We present a methodology and database mediator tool for integrating modern knowledge-based systems, such as the Stanford EON architecture for automated guideline-based decision-support, with legacy databases, such as the Veterans Health Information Systems & Technology Architecture (VISTA) systems, which are used nation-wide. Specifically, we discuss designs for database integration in ATHENA, a system for hypertension care based on EON, at the VA Palo Alto Health Care System. We describe a new database mediator that affords the EON system both physical and logical data independence from the legacy VA database. We found that to achieve our design goals, the mediator requires two separate mapping levels and must itself involve a knowledge-based component.

Context

Which drug is most effective as a first-line treatment for stable angina is not known.

Objective

To compare the relative efficacy and tolerability of treatment with {beta}-blockers, calcium antagonists, and long-acting nitrates for patients who have stable angina.

Data Sources

We identified English-language studies published between 1966 and 1997 by searching the MEDLINE and EMBASE databases and reviewing the bibliographies of identified articles to locate additional relevant studies.

Study Selection

Randomized or crossover studies comparing antianginal drugs from 2 or 3 different classes ({beta}-blockers, calcium antagonists, and long-acting nitrates) lasting at least 1 week were reviewed. Studies were selected if they reported at least 1 of the following outcomes: cardiac death, myocardial infarction, study withdrawal due to adverse events, angina frequency, nitroglycerin use, or exercise duration. Ninety (63%) of 143 identified studies met the inclusion criteria.

Data Extraction

Two independent reviewers extracted data from selected articles, settling any differences by consensus. Outcome data were extracted a third time by 1 of the investigators. We combined results using odds ratios (ORs) for discrete data and mean differences for continuous data. Studies of calcium antagonists were grouped by duration and type of drug (nifedipine vs nonnifedipine).

Data Synthesis

Rates of cardiac death and myocardial infarction were not significantly different for treatment with {beta}-blockers vs calcium antagonists (OR, 0.97; 95% confidence interval [CI], 0.67-1.38; P=.79). There were 0.31 (95% CI, 0.00-0.62; P=.05) fewer episodes of angina per week with {beta}-blockers than with calcium antagonists. {beta}-Blockers were discontinued because of adverse events less often than were calcium antagonists (OR, 0.72; 95% CI, 0.60-0.86; P.001). The differences between {beta}-blockers and calcium antagonists were most striking for nifedipine (OR for adverse events with {beta}-blockers vs nifedipine, 0.60; 95% CI, 0.47-0.77). Too few trials compared nitrates with calcium antagonists or {beta}-blockers to draw firm conclusions about relative efficacy.

Conclusions

{beta}-Blockers provide similar clinical outcomes and are associated with fewer adverse events than calcium antagonists in randomized trials of patients who have stable angina.