QJM Advance Access originally published online on July 22, 2006
QJM 2006 99(8):523-530; doi:10.1093/qjmed/hcl072
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The population mortality benefits of maximizing the number of eligible patients receiving appropriate cardiology treatments in Ireland
From the 1Department of Pharmacology and Therapeutics, Trinity College and St James's Hospital, Dublin, 2Department of Health and Children, Hawkins House, Dublin, Ireland, 3Department of Public Health, Dokuz Eylul University School of Medicine, 
zmir, Turkey, 4School of Population and Health Sciences, University of Newcastle upon Tyne, and 5Department of Public Health, University of Liverpool, Liverpool, UK
Address correspondence to Dr Z. Kabir, Department of Pharmacology & Therapeutics, Trinity Centre for Health Sciences, St James's Hospital, Dublin 8, Ireland. email: kabirzin{at}yahoo.com
Received 25 February 2006 and in revised form 21 April 2006
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Summary |
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 Top Summary IntroductionMethodsResultsDiscussionAppendix 1Appendix 2References |
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Background: Coronary heart disease (CHD) mortality rates have been decreasing in many industrialized countries since the 1980s. Up to half this decrease can be attributed to evidence-based medical and surgical cardiology interventions. However, recent studies suggest that modern cardiology treatment uptake levels remain disappointingly low in many patient categories.
Aim: To determine the potential for further reductions in CHD mortality in Ireland from increasing the number of eligible patients receiving cardiology treatments.
Methods: A previously validated, cell-based IMPACT CHD mortality model was used to integrate large amounts of data describing CHD patient numbers, and the effectiveness and uptake levels of specific medical and surgical treatments. The CHD mortality reductions potentially achievable through the increased use of specific treatments were then calculated, stratified by age and gender and tested using sensitivity analyses.
Results: In 2000, medical and surgical coronary disease treatments together prevented or postponed approximately 1950 CHD deaths in the adult population aged 25–84. However, increasing treatment levels to reach 80% of eligible patients might have prevented or postponed a further 2280 CHD deaths in 2000 (minimum estimate 860, maximum estimate 4000). The biggest gain was from maximizing the treatment uptake of eligible heart failure patients, followed by those receiving statins and secondary prevention therapies.
Discussion: Many eligible patients are currently not receiving appropriate evidence-based treatments that would reduce CHD mortality and morbidity. Our results suggest that increasing cardiology treatment uptake in Ireland could at least double the current therapeutic reduction in CHD mortality.
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Introduction |
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TopSummaryIntroductionMethodsResultsDiscussionAppendix 1Appendix 2References |
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Coronary heart disease (CHD) is the largest single cause of mortality in Ireland. It accounted for some 6600 deaths in 2000; of which half occurred prematurely.1 CHD also causes considerable distress and disability. Its health-care costs in Ireland are substantial, with over 23 000 hospital admissions annually.1
CHD mortality rates have been declining in many industrialized nations since the early 1980s. A number of cardiological interventions are clearly effective in reducing coronary deaths and morbidity.2–9 However, the recent European Action on Secondary Prevention through Intervention to Reduce Events (EURO-ASPIRE II) Study showed that treatment uptake rates remained disappointingly low in Ireland and elsewhere.10 In 2003, only 44% of suspected acute myocardial infarction (AMI) patients in Ireland received thrombolysis, 66% were prescribed beta-blockers, and 56%, angiotensin-converting-enzyme (ACE) inhibitors.11 Clearly, there is scope for considerable improvement in treatment uptake in Ireland, and hence substantial reductions in CHD morbidity and mortality.
Simultaneously tackling all groups of CHD patients would require substantial effort and resources: prioritization is thus essential. The aim of this study was to estimate the magnitude of CHD mortality reduction achievable through increased uptake of specific modern cardiology treatments in Ireland, in order to identify those therapies likely to contribute most.
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Methods |
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TopSummaryIntroductionMethodsResultsDiscussionAppendix 1Appendix 2References |
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The IMPACT CHD mortality model has been described in detail elsewhere.12 This model has previously been validated in England and Wales, Scotland, New Zealand, Finland, China, and most recently, in Ireland.12–17 The Irish IMPACT CHD mortality model has been further refined and updated to include recent data on the absolute differences.15 In brief, the number of CHD deaths prevented or postponed by each specific cardiac intervention (and for each population cardiovascular risk factor change) is calculated for Ireland for the base year 1985, and again for the year 2000. In this study, only the treatment effects are analysed.
We identified and incorporated data for men and women aged 25–84 years in the total Irish population of 3.8 million, stratified by age and sex, detailing: (a) CHD patient numbers (ICD 9 codes 410–414), categorized by disease subgroup; (b) use of specific medical and surgical treatments; (c) population trends in major cardiovascular risk factors (smoking, total cholesterol, hypertension, obesity, diabetes, and physical inactivity); (d) effectiveness of specific cardiology treatments; and (e) effectiveness of population cardiovascular risk factors. All public and private patients were included. Those aged 85 years or over were excluded from the model, due to uncertainties regarding death certification accuracy.
Sources of data and cardiology treatment uptake levels
Details of the sources of data considered in this study are shown in Appendices I and II. Appendix II also shows the treatment uptake levels of 2000 for various interventions in Ireland. Data on the effectiveness of therapeutic interventions came from published randomized controlled trials, meta-analyses and cohort studies,2–9 and are also detailed in reference 18, available from the IMPACT website.18
The model included all known medical and surgical treatments in 1985 and 2000
The interventions are listed in Table 1, and included all the interventions considered in earlier versions of the IMPACT Model,13,14 plus primary angioplasty (including stenting) for myocardial infarction, statins for primary prevention, platelet IIB/IIIA inhibitors and clopidogrel for unstable angina, plus spironolactone and beta-blockers for heart failure.12,17 A number of effective therapies were already in limited use in 1985. These included CABG surgery, cardiopulmonary resuscitation, beta-blockers for acute myocardial infarction, diuretics for acute left ventricular heart failure, and therapy for moderate and severe hypertension (defined as diastolic blood pressure >105 mmHg). Patient data for most of these interventions, such as CABG surgery, and eligible hypertensives, were obtained from the data sources detailed in the Appendices.
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The mortality reduction for each treatment was calculated using the absolute mortality reduction reported in published meta-analyses and trials, applied to the age-specific case-fatality rate observed in large unselected patient cohorts.12,17
Polypharmacy issues
The potential effect of multiple treatments in an individual patient was examined using the Mant and Hicks cumulative relative benefit approach:19
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Potential overlaps between patient groups
Patient groups are seldom mutually exclusive. For example, approximately half the patients having CABG surgery have had a previous myocardial infarction, and approximately one fifth of myocardial infarction survivors develop clinical heart failure within 12 months. To avoid double counting, potential overlaps between different groups of patients were identified, and adjustments made using published methods.18
Treatment compliance/adherence
Compliance or adherence, the proportion of treated patients actually taking therapeutically effective levels of medication, was based on recent studies where available. The IMPACT CHD mortality model default assumes levels of compliance were 100% in hospital patients, 70% in symptomatic community patients, and 50% in asymptomatic community patients.20 In summary, this study also looked at patients' adherence to therapeutically effective levels of medication for the general calculation of the number of deaths prevented or postponed due to treatments.
Deaths prevented or postponed due to treatments
This was calculated based on the product of four variables: number of eligible patients for each age-sex-specific cardiology intervention (e.g. number of AMI patients for secondary prevention following AMI), treatment uptake levels, compliance rate (patients' adherence) and absolute risk reduction due to the particular intervention (a product of relative risk and case-fatality rates). Details of the calculations, with examples, are shown in Appendix 5 of the PDF available from the IMPACT website.18
Calculating the effects of increasing treatment uptake
The present study investigates the potential reduction in CHD deaths following a ‘maximum feasible’ treatment uptake level of 80% of eligible patients (100% treatment uptake was considered unrealistic).12,17,18 Such a clinically feasible benchmark of 80% is prescriber-driven, consistent with the methods used in a recent study in the UK.21
Sensitivity analyses
Because of the uncertainties surrounding many of the values, a multi-way sensitivity analysis was performed using the 'analysis of extremes' method.22 Minimum and maximum mortality reductions were generated using 95% CIs from meta-analyses for treatment efficacy, and minimum and maximum plausible values for patient numbers, treatment uptake and adherence.23 This method does not involve any probabilistic interpretation, as in confidence interval estimation, nor does it contain details on the statistical variations around the estimates. Illustrative examples of specific analyses and calculations are shown in the appendices of the recent England and Wales model publication,12 and also in the IMPACT PDF, Appendix 5.18
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Results |
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TopSummaryIntroductionMethodsResultsDiscussionAppendix 1Appendix 2References |
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In 2000, medical and surgical cardiology treatments together prevented or postponed approximately 1950 CHD deaths (minimum estimate 925, maximum estimate 3545) (Table 1). However, increasing the treatment uptake to reach 80% of eligible patients would have prevented or postponed 2180 further CHD deaths (minimum estimate 860, maximum estimate 4000) in the year 2000. The largest reduction in CHD deaths would have come from treating more heart failure patients (43%), and almost 25% from providing statins as primary prevention to 80% of the 915 000 eligible subjects (Table 1). Potential additional gains were modest from increasing the uptake levels of acute myocardial infarction therapies (7%) or secondary prevention in patients following myocardial infarction or revascularization (15%). An 80% increase in surgical revascularization and angioplasty procedures would have gained about 72 fewer deaths, 3.2% of the total (Table 1).
Figure 1 summarizes the proportional contribution of each of the specific cardiology interventions to CHD mortality, if the treatment uptake was increased to reach 80% of eligible patients. The sensitivity analyses in Figure 2 also show that the proportional contribution from each of the modern cardiology interventions remains relatively consistent, irrespective of whether the best, minimum or maximum estimates are considered.
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Discussion |
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TopSummaryIntroductionMethodsResultsDiscussionAppendix 1Appendix 2References |
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In Ireland in 2000, as elsewhere, many eligible patients failed to receive evidence-based therapies. Increasing the treatment uptake level to a clinically feasible 80% might have doubled the actual mortality benefits from modern cardiology treatments (some 2280 fewer CHD deaths, in addition to the baseline of 1950). The largest additional treatment benefit would have come from increasing the proportions of the 12 000 new heart failure cases each year in Ireland.24 This has substantial public-health implications, because the prevalence of heart failure in Ireland is predicted to double by 2010. Additional, important gains could have come from ensuring more patients received secondary prevention therapies after infarction or revascularization.25 An 80% increase in expensive revascularization interventions such as angioplasties and CABG surgery would have very little additional impact (<3%), much as in the UK.25 Similarly, substantial potential reductions in CHD deaths through increased treatment uptake have already been reported in England, Wales and Scotland.21,26
In 1999, the Irish Cardiovascular Health Strategy was launched. This recommended the need for maximizing access to treatment by increasing treatment uptake levels.27 Some specific treatments have indeed increased since then, including a provision of cardiac rehabilitation services to 77% of the eligible patients in 2003 (from a disappointing 29% service provision in 1998).28 Furthermore, the national Heartwatch programme in general practice for the secondary prevention of cardiovascular disease in Ireland, also reported that approximately 50%, 58.3%, and 82.8% of patients were receiving ACE inhibitors, beta-blockers and statins, respectively, in 2004.29 These observations, along with positive UK experiences of the National Service Framework and new General Medical Services Contract, suggest that the 80% modelling targets are clinically realistic and achievable.25
The current uptake of statins for primary prevention is disappointingly low, at around 6% in Ireland. The 565 fewer CHD deaths if statins for primary prevention were extended to reach 80% of some 915 000 eligible subjects appear slightly controversial, given the current Irish health care system. Such a ‘preventative’ measure would medicalize almost one-third of the adult Irish population, and would have substantial resource implications. Although the use of statins for primary prevention is complex, the WOSCOPS study showed the cost-effectiveness of such an intervention.30 Nonetheless, the potential benefit of statins as a primary prevention for CHD deaths is interesting and, justifies rigorous cost-effectiveness evaluations to inform future policy debates.
Limitations of the study
This study focused on the number of deaths rather than events incidence or improvements in case fatality.12,13,17 There are obvious limitations with this type of modelling study. It is very dependent on the quality and extent of data available on treatment uptakes. Explicit assumptions and robust sensitivity analyses become essential to check the validity of the model whenever the data are sparse, or the quality is poor.22,23 Polypharmacy and the potential overlapping of treatment groups were also explicitly addressed.19 That different countries have shown consistent results when the IMPACT CHD model is applied, is also reassuring.21,26 The model included only those aged 25–84 years old, because of very limited data in older groups. The IMPACT model assumes that estimates of efficacy from randomized controlled trials can be generalized to effectiveness in clinical practice.12,17 Although this seems reasonable, further development work is clearly needed.31
In conclusion, effective modern cardiology treatments have already contributed substantially to the overall reduction in coronary mortality in many developed countries, including Ireland. Because resources are always limited, future strategies should prioritize the delivery of secondary prevention and heart failure therapies to all eligible patients. However, a more systematic and widespread application of individual specific therapies to reach 80% of all eligible patients, might more than double the number of deaths prevented or postponed by treatments in Ireland, and in comparable countries.
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Appendix 1 |
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TopSummaryIntroductionMethodsResultsDiscussionAppendix 1Appendix 2References |
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Appendix 2 |
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TopSummaryIntroductionMethodsResultsDiscussionAppendix 1Appendix 2References |
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Acknowledgments |
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Dr Zubair Kabir is funded through a research grant from the Irish Heart Foundation.
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References |
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TopSummaryIntroductionMethodsResultsDiscussionAppendix 1Appendix 2References |
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