Dr Scott Murray: Preventing the heart of the future
Dr Scott Murray works as a consultant preventative cardiologist in Liverpool and is president of the British Association for Cardiovascular Prevention and Rehabilitation (BACPR). Having previously worked in interventional cardiology, Dr Murray has now become, as his titles suggest, extremely interested in preventing heart disease, rather than simply treating it once it has been established. This talk was given at the Public Health Collaboration conference 2018 at the Royal College of General Practitioners in London.
Dr Murray begins the talk by outlining his issues with current cardiology practice. As he says, current cardiology is largely interventional, rather than preventative, and has a focus on drug, device and surgical interventions which are owned by large, powerful companies. Unfortunately, the interests of these companies to do some extent influence the cardiology literature and guidelines.
In recent years, there has been some improvement in the rates of heart disease, yet it does remain the leading cause of death in the UK. Studies such as INTERHEART have found the vast majority of risk factors for heart attacks to be preventable and it’s these, according to Dr Murray, that we should be focusing on.
Studies, including INTERHEART, have also suggested that our current view risk factors for heart disease may be too simplistic. Rather than focusing on markers such as total cholesterol, other markers such as ApoB/ApoA1 ratio and total/HDL cholesterol ratio have been highlighted as more important for reflecting overall metabolic health, as they provide important context. Dr Murray explains that insulin, under normal conditions, should limit the amount of cholesterol produced in the liver, yet in people with insulin resistance, the liver is instead stimulated by insulin to produce more cholesterol. Thus, high cholesterol levels are occurring downstream of insulin resistance and hyperinsulinaemia. What this means is drugs such as statins, that target cholesterol synthesis, are targeting a symptom of metabolic dysfunction, rather than the dysfunction itself. In this case, hyperinsulinaemia, which leads to insulin resistance, is the root cause of the metabolic problem.
Dr Murray presents data from Liverpool that, despite showing decreasing rates of coronary heart disease, displays increasing rates of atrial fibrillation, heart failure, hypertension and stroke. He opines that lifestyle or ‘environmental’ factors play a role in this as well as genetics.
Clinically, Dr Murray can tell which patients are at more risk of heart disease due to the amount of visceral fat (fat around the organs) that they have. This fat feels hard when poked, as opposed to subcutaneous fat which is soft. It is this visceral fat that is particularly correlated with both insulin resistance and heart disease. Over time, poor metabolic health (including obesity, hypertension and diabetes) contributes to ‘Heart Failure with preserved Ejection Fraction’ (HFpEF or huff-puff). Dr Murray explains that HFpEF results in breathless patients that have a range of cardiovascular dysfunctions, again based on the root problem of hyperinsulinaemia and insulin resistance.
Interestingly, under normal physiological conditions, a healthy adult heart gets 60-70% of its energy from long chain fatty acids. Fatty acids are a more efficient and energy dense fuel than glucose, providing adequate oxygen is available. However, in a situation of heart disease, there is less oxygen available, fat oxidation decreases and the heart has to rely instead on burning mostly glucose as an unideal coping mechanism. In short, given the choice, a healthy heart wants to burn fat for fuel. Dr Murray uses an analogy to help illustrate the two situations: a healthy heart running on fat is like a truck taking constant efficient fuel from a large tanker to run its engine at low revs, while an unhealthy heart is like that same truck tapping into its inefficient emergency fuel and running at high revs thus burning the engine out.
On the topic of fat oxidation in the heart, an SLGT-2 inhibitor drug known as Empagliflozin is recommended early in European Society of Cardiology guidance for diabetes. This drug shifts the body’s metabolism from a state of burning mostly glucose to burning mostly fat for fuel. This results in the production of ketones, which are fat-derived energy sources seemingly used preferentially by the heart. Therefore, Empagliflozin effectively works via the same mechanism as a low carb, ketogenic diet. However, while use of Empagliflozin is recommended for diabetes, a ketogenic diet is considered by mainstream guidelines to be unsafe.
In order to minimise insulin resistance and improve metabolic health, Dr Murray says we can maximise the nutrient density and minimise the glycaemic impact of our food, allowing us to keep insulin levels pulsatile and within normal range. In addition, factoring high intensity exercise into our lifestyles improves our muscles’ insulin sensitivity.
At a community and population level, it is clear that there is a culture of CRAP (completely refined and processed) foods. These foods, usually high in carbohydrate, that contribute to high blood sugars, insulin resistance and poor health, are all too readily available. As Dr Murray points out, the financial interests of big food companies play a large part in the availability, legitimisation and marketing of such foods. This is an issue that needs to be tackled at a societal level, and there are successful efforts being made by some groups, including Dr Murray’s, to raise awareness of the sugar in foods and to put pressure on the food companies to reduce it.
Dr Murray boils down his advice for improving metabolic health into two key strategies: exercise (specifically high intensity interval training) and carbohydrate restriction. He also presents a comical alliteration-laced list of things that can worsen metabolic health and make us sick:
Dr Murray ends with a call for more funding to go not into intervention with drugs and medical devices (which make money for industry) but instead to go into cardiac rehabilitation and disease prevention via lifestyle change – strategies that have proven to be cheap and effective. He hopes that by doing this, we can effectively improve the health and wellbeing of the population.