Cardiovascular Risk Assessment- Its Limitations and Modern Approaches

Why do we assess Cardiac Risk?

It has classically been performed to assess a person’s risk of heart attack or stroke within a fixed period. In Australia our current endorsed calculator assesses this risk over a 5 year period so is not overly useful to determine longer term risk especially in younger patients.

Australian CV Risk Calculator: https://www.cvdcheck.org.au/calculator

What are the limitations of current Cardiac Risk models?

There are many limitations in cardiac risk models that are not well discussed and leads to a system that fails many patients.

1. Only the end points of stroke and heart attack are assessed, yet the number one killer in the world at present is dementia, which half is attributed to progressive artery disease known as atherosclerosis. Atherosclerosis also leads to cognitive decline, visual loss, kidney disease, erectile dysfunction, hypertension (and the large pill burden that comes with it, need for stents, bypasses.

2. The short term nature is not helpful to assess lifetime risk but an accurate tool would suggest a higher short term risk would predict a higher long term risk. However the process of choosing the cut-off between low, intermediate and high risk is a pure guess and setting it as 5% in 5 years for a young patient is clearer too high (especially when compared to international guidelines) and nearly every young person is labelled as low risk despite them ending up as one of the worst patients in the long term. I have tested many females at the time of their coronary bypass around 70 years of age, what that would have scored at the age of 50 and they all come out as low risk 1-2%, yet turn out to be one of the fastest growers of plaque.

3. The lack of meaningful risk factors is likely the largest drawback. The PREVENT system was a scientific method created from large datasets of patients but only allowed the inclusion of data that was collected and everything else was ignored. Unfortunately some of the highest predictors for atherosclerosis are not included such as: family history, LDL (the bad cholesterol), lipoprotein a (a very strong driver) obesity, autoimmune/inflammatory conditions, hormonal and pregnancy issues, cancers and treatments. There is also no allowance for duration of the body’s exposure (except for diabetes), so does not allow for smoking severity, duration of untreated risk factors like cholesterol and hypertension.

4. There is acknowledgement from the experts in prevention that the calculator does work but only for the average person as the result is averaged for a large dataset. For example in a typical 50 year old female with low risk factors there is a 2 in 100 chance of them having a stroke or heart attack in 5 years but there is no way to decide if that patient is in the 2 or the 98. Hence the recommendation from Stephen Nissen form the AHA/ACC is that CV risk calculators in isolation ARE NOT TO BE USED TO DICTATE TREATMENT IN ANY PATIENT, yet this is what it is recommended to use them for at present in Australia.

5. Then there is the issue that the new PREVENT system has shown a much lower estimate of risk and less recommendation for treatment that the previous Pooled Cohort Equation (PCE) model despite being recommended for earlier and more intensive treatment it has done the opposite. The American system is based on the same data but picked a 10 year calculator and has a few extra parameters but even that found it incorrectly labelled females in up to 81% of cases.

For example if you use a 40 year old male and see what parameters would be required to class them as not a low risk patient and for treatment you can trial different scenarios, a current 40 a day smoker is still classed as low risk (noting burden is not accounted for), a blood pressure of 200mmHg systolic is low risk, a TC/HDL ratio of 15 is low risk (noting FH is an automatic high risk), a type 1 diabetic for 20 years can also be classed as low risk.

So If the Australian CV Risk Calculator is no good what should we do?

This is where you have several options but they are yet to be proven which is the best and which are a failure.

1. Simple rule if you have a risk factor then treat it, ie if you have an LDL >3 you try a low low cholesterol/Portfolio diet and then if needed a statin, if you have high blood pressure you reduce weight, alcohol, salt and try the Dash diet, failing that blood pressure tablets. If you have a high blood sugar you lose weight, ketogenic diet and failing that diabetic medications.

2. Pre-emptive approach by taking a statin early even without high cholesterol to prevent atherosclerosis from forming.

3. Creating more comprehensive risk assessment tools. This is my current research work to incorporate more than 50 parameters to try and better estimated CV risk and rate of atherosclerosis to see how much better we can assess risk, but this will take time and large datasets to modify and refine and hopefully it will work for closer to 100% but still won’t be for everyone until there is access to polygenic risk scores and we know all the risk factors to include in the algorithms. For example if current models lets say miss 20% of high risk patients can we get it closer to 2% with more detailed assessments.

4. Coronary imaging for everyone. This is my current second step until we can fully rely on better CV risk tools. The concept is by directly imaging the arteries then you don’t miss anyone. Every patient who is destined to develop significant artery disease is identified and treated with lifestyle and medication earlier before the plaque has formed and can be prevented to effectively cure the need for bypasses, reduce the incidence of dementia, erectile dysfunction, dramatically reduce pill burden by slowing hypertension, reduce need for stents, reduce dialysis, visual loss and reduce strokes and heart attacks.

5. Hybrid approach of mine is to combine both 3) and 4) to use a comprehensive CV risk assessment to decide on the best age to perform coronary imaging and then use the combined information to assess a person’s rate of plaque growth, estimate their current status, future progression and intensity and targets for each risk factor to slow their atherosclerosis enough to avoid future complications.

So what do I recommend?

Do not mistake being fit, feeling well as a marker for healthy arteries. Data clearly shows people with higher exercise and fitness levels are associated with up to double the amount of plaque as non- athletes. You don’t feel cholesterol, hypertension, elevated BSL, lipoprotein a or artery disease not until you need your bypass or have a heart attack or stroke whether that be in your 30s or 80s. Noting in Tasmania 2% of heart attacks occur before the age of 40 and 9% before the age of 50, and these patients’ are typically shocked when it occurs.

The CV Risk Calculator website has a very good reference into the extended risk factors to consider and is definitely worth reading and can be found here: https://www.cvdcheck.org.au/reclassification-factors-other-considerations

Everyone should have a cholesterol and Lipoprotein a level check as early as possible in life from the age of 5 and if elevated are automatically at risk and need a plan for future prevention and if normal then simply to watch for the development of other risk factors especially blood pressure with intermittent checking.

If you identify in yourself or others that you have any included risks you should either treat them or partake in a comprehensive assessment to take into account your whole profile.

Then consider at what age it is appropriate to have coronary imaging performed either via your GP or ideally via a CT trained imaging cardiologist to very carefully assess the burden of plaque, the type of plaque to give your current risk of heart attack and future risk. The bigger issue is there is only a small number of these CT trained cardiologists across the country and there is currently no way to scale the required assessments across the entire population and will be awaiting AI and algorithms to help scale to meet demand.