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Aim

  • To demonstrate the clinical application of absolute cardiovascular disease (CVD) risk assessment

Learning objectives

  • 1. Explain the benefits of absolute CVD risk assessment
  • 2. Identify the information required to use the CVD risk charts and calculator
  • 3. Demonstrate the use of the CVD risk assessment tools
  • 4. Describe the management of a patient’s cardiovascular risk according to best practice guidelines

Two patients

  • Wendy
    • Age 53
    • Ex‐smoker for 7 years
    • 2‐3 standard drinks/day
    • BP 165/95
    • 2 serves of fruit a day
    • BMI=30
    • Total chol = 7.0 mmol/l
    • HDL = 1.4 mmol/l
    • No diabetes
  • Greg
    • Age 65
    • Non smoker
    • 2 standard drinks/day
    • BP 145/92
    • 10 min of exercise a day • BMI=25
    • Total chol = 5.6mmol/l
    • HDL = 0.7 mmol/l
    • No diabetes

What is “cardiovascular disease”?

  • Coronary heart disease
    • e.g., angina pectoris, myocardial infarction
    • Sudden coronary death
  • Cerebrovascular disease
    • e.g., stroke, TIA
  • Peripheral vascular disease
    • e.g., intermittent claudication

All linked by atherosclerosis = arterial disease.

CVD – important, common and preventable

  • Prevalence
    • 3.7 million people (1 in 6 Australians)
  • Death
    • 1/3 of all deaths (2010)
    • Most common cause
  • Disability
    • 1.4 million people
  • Impact
    • 1/2 million hospitalisations per year (2009‐10) as a primary reason. Even more in admissions that are related to it
    • $$$ ‐ about 11% of total health expenditure (2004‐5)
  • Risk factors
    • 9 in 10 adults at least one
    • 1 in 4 with 3+ risk factors
      • --> we can do something about it

Burden of disease (DALY)

  • DALY = YLL + YLD
    • Impact of the disease on the population (total burden)
    • Health utility (utilitarianism - best outcome for most people)

File:AbsRiskCVD.png

Cost and volume of drugs

CVD risk factors

  • Modifiable risk factors
    • smoking
    • blood pressure
    • serum lipids
    • waist circumference and BMI
    • nutrition
    • physical activity level
    • alcohol intake
  • Non‐modifiable
    • age and sex
    • family history
    • social history (cultural identify, ethnicity, SES, mental health)
  • Related conditions
    • diabetes
    • chronic kidney disease
    • familial hypercholesterolaemia
    • atrial fibrillation

What is “absolute risk”?

  • Absolute risk
    • The numerical probability of an event occurring within a specified period.
    • e.g., in Australia we use 5‐year CVD absolute risks = the probability of having CVD in the next 5‐year period.
  • Relative risk
    • The ratio of the rate of events between two populations.
    • e.g., smokers have a higher relative risk of CVD compared to non‐smokers.
  • The risk value can be expressed in a number of different ways,
    • e.g.: 1 in 10 = 10% = 0.1

Working with numbers – examples

  • Let’s say that the baseline risk of CVD is 12% by age 60:
    • i.e., absolute risk(baseline) = 0.12 = 12%
  • If drug X reduces the likelihood of CVD by 25%, then:
    • relative risk reduction(drug X) = 0.25 = 25%
  • The absolute risk of CVD by age 60 if drug X is used:
    • AR(drug X) = AR(baseline) × (1 ‐ RRR(drug X))
    • = 0.12 × 0.75
    • AR(drug X) = 0.09 = 9%
  • Absolute risk reduction = AR(baseline) - AR(drug) = 0.12-0.09
    • ARR = 0.03 = 3%
  • Also, NNT = 1/ARR
    • = 1/0.03 = 33

Why use ARR and NNT?

[[File:]]

  • Patient 1 is recent aMI, patient 4 is a random normal person in the community. 2 and 3 are in between.
  • Statins reduce the risk of heart attack by 25% across the board
  • The ARR for these patients is different, based on their AR(baseline), and NNT is showing us that it's more or less useless prescribing these drugs to the general population, and that it's very important to prescribe these drugs to the at-risk groups

"Absolute” vs. “Individual” CVD risk approach

  • Prioritise your time to work on low-NNT activities
    • Health is zero sum. Zero sum game: the pot of money we have to spend on health is limited. Expenditure on health is 8-12% GDP. If we spend money on things that don't work very well, then somewhere else, something useful is lost. Hence zero sum - someone gets something, someone else does not. So we choose operations that are useful to maximise utility.
  • “...[risk] depends more closely on the combination and intensity of risk factors than on the presence of a single risk factor, because the cumulative effects of multiple risk factors may be synergistic.”
    • E.g. in T2DM it is actually a bigger deal to focus on getting BP and lipids down compared to bringing HbA1c down to below 7%

Risk assessment algorithm

  • Target group Information to gather
  • Already at high risk?
    • if “no”, use risk calculator
  • Management

File:NVDPA-Managment-Guideline-Quick-Reference-Guide.pdf

CVD absolute risk categories

  • Australia: 5‐year risks
  • Low: < 10%
  • Moderate: 10‐15%
  • High: > 15%

Target group

  • All adults aged 45 years and over without known history of CVD.
  • Aboriginal and Torres Strait Islander peoples aged 35 years or older.

Comprehensive risk assessment

  • Modifiable risk factors
    • smoking
    • blood pressure
    • serum lipids
    • waist circumference and BMI
    • nutrition
    • physical activity level
    • alcohol intake
  • Non‐modifiable
    • age and sex
    • family history
    • social history (cultural identify, ethnicity, SES, mental health)
  • Related conditions
    • diabetes
    • chronic kidney disease
    • familial hypercholesterolaemia
    • atrial fibrillation

Who is already at “high risk" of CVD?

  • Existing history of CVD
    • angina
    • myocardial infarction
    • ischaemic heart disease
    • stroke
    • TIA
    • peripheral vascular disease
    • intermittent claudication
    • etc.
  • These conditions
    • diabetes and age > 60 years
    • diabetes with microalbuminuria
    • moderate or severe chronic kidney disease (persistent proteinuria or eGFR < 45)
    • familial hypercholesterolaemia
    • systolic BP ≥ 180, or diastolic BP ≥ 110 mmHg
    • serum total cholesterol > 7.5

Using the calculator

  • We need to learn how to use the chart at http://www.cvdcheck.org.au
    • So for those who are not already considered to be at “high risk” we should use the Framingham Risk Equation to calculate risk levels.
  • Works out the risk of CVD in the next 5 years

Framingham Heart Study

  • Demonstrate the use
    • Major epidemiologic research
    • Started 1948 in Framingham, MA
    • Study into the causes of CVD
    • Now into the 3rd generation of participants
  • NOTE: if you have stopped smoking, in one year, your risk of CVD after quitting for 12 months, your risk drops down to similar level as non-smokers

Wendy vs Greg

  • A lot of Wendy's risks are not independent (interrelated)
  • Greg is fitter and Wendy is fatter so it might be slightly overestimated/underestimated
    • But Greg is categorically worse.
  • Gut intuition is no good, use the chart.


Management strategy – low risk

[[File: ]]

  • Absolute RR of pharmacotherapy at this level for Wendy is insignificant.
  • Long-term, lifestyle changes for everyone (even low risk). Not super high priority
  • Don't need to do the bloods again for 2 more years

Management strategy - high risk

  • Treat with pharmacotherapy (antihypertensives and lipid lowering medication)
  • Enforce lifestyle change and make sure he is doing it
  • Keep a close eye on his bloods until his risk drops, and then watch him every 3-6 months
  • counterintuitive

[[File: ]]

Overview

  • Intensity of intervention determined by CVD absolute risk
  • High risk = aggressive lifestyle interventions + immediate drug therapy
  • Trial of lifestyle interventions prior to drugs for moderate and low risk
  • Know your targets and follow up.

References (examinable)

  • Algorithm for CVD risk
  • http://www.heartfoundation.org.au/information‐for‐professionals/Clinical‐Information/Pages/absolute‐risk.aspx
  • National Vascular Disease Prevention Alliance. Guidelines for the assessment of absolute cardiovascular disease risk. 2009.
  • National Vascular Disease Prevention Alliance. Quick reference guide for health professionals ‐ Absolute cardiovascular disease risk assessment. 2009.
  • National Vascular Disease Prevention Alliance. Technical report: review of the evidence and evidence‐based recommendations for practice. 2009.
  • National Vascular Disease Prevention Alliance. Guidelines for the management of absolute cardiovascular disease risk. 2012.
  • National Vascular Disease Prevention Alliance. Quick reference guide for health professionals ‐ Absolute cardiovascular disease risk management. 2012.