What is a cardiac risk assessment?
As we get older we all have some risk of developing ‘hardening of the arteries’ (atheroma) which can lead to cardiovascular disease – a heart attack or stroke. Factors that increase the risk are used in cardiac risk assessment which calculates the probability of cardiovascular disease developing within a defined period.
What is included in a cardiac risk assessment?
The risk factors for heart attack and stroke can be divided into those that can be reduced by altering life-style, those that are potentially treatable and those that are fixed.
Life-style risk factors are smoking, lack of exercise, obesity, an unhealthy diet and excess alcohol.
Fixed risk factors include having a strong family history, belonging to certain ethnic groups (for example, being of South Asian ancestry), your age, and being male or being female after an early menopause. Age and social deprivation are risk factors that are, of course, not permanently fixed.
How is a risk assessment carried out?
NHS GP practices invite patients aged between 40 and 75 who are not already being treated for heart disease, diabetes or kidney disease to attend for cardiac risk assessment. The assessment is repeated every five years.
First, you are asked to answer questions about the three kinds of risk factor. If you have a strong family history (your mother, father, sister or brother having had a heart attack or angina before 60) it is likely that your immediate family of all ages will also be invited to attend for risk assessment.
Your blood pressure is taken and your height and weight are measured. Height and weight are used to calculate your body mass index (BMI) as a measure of obesity.
A blood sample is sent to a laboratory for measurement of a lipid profile, the most important blood test for risk assessment. It measures cholesterol, high density lipoprotein cholesterol (HDL-C, “good cholesterol”), low density lipoprotein cholesterol (LDL-C, “bad cholesterol”) and triglycerides. Triglycerides are the major form of fat found in the body. Below are the desirable ranges for the components of the lipid profile:
- Total cholesterol 5.0 mmol/L or less
- HDL-cholesterol 1.20 mmol/L or more
- LDL-cholesterol 3.0 mmol/L or less
- Total cholesterol/HDL ratio 4.5 or less
- Triglycerides 1.70 mmol/L or less
The blood sample may be analysed for two other potentially treatable risk factors. Plasma glycated haemoglobin (HbA1c) may be measured for the diagnosis of diabetes. Plasma creatinine may also be measured. Together with your age, weight and gender, it is used to calculate your estimated glomerular filtration rate (eGFR) for the diagnosis of kidney disease.
Other blood tests that have been proposed for cardiac risk prediction include high sensitivity C-reactive protein (hsCRP) and lipoprotein A (Lp(a)). However, there is no clear consensus about their use and they are not routine tests.
How is risk calculated?
There has been a large amount of research into the best way of calculating cardiovascular risk from assessed risk factors. The National Institute for Health and Care Excellence (NICE) recommends the computer program QRISK®2 as the preferred method, and this is now integrated into all four of the main UK general practice computer systems. Computer input includes age, sex, ethnicity, postcode (to assess social deprivation), smoking status, and selected medical and family history together with systolic blood pressure, body mass index (BMI) and the total cholesterol/HDL-cholesterol ratio.
QRISK®2 calculates a risk score for the chance of developing cardiovascular disease over the next ten years. A risk score of 10%, for example, means that there is a one in five chance. Because risk increases with age, and is higher in men than women and also in certain ethnic groups, the program also produces a relative risk score: the ratio of the calculated risk to the risk in healthy people of the same age, sex and ethnicity. For example, an elderly man might have a risk score of 20% but a relative risk score of 1.0 because he has the risk to be expected in a healthy man of his age. For more about QRISK®2 click its ‘Information’ tab.
How is the result used?
Most people, but not all, can reduce whatever risk they have of developing a cardiovascular disease by changes to their lifestyle. They should stop smoking, avoid passive smoking, increase physical activity, lose weight if overweight, eat a healthy diet and limit alcohol consumption. Repeat assessment will show how well they have succeeded in reducing their risk.
In 2014 NICE recommended that for people with a Q®RISK risk score of 10% or more, GPs should not only offer life-style advice and help but also discuss the benefits and risks of taking a cholesterol-lowering drug. It suggested a statin should be offered unless the person is committed to life-style changes likely to reduce their risk score below 10%. This suggestion has sparked a lively controversy about the ‘medicalisation of five million healthy individuals’.