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Purpose: To summarize available evidence on preoperative cardiac risk stratification so that the internist may 1) use clinical and electrocardiographic findings to stratify a patient's perioperative risk for myocardial infarction and death; 2) decide which tests provide useful additional risk-related information; and 3) understand the benefits, risks, and evidence surrounding the decision to undertake coronary revascularization before elective noncardiac surgery. Data Sources: A MEDLINE search and review of the reference lists of identified articles. Sensitivities, specificities, and likelihood ratios for diagnostic tests were calculated, and a quality rating for study methods was applied. Data Extraction: Myocardial infarction and mortality were the major outcomes considered, and a quality rating for study methods was applied. Data Synthesis: Clinical and electrocardiographic findings, organized by multivariate prediction indices, accurately identify patients as having low, intermediate, or high risk for myocardial infarction or death. Pharmacologic stress imaging with thallium or echocardiography probably improves risk stratification for intermediate-risk patients having vascular surgery. These tests have not been shown to be effective prognostic indicators for patients having nonvascular surgery. No studies of angiography for risk prediction have been reported. Decision analyses and retrospective series suggest that the risks incurred by doing coronary angiography and revascularization before elective surgery outweigh the benefits. Prospective, controlled studies of coronary revascularization are lacking. Evidence from a randomized, controlled trial has shown a survival benefit with the perioperative use of [Beta]-blockers in patients at risk for coronary artery disease. Conclusions: Evaluation of all surgical patients by use of clinical indices is recommended. Low-risk patients need no further evaluation before surgery. High-risk patients need optimal management of their high-risk problems, including (if appropriate) [Beta]-blocker use, and may need to have their elective procedures canceled. Intermediate-risk patients probably benefit from further noninvasive stress testing, especially if they are having vascular surgery. Further clinical trials are needed for most areas of concern., The relative value of various tests used to evaluate risk for heart complications among prospective elective surgical patients is presented. Patients identified as low-risk or intermediate-risk using baseline assessment tools likely do not need any further testing before non-vessel surgery. Imaging or stress tests may be valuable in further identifying risk among intermediate-risk patients before vessel surgery. High-risk patients may require preliminary corrective surgery, treatment with beta-blocking medication, or counseling about canceling elective surgery.

* Purpose: To determine whether alpha-interferon is effective in terminating viral replication and in eradica1ing the carrier state in patients with chronic hepatitis B virus 1HBV) infection. * Data Sources: Randomized controlled studies published in the English literature between January 1966 and June 1992 were identified through a MEDLINE computer search. * Study Selection: Fifteen randomized controlled studies with a total of 837 adult chronic HBV carriers who were positive for hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) were identified. Studies were included if patients were treated for at least 3 months and followed for at least 6 months after cessation of therapy. * Results: Overall, the loss of HBsAg occurred 6% more often in interferon-treated patients than the natural seroconversion seen in controls (7.8% compared with 1.8%, P = 0.001), and the los of viral replication occurred approximately 20% more often in treated patients than in controls (33% compared with 12% for loss of HBeAg and 37% compared with 17% for the loss of HBV DNA, P = 0.0001) if patients received interferon for 3 to 6 months and were followed for 6 to 12 months. Interferon also had a significant treatment effect on the development of antibodies to HBsAg (anti-HBs), antibodies to HBeAg (anti-HBe), and on the normalization of alanine aminotransferase levels. * Conclusions: Alpha-interferon is effective in terminating viral replication and in eradicating the carrier state in patients with chronic HBV infection who are HBeAg positive when these patients are treated for 3 to 6 months and followed for 6 to 12 months after cessation of therapy. Follow-up studies are required to determine whether interferon reduces the risk for developing cirrhosis or hepatocellular carcinoma., Alpha-interferon may be an effective treatment for chronic hepatitis B virus (HBV) infection in individuals positive for hepatitis B e antigen (HBeAg). Some individuals can be carriers of HBV without developing active hepatitis. A study reviewed 15 articles in the medical literature that examined the use of alpha-interferon to treat chronic HBV infection in individuals positive for HBeAg and hepatitis B surface antigen (HBsAg). Individuals were treated between three and six months with alpha interferon and were followed between six and 12 months. Eight percent of the individuals treated with alpha interferon became negative for HBsAg, compared with 2% of those who were not treated with alpha interferon. Thirty-three percent of the individuals treated with alpha interferon became negative for HBeAg, compared with 12% of those who were not treated.

* Purpose: To review the methods used for preoperative cardiac risk stratification of patients having peripheral vascular surgery. * Data Sources: Relevant studies published before August 1991 were identified using a MEDLINE search of the English-language literature, followed by a manual search of the references of all identified articles. * Study Selection: All clinical studies evaluating methods used for preoperative cardiac risk stratification of patients having peripheral vascular surgery. * Data Extraction: The key data extracted from each article included the inclusion and exclusion criteria of the study patients, the techniques used for testing and the corresponding definitions of positive test results, and the clinical outcomes of the tested patients. Data were analyzed using a Bayesian conceptual framework, and pretest probabilities were converted to post-test probabilities using calculation of likelihood ratios. * Results: Patients with high scores on clinical cardiac risk indexes (Goldman index > 12 or Detsky index > 15), or more than three of the criteria identified by Eagle (age > 70 years, diabetes, angina, Q waves on electrocardiogram, or ventricular arrhythmias) are likely to be at higher risk for cardiac death and myocardial infarction after vascular surgery. Those with both low scores and none of Eagle's criteria may be at lower risk, but this result has not been reproduced by independent studies. Neither group of patients would benefit from further investigation for cardiac risk stratification. Patients with one or two of these criteria may be at intermediate risk and would benefit most from further testing for the purposes of risk stratification. Most of the published evidence shows that the absence of redistribution on dipyridamole-thallium scanning identifies a low risk for postoperative cardiac complications, whereas the presence of redistribution predicts a high risk. Preliminary reports suggest that preoperative monitoring for silent myocardial ischemia may also be useful in identifying a high-risk subset of patients. * Conclusions: Patients identified clinically to be at either very low or high risk for cardiac complications after peripheral vascular surgery are unlikely to benefit from further risk stratification. Dipyridamole-thallium scanning is the test of choice for further evaluation of patients at intermediate clinical risk because studies have shown that it is sensitive enough to rule out a high-risk status for patients who do not have redistribution.

In recent years, the United States has seen a concerted effort by organized medicine to promote education about cholesterol and its role in heart disease. This approach has included identifying people with high blood cholesterol levels, and treating, with either diet, drugs, or both, those who are perceived to have the greatest risk of heart disease. How much reduction in heart disease can be expected is still unknown. By contrast, in Canada, a far less aggressive approach to the treatment of high cholesterol is the norm. A statistical study was performed to determine the utility or disutility of an aggressive policy regarding the diagnosis and treatment of high cholesterol. Among the factors studied were the impact of labelling a person as 'sick' on the basis of a high blood cholesterol level, and the impact of regular medical check-ups, dietary changes, and drug therapy. If any negative value is assigned to these factors, a conservative approach, like that in Canada, is warranted. Adopting an aggressive approach to the treatment of high cholesterol is problematic, too, in that most studies of cholesterol-lowering efforts have focussed on middle-aged, white males, and the applicability of the results to women and other races is unknown. Aggressive treatment is also more expensive. Until further data on the effectiveness of cholesterol-lowering treatment are available, the Canadian approach, with its more conservative view, seems more justifiable, at least on the basis of statistical utility. (Consumer Summary produced by Reliance Medical Information, Inc.)

In the December 1, 1991 issue of the Annals of Internal Medicine, a physician presents the development of a neural network computer program for the diagnosis of heart attacks. When tested on a series of emergency room patients, this neural net performed somewhat better than physicians. Unlike most computer programs, neural networks operate by varying the values assigned to nodes and interconnections of a large network modelled in the computer's memory. These values change with experience, and the output of the neural network gradually becomes more accurate as its ''experience'' increases. Such programs have proved capable of many tasks involving pattern recognition, tasks which have proved extremely difficult for more conventional programming techniques. However, one consequence of the architecture of the neural network is that the relationship between the input data and the output diagnosis is obscure. Just as a child may readily tell a cat from a dog, but be unable to explain the difference in a satisfactory way, a neural network cannot explain why the diagnosis of myocardial infarction was given, even if it is indeed correct. Are physicians likely to use such a mysterious device? Physicians should already be familiar with many cases in which the empiric evidence that something works is more important than knowing why. The action of some drugs is poorly understood, but large amounts of data indicate that they should be effective in certain cases; physicians have no qualms about using them in these cases. Neural networks should be treated in the same way. The must be evaluated in a reliable, objective, and unbiased manner. Their use should be determined on the basis of experimental data which support their value, or not. (Consumer Summary produced by Reliance Medical Information, Inc.)