Audit of secondary prevention in CHD patients in Dr Rob Wicks' practice highlighted the need to improve targeting, particularly among patients with angina


   

Cardiovascular disease is the main cause of death in the UK, accounting for 300 000 deaths in 1996 alone. Although the overall mortality is falling, the UK is still the 8th worst country in the world behind Russia, Lithuania and Latvia, and is the worst among the other developed nations. Our progress in reducing mortality also lags behind other similarly developed nations.

The importance of avoiding known risk factors for coronary heart disease (CHD), such as high blood pressure, smoking and raised cholesterol levels, is well known, but primary prevention is costly and not as effective as secondary prevention.

Secondary prevention strategies need far fewer patients to be treated to save a life or prevent a further clinical event. One third of myocardial infarctions (MIs) occur in those with known CHD. Despite this, in the UK heart attack survey, 46% of those who died were already known to have CHD.1

 

The risk of a secondary vascular event can be reduced by:

Antiplatelet therapy, i.e. aspirin or clopidogrel
Beta-blockers
Angiotensin-converting enzyme (ACE) inhibitors

Cholesterol-lowering drugs.

It is well known that aspirin reduces the risk of a secondary event in CHD.

Eleven randomised trials of antiplatelet therapy in patients with MI over 27 months showed a significant reduction (P<0.00001) in the risk of suffering a further vascular event.2 This paper suggested that unless therecwere contraindications, all at-risk patients should be taking some sort of antiplatelet therapy.

We decided to concentrate our health promotion activities on secondary prevention of CHD and stroke for the reasons outlined above.

In the last year we have concentrated on getting all of our patients at risk of a secondary event onto aspirin or clopidogrel, and for the purpose of the audit we also included patients who were on warfarin.

We wanted a treatment that would be both cheap and cost-effective. Apart from aspirin, the available drugs, although proven, were costly.

 

East Sussex MAAG published a protocol for audit of secondary prevention in May 1999. The following suggested acceptable standards are from this protocol:

Myocardial infarction
90%
Atrial fibrillation
75-90%
Angina
90%
Coronary artery bypass graft (CABG)
90%
Transient ischaemic attack (TIA)/cerebrovascular accident (CVA)
80%

 

The computer database was searched for all patients with MI, CVA or TIA, atrial fibrillation, angina or CABG. The patients' records were then searched for evidence of aspirin, clopidogrel or warfarin therapy.

The results for September 1999 are shown in Table 1 (below).

Table 1: Audit results for September 1999
Diagnosis
Numbers
Numbers on prophylaxis
Percentage on prophylaxis
Acceptable standard
Myocardial infarction
73
61
83%
90%
Atrial fibrillation
25
22
88%
75–90%
Angina
83
54
65%
90%
Coronary artery bypass graft
13
9
65%
90%
Transient ischaemic attack/ cerebrovascular accident
59
52
88%
80%
Totals
253
198
78%
 

 

The initial audit showed that althoughlwe were close to the suggested target for secondary prevention in many areas, we seemed to be missing many patients, particularly those with angina.

We decided to produce lists for each doctor in the practice to try to find out why these patients were not receiving prophylactic medication. The results were interesting.

Of the 55 patients not taking prophylactic aspirin, 8 had contraindications to therapy, 20 were already taking aspirin, usually buying it themselves, one proved to be a ghost, six were wrongly listed as having angina, and for the remaining 10 there were no excuses!

We decided to update the records and start those at risk of a secondary cardiovascular event on prophylaxis. A re-audit was planned for December 1999.

The results of the re-audit are shown in Table 2 (below). The method was exactly the same, but the numbers of patients had changed slightly from the time of the first audit.

Table 2: Audit results for December 1999
Diagnosis
Numbers
Numbers on prophylaxis
Percentage on prophylaxis
Acceptable standard
Myocardial infarction
69
62
90%
90%
Atrial fibrillation
26
24
92%
75–90%
Angina
83
61
73%
90%
Coronary artery bypass graft
13
15
93%
90%
Transient ischaemic attack/cerebrovascular accident
71
66
92%
80%
Totals
262
228
86%
 

The re-audit results are gratifying in that we have reached the standard in four of the five areas. We are still missing some angina patients, possibly because the diagnosis has a less definite end-point than the other categories.

We also now know that most of those not on prophylactic medication have contraindications to therapy.

We hope that this strategy will lead to fewer complications and secondary vascular events in the future.

 

The other three therapeutic areas mentioned earlier should also be addressed if we are to have a coherent secondary prevention strategy. An NHS circular that arrived early in the new year stresses the Government's commitment to reducing the burden of CHD. The experience in Stockport published in this journal last month3 also provides food for thought.

Patients with CHD who have a cholesterol level >6.2 mmol/l have 10 times the risk of a further cardiovascular event compared with those with a cholesterol level <5.2 mmol/l. Both the CARE trial4 and the LIPID study5 in 1991 have demonstrated the benefits of statin medication for patients with CHD.

It is well known that beta-blockers reduce the rates of death, re-infarction and sudden death by 20–30% and are thus an effective therapeutic agent for secondary prevention.

ACE inhibitors produced a 27% reduction in the death rate post-MI and a 19% reduction in further vascular events, in the AIRE study in 1993.6

In our audited cohort, only 21% are taking ACE inhibitors and the figure for beta-blockers and statins is only a little better at 28%. A rough estimate shows that we would spend an extra £42 000 a year in just this area if we were to treat all patients requiring secondary prevention. The question is how committed is the Government to reducing the incidence of CHD to that in the other developed nations.

Unless some extra money is found it is going to be difficult to reduce mortality and morbidity without cutting back in other clinical areas.

 

  1. Norris RM. UK Heart Attack Survey. Br Med J 1998; 316: 1065.
  2. Antiplatelet Trialists Collaboration. Overview of randomised trials of antiplatelet therapy. Br Med J 1994; 308: 81.
  3. Bell N, Jones M. Audit improves GP management of raised cholesterol. Guidelines in Practice, December 1999; 2: 43-8.
  4. CARE (Cholesterol and Recurrent Events) trial. N Engl J Med 1996; 335(14): 1001.
  5. LIPID (Long-term Intervention with Pravastatin in Ischaemic Disease) Study. N Engl J Med 1998; 339(19): 1349.
  6. AIRE (Acute Infarction Ramipril Efficacy) Study. Lancet 1993; 342: 821.

Guidelines in Practice, March 2000, Volume 3
© 2000 MGP Ltd
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