Mortality from coronary heart disease and incidence of acute myocardial infarction in Auckland, Newcastle and Perth

Changing patterns of medical treatment in acute myocardial infarction

TYPE OF STUDY

Descriptive study of trends in the drug therapy for acute myocardial infarction.

SETTING

Population-based register of acute coronary events compiled for the years 1984 to 1990 in the course of the Perth MONICA project.

CASES

5294 cases meeting clinical criteria for acute myocardial infarction.

RESULTS

Striking changes were seen in the use of aspirin before admission to hospital (from 4% to 18%). During the stay in hospital the use of beta-blockers increased steadily from 52% to 76%, while the use of aspirin increased 3.5-fold from 25% to 88% and the use of streptokinase increased 13.5-fold from 2.4% to 32.4%. The proportion of patients prescribed beta-blockers on discharge from hospital increased from 46% to 65% and that for aspirin rose from 16% to 83%. There were also major relative increases in the use of lipid-lowering agents and declines in the use of antiarrhythmic drugs.

CONCLUSION

These trends in the pharmacological management of myocardial infarction mirror the emerging evidence from clinical trials, although the increases in the use of certain types of drugs antedated publication of the results of major randomised studies. The changes in therapy would partly explain observed improvements in case fatality and may have contributed to the decline in coronary mortality observed in the Perth community.

Underuse of beta-blockers following myocardial infarction: a tale of two cities

AIMS

To measure factors associated with underuse of beta-blocker therapy after myocardial infarction (MI).

METHODS

The Newcastle and Perth collaborating centres of the World Health Organization (WHO) MONICA project (to MONItor trends and determinants of Cardiovascular disease) systematically evaluated all patients admitted to hospital in their respective regions with possible MI. A total of 1766 patients in Newcastle and 4,503 patients in Perth, discharged from hospital after confirmed MI from 1985 to 1993, were studied. Rates of beta-blocker use before and after hospital discharge were evaluated and correlates of beta-blocker use determined.

RESULTS

Beta-blocker use was similar in Newcastle and Perth before MI (21% of patients in each centre). During hospital admission, beta-blocker therapy was initiated nearly twice as frequently in Perth compared with Newcastle (66 vs 36%, respectively) and more patients were discharged from hospital on beta-blockers in Perth (68%) than in Newcastle (45%). The main factors associated with underuse of beta-blockers in multivariate analysis were geographical centre (odds ratio (OR) for Newcastle compared with Perth 0.3; 95% confidence interval (CI) 0.3-0.3), a history of previous MI (OR 0.6, 95% CI 0.5-0.7), admission to hospital in earlier years (OR 0.4, 95% CI 0.3-0.4 for years 1985-87 compared with years 1991-93), diabetes (OR 0.6, 95% CI 0.5-0.8) and the concomitant use of diuretics (OR 0.5, 95% CI 0.4-0.6) and calcium antagonists (OR 0.6, 95% CI 0.5-0.8).

CONCLUSIONS

Underuse of beta-blockers after MI was strongly related to hospital prescribing patterns and not to community use of beta-blockers. Underuse occurred in patients with diabetes and in patients with left ventricular dysfunction, patients who stand to benefit most from beta-blocker use following MI.

Projecting coronary heart disease incidence and cost in Australia: results from the incidence module of the Cardiovascular Disease Policy Model

OBJECTIVE

To project the incidence rates of coronary heart disease and the number of hospitalised incident coronary heart disease cases and hospital costs associated with the first hospital admission, for males and females aged 45-69, up to 2014 in Australia.

METHOD

A computer simulation model using a microsimulation technique was developed to simulate individuals' coronary heart disease history over time for a sampled Australian population characterised by major coronary risk factors. Using the simulated incidence rates, population and hospital cost data, the number of hospitalised incident coronary heart disease events and hospital costs associated with the first hospital admission were projected.

RESULTS AND CONCLUSIONS

If current cohort-specific coronary risk factor distributions change only by a location shift and the availability and efficacy of current treatment patterns prevail, the model projects declines of 13% and 24% in incidence rates for males and females aged 45-69 respectively by 2014. However, because the population aged 45-69 is projected to increase over the same period, the number of projected hospitalised coronary heart disease events and the hospital costs associated with the first admission will increase by more than 40%.

IMPLICATIONS

A modeling strategy which integrates information on coronary risk factor distributions, epidemiologic, demographic and economic data can provide comprehensive projections that assist future health care planning in the area of coronary heart disease.

Ethnic differences in coronary heart disease case fatality rates in Auckland

Data from the Auckland Coronary or Stroke (ARCOS) study for the years 1983 to 1992 were analysed to describe 28-day case fatality rates from coronary heart disease among Europeans, Maori and Pacific Islands people in Auckland, New Zealand. The case fatality rate was consistently higher in each age group and for both sexes among Maori and Pacific Islands people than in Europeans. Age-standardised case fatalities for Maori and Pacific Islands people were similar at around 65 per cent, compared with around 45 per cent among Europeans, and these differences were not explained by ethnic differences in possible underreporting of nonfatal myocardial infarction, in socioeconomic status, smoking, symptoms or past myocardial infarction. There was evidence of a more rapid progression of acute coronary events to a fatal outcome among Maori and Pacific Islands people, partly explained by delays in access to life support and coronary care: greater proportions of Pacific Islands people than Maori or Europeans who died did so within an hour of onset of symptoms (56 per cent of Pacific Islands people, 47 per cent of Maori, 45 per cent of Europeans). Pacific Islands and Maori people with acute coronary events took longer to reach a coronary care unit (mean times: Pacific Islands people 8.6 hours, Maori 7.4 hours, Europeans 6.7 hours, P < 0.05), although the median times were not significantly different; life-support units were used by a majority of Pacific Islands people and Europeans (57 per cent and 55 per cent, respectively), compared with only 46 per cent of Maori, but hospital care was similar for the three groups. Further qualitative and quantitative research is needed to investigate the reasons for these ethnic disparities in case fatality rates.

Trends in in-hospital mortality following acute myocardial infarction (AMI) in Victoria, 1987-1994

BACKGROUND

Death rates from coronary hearts disease have exhibited remarkable declines in most industrialised countries. Cardiovascular mortality has been the subject of extensive research and we considered it important to analyse recent local population based data on hospital outcomes of acute myocardial infarction (AMI).

AIM

To document the trends in in-hospital mortality from AMI in Victoria from 1987-1994.

METHODS

This was a retrospective analysis of data from the Victorian Inpatient Minimum Database relating to all public acute care hospitals. All separations recording a principal diagnosis 410 (AMI) were selected. Changes in distribution of AMI separations, in-hospital mortality, and changes in length of stay were examined.

RESULTS

The mean age of women admitted was 72 years compared with 64 years for men. Women comprised around a third of the overall sample but the proportion varied from 13% in those under 50 years to 57% among those aged 80 years and over. A striking decline in mortality was observed throughout the eight year period. The relative age adjusted decline was 33.5% (40% in males and 26% in females) with rates remaining higher in women. This decline occurred despite the increasing representation of those aged over 80 years. There was a significant decline in the mean length of stay (1.8 days) over the eight year period but this is likely to have had only minimal impact on mortality rates.

CONCLUSION

We have documented welcome declines in in-hospital mortality from AMI that are not an artefact of declining lengths of stay. Our observations parallel those in similar overseas studies. Large changes in medical management have taken place from the mid 1980s and may be partly responsible, but a change in disease process cannot be ruled out.

Can regional variation in "avoidable" mortality be explained by deaths outside hospital? A study from Sweden, 1987-90

STUDY OBJECTIVE

This study aimed to calculate the proportion of deaths outside hospital in Sweden for some conditions for which the acute medical management may be important to the outcome and to analyse whether the proportion of deaths outside hospital can explain regional variations in mortality from these causes of death.

DESIGN

The place of death was registered on all death certificates in Sweden during the period 1987-90. The proportion of deaths outside hospital was calculated at the national level for selected causes of death. Variation in cause-specific mortality among the 26 administrative health areas in Sweden was analysed. Death rate ratios were calculated with standardisation for age and sex using the national rate as standard. The correlation between the proportion of deaths outside hospital in each health area and the cause specific mortality irrespective of place of death was calculated. For areas with a significantly high death rate the ratios for mortality outside hospital as well as in hospital were analysed in order to decide which component of mortality represented a high mortality risk.

SETTING AND PARTICIPANTS

All death registration in Swedish citizens and other residents in Sweden aged under 70 years between 1987 and 1990 which gave diabetes, asthma, ischaemic heart disease, cerebrovascular diseases, or ulcer of the stomach or duodenum as the underlying cause of death.

MAIN RESULTS

For asthma (58%) and ischaemic heart disease (54%), most deaths occurred outside hospital. For most causes of death, however, no correlation was found among the health areas between the proportion of deaths outside hospital and the SMR for mortality irrespective of the place of death. A high death rate was associated with a high proportion of deaths outside hospital, for diabetes in one area in the north of Sweden (Norrbotten) and for ulcer of the stomach and duodenum in one large municipality (Göteborg).

CONCLUSIONS

The high proportion of deaths outside hospital at the national level for some of the conditions studied suggests that in-depth studies of the process preceding death and the functioning of medical care are needed. In most cases, however, no evidence was found that regional variation in mortality could be explained by death outside hospital. The results for diabetes in Norbotten and ulcer of stomach and duodenum in Göteborg indicate that in-depth studies on the quality of care are required.

Hospital discharge register data in the assessment of trends in acute myocardial infarction. FINMONICA AMI Register Study Team

We evaluated the reliability hospital discharge register data in the assessment of acute myocardial infarction trends. In the FINMONICA study areas, trends in age standarized attack rates for the years 1983-90 were calculated independently from two sources: the nationwide Finnish hospital discharge register and the FINMONICA acute myocardial infarction register. The trends were compared by a statistical regression model. The trends obtained from the hospital discharge register were very similar to the trends obtained from the FINMONICA acute myocardial infarction register. The attack rates differed significantly, however, and the change in the International Classification of Diseases version from version 8 to version 9 brought on a change in the attack rates obtained from the hospital discharge register. Thus, hospital discharge register data can be used to assess acute myocardial infarction trends in the community. However, modifications of the International Classification of Diseases codes (new versions of the classification) and changes in the clinical use of the codes for coronary heart disease can have an impact on the attack rates obtained from the hospital discharge register, and the reliability of the hospital discharge register data should be regularly assessed.

Stroke incidence and case fatality in Australasia. A comparison of the Auckland and Perth population-based stroke registers

BACKGROUND AND PURPOSE

Population-based studies are crucial for identifying explanations for the decline in mortality from stroke and for generating strategies for public health policy. However, the present particular methodological difficulties, and comparability between them is generally poor. In this article we compare the incidence and case fatality of stroke as assessed by two independent well-designed incidence studies.

METHODS

Two registers of acute cerebrovascular events were compiled in the geographically defined metropolitan areas of Auckland, New Zealand (population 945,369), during 1991-1992 for 12 months and Perth, Australia (population 138,708), during 1989-1990 for 18 months. The protocols for each register included prospective ascertainment of cases using multiple overlapping sources and the application of standardized definitions and criteria for stroke and case fatality.

RESULTS

In Auckland, 1803 events occurred in 1761 residents, 73% of which were first-ever strokes. The corresponding figures for Perth were 536 events in 492 residents, 69% of which were first-ever strokes. Both studies identified a substantial proportion of nonfatal strokes managed solely outside the hospital system: 28% in Auckland and 22% in Perth of all patients registered. The age-standardized annual incidence of stroke (all events) was 27% higher among men in Perth compared with Auckland (odds ratio, 1.27; P = .016); women tended to have higher rates in Auckland, although these differences were not statistically significant. In both centers approximately a quarter of all patients died within the first month after a stroke. There were significant differences in the prevalence of hypertension among first-ever strokes.

CONCLUSIONS

These two studies emphasize the importance of identifying all patients with stroke, both hospitalized and nonhospitalized, in order to measure the incidence of stroke accurately. The incidence and case fatality of stroke were remarkably similar in Auckland and Perth in the early 1990s. However, there are differences in the sex-specific rates that correspond to differences in the pattern of risk factors.

Medical care and case fatality from myocardial infarction and coronary death in Newcastle and Perth

Coronary mortality rates are significantly higher in Newcastle than Perth. In this paper we examine the extent to which this might be due to differences in medical treatment and case fatality. Population-based disease registers were used to identify all cases of non-fatal definite myocardial infarction (MI) and coronary death in people aged 25-64 years in the study populations between July 1988 and June 1990. Case fatality (at 28 days from onset of symptoms) was not significantly different between the centres. Thrombolytic therapy was used for one third of all hospitalised events in both centres. Other drugs of proven benefit were, however, used more often in Perth than in Newcastle. For example, during hospitalisation 74% of patients in Perth received beta-blockers compared with 41% in Newcastle (difference = 33%, 95% confidence interval (CI): 28%, 37%) and 85% of patients in Perth compared with 72% in Newcastle received aspirin (difference = 13%, 95% CI: 9%, 17%). Median lengths of stay in a coronary care unit (CCU) and total hospital stay were one day shorter in Perth. As case fatality was similar, the differences in mortality rates can be attributed mainly to differences in attack rates. Greater use of cardio-active drugs in Perth apparently did not result in improved short-term outcome although potential long-term benefits cannot be judged yet.

Ascertaining the true incidence of stroke: experience from the Perth Community Stroke Study, 1989-1990

OBJECTIVE

To determine the age and sex specific incidence, and case fatality of stroke in Perth, Western Australia.

DESIGN AND SETTING

A population-based descriptive epidemiological study.

SUBJECTS

All residents of a geographically defined segment of the Perth metropolitan area (population 138,708) who had a stroke or transient ischaemic attack between 20 February 1989 and 19 August 1990, inclusive.

MAIN OUTCOME MEASURES

Definite acute "first-ever-in-a-lifetime" (first-ever) and recurrent stroke classified according to standard definitions and criteria.

RESULTS

During the 18-month study period, 536 stroke events occurred among 492 patients, 69% of which were first-ever strokes. The crude annual event rate for all strokes was 258 (95% confidence interval 231-285) per 100,000, and the overall case fatality at 28 days was 24% (95% CI, 20%-28%). The crude annual incidence for first-ever strokes was 178 (95% CI, 156-200) per 100,000; 189 (95% CI, 157-221) per 100,000 in males and 166 (95% CI, 136-196) per 100,000 in females. The corresponding rates, age-adjusted to the "world" population, were 132 (95% CI, 109-155) for males and 77 (95% CI, 60-94) for females.

CONCLUSIONS

In contrast to mortality rates for ischaemic heart disease, the incidence of stroke in Australia appears little different from that for several other Western countries. For both males and females the incidence of stroke rises exponentially with increasing age. Although the sex-dependent difference in the risk of stroke is greatest in middle age, males are at greater risk of stroke even among the most elderly. To determine the incidence of stroke accurately, population-based studies of stroke need exhaustive and overlapping sources of case ascertainment. If only cases admitted to hospital had been used, we would have underestimated the rate of stroke among the most elderly by almost 40%. We estimate that approximately 37,000 people, about 50% of whom are over the age of 75, suffer a stroke each year in Australia.

Coronary artery stenosis in an Australian population

The purpose of this study was to examine the extent and severity of coronary stenosis in an Australian population. The subjects were autopsy cases among people aged 20-69 yrs dying in and out of hospital in the Newcastle area of New South Wales in 1985-86. Three groups were compared: coronary deaths, deaths from other natural causes and deaths due to external causes. Cross-sectional luminal narrowing in each major subepicardial artery was measured by stereological point counting. Stenosis was found, as expected, to be more severe in males than in females, increased with age and was greatest in those who died from coronary disease. Even in non-coronary deaths mean percentage luminal narrowing in the narrowest segments ranged from about 40% in people aged 20-29 yrs to over 60% in those aged 60-69 yrs. Narrowing was more pronounced in the left anterior descending artery and least in the left circumflex artery. To the extent that results from this autopsy study can be generalized to the whole population, these findings illustrate that, despite declining mortality from ischemic heart disease in Australia, coronary atherosclerosis remains a widespread problem.

Regional variation in coronary mortality within Tasmania

OBJECTIVE

To measure regional rates of mortality from ischaemic heart disease (IHD) within Tasmania and to analyse factors associated with regional differences.

DESIGN

Descriptive epidemiological study.

SETTING

Community-based study.

SUBJECTS

Male residents of Tasmania aged 30-69 years dying from IHD between 1986 and 1989.

MAIN OUTCOME MEASURES

Coronary death as coded by the Australian Bureau of Statistics and place of death validated by hospital and community data.

RESULTS

This study identifies substantial differences in coronary death rates among the three Health Regions of Tasmania. These differences are real and are not caused by variations in diagnostic or coding practices between regions. The two northern Health Regions, which represent approximately 52% of the total population, account for 98% of the excess mortality from IHD in Tasmania compared with the national rate. More detailed analysis of these differences suggests that variation in the number of deaths occurring in hospital contributes significantly to the regional differences in death rate from IHD.

CONCLUSION

Rates of coronary mortality in Tasmania have been significantly higher than in all other Australian States for much of the past decade because of a higher death rate within the population of the northern half of Tasmania. Differences in mortality rates between regions in Tasmania provide a focus for further study into the causes of the unacceptably high rates of death from IHD in Tasmania and underline the need for the funding of a coronary register in Tasmania.

Changes in drug treatment and case fatality of patients with acute myocardial infarction. Observations from the Newcastle MONICA Project, 1984/1985 to 1988/1990

OBJECTIVE

To describe changes in medications administered to patients with acute myocardial infarction between 1984/1985 and 1988/1990 and changes in case fatality.

DESIGN

Descriptive study from the Newcastle MONICA Project, which monitors all heart attacks in men and women aged 25 to 69 years in the Lower Hunter Region of New South Wales.

SUBJECTS

All patients admitted to hospital with a "definite" acute myocardial infarction who survived at least 28 days during periods in 1984/1985 (513 events) and 1988/1990 (790 events).

MAIN OUTCOME MEASURES

Changes in drugs being taken immediately before the onset of the myocardial infarction, prescribed during hospitalisation and on discharge from hospital, and changes in case fatality rates.

RESULTS

From the first time period to the second there were significant increases in the use of aspirin, calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors and hypolipidaemic agents, and significant reductions in the use of diuretics. In 1988/1990, 34% of patients with a definite myocardial infarction received thrombolytic therapy compared with fewer than 1% in 1984/1985. Among those patients who survived at least one hour from onset of symptoms, the case fatality rate declined from 13.5% to 7.9% (change -5.6%; 95% confidence limits, -8.9%, -2.2%).

CONCLUSION

Large changes in drug treatment of patients with acute myocardial infarction have occurred in the second half of the 1980s. These may be responsible for the reduction in case fatality. Nevertheless, use of drugs of proven effectiveness in acute care and for secondary prevention is surprisingly low in this population.