Unstable angina--report from a Canadian expert roundtable

Unstable angina is generally considered to encompass a spectrum of symptomatic manifestations of ischemic heart disease, intermediate between stable angina and acute myocardial infarction. Approximately 75,000 Canadians are hospitalized yearly with unstable angina. The pathophysiology of unstable angina is still imperfectly understood, but is related to the same pathophysiological factors underlying myocardial infarction and sudden cardiac death. In March 1995 a group of Canadian cardiologists met to review the current understanding of unstable angina and to define a Canadian approach to this common problem. Important issues and questions regarding the diagnosis and management of unstable angina were defined. The objective was to outline approaches to the management of unstable angina that would be appropriate in Canada. Topics discussed included definition, incidence, clinical presentations, pathophysiology, initial diagnostic and risk stratification approaches, acute medical management, role of invasive interventions and long term management.

The modification of human society by natural systems: discontinuities caused by the exploitation of endemic species and the introduction of exotics

Drastic reductions in Earth's biodiversity, old growth forests, top soil, clean water and air, and truly wild areas are occurring during a period when discussions of sustainable growth and sustainable production are becoming common. Using such terms as sustainable growth and sustainable production rather than the more accurate sustainable use of the planet leaves the impression that, with a little more skill, society can continue its present practices indefinitely. A number of explanations are possible for this desire to maintain two conflicting beliefs (i.e., severe environmental destruction occurs but society can continue its basic practices indefinitely): 1) the idea that a technological solution can be found for every problem; 2) an addiction to present behavioral norms, which is so strong that the consequences of continuing such behavior are irrelevant; and 3) the concept that, while human society can alter natural systems to suit its own needs, natural systems are incapable of altering human society. This last issue is the focus of this discussion: if human society eliminates all species on the planet that are incapable of tolerating human society's present practices, the only species remaining will be those that human society is unable to control successfully or eliminate; these species are called pests. Another hypothesis could be stated: a world of pests that human society cannot control effectively will inevitably reshape human society through disease and famine, technological breakdown, and interference with domesticated and wild species upon which the integrity of human societal structure depends.

Sudden unexplained death in Asian immigrants: recognition of a syndrome in metropolitan Toronto

OBJECTIVE

To determine the number of Southeast Asians in Ontario who died of the sudden unexplained death syndrome in Asian immigrants.

DESIGN

Retrospective review.

SETTING

Ontario.

CASES

All deaths reported to the Office of the Chief Coroner for Ontario from 1992 to 1995.

OUTCOME MEASURES

Age, residence and country of origin of people who died of sudden unexplained death syndrome in Asian immigrants, as defined by standard criteria, autopsy findings and social history of cases.

RESULTS

Eight cases of sudden unexplained death in Asian immigrants were reported during the study period. All involved men, and the mean age at death was 34 (standard error of the mean 7) years (range 23 to 44 years). All of the people were residents of metropolitan Toronto. Four were from Vietnam, three from China and one from the Philippines. Seven people lived with family members; the eighth was unemployed and lived alone. Death occurred during sleep or in the waking hours of the morning in six cases; in two of these cases the person's spouse was awakened by loud, laboured breathing. Two men experienced chest pain, and one of them also had sudden-onset dyspnea. There was no prodromal illness in any case. The only consistent autopsy finding was acute nonspecific pulmonary edema and congestion. Analysis of heart weights failed to reveal signs of significant cardiomegaly.

CONCLUSION

Men from Southeast Asia aged 20 to 45 years are at risk of sudden unexplained death, which usually occurs during sleep. No specific factors have been found that could be used to identify people at risk.

Cost-effectiveness of antenatal anti-D prophylaxis

This paper estimates the incremental cost-effectiveness of providing antenatal anti-D prophylaxis in varying dose sizes to either primigravidae or all Rh D negative women. It presents a model for calculating the net cost per 1000 'at risk' women based on the costs of anti-D prophylaxis and the future NHS costs avoided. Incremental cost-effectiveness is measured in terms of the net cost per Rh D-alloimmunization and the net cost per Rh HD loss prevented. Programmes for Rh D negative primigravidae are more cost-effective than the same dose protocol extended to all Rh D negative women. The 1 x 1250 iu programme is the most cost-effective option.

Evaluating the benefits of antenatal screening: an alternative approach

This paper presents an alternative method of valuing the benefits of antenatal screening programmes based on individual preferences. The methods of benefit measurement used to date, namely averted costs, QALYs, and willingness to pay, are critically reviewed. The alternative method assumes that screening can be regarded as an investment in improved information, and that the benefits of screening can be measured by the value placed upon this information. The information is valued by presenting individuals with standard gamble questions framed in terms of a prenatal diagnostic choice. The approach is developed in the context of antenatal screening for Down's syndrome and for cystic fibrosis carrier status. Some empirical testing of the approach is reported for the latter.

Decision making with respect to diagnostic testing: a method of valuing the benefits of antenatal screening

This paper outlines a model for valuing the benefits of antenatal screening based on the analysis of individual decision making with respect to consequent diagnostic testing. Central to the model is the idea that the benefits of screening can be measured by valuing the improved information generated from screening. The model is developed in the context of antenatal carrier screening for cystic fibrosis (CF). Benefits are assessed by surveying women in the general population in order to establish their preferences for two alternative methods of CF carrier screening-stepwise and couple screening. Preferences are elicited using standard-gamble questions in which women from a population-based random sample are asked to trade off risk of fetal loss with improved information from diagnostic testing. A series of standard-gamble questions is employed to elicit utility values for each of the possible information outcomes from screening. The expected utilities of both screening methods are calculated at both individual and group levels. The results suggest that the use of individual decision making with respect to diagnostic testing as a means of valuing the benefits of screening may have wide applications.

Toxicity testing with communities: microcosms, mesocosms, and whole-system manipulations

Present ecotoxicological methodology is not adequate for providing evidence for decisions on sustainable use of the planet, maintenance of ecosystem services, or ecosystem health. However, particularly in the area of ecosystem health, promising beginnings have been made. Presumably, if ecosystems are maintained in robust health, then sustainability and reliable delivery of ecosystem services should result. On the other hand, one cannot ignore either human population size or expectations of affluence. Whether the number of ecosystems in robust health will be adequate for appropriate delivery of ecosystem services not only for existing generations but for future generations still has very unacceptably high levels of uncertainty. All ecosystems are dynamic, and one of the problems will be distinguishing normal cyclical or successional changes from trends away from established norms. Furthermore, toxicity tests are extremely useful for determining deleterious effects and those concentrations at which no-observable-deleterious effects occur. They are not suitable for determining how successfully various materials are being reincorporated into natural systems without disturbing ecological integrity. In a very real sense, however, this is a toxicological problem because, like vitamins and other essential materials for humans, excessive amounts of at least some types can be deleterious as can other materials such as ordinary table salt. It seems inevitable that different criteria, standards, endpoints, and methodologies that revolve around sustainability, ecosystem services, and reincorporating extracted and manufactured materials into natural systems following their use by human society will be required. Furthermore, ecosystems are different, both structurally and functionally, in different climatic zones, different altitudes, different soil conditions, and the like. Therefore, widespread uniform standards seem unlikely to function well, particularly for toxic materials. Prescriptive legislation, as opposed to that requiring site-specific professional judgment, is not likely to serve well under these circumstances. How success will be determined, how deleterious effects will be supported by evidence, and how effective extrapolations from one system to another will be are just a few of the many questions that need resolution. Finally, both temporal and spatial scales of systems under examination must increase, as will the diversity of information used as a basis for professional judgment. All of these factors are occurring in other areas of human societies, increasing globalization, and entry into the information age. Thus, the trends for ecotoxicology are in many ways quite similar to those in other professions as well.

Ecosystem services: an essential component of sustainable use

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Restoration of urban waterways and vacant areas: the first steps toward sustainability

Increased population pressure and human activities have significantly altered the effectiveness of functions of ecosystems ("ecosystem services") at the local and regional scale. Of primary importance is the decrease in water quality due to urban storm water runoff. A number of communities have initiated restoration strategies to improve water quality standards. One such strategy is the incorporation of riparian walkways with native flora. As a result of such restoration efforts, habitats for native fauna have improved, and the number and diversity of wildlife have increased in urban settings. Restoration of urban habitats also provides social and economic benefits to the surrounding community. Efforts to mitigate the loss of ecological resources by restoring native habitats on lots that cannot be developed or on abandoned lots hold a high, unrealized potential. Habitat restoration not only provides natural diversions to urban surroundings, but also enlightens and educates individual citizens about the importance of balanced ecosystems and the role of humans within ecosystems. Education is the primary step toward creating ecologically sustainable communities.

Maximizing the benefits of thrombolytic therapy for acute myocardial infarction

Thrombolytic therapy is a huge advance in the management of acute myocardial infarction (AMI). The results of large clinical trials over the past 9 years have unequivocally demonstrated its benefit: of every 1000 patients treated 30 will be saved, at a cost of two cases of nonfatal cerebral hemorrhage and seven of noncerebral major hemorrhage. The concurrent use of acetylsalicylic acid increases the benefit of thrombolytic therapy. Sales figures for thrombolytic agents indicate that their use in Canada is less than optimal and lags behind that in several European countries. Major educational efforts are needed to promote awareness of the efficacy of thrombolytic therapy and of optimal approaches for maximizing its potential benefit for patients with AMI.

Unrealistic optimism: a behavioural sciences classroom demonstration project

Unrealistic optimism may contribute to risky health practices and to a delay in seeking treatment for medical conditions, as most individuals perceive themselves to be at little risk for various disorders. It is thus an important concept to present to medical students as part of their behavioural sciences training. Social psychological concepts such as unrealistic optimism may appear, on initial presentation to students, to be a misjudgement based on faulty understanding of risk estimates by the general population. This project aimed to teach the principle of unrealistic optimism by having students document their own beliefs about health risks. Students rated their own risk, relative to other classmates, of experiencing a range of 17 health problems. Questionnaires were completed by two classes of medical students (n = 257). Class results showed varying levels of unrealistic optimism for all 17 conditions. Males and females differed significantly on three of the 17 conditions. Student data were obtained rapidly in a large didactic setting and served to illustrate the concept of unrealistic optimism which was subsequently taught in class. Such exercises may be a useful teaching aid to students providing them with feedback on their own cognitive processes and illustrating that they display cognitive distortions similar to those of patients.

The occurrence of heritable Mu excisions in starving cells of Escherichia coli

A strain of Escherichia coli constructed by Shapiro has a segment of Mu bacteriophage DNA inserted between the araC and lacZ genes. Excision events that produce an in-frame fusion of lacZ to araB result in a cell (here designated Ara-Lac+) that can grow on lactose if arabinose is present as an inducer. Whether or not these excision events occur in the absence of selection for the Ara-Lac+ phenotype has figured prominently in the debate of the phenomenon known as 'directed' or 'adaptive' mutation. In an attempt to settle the issue, we have used classic fluctuation tests to show that cells capable of producing a clone of descendants that are phenotypically Ara-Lac+ do, indeed, arise in stationary phase cultures kept starving in depleted minimal medium. We found that Ara-Lac+ progenitors arise rapidly under these conditions, in contrast to the delayed appearance of Ara-Lac+ mutants when cells are incubated on lactose-arabinose minimal plates. Similar results are reported in the accompanying paper by Maenhaut-Michel and Shapiro, who used indirect selection to isolate Ara-Lac+ cells in the absence of selection. However, their sequencing data have introduced a new unexpected complication to the interpretation of all such experiments, and it is no longer clear exactly when the fusions arise.

Estimating the effects of toxicants on ecosystem services

Numerous functions of ecosystems are essential to the quality of human life, including the provision of food, the decomposition of sewage, the provision of portable water, and the replacement of breathable air. Although attributes of ecosystems directly of use to human societies are not the only ones worth protecting, emphasizing their services may be the most effective means of communicating risks of toxicants to the general public. However, although spatial and temporal scales of experiments to assess risk vary relatively little, actual spatial scales vary considerably, from local environments to global ecosystems. Generally, models are used to bridge these gaps in scale. In this paper, we examine ways in which toxicity test endpoints have been developed to describe effects of pollutants on essential ecosystem functions and the ways in which results are then extrapolated to scales that risk managers can use.