Let’s Have Our Best Interests At Heart

IN May 2005, cardiologist Warrick Bishop was involved in the successful roadside resuscitation of a 52-year-old man who had a heart attack while competing in Hobart’s City to Casino Fun Run. The man, whose story made the front page of the Mercury at the time, was rushed to hospital for surgery. He survived, but Dr Bishop later realised he’d assessed the man’s heart health as being fine during an exercise treadmill test two years earlier.

“This revelation shocked me,” writes Dr Bishop in his new book Have You Planned Your Heart Attack?. “Had I done the wrong thing by this man? Had I misinterpreted the result? Were there other factors of which I had not been aware? As it turned out, I had done nothing wrong; the test was appropriately reported and he was given reassurance consistent with his risk assessment at the time.”

The incident highlights an unfortunate truth: not even best-practice assessments such as treadmill stress tests or the current model for calculating heart health risk in individuals can tell someone for sure if they’re going to have a heart attack or stroke.

Heart disease is the leading cause of death in Tasmania. Australia-wide, it causes more than 30 per cent of deaths a year. Common, preventable risk factors for it include poor diet, lack of physical activity and smoking.

The heart risk calculator, routinely used in general practice, is a population-based assessment, which relies on observational data, including lifestyle and clinical factors such as age, sex, family history, smoking, exercise levels, diet, cholesterol and diabetic status, and increased blood pressure.

These factors are associated with having a possible coronary event but are not necessarily causal, which means there’s a chance some people who are assessed as high risk and thus treated accordingly will never have a heart attack, while others who are considered low risk and not treated at all, will.

In Have You Planned Your Heart Attack?, Dr Bishop argues in favour of individual risk assessments and the use of technologies such as calcium scoring (a measurement of the amount of calcium in the walls of the arteries) through CT imaging to evaluate the health of an individual’s arteries before the onset of coronary artery disease. His view has detractors who say there is no clinical evidence to support the routine use of calcium scoring through CT imaging as a preventive measure to determine heart health risk, and it is costly (because no medical benefits scheme rebate applies).

Heart Foundation Tasmania chief executive Graeme Lynch says more research is needed to assess the need for calcium scoring “to determine whether it would be an effective public-health screening device”.

“The Heart Foundation’s position is there is no evidence to support a role for coronary artery calcium scoring in patients who already have known coronary artery disease,” Lynch says. “Further research is needed to assess the role of coronary artery calcium scoring in clinical practice. There’s a fair bit of research going on in this space.

“One of the issues is affordability. If a patient requests the test, they will pay the full cost of it unless the request is made by a specialist or consultant physician. There’s nothing to stop a patient asking for it, but they would have to pay for it. Another reason additional research is needed is that the procedure does expose the patient to radiation.”

The Heart Foundation supports the current population-based approach. “That means for all people over 45 — or if they’re an Aboriginal Torres Strait Islander it’s 35 — we recommend they see their GP and undertake an integrated health check to determine the risk of heart disease,” Lynch says.

“From that, the GP can determine a person’s chance of having a heart attack, developing diabetes, kidney disease or having a stroke over the next five years, and depending on that probably can recommend lifestyle modifications such as being physically active for at least 30 minutes a day, quitting smoking, or eating a healthier diet, or whether there’s a need to treat high blood pressure or high cholesterol through medication.”

Dr Bishop agrees more research is needed to validate the use of cardiac CT imaging as part of a primary prevention approach to heart care. The Hobart-based cardiologist works predominantly in private practice, combined with public sessions, and was an early adopter of cardiac CT imaging technology in Tasmania.

When we meet in Hobart, the lean, fit-looking doctor is passionate but clear-minded when explaining his motivations for writing the book. “I thought [CT imaging] allowed far more precision around our risk prediction so we could find people who were high-risk much sooner and put in primary preventive strategies and try to stop people from having heart attacks,” he says. “Because it was new and because of other issues, the local adoption was slow — particularly by my specialist colleague group. One of the main reasons for this is the technology has evolved rapidly so it’s very hard to get long-term data on something that’s changing all the time.

“A lot of what we do in medicine is based on the results of large clinical trials, but one of the problems with imaging is if we image the heart and we find a group of patients who are at high risk, we can’t then take half of those high-risk patients into a treatment group and half of them into a non-treatment group to prove the treatment is safe. You wouldn’t do it.

“There is the opportunity to generate data. It just has to be organised and done in a way that’s different from our standard medical clinical trial. We can’t randomise people to treatment or non-treatment. We would have to track people, follow the outcomes, follow side-effects, track costs, all of those sorts of things to validate the technology.”

He says the book is aimed at the educated public who want to know more about their heart health and how to reduce their risk. “I thought, ‘If I can produce a book that can educate a motivated individual to get the information and understand the technology, then they can go and have a conversation with their GP’,” he says. “If they don’t know, they won’t ask.

“The technology is very safe and it’s very specific and the difference between what we currently do and what imaging can offer is huge. This testing gives us one of the highest degrees of precision around evaluation and risk. It’s still not perfect because we find people with terrible-looking arteries and for some reason haven’t or don’t end up having a heart attack. We can’t explain that.”

Dr Bishop believes the risk of radiation associated with imaging is low and the cost is reasonable ($300-$350 for a calcium score, or $650-$700 for a calcium score and CT coronary angiogram).

He says men and women should more actively manage their heart health from ages 50 and 60, respectively (“unless there’s some other factor which would drive it”), adding people who have been assessed as being intermediate risk by the population-based risk calculator should consider cardiac CT scanning.

“If you’re at really high risk you should probably be on therapy and if you’re at really low risk then you probably shouldn’t be fussing about it, but if you’re intermediate — in that group where 10 out of 100 of that cohort will have an event — then that’s a good place to be more accurate and go from a population-based assessment to an individual-based assessment.”

Hobart GP Graeme Alexander, of Claremont Village Medical Centre, believes messages about heart health, including the importance of being physically active, a healthy diet and not smoking, should be delivered “long before we are looking at scanning”.

“GPs will know their patients. We live in the real world and look first at modifying lifestyle factors such as diet,” he says. “Almost without exception the general public doesn’t do enough physical activity, we all at times eat poorly and overall need to make better decisions about our health. We have to start early, talking to mums about what they feed their children and encouraging them to be physically active. If we can modify people’s behaviour earlier then there will be huge savings in terms of health dollars and human health.”

Lynch says the healthy heart messages promoted by the Heart Foundation and clinicians are having an impact, with a “flattening of the incidence of heart attacks and stroke” across Australia. There has also been a nationwide reduction in the number of have a heart attack, but there’s a growing burden of disease,” Lynch says. “There are more people who have had a heart attack who are now living with the disease and this may have an impact on their quality of life and is a burden on the healthcare system.”

In the long term, Dr Bishop hopes routine cardiac CT scanning for heart problems will play a role in addressing this. “Coronary artery disease still is the major killer in our community and is one of the major causes of mortality and morbidity in that middle age group — men at 50 and women over 60,” he says.

“If we are able to get the data and support, I think we can use this technology to screen — as we screen for breast cancer, bowel cancer and blood pressure. The first step is to get some clear, longitudinal data to show it really is an effective intervention and then we need to move to screening.”

Research may yet vindicate Dr Bishop’s ambition. “There are research projects under way, which are looking at the efficacy of calcium scoring and particularly what is the appropriate way to do this across a whole population,” Lynch says.

“Most of the population who are the highest risk are socially and economically disadvantaged and are on lower incomes. When we look at public health interventions, we need to take into account equity considerations and what is affordable. So it’s not to say in the future, if the evidence becomes so strong that for certain types of patients calcium scoring might become an effective way to screen a whole population.”

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Story Credit: http://www.themercury.com.au/lifestyle/tasweekend-lets-have-our-best-interests-at-heart/news-story/1830743fb2e57699a97238966d1f8aeb