Overview of atherosclerotic cardiovascular disease risk estimation

Australian Chronic Disease Prevention Alliance 2023

Cardiovascular disease (CVD) is a broad term encompassing all diseases affecting the heart and vascular system irrespective of an association to atherosclerosis. The cause of CVD is often atherosclerosis. Atherosclerotic cardiovascular disease (ASCVD) includes coronary artery disease, stroke, aortic disease, and other vascular diseases such as peripheral artery disease and renovascular disease.

Heart attack and stroke are the leading causes of death and ill health in the world. The majority of patients who develop a cardiovascular event (eg heart attack, stroke) have identifiable cardiovascular risk factors, many of which are amenable to lifestyle and therapeutic (including drug) interventions.

Estimates of ASCVD risk indicate the probability of a person having a cardiovascular event within a specified period of time. Risk calculators take into account multiple interacting risk factors (eg age, sex, blood pressure [BP], diabetes status) to estimate a person’s ASCVD risk. This is superior to using a single risk factor (eg elevated BP) for clinical decision-making, as it more accurately predicts who will have a subsequent cardiovascular event. Risk calculation can identify people who would otherwise not be recognised as being at high risk (because their individual risk factors are not markedly elevated), as well as those at low risk who might otherwise be treated (because a single risk factor is elevated).

The recommendations in this topic are based on the 2023 Australian Chronic Disease Prevention Alliance (ACDPA) ‘Guideline for assessing and managing cardiovascular disease risk’. The ACDPA Aus CVD risk calculator is the most appropriate tool for estimating ASCVD risk in the Australian context. The calculator is based on the PREDICT risk equation, which was developed from a large New Zealand population cohort study and modified to apply to the Australian context. Previously, a calculator based on the Framingham risk equation was used in Australia.

The Aus CVD risk calculator estimates a person’s risk over 5 years based on the PREDICT risk equation and stratifies risk into the following categories:

  • high risk – more than 10% risk of a cardiovascular event over 5 years
  • intermediate risk – 5 to 10% risk of a cardiovascular event over 5 years
  • low risk – less than 5% risk of a cardiovascular event over 5 years.

The thresholds for each risk category according to the PREDICT risk equation are 5% lower than those in the previously used Framingham risk equation (eg the PREDICT equation categorises 10% as high risk, compared to 15% with the Framingham equation). However, it is believed that each risk category is clinically comparable to the corresponding category in the previous risk calculator, because the Framingham risk equation likely overestimated risk.

For further information on estimating ASCVD risk, see:

Consider the goals of therapy when managing and counselling a person based on their ASCVD risk estimate. For example, the primary purpose of BP-lowering drugs is not blood pressure reduction, but to reduce the long-term risk of a cardiovascular event or other adverse outcome. Drug therapy for ASCVD is usually used long term. Continue therapy until goals of care change. Stopping drug therapy may be appropriate in a patient who is no longer likely to benefit from treatment (eg patients with palliative care needs); see also Rationalising cardiovascular drugs in palliative care.