Cardiovascular Risk Assessment and Primary Prevention

Medical Student Learning Objective: MS_CARD_025

Definition / Overview

Cardiovascular disease (CVD) - encompassing coronary artery disease, ischaemic stroke, transient ischaemic attack, and peripheral arterial disease - remains a leading cause of premature mortality and morbidity in Australia. Primary prevention refers to interventions applied before a first clinical cardiovascular event, with the goal of reducing both the incidence and burden of atherosclerotic disease.

The cornerstone of the Australian approach is absolute cardiovascular risk assessment: calculating the probability that an individual will experience a major cardiovascular event over the next 5 years, then using that probability to guide the intensity of preventive intervention. This contrasts with older paradigms that treated individual risk factors in isolation.

• The current national framework uses a validated risk calculator specifically updated in 2023 and available online via the national CVD check resource.
• Risk is expressed as a percentage probability of a major CVD event over 5 years.
• Management intensity is matched to absolute risk category (low, intermediate, high).

Pathophysiology of Atherosclerotic CVD

Understanding the underlying biology informs why modifiable risk factors matter.

• Endothelial injury (from hypertension, dyslipidaemia, smoking, hyperglycaemia, inflammation) initiates a cascade of monocyte recruitment, foam cell formation, and lipid deposition beneath the arterial intima.
• Atherosclerotic plaques develop over decades, progressively narrowing the arterial lumen and reducing perfusion reserve.
• Plaque rupture or erosion triggers acute thrombosis, producing unstable angina, acute myocardial infarction (MI), or ischaemic stroke.
• Atherosclerosis is a systemic process - disease in one vascular territory (e.g., coronary) is frequently coexistent and advanced in others (peripheral, cerebrovascular).
• Established CVD in any territory substantially amplifies the risk of events in all other territories - hence patients with prior MI, stroke, or peripheral vascular disease are managed under secondary prevention principles and fall outside the primary prevention absolute risk framework.

Who to Screen: Identifying the At-Risk Population

Standard Adult Population

Australian guidelines recommend that absolute CVD risk assessment should begin at:

• Age 45 years and over for the general adult population
• Age 30 years and over for Aboriginal and Torres Strait Islander peoples, who carry a substantially higher burden of CVD risk at younger ages
• Age 12 years and over - annual discussion of CVD risk is now recommended lifelong from this age under the most recent Australian guidelines, though this is primarily education and risk factor identification rather than formal calculator-based assessment in young people

Populations Automatically Classified as High Risk (No Calculator Needed)

Certain groups carry absolute risk high enough that formal risk calculation is bypassed - these individuals proceed directly to intensive risk factor management:

The Absolute CVD Risk Tool: Inputs and Outputs

Variables Entered into the Calculator

The Australian calculator integrates the following parameters:

• Age and sex
• Total cholesterol and HDL-cholesterol (and therefore the total:HDL ratio)
• Systolic blood pressure
• Smoking status (current smoker or non-smoker)
• Presence or absence of diabetes mellitus
• Left ventricular hypertrophy on ECG (in some versions)
• Indigenous Australian status - captured as a separate input because traditional risk equations tend to underestimate CVD risk in Aboriginal and Torres Strait Islander peoples; correction factors are applied

Risk Categories

Clinical tip: When in doubt about which calculator version your software is running, use the national online calculator directly to avoid outdated risk estimates.

Modifiable Risk Factors and Their Clinical Significance

Dyslipidaemia

• LDL-cholesterol is the primary atherogenic driver; lowering LDL by $1\,\text{mmol/L}$ reduces all-cause mortality by approximately 10%.
• A lipid panel (total cholesterol, HDL-C, LDL-C, triglycerides) is required for risk calculation; a fasting sample is preferred for accurate triglycerides but non-fasting total:HDL ratio is acceptable for risk assessment.
• Statins are the evidence-based first-line agents for primary prevention in high-risk individuals:
• Rosuvastatin 5-20 mg daily or atorvastatin 10-40 mg daily are typical first-line choices.
• Statins reduce both fatal and non-fatal MI and stroke in high-risk primary prevention populations.
• For intermediate-risk patients, a shared decision-making discussion weighing absolute benefits, side-effect risk, and patient preference guides the decision to commence.
• Plant sterol-enriched foods provide modest LDL-C reduction (~10%) and are a reasonable dietary adjunct.
• Vitamin E, garlic supplements, and lecithin do not have sufficient evidence to recommend for lipid lowering.

Hypertension

• Defined as sustained $\text{SBP} \geq 140\,\text{mmHg}$ or $\text{DBP} \geq 90\,\text{mmHg}$ on at least two separate occasions.
• Diagnosis should never rest on a single reading.
• Home blood pressure monitoring or 24-hour ambulatory monitoring reduces white-coat effect and informs true treatment thresholds.
• First-line antihypertensive choice depends on age and comorbidity:
• Younger patients respond better to ACE inhibitors (e.g., ramipril 2.5-10 mg daily) or angiotensin receptor blockers.
• Older patients respond well to thiazide diuretics or calcium channel blockers.
• Combination therapy is frequently required.
• Target $\text{SBP} < 130\,\text{mmHg}$ is appropriate for most high-risk patients; individualise in elderly or frail patients.

Smoking

• The single most powerful modifiable cardiovascular risk factor.
• Even modest reduction in cigarette consumption reduces event rates; cessation is the goal.
• Offer brief intervention at every contact; combination pharmacotherapy (nicotine replacement therapy plus varenicline or bupropion) has superior quit rates to NRT alone.
• Note: smoking's measured effect on 10-year CVD risk may not fully capture lifetime risk because smokers also carry substantially elevated cancer mortality - this is an important nuance when counselling patients about lifetime rather than 10-year risk.

Diabetes Mellitus

• Target HbA1c $\leq 7\%$ for most individuals with diabetes; individualise for the elderly, those with frequent hypoglycaemia, or limited life expectancy.
• Tight glycaemic control contributes to microvascular risk reduction; macrovascular benefit is mediated more by blood pressure and lipid management.
• SGLT-2 inhibitors (e.g., empagliflozin, dapagliflozin) and GLP-1 receptor agonists (e.g., liraglutide, semaglutide) have demonstrated cardiovascular event reduction in people with type 2 diabetes and established CVD or very high risk - relevant at this level as an escalation option.

Physical Inactivity, Obesity, and Diet

• Recommend $\geq 150$ minutes of moderate-intensity aerobic activity per week.
• Waist circumference is a practical surrogate for visceral adiposity (target $< 94\,\text{cm}$ men, $< 80\,\text{cm}$ women in Caucasian populations; lower thresholds for Asian populations).
• Dietary principles: Mediterranean-style diet, reduced saturated fat, increased fruit, vegetables, and wholegrains, and reduced sodium for blood pressure.
• Alcohol: limit to $\leq 2$ standard drinks per day with alcohol-free days.

Management Framework: Matching Intervention to Risk

Lifestyle Interventions - All Risk Categories

Lifestyle modification is recommended for every patient regardless of absolute risk category. These interventions are not merely adjuncts; they have independent event-reduction evidence.

1. Smoking cessation - first priority
2. Heart-healthy diet counselling (refer to dietitian if available)
3. Regular aerobic exercise prescription
4. Weight management towards healthy BMI and waist circumference
5. Alcohol reduction
6. Blood pressure management including sodium restriction

Pharmacotherapy - Intermediate and High Risk

Statins: - Indicated for high-risk primary prevention ($> 15\%$). - At intermediate risk ($10-15\%$), use shared decision-making; trial lifestyle modification for 3-6 months first if the patient is engaged and ready. - PBS subsidy for statins in primary prevention requires meeting the lipid or absolute risk thresholds specified in PBS criteria - check the PBS for current requirements.

Antihypertensives: - Initiate pharmacotherapy when lifestyle changes alone are insufficient to achieve blood pressure targets, or earlier in high-risk individuals. - Start one agent at a time; allow 4 weeks between dose adjustments. - Combination therapy is usually needed for $\text{SBP} > 160\,\text{mmHg}$.

Aspirin - Primary Prevention: - Aspirin is not routinely recommended for primary prevention, even in high-risk individuals or those with diabetes. - The modest reduction in non-fatal MI is offset by increased risk of gastrointestinal and intracranial bleeding. - This represents a significant shift from older guidelines - emphasise this distinction to avoid prescribing aspirin to patients who have not had a prior CVD event. - Aspirin remains a cornerstone of secondary prevention (post-MI, stroke/TIA) at 75-150 mg daily unless contraindicated.

Aboriginal and Torres Strait Islander Peoples: Special Considerations

This population warrants specific attention given substantially elevated CVD burden:

• CVD risk assessment should begin from age 30 years (some guidelines and consensus statements suggest starting even earlier for high-risk individuals from age 18-35).
• Standard risk equations tend to underestimate true cardiovascular risk in Aboriginal and Torres Strait Islander peoples; the Australian calculator applies corrections.
• Risk factor screening should be integrated into routine health assessments (e.g., the Medicare-funded adult health check for Aboriginal and Torres Strait Islander peoples).
• Cultural safety and the involvement of Aboriginal and Torres Strait Islander health practitioners and health workers is essential - they can contribute meaningfully to risk discussion, calculation, and shared decision-making.
• The Heart Health Yarning Tool and shared decision-making aids (e.g., Finding Your Way model) support culturally appropriate risk communication.
• Clinicians should be aware that annual CVD risk conversations, while recommended, risk becoming formulaic - long-term relationships with trusted services, and sensitivity to competing priorities, improve engagement and outcomes.
• Atrial fibrillation is more prevalent in this population than often recognised and represents an additional modifiable stroke risk factor requiring targeted management (anticoagulation where indicated).

Complications & Special Considerations

Familial Hypercholesterolaemia (FH)

• Autosomal dominant; LDL-C markedly elevated from birth.
• Suspect in adults with $\text{LDL-C} > 5\,\text{mmol/L}$, premature CVD (men $< 55$, women $< 60$), tendon xanthomata, or first-degree relative with severe hypercholesterolaemia or premature CVD.
• Automatically classified as high cardiovascular risk - does not use the standard absolute risk calculator.
• Refer to lipid specialist; high-intensity statin plus ezetimibe often required; PCSK9 inhibitors available on PBS for FH with established CVD or inadequate response.

Polypill Approach

• In resource-limited or high-risk settings, fixed-dose combination pills containing a statin and antihypertensive(s) improve adherence and have been shown to reduce both cardiovascular risk factor levels and major cardiovascular events compared with placebo.
• This approach is increasingly discussed for high-risk primary prevention in remote and underserved settings, including some Aboriginal and Torres Strait Islander communities.

Menopausal Hormone Therapy (MHT)

• Cardiovascular risk should be formally assessed before initiating MHT.
• MHT is generally recommended only in women aged under 60 years, within 10 years of menopause onset, and at low cardiovascular risk.
• Women at moderate or high cardiovascular risk require careful individualised risk-benefit discussion.

Long-Term Care and Monitoring

Follow-Up Schedule

Monitoring Parameters on Pharmacotherapy

• Statins: fasting lipid panel and LFTs at baseline; repeat lipids at 6-12 weeks after initiation; routine LFT monitoring thereafter is not required unless symptomatic. Monitor for myalgia - check CK if symptomatic; routine CK monitoring is unnecessary.
• Antihypertensives: renal function and electrolytes at baseline and 4-8 weeks after initiating ACE inhibitor or ARB; ongoing monitoring every 6-12 months.
• Blood pressure targets: re-examine regularly - targets may need adjustment in chronic kidney disease, diabetes, or the elderly.

Key Communication Points for Patients

• Absolute risk tools give a probability, not a certainty - many people at 15% risk will not have an event, and some at 5% will. Frame this clearly.
• Lifestyle change has real and meaningful impact on event rates.
• Statins do not replace lifestyle change; they add to it.
• Motivational interviewing principles support patient engagement; selecting areas the patient is ready to change first leads to better adherence.
• More than one consultation is often needed - this is normal and expected in chronic disease prevention.

Summary: Clinical Decision Algorithm

1. Identify patients due for assessment (age, Indigenous status, presence of established CVD or automatic high-risk conditions).
2. Exclude automatic high-risk groups - manage under appropriate secondary prevention or high-risk protocols.
3. Calculate absolute 5-year CVD risk using the current Australian online calculator with full risk factor inputs.
4. Categorise as low, intermediate, or high risk.
5. Advise lifestyle modification for all.
6. Prescribe pharmacotherapy for high-risk patients and consider for intermediate-risk patients after shared decision-making.
7. Do not prescribe aspirin for primary prevention.
8. Reassess at appropriate intervals; update risk calculation when clinical status changes.
9. Document and use clinical software reminders to support recall and review.