CVD risk categories

The Aus CVD Risk Calculator produces a CVD risk estimate expressed as a percentage probability of dying or being hospitalised due to myocardial infarction, angina, other coronary heart disease, stroke, transient ischaemic attack, peripheral vascular disease, congestive heart failure or other ischaemic CVD-related conditions within the next 5 years. To streamline this terminology for consumer-facing communications and aid implementation, the CVD risk estimate can be simplified to: the probability of experiencing a heart attack, stroke or vascular disease in the next 5 years.

Based on this score, people can be placed into one of three risk categories, which will determine the management approach: low (<5%), intermediate (5% to <10%), or high (≥10%) risk (see Table 5).

Although this updated guideline recommends initiating treatment in people at CVD risk ≥10%, this risk level for initiating treatment is likely to be comparable to the previously recommended 15% CVD risk level calculated using the Framingham equation.

For more information on treatment thresholds, refer to Manage CVD risk - Pharmacotherapy. 

Table 5: Estimated 5-year CVD risk categories based on the Aus CVD Risk Calculator

CVD risk assessment frequency and intervals using the Aus CVD Risk Calculator

General considerations

The optimal interval between baseline CVD risk assessment and subsequent CVD risk reassessments balances the objective of detecting increased risk as early as possible to inform treatment decisions with that of avoiding unnecessary assessments.

Available evidence indicates that, in general, CVD risk increases slowly and gradually.³³,³⁴ Therefore, assessments to detect meaningful increases in risk are best conducted several years apart; more frequent assessments are unlikely to be necessary and may also detect fluctuations in CVD risk factors rather than substantive changes in overall risk.

Those with estimated risk closer to the 5% or 10% thresholds may benefit from earlier reassessment.

Within any risk category, people closer to the upper risk threshold will tend to cross into the next risk category soonest. Accordingly, earlier assessment of people closer to the upper risk treatment threshold will help to detect the need for intervention to reduce CVD risk.

Practice points

• For people in the low risk category whose estimated CVD risk is close to 5%, the decision to reassess risk earlier than 5 years should be made in partnership with the person.
• Similarly, for people in the intermediate risk category whose estimated risk is close to 10%, the decision to reassess risk earlier than 2 years should be made in partnership with the person.
• For people in a high risk category, reassessing CVD risk with the Aus CVD Risk Calculator is not necessary, but can be considered in cases where it may promote continuing pharmacological treatment or lifestyle^* modifications (e.g. when the agreed management goal is to reach a lower risk level, rather than to reach a specific blood pressure or lipid target).

* This guideline refers to certain modifiable risk factors as ‘lifestyle’ factors. However, it is recognised that these behaviours are not necessarily an individual’s choice, but reflect the complex interplay of social, cultural, and environmental factors, which may be further influenced by clinical conditions. Use of the term ‘lifestyle’ does not attribute blame to a person.

First Nations people

Practice points

It is recommended that First Nations people receive a CVD risk assessment as part of an annual health check, or opportunistically, or at least every 2 years.³⁵

This recommendation is based on:

• the higher rate of CVD compared with non-Indigenous peers
• greater prevalence and earlier onset of risk factors such as diabetes and CKD
• limited literature on population-specific risk transition and progression of disease.³⁵

Support for the recommendations

No evidence specific to the Australian intermediate risk category (5% to <10% probability of a cardiovascular event within 5 years) was identified. The recommendation for assessing risk at 2-year intervals is based on evidence that assessment should be more frequent at higher levels of risk, and this is broadly consistent with the previous guideline.

Cohort study data from people in Japan and the US aged 30–74 years and at low CVD risk (<5% probability of a cardiovascular event within 5 years) suggest that reassessment after 3 years is likely to detect a transition to high risk (≥10% probability of a cardiovascular event within 5 years) in <1% of this group. Reassessment after 8 years is likely to detect transition to high risk in about 0.5–9% of this group.³⁴ In the absence of more specific evidence, a reassessment interval of 5 years is likely to be sufficient to detect a meaningful change in risk, as well as early detection of progression to a higher risk status.

A UK cohort study in adults aged 40–64 years without CVD, who were screened every 5 years to determine 10 year risk of a major cardiovascular event (fatal CHD, non-fatal MI, and fatal or non-fatal stroke), found that more frequent risk category-based assessments in people with a 5% to 7.5% 10-year risk were associated with prevention of cardiovascular events.³³