1%, 78.5%, and 94.3%, respectively). Minnesota Code discrepancies occurred in 16%, 19%, and 22% of the ECGs in the minute-to-minute, day-to-day, and year-to-year groups, respectively. Reproducibility within specific code categories was much better. Overall, variability tended to increase with time. In the routine setting, electrode positioning had relatively little effect on total variability.

Aged↗
PubMed1998

T-loop morphology as a marker of cardiac events in the elderly.

ST-T wave changes of electrocardiographic (ECG) leads have long been recognized as predictors of future cardiac events, but they only imperfectly characterize T-loop morphology. Using vectorcardiographic (VCG) parameters, we investigated the predictive value of T-loop abnormality for fatal and nonfatal cardiac events in a prospective cohort study among 5,815 elderly. Separately, the predictive value of an easily obtainable T-loop parameter, the T axis, was also assessed. Measurements were determined by a computer program, using VCGs reconstructed from the standard 12-lead ECGs. During the 3 to 6 (mean 4) years of follow-up, 166 fatal and 193 nonfatal cardiac events occurred. Subjects with an abnormal T-loop morphology had increased risks for fatal cardiac events (hazard ratio 4.3; 95% CI 3.0-6.4) and nonfatal cardiac events (3.0; 1.9-4.8). Risks associated with an abnormal T axis alone were only slightly lower. Additional adjustment for established cardiovascular risk indicators resulted in lower, but still highly significant risks. Both T-loop and T-axis abnormalities appear to be strong, independent risk indicators of cardiac events in the elderly.

Aged↗
PubMed1998

Integration and communication for the continuity of cardiac care (I4C).

The project I4C (Integration and Communication for the Continuity of Cardiac Care) is carried out for the advancement of cardiac care, from prevention to follow-up. The goals of I4C are: (1) integrated access to patient data, wherever they are stored; (2) support of evidence-based care; (3) consistent recording of patient data (eg, patient history, electrocardiograms IECGs] or cine-angios) in a multimedia patient record; and (4) a documented reference data set for research. In several clinics, workstations are being installed to serve the four goals. Integration with other information systems in clinical care is realized by encapsulation. A computer-based patient record (ORCA) has been developed to support the collection, consultation, and sharing of patient data. In I4C, ORCA is intended for use in a research setting as well as routine patient care. The functionality of ORCA covers the collection of patient history data in a highly structured manner, the recording of drug prescriptions, an overview of laboratory test results, and viewers for ECGs and angiographic images. At present, structured data entry and consultation is supported in six European languages.

Cardiac Care Facilities↗
PubMed1998

Education and training of medical informatics in the medical curriculum.

The teaching of medical informatics is of importance for students in medicine and health care, realizing that they will be the health professionals of the future. Training in medical informatics is also of value for practicing clinicians who are overwhelmed by the avalanche of systems that are available on the market. Some examples of operational systems are presented here to indicate that health care has changed dramatically over the last decades. This paper intends to contribute to the drafting of IMIA guidelines for teaching medical informatics by (1) reporting on the experience at the Faculty of Medicine and Health Sciences of the Erasmus University Rotterdam as part of the curriculum, (2) reporting on the implementation of guidelines for teaching medical informatics in The Netherlands since these guidelines were drafted in 1986, and (3) by introducing the teaching material contained in the new Handbook of Medical Informatics and on its Web site.

Curriculum↗
PubMed1998

Communication between physicians and with patients suffering from breast cancer.

BACKGROUND: The communication between GP and specialists is vital for the patient suffering from breast cancer. OBJECTIVES: The aim of this study was to investigate (i) the speed and type of communication between GPs, specialists and patients with breast cancer, and (ii) the problems that GPs encounter in the communication with specialists concerning these patients. METHOD: In April 1995, 246 Dutch GPs from the Zwolle region (600 000 inhabitants) were invited to complete a questionnaire, using the information from the medical record and focusing on the last patient consulted with a confirmed diagnosis of breast cancer. RESULTS: Valid replies were received from 150 (61 %) GPs. The median period between initial referral date and receipt of the definite diagnosis from the surgeon was 4 weeks. After the patient's first appointment with the surgeon, the GPs received reports for 24% of the patients within 3 days; for 31% within 3-7 days; and for 16% of the patients after more than 2 weeks. After the first consultation between patient and surgeon, 68 (45%) of the 150 GPs reported that the patient contacted them; at this stage only 30 (20%) of these GPs had received a report from the surgeon. Thirty-one (21%) GPs did not contact the patient after receival of the definite diagnosis. GPs stated that the communication on patients with breast cancer is too slow (49%), or not frequent enough (25%); 25% of GPs found that the distribution of tasks between them and the specialists are not well described. CONCLUSION: In the diagnostic stage of breast cancer the communication between GPs, specialists and patients varies widely, is too slow and is incomplete. An effect of this unsatisfactory communication is that the patient herself is the messenger of the bad news.

Breast Neoplasms↗
PubMed1998

The handbook of medical informatics and its web site.

Since the new Handbook of Medical Informatics was published in 1997, a beta-version of a web site ("MI WEB") has been opened that supports the teaching of the Handbook. MI Web refers to the text of the full Handbook, using an extensive Glossary that is shared by both the paper Handbook and the web site. New material for teaching will continuously be added to the MI Web, realizing that the field of health informatics is progressing exponentially, that the teaching of medical informatics is of great importance for students in medicine and health care, and that these students will be the health professionals of the future. Training in medical informatics is also of value for practicing clinicians who are overwhelmed by the avalanche of systems that are available on the market.

Humans↗
PubMed1998

An analysis of 5 years of medical informatics publications.

This study describes an analysis of 1520 papers that were published in six medical informatics journals from 1992 through 1996, and indexed in NLM's MEDLINE. Of retrieved publications the countries of origin were determined, and insight in the subject of the publication was obtained by analysing the used MeSH terms. The main conclusion is that despite the fact that publications in medical informatics stem from a wide international community, scientific recognition can still not be demonstrated by high impact factors of journals.

Abstracting and Indexing↗
PubMed1998

Shared care for diabetes: supporting communication between primary and secondary care.

As health care becomes more complex, interest in the benefits of coordination of care has increased. Especially patients that are being treated jointly by more than one physician (shared care), are vulnerable to adverse effects resulting from inadequate coordination and communication. We describe a study in which care providers support shared care by using computer-based patient records for data storage, and structured electronic data interchange (EDI) as a means of communication. The study showed that the electronic communication network for exchanging consultation outcomes significantly increased frequency of communication and the availability of data to the general practitioner on diagnostic procedures performed in the hospital, thus providing more complete information about the care that patients are receiving.

Computer Communication Networks↗