Lucan · Conditions
Primary CVD risk assessment
Australian guidance: Australian Chronic Disease Prevention Alliance CVD Risk Guidelines + Calculator (2023)
1. Definition and epidemiology
Atherosclerotic cardiovascular disease (ASCVD) encompasses coronary artery disease, stroke, aortic disease, peripheral artery disease, and renovascular disease — all driven primarily by atherosclerosis. Heart attack and stroke are the leading causes of death and ill health in Australia. Primary CVD risk assessment refers to the structured estimation of a person's probability of experiencing a cardiovascular event within five years in people who do not yet have established ASCVD.
2. Pathophysiology
The underlying mechanism of ASCVD is atherosclerosis, a chronic inflammatory process of medium and large arteries described in detail in Robbins Ch 11. Atherosclerosis begins when circulating low-density lipoprotein (LDL) particles enter the sub-endothelial space and undergo oxidative modification, triggering recruitment of monocytes that differentiate into macrophages. Macrophages ingest oxidised LDL via scavenger receptors and become lipid-laden foam cells, forming the fatty streak. Smooth muscle cells migrate from the media into the intima under the influence of platelet-derived growth factor and proliferate, secreting extracellular matrix to form a fibrous cap over the lipid-rich necrotic core. Rupture or erosion of a vulnerable plaque exposes thrombogenic material, activating platelets and the coagulation cascade and producing an acute occlusive thrombus. This final step, superimposed on chronic plaque burden, is the proximate event in most myocardial infarctions and ischaemic strokes. Modifiable risk factors including hypertension, dyslipidaemia, smoking, and diabetes each accelerate one or more phases of this cascade.
3. Clinical presentation and diagnostic criteria
Primary CVD risk assessment is asymptomatic by definition: there is no presenting complaint. The clinician's task is proactive case-finding among patients who have not yet had a cardiovascular event. Relevant history items include smoking status, personal or family history of premature CVD (first-degree male relative under 55 years or female relative under 65 years), diabetes diagnosis and duration, known hypertension or dyslipidaemia, and use of relevant medications in the preceding six months. Examination findings that directly enter the risk calculation are blood pressure and, indirectly, the presence of atrial fibrillation. The diagnosis of clinically determined high risk is made without formal calculation in two conditions: moderate to severe chronic kidney disease (estimated glomerular filtration rate persistently below 45 mL/min/1.73 m2, or urine albumin-creatinine ratio above 25 mg/mmol in men or above 35 mg/mmol in women) and confirmed familial hypercholesterolaemia. All other patients require formal calculation using the Aus CVD Risk Calculator.
4. Investigations and AU-specific cutoffs
The following are required to run the Aus CVD Risk Calculator:
- Age and sex
- Smoking status (current, ex, never)
- Systolic blood pressure (measured on the day or averaged over recent visits)
- Total cholesterol to high-density lipoprotein cholesterol ratio (TC:HDL-C ratio)
- Diabetes status (absent, type 2 with additional variables, type 1 not validated)
- Atrial fibrillation status
- Postcode (used as a Socioeconomic Indexes for Areas quintile proxy)
- Current use of blood pressure-lowering, lipid-modifying, or antithrombotic medicines in the last six months
For patients with type 2 diabetes, additional inputs refine the estimate: glycated haemoglobin (HbA1c), time since diagnosis in years, urine albumin-creatinine ratio, estimated glomerular filtration rate, body mass index, and whether insulin is being used.
Coronary artery calcium (CAC) scoring by computed tomography is available as an optional reclassification tool but is not Medicare Benefits Schedule subsidised and must not be used in patients with established ASCVD, confirmed high risk, or those already on lipid-modifying therapy.
AU risk category thresholds (five-year event probability, based on PREDICT equation):
| Category | Five-year risk |
|---|---|
| High | 10% or above |
| Intermediate | 5% to below 10% |
| Low | Below 5% |
These thresholds are five percentage points lower than the superseded Framingham-based categories, though each category is considered clinically equivalent because the Framingham equation overestimated absolute risk.
5. Management
Management is stratified by calculated or clinically determined risk category.
High risk (five-year risk 10% or above, or clinically determined high risk) Lifestyle modification advice should be intensive, specific, and sustained, with referral to an accredited practising dietitian or exercise physiologist where appropriate. Both blood pressure-lowering and lipid-modifying pharmacotherapy are recommended unless contraindicated or clinically inappropriate, even when individual risk factors are only mildly elevated. Aspirin is not routinely recommended for primary prevention regardless of risk category, because the incremental benefit is outweighed by bleeding risk in patients already receiving statin and antihypertensive therapy. Formal reassessment using the calculator is not required once pharmacotherapy has been initiated.
Intermediate risk (five-year risk 5% to below 10%) Intensive lifestyle advice is required. Pharmacotherapy should be considered depending on clinical context and patient preference, after shared discussion of the likely benefits and harms. Reassessment using the Aus CVD Risk Calculator is recommended every two years if pharmacotherapy has not been started, or sooner if risk factors worsen or the patient is close to the high-risk threshold.
Low risk (five-year risk below 5%) General lifestyle advice is appropriate. Pharmacotherapy is not routinely recommended but may be discussed if the patient wishes. Reassessment every five years is standard, or sooner if risk factors change.
Reclassification factors that can move a patient to a higher category include: First Nations, Maori, or Pacific Islander ethnicity; South Asian ethnicity; family history of premature CVD; mild chronic kidney disease; and severe mental illness (defined as a condition requiring specialist treatment in the last five years). East Asian ethnicity may support reclassification to a lower category.
For First Nations patients, risk factor screening begins from age 18 years and formal Aus CVD Risk Calculator assessment begins from age 30 years, with reassessment every year or at least every two years regardless of risk category.
6. Pharmacology and AU PBS notes
Blood pressure-lowering therapy First-line agents for ASCVD risk reduction include angiotensin-converting enzyme inhibitors (e.g. perindopril, ramipril), angiotensin II receptor blockers (e.g. irbesartan, candesartan), calcium channel blockers (e.g. amlodipine), and thiazide or thiazide-like diuretics (e.g. indapamide). Choice is guided by comorbidities, tolerability, and blood pressure target. PBS listing for antihypertensives is unrestricted for most agents at standard doses.
Lipid-modifying therapy Statins are first-line for ASCVD risk reduction. Rosuvastatin (e.g. Crestor, generic) and atorvastatin (e.g. Lipitor, generic) are the most commonly used in Australia, with high-intensity dosing preferred for high-risk patients (rosuvastatin 20 to 40 mg or atorvastatin 40 to 80 mg daily). PBS authority is required for some high-intensity statin prescribing. Ezetimibe (e.g. Ezetrol) can be added as a second-line agent when statin monotherapy is insufficient or not tolerated. PCSK9 inhibitors (evolocumab, alirocumab) are PBS-listed under Streamlined Authority for patients with familial hypercholesterolaemia or established ASCVD with LDL-C above threshold despite maximum-tolerated statin plus ezetimibe therapy, but not for primary prevention in the general population.
Additional agents for type 2 diabetes with high ASCVD risk GLP-1 receptor agonists (semaglutide, dulaglutide) and SGLT2 inhibitors (empagliflozin, dapagliflozin) have demonstrated independent cardiovascular benefit in patients with type 2 diabetes at high absolute ASCVD risk. These agents should be considered in this population alongside standard lipid and blood pressure management.
Antiplatelet therapy Aspirin is not recommended for primary prevention in any risk category.
7. Complications and monitoring
Untreated or undertreated ASCVD risk leads to the following complications: acute myocardial infarction, ischaemic stroke, transient ischaemic attack, peripheral artery disease, aortic aneurysm, and sudden cardiac death. In patients with type 2 diabetes, cumulative cardiovascular risk compounds with microvascular complications (nephropathy, retinopathy, neuropathy).
Monitoring schedule by risk category:
- Low risk: reassess five-yearly with repeat lipid panel, blood pressure, and fasting glucose or HbA1c
- Intermediate risk: reassess two-yearly if not on pharmacotherapy; annually once therapy commenced
- High risk: ongoing clinical monitoring of blood pressure response and lipid levels after initiating pharmacotherapy; formal calculator reassessment is not required
- First Nations patients: at minimum every two years regardless of category, ideally annually as part of the annual health check (Medicare item 715)
- All patients on statins: baseline liver function tests and creatine kinase; repeat if symptomatic; annual fasting lipids to assess treatment response
- All patients on ACE inhibitors or ARBs: electrolytes and creatinine at baseline and six to eight weeks after initiation or dose change, then annually
Written for Australian practice and grounded in the guidance named above. Study material only — not medical advice. Always check against current guidelines.