The NICE guideline provides GPs with a clear sequence of evidence-based interventions for the management of post-MI patients, as Dr Malcolm Thomas explains

Ischaemic heart disease (IHD) is the most common cause of death in the UK, accounting for around 24% of all mortality. Acute myocardial infarction (MI) is the most common fatal manifestation of IHD. A GP with a list of 2000 patients would expect five deaths and 12 hospitalisations due to IHD per annum.1

The standardised mortality ratio from IHD in Northumberland, where I practise, is falling, but is still around 10% above the national figure.2 This partly accounts for my interest in this issue.

Post-hospital mortality rates for MI patients are in the order of 5-10% per annum in the UK.3 This statistic, combined with the above prevalence data, indicates a significant population who are amenable to secondary prevention.

Some interventions are long established (e.g. aspirin and beta-blockers). More recently there has been increasing evidence for the effectiveness of newer agents (e.g. statins). Finally, there are interventions for which the evidence is uncertain (e.g. diet and rehabilitation).

Research has shown that even the long-established treatments are not being applied as effectively as possible.4 The time was therefore right for a user-friendly summary of the evidence, hence the Department of Health commissioned the guideline from the Centre for Health Services Research at the University of Newcastle upon Tyne. After NICE was formed, the guideline was inherited by the institute.

The guideline development process is described in detail in the full guideline document5 and has been laid down by the North of England Guideline Development Group.6

Our group (see Table 1, below) met seven times over the course of nearly a year. It was composed of a wide variety of relevant people, including three experts on evidence, and was chaired by Professor Martin Eccles.

Table 1: Composition of the
Guideline Development Group
Designation
Number in group
Group leader
1
Health economist
1
Epidemiologist
1

Patient representative

1
Nurse
1
GP
4
Secondary care doctor
2
Public health doctor
1

The group leader, together with the health economist and the epidemiologist, constituted the research team. They found and collated the evidence and were responsible for drafting the guideline and resourcing the group.

The group members helped to limit and refine the questions. We discussed the significance of the evidence presented to us from the searches and made recommendations based on the strength and quality of the evidence. The specialist members' experience was of great benefit in bringing consistency to our deliberations.

The searches were performed electronically. Meta-analyses and randomised controlled trials (RCTs) were preferred. New meta-analyses were constructed if necessary and individual patient data were tracked down from contact with the researchers where it seemed likely to be worthwhile.

The scale of the task was huge. It was agreed at the first meeting that we needed to limit the scope of the work in order to have a chance of success. The interventions shown in Table 2 (below) were thus excluded from consideration, despite having some or much relevance to the goal of prophylaxis against further MI.

Table 2: Interventions excluded from the remit of the guideline
  • Smoking cessation
  • Symptomatic management of angina
  • Exercise programmes in heart failure
  • Diet (other than the 'Mediterranean diet')
  • Referral to secondary care for worsening symptoms of IHD

The final outcome of our searches was enlightening (see Tables 3 and 4, below). Nearly all the interventions considered had evidence for their effectiveness in relation to mortality, which is a solid endpoint.

Table 3: Interventions not improving mortality
  • Calcium-channel blockers
  • Potassium-channel activators
  • Nitrates
Table 4: Interventions effective at improving mortality
  • ACE inhibitors
  • Antiplatelet agents
  • Beta-blockers
  • Cardiac rehabilitation
  • Mediterranean diet
  • Statins

With respect to the effective interventions, the group faced a number of challenges:

  • Ranking the interventions in order of importance, based on estimates of cost-effectiveness
  • Comparing the evidence between similar interventions, e.g. the trials of drugs typically recruited different patient groups, on different doses of drugs and for different lengths of time.
  • Identifying subgroups of patients who might benefit differentially from different interventions.

The fact that the development group was so representative and the process so rigorous should give end users of the guideline (i.e. GPs) great confidence in its recommendations.

The group discussion was illuminating – there was even some well argued scepticism about some of the enthusiasm for aspirin. In the end we achieved solid consensus on the main conclusions.

The lack of direct comparability between trials was overcome by using two different approaches: profiling and modelling. The profile approach was an attempt to bracket the extremes of cost-benefit calculations, based on the drug acquisition costs and the benefits in reported trials. The modelling approach was an attempt to produce life curves projected beyond the scope of the trials in order to estimate the overall impact that might accrue with the interventions.

It is further evidence of the robustness of the guideline that these two approaches did not come up with materially different conclusions.

The final conclusions suggested that each of the effective interventions would be expected to gain around 6 months of life per patient and that the effects of the interventions were largely additive.

Figure 1 (below) shows the Summary Table derived from the guideline.

Figure 1: Summary table from the NICE guideline 'Prophylaxis for patients who have experienced a myocardial infarction'*
NICE summary table
* Reproduced from Inherited Clinical Guideline A: Prophylaxis for patients who have experienced a myocardial infarction – drug treatment, cardiac rehabilitation and dietary manipulation by kind permission of the National Institute for Clinical Excellence

The summary shown in Figure 1 is a very user-friendly presentation of the evidence. Clear sequencing of a limited and feasible number of interventions is laid out. Three clear subgroups of MI patients are identified.

The upshot is that GPs now have a clear, up-to-date, sequenced summary to guide the processing of patients returning to their care following hospitalisation with MI. This should allow individual patient management and practices' service provision to incorporate best current evidence.

The guideline development group was also able to identify some important unanswered questions (see Table 5, below) and these raise the possibility of commissioning research to answer them to the benefit of future patients.5

Table 5: Unanswered questions
  • What are the important elements of cardiac rehabilitation packages?
  • What is the effectiveness of cardiac rehabilitation in those patient groups excluded from the trials?
  • Which patients with heart failure can have beta-blockers initiated safely in primary care?
  • How effective can dietary manipulation be?
  • How often do serum lipids need measuring after initiation of a statin?
  • What is the role of statins in patients with heart failure?
  • Is spironolactone beneficial in patients with mild (NYHA 1 or 2) heart failure?

A further benefit to patient care is the advice to patients contained in the full NICE version of the guideline, available on the website.7,8 This contains a restatement of the key messages and would allow a patient to become a much more informed and influential agent in his or her own management, very much in line with modern consultation trends.

General practice now has a clear framework to determine the costs of full implementation of the evidence-based treatments for its post-MI patients.

Patients returning after MI will already have had many treatments started. GPs will be able to identify which subgroup they are in and ensure that patients are offered all the treatments for which there is evidence of benefit.

The guideline is relatively simple to audit. The entry point for audit (survival of an MI) is very clear and the treatments are discrete and easily coded electronically. The full guideline5 proposes a number of audit criteria (see Table 6,below).

Table 6: Audit criteria
  • % of all patients with and without heart failure appropriately taking beta-blockers
  • % of all patients with and without heart failure appropriately taking aspirin
  • % of all patients with and without heart failure appropriately taking a statin
  • % of patients with and without heart failure appropriately taking an ACE inhibitor
  • % of patients with heart failure appropriately taking spironolactone
  • % of all patients (i) offered and (ii) enrolled into a rehabilitation programme

Given the relatively small number of patients that each GP will see (fewer than one every 2 months) returning home immediately post-MI, and given that much treatment will typically have been started in hospital, this guideline is not as onerous as many other recent exhortations to GPs.

If the guideline can be implemented effectively, a substantial amount of morbidity and mortality can potentially be avoided.

There are a number of resource costs, which the guideline does not specifically mention, with its focus on the individual patient:

  • Drug acquisition costs
  • Clinical time costs (notably GP and practice nurse)
  • Expanded referral services (dietary and exercise).

This is a very important guideline. It identifies a clear target group of patients and proposes a defined and sequenced range of evidence-based interventions for them.

It promises significant reductions in mortality and morbidity and it is to be hoped that its adoption by NICE will lead to its effective implementation throughout England and Wales.

  1. Office for National Statistics. 1997 Mortality Statistics: cause. Series DH2 No. 24. London: The Stationery Office, 1998.
  2. Northumberland Health Authority Annual Reports. Morpeth. Northumberland Health Authority. Various years.
  3. Rouleau JL, Talajic M, Sussex B et al. MI patients in the 1990s – their risk factors, stratification and survival in Canada: The Canadian Assessment of MI (CAMI) Study. J Am Coll Cardiol 1996; 27: 1119-27.
  4. Eccles MP, Bradshaw C. Secondary prophylaxis of myocardial infarction in the North of England. Br Med J 1991; 302: 91-2.
  5. North of England Evidence-based Guidelines Development Project. Prophylaxis for patients who have experienced a myocardial infarction: drug treatment, cardiac rehabilitation and dietary manipulation. Centre for Health Services Research Report No 106. University of Newcastle upon Tyne. 2000.
  6. Eccles M, Freemantle N, Mason JM. Methods of developing guidelines for efficient drug use in primary care: North of England Evidence-based Guidelines Development Project. Br Med J 1998, 316: 1232-5.
  7. National Institute for Clinical Excellence. 2001. Compilation Vol. 2: 9-14.
  8. National Institute for Clinical Excellence website: www.nice.org.uk

 Dr Malcolm Thomas is a GP in Guidepost, Northumberland, and a member of the Guideline Development Group

Guidelines in Practice, September 2001, Volume 4(9)
© 2001 MGP Ltd
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