19 April 2021
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Heart disease: the cause isn’t always obvious

Dr Ross Walker
16 March 2021

When a person develops heart disease, such as a heart attack, needing a coronary stent or undergoing coronary artery bypass grafting, most people associate this with poor lifestyles, high cholesterol, high blood pressure, cigarette smoking and diabetes, as the major causes.

It may, however, surprise you to learn that all major cardiovascular diseases are genetic but your genes load the gun and your environment then pulls the trigger. To date, medical science has mapped at least 60 genes that code for cardiovascular disease, with less than half, coding for issues around cholesterol and high blood pressure. So, if in your case, the majority of these 60 genes place you at high risk for heart disease, poor lifestyle behaviours and stress will bring out the condition probably relatively early in your life, typically over the age of 40 to 50.

If you have a separate set of genes that predispose you to cancer and also have poor lifestyle or significant stresses, then you may activate these genes and possibly develop cancer at some stage during your life.

Professor Gemma Figtree, one of the leading cardiovascular researchers (not just in Australia but internationally) has recently published a large study in The Lancet journal where she and her team reviewed 62,048 patients who presented with a major heart attack, average age 68. She gave the interesting terminology SMuRF to explain the standard modifiable  risk factors for heart disease which include hypertension, diabetes, hypercholesterolaemia and smoking.

The reality is that 70% of heart disease in our modern world is typically related to the most common genetic abnormality in the world i.e. insulin resistance, which predisposes people with this gene to varying degrees of Type 2 diabetes, hypertension, cholesterol abnormalities where the triglycerides are elevated and the HDL is low. Insulin resistance is also associated with significant abdominal obesity with a waist circumference greater than 95 cm in men and 80 cm in women. Insulin resistance is also associated with fatty liver, gout and even an increased risk for cancer.

When Professor Figtree analysed the data, 85% had at least one SMuRF whereas 15% were SMuRF-less. The fascinating piece of information that emerged from this study was that at 30 days after a major heart attack, patients who were SMuRF-less were 50% more likely to die and interestingly this was even worse in the SMuRF-less women.

This study really did not take into account those with a strong family history and most importantly did not analyse the data for what I believe to be a major risk factor — lipoprotein(a). Lipoprotein(a) occurs in 20% of the population and those who have this purely genetic cholesterol abnormality are at a 70% higher risk for heart disease. At the time of presentation, they often have more extensive disease and thus, if they suffer a heart attack, don't appear to fare as well as those who do not have this abnormality. Thus, a study that purely looks at the obvious risk factors for heart disease – hypertension, diabetes, hypercholesterolaemia and smoking will not detect at least 20% of the population with an elevated lipoprotein (a) which, in my opinion, clearly explains the findings of this study.

I have been measuring lipoprotein(a) in all of my patients for over 25 years but the medical profession is just starting to develop an interest in this abnormality because a new drug has been developed which markedly reduces the level in the bloodstream. Studies are being performed to see whether reducing lipoprotein(a) may also reduce the risk for heart disease and the consequences of having a heart attack.

Professor Figtree has to be congratulated for a superb study and for bringing this extremely important issue, not only for discussion by the medical profession, but also making the public aware that just because a person doesn’t have standard risk factors for heart disease they are not at risk.

It has been my suggestion for many years that every male at 50 and every female at 60 should have a coronary calcium score (not an intravenous CT coronary angiogram), which is the most important risk predictor for heart disease. If you have a strong family history of heart disease, this test should be performed earlier in discussion with your treating doctors.

A simple test such as a coronary calcium score (using a standard modern CT scanner) and measurements beyond cholesterol such as lipoprotein (a) may not only prevent you from having a major heart attack, but also potentially save your life.

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