Professor David Wood explains why an integrated strategy involving both primary and secondary care is essential to reduce the burden of cardiovascular disease

The scientific evidence for prevention of coronary heart disease (CHD) is among the best of any aspect of contemporary medicine, and yet clinical practice often falls short in implementing this evidence.1

The European societies of cardiology, atherosclerosis and hypertension joined forces to publish recommendations on CHD prevention in 1994 and these were updated in 1998.2

This valuable collaboration between the professional societies with a common interest in reducing the burden of cardiovascular disease in Europe encouraged the British Cardiac Society to cooperate with the British Hyperlipidaemia Association and the British Hypertension Society in preparing national recommendations, which have also been endorsed by the British Diabetic Association.3

In putting forward joint recommendations on CHD prevention, the professional societies hoped to promote a more unified, and hence effective, approach to prevention of CHD in clinical practice. To achieve a unified approach it is necessary to embrace allqof the cardiovascular risk factors, rather than focusing on a single risk factor and treating it in isolation.

Hospital specialists and GPs need to coordinate their efforts and, with the support of other health professionals, create an integrated hospital- and community-based clinical strategy for prevention of CHD and other atherosclerotic diseases.

Priorities for CHD prevention in clinical practice

  • a. Patients with established CHD

    b. Patients with other major atherosclerotic disease

  • Individuals with hypertension, dyslipidaemia, diabetes mellitus,family history of premature CHD, or a combination of these risk factors, which puts them at high risk of developing CHD or other atherosclerotic disease. Patients with diabetes0mellitus are at particularly high risk of CHD.

  •  In patients with established CHD and/or other major atherosclerotic disease: to reduce the risk of a further major cardiac event, i.e. unstable angina or myocardial infarction (MI), or re-infarction, and the need for coronary revascularisation procedures, and to reduce overall mortality.
  • In high-risk individuals in the general population: to reduce substantially the risk of such individuals developing CHD or other major atherosclerotic disease.

In 1994 the Health Survey for England reported that 7.1% of men and 5.2% of women aged 16-74 years gave a history of angina, MI or stroke. These patients are already known to hospital and general practice, and are at high risk of recurrent CHD or other atherosclerotic disease. They are therefore the first priority for CHD prevention in clinical practice and every effort should be made to achieve the lifestyle, risk factor and therapeutic goals given in the summary (Figure 1).

Figure 1: Summary of the Joint British recommendations on prevention of CHD in clinical practice

In patients with CHD or other major atherosclerotic disease, and individuals at high multifactorial risk* of developing CHD, the following lifestyle, risk factor and therapeutic targets should be achieved:

Lifestyle

Discontinue smoking, make healthier food choices, increase aerobic exercise, and moderate alcohol consumption.
Other risk factors
Body mass index <25 kg/m2 is desirable, with no central obesity
BP <140mmHg systolic and <85mmHg diastolic
Total cholesterol <5.0mmol/l (LDL cholesterol <3.0mmol/l)
Optimal control of diabetes mellitus and BP reduced to <130 mHg systolic and <80mmHg diastolic (and when there is proteinuria BP <125mmHg systolic and <75mmHg diastolic)

Cardioprotective drug therapy

Aspirin for all coronary patients and those with other major athero- sclerotic disease, and for healthy individuals who are older than 50 years and are either well-controlled hypertensive patients or men at high risk of CHD
Beta-blockers at the doses prescribed in the clinical trials following MI, particularly in high-risk patients, and for at least 3 years
Cholesterol-lowering therapy (statins) at the doses prescribed in the clinical trials
ACE inhibitors at the doses prescribed in the clinical trials for patients with symptoms or signs of heart failure at the time of MI, or for those Pith persistent left ventricular systolic dysfunction (ejection fraction <40%)
Anticoagulants for patients at risk of systemic embolisation

Screening of first-degree blood relatives

Screening of first-degree blood relatives (principally siblings and offspring aged 18 years or older) of patients with premature CHD (men <55 years and women <65 years) or other atherosclerotic disease is encouraged, and in the context of familial dyslipidaemias is essential

* For the healthy population, high multifactorial risk is defined as an absolute risk of >15% of developing CHD (non-fatal MI or coronary death) over the next 10 years, which can be estimated from the coronary risk prediction chart (see pp. 32-33) or the coronary risk assessor computer program.

The hospital care of patients with CHD or other atherosclerotic disease should embrace all aspects of cardiac prevention and rehabilitation. Such an integrated service should be available to all patients post-MI, to those with treated unstable angina or exertional angina and to all patients following revascularisation by angioplasty or coronary artery surgery.

It is essential to integrate the care of these patients between hospital and general practice, through the use of common protocols to ensure optimal long-term lifestyle, risk factor and therapeutic management.

Auditing the impact of these common clinical protocols on management is strongly recommended.

For those individuals without symptomatic disease, attendance at hospital or general practice should be seen as an opportunity to assess the risk of CHD – the probability of developing non-fatal MI or fatal CHD over a defined time period, given a particular combination of risk factors – and to intervene appropriately depending on the degree to which they are at risk. Taking account of all major cardiovascular risk factors avoids undue emphasis being placed on an individual risk factor at the expense of overall CHD risk.

Risk factors exert a cumulative effect on absolute CHD risk. Therefore, an individual with a number of mildly abnormal risk factors may be at a level of absolute CHD risk greater than that of someone with just one high risk factor.

For example, using the Framingham risk equation one can calculate that a man of age 50 years, a non-smoker, with a systolic blood pressure (BP) of 125mmHg, a serum cholesterol reading of 8.2mmol/l, and a high density lipoprotein (HDL) cholesterol of 1.0mmol/l, has an absolute risk of developing a CHD event of about 15% over the next 10 years.

In contrast, a man of the same age who as diabetes mellitus, smokes cigarettes, has a systolic BP of 140mmHg, a cholesterol of 6.2mmol/l, and an HDL cholesterol of 0.8mmol/l has an absolute risk of about 30% over the same period. In other words, his risk of developing a CHD event compared with the first man (relative risk) is increased twofold, despite the fact that none of his risk factors (apart from smoking), when considered individually, would be deemed sufficiently high to merit intervention.

Taking a unified, unifactorial approach, the first man's cholesterol may be thought sufficiently high to require treatment by diet, and possibly even drug therapy, although his absolute CHD risk is lower than that of the second man.

In individuals without symptomatic disease, absolute risk of developing CHD or other atherosclerotic disease, should always be estimated before the decision to introduce medication, e.g. to decrease BP or serum cholesterol.

The coronary risk prediction chart (below) can be used to estimate an individual's absolute risk of developing CHD based on his/her age, gender, smoking habit, systolic BP, total cholesterol to HDL cholesterol ratio, and whether or not they have diabetes mellitus. A computer program (cardiac risk assessor program) is also available for making the same calculation. It can be used to calculate CHD and cardiovascular risk (including stroke).

Coronary Risk Prediction Chart
coronary risk prediction chart - no diabetes
coronary risk prediction chart - diabetes

The chart is for estimating coronary heart disease (CHD) risk (non-fatal MI and coronary death) for individuals who have not developed symptomatic CHD or other major atherosclerotic disease. Patients with CHD are already at high risk and require intensive lifestyle intervention, and, as necessary, drug therapies to achieve risk factor targets.

To estimate an individual's absolute 10-year risk of developing CHD, find the table for their gender, diabetes (yes/no), smoking status (smoker/non-smoker) and age. Within this square, define the level of risk according to systolic blood pressure (BP) and the ratio of total cholesterol to HDL cholesterol. If there is no HDL cholesterol result, assume this to be 1.0 and then use the lipid scale as for total cholesterol alone.
High-risk individuals are defined as those whose 10-year CHD risk exceeds 15% (equivalent to a cardiovascular risk of 20% over the same period). As a minimum, those at highest risk (>30% red) should be targeted and treated now, and, as resources allow, those with a risk of >15% (orange) should be progressively targeted.
Smoking status should reflect lifetime exposure to tobacco and not simply tobacco use at the time of risk assessment.
The initial BP and the first random (non-fasting) total cholesterol and HDL cholesterol should be used to estimate an individual's risk. However, a decision on using drug therapy must be based on repeat measurements over a period of time. Where drug therapy has already been prescribed the BP or blood lipid levels before treatment should be used to estimate CHD risk.

CHD risk is higher than indicated in the chart for:

  • Those with a family history of premature CHD ( men <55 years and women <65 years), which increases the risk by a factor of approximately 1.5
  • Those with raised triglyceride levels
  • Those with impaired glucose tolerance
  • Women with premature menopause
  • Those approaching the next age category. As risk increases exponentially with age, the risk will be closer to the higher decennium for the last 4 years of each decade.

The chart should not be used for predicting risk in patients with:

  • CHD or other major atherosclerotic disease
  • Familial hypercholesterolaemia or other inherited dyslipidaemia
  • Severe hypertension (systolic BP >160 mmHg and/or diastolic BP >100mmHg) or associated target organ damage
  • Diabetes mellitus with associated target organ damage
  • Renal dysfunction
In ethnic minorities the risk chart should be used with caution as it has not been validated in these populations.
The estimates of CHD risk from the chart are based on groups of people, and in managing an individual the physician also has to use clinical judgment in deciding how intensively to intervene on lifestyle and whether or not to use drug therapies.
An individual can be shown on the chart the effect of changing smoking status, BP or cholesterol on their risk of CHD.

A staged approach to the management of high-risk individuals is advised to ensure that resources for identification, investigation and management are used appropriately and effectively, starting with those at highest risk. As a minimum, individuals with an absolute CHD risk of 30% or greater over 10 years should be targeted and treated now.

Then, as resources allow, individuals with a 10-year absolute CHD risk of 15% or greater should be progressively targeted. The coronary risk prediction chart identifies healthy individuals at highest CHD risk (30% or higher, red band), those at the next level of CHD risk (15% or higher, orange band) and finally those whose CHD risk is <15% (green band). [back to chart]

For individuals with a 10-year absolute CHD risk of <15%, appropriate lifestyle advice (e.g. stop smoking) should still be given, but drug treatment is usually not justified unless there is severe hypertension (systolic BP >160mmHg and/or diastolic BP >100mmHg) or associated target organ damage, familial hypercholesterolaemia or other inherited dyslipidaemia, or diabetes mellitus with associated target organ damage.

The proportions of men and women aged 30-74 years with an absolute CHD risk of 15% or greater in England are 12% and 5% respectively.

Taking a progressive staged approach to CHD prevention ensures that those at highest risk are targeted first and the delivery of care is commensurate with the ability of medical services to identify, investigate, and manage patients properly over the long term.

In these high-risk individuals, every effort should be made to achieve the lifestyle, risk factor (Figures 2 and 3 for the management of blood pressure and blood lipids in primary prevention) and therapeutic targets defined in the summary (Figure 1, above).

Figure 2: Management of blood pressure in the primary prevention of CHD and other atherosclerotic disease
algorithm
The British Hypertension Society guidelines on measurement of blood pressure (BP) are recommended. The initial BP measurement should be used in estimating an individual's absolute risk of CHD (or cardiovascular disease).
Lifestyle advice should be given to everyone, and in the context of BP particular attention should be paid to obesity, dietary salt and consumption of alcohol.
Antihypertensive drug therapy should only be considered after an appropriate period of observation during which lifestyle measures are reinforced, BP is repeatedly measured and the result is interpreted in the context of absolute CHD (or cardiovascular) risk.
Secondary causes of hypertension should always be considered before starting drug therapy and, where appropriate, referral to a specialist should be made.
 
Figure 3: Management of blood lipids in the primary prevention of CHD and other atherosclerotic disease
algorithm
Total blood cholesterol and HDL cholesterol can be measured in a non-fasting state. The initial random (non-fasting) cholesterol measurement should be used in estimating an individual's absolute risk of CHD.
When an HDL cholesterol measurement is not available, assume this is 1.0mmol/l and use the lipid scale on the risk chart as for total cholesterol.
Lipid modification with drug therapy should only be considered after an appropriate period of observation during which lifestyle measures are reinforced, blood lipid measurements are repeated, including at least one fasting sample, and the result is interpreted in the context of absolute CHD risk.
Fasting lipids should be measured on a blood sample taken after at least a 12-hour fast (usually from 10pm the previous evening); in addition to total and HDL cholesterol, this will provide a reliable measure of triglycerides.
Secondary causes of dyslipidaemia should always be considered before starting drug therapy, and, where appropriate, referral to a specialist should be made.
LDL (low density lipoprotein) cholesterol can be calculated using the Friedewald formula: LDL cholesterol (mmol/l) = total cholesterol – HDL cholesterol – 0.45 x triglyceride (fasting). This formula cannot be used if the triglyceride level is higher than 4.5mmol/l.

In the hospital sector, the care of high-risk patients in hypertension, lipid and diabetes clinics should be coordinated between specialists, based on agreed protocols to ensure a common approach to multifactorial risk assessment, lifestyle and therapeutic interventions. The care of such high-risk patients treated in specialised hospital clinics should be integrated with general practice to ensure, through the use of agreed clinical protocols, optimal long-term management.

Auditing the impact of these clinical protocols for hospital and general practice, on the identification and management of high-risk individuals, is strongly recommended.

  • Copies of the Joint British Recommendations on Prevention of Coronary Heart Disease in Clinical Practice, together with the Cardiac Risk Assessor computer program, can be obtained from the British Cardiac Society, 9 Fitzroy Square, London W1P 5AH; Tel: 020 7383 3887; Fax: 020 7388 0903.

  1. Bowker TJ, Clayton TC, Pyke SDM, Wood DA. ASPIRE Steering Group. A British Cardiac Society survey of the potential for the secondary prevention of coronary disease: ASPIRE principal results. Heart 1996; 75: 34-342.
  2. Wood DA, De Backer G, Faergeman O, Graham I, Mancia G, Pyorala K on behalf of the Task Force members. Prevention of Coronary Heart Disease in Clinical Practice. Recommendations of the Second Joint Task Force of European and other Societies on Coronary Prevention. Eur Heart J 1998; 19:1434-503.
  3. Wood DA, Durrington P, McInnes G, Poulter N, Rees A, Wray R. Joint British Recommendations on Prevention of Coronary Heart Disease in Clinical Practice. Heart 1998; 80(Suppl 2):1-28.

Guidelines in Practice, May 1999, Volume 2
© 1999 MGP Ltd
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