The eye may be the window to the soul but the heart is the engine that keeps it blinking. It is a four-chambered, ‘double circulation’ pump system. The heart, arteries and veins carries blood in a constant stream round the body, delivering oxygen to supply the needs of muscles and vital organs and removing waste products which would poison our bodies if they built up.
Blood arrives at the heart via the two vena cavas (the largest collecting veins in the body). These connect to the two chambers of the right side of the heart, from where the blood is pumped at relatively low pressure to the lungs to collect oxygen. It returns to the left side of the heart and is pumped out at high pressure into the largest artery in the body, the aorta, and on to all the body’s organs.
The system is highly efficient, allowing adaptation of blood supply in response to exercise, adrenaline and outside conditions. But it relies on clear passage through the arteries and veins, and synchronised contraction of the heart muscles. This contraction is triggered by regular waves of electrical activity passed over the heart’s surface. Blockage of an artery supplying blood to the heart results in a heart attack; blockage of an artery supplying part of the brain is a stroke. Abnormalities of the electrical conduction system — the most common in the UK is atrial fibrillation — can cause everything from shortness of breath and palpitations to stroke.
Heart attack, stroke and other diseases of the circulatory system are known collectively as ‘cardiovascular disease’. Fifty years ago, this accounted for more than half of UK deaths; today the figure is 32 per cent. Death rates in the UK from heart attack have halved in the past decade alone. But despite all the advances we have made, it’s still the biggest killer in the UK. In 2010, almost 180,000 people in the UK died from cardiovascular disease, about 80,000 from heart attack and 49,000 from stroke. And it doesn’t just strike the elderly and infirm — in 2010, 46,000 people died prematurely of cardiovascular disease in the UK. We need to learn the lessons of history and put them into practice to prevent ourselves from becoming victims.
Much of the progress in preventing cardiovascular disease has come from understanding of the risk factors that predispose people to it. Many of the big research findings were designed to inform public health policies, so are biased towards the general population rather than to individuals. For instance, an individual who stopped smoking might reduce their risk of heart disease by 40 per cent. Doing more exercise might cut their risk by 10 per cent. But if only 10 per cent of a population smoke, and 40 per cent don’t take enough exercise, then for the population as a whole those two changes would carry the same weight.
One of the most important international studies of risk factors for heart disease, the Interheart study, was published in 2004. The study recruited 15,000 patients admitted for a first heart attack in hospital centres in 52 countries, and matched them with controls, people who had not suffered a heart attack. Until then, the consensus was that the relative impact of risk factors for cardiovascular disease varied with country, ethnicity and gender. In fact, it emerged that just nine modifiable risk factors account for over 90 per cent of the population-level risk of having a first heart attack, across gender, geographical and ethnic boundaries.
Of these, the top five (smoking, lipids, hypertension, diabetes and obesity) accounted for about 80 per cent of the population-level risk. Since many of the same risk factors predispose to atrial fibrillation and stroke as well as to heart attack, the implications are far-reaching.
Smoking showed a ‘dose dependent’ effect on risk — for instance, smoking one to five cigarettes a day increased the risk of heart attack by 38 per cent, with a steady positive correlation between cigarettes smoked and risk, up to 900 per cent for 40 a day. Moderate alcohol consumption was found to have a protective effect, but this needs to be balanced against the harmful effects of excess alcohol on the liver and also against the risk of cancer (every two units a day of alcohol increases the risk of bowel cancer by 8 per cent and for women, every unit a day increases the risk of breast cancer by 7 to 11 per cent).
One of the major game-changers for doctors from this study was the finding that abdominal obesity correlated more closely with the risk of heart attack than body mass index, the ration of height to weight traditionally used to measure obesity. Particularly among people whose BMI would be considered normal or overweight, risk of both cardiovascular disease and type 2 diabetes is affected not just by amount of fat but by its distribution. Intra-abdominal or visceral fat seems to affect the metabolism in a way that other, subcutaneous fat doesn’t. It increases insulin resistance (and thus the risk of type 2 diabetes); predisposes people to the clogging of arteries; and ups the level of immune system chemicals called cytokines, which further increase the risk of heart disease.
Fortunately, stomach fat responds extremely well to weight reduction. Thus, tackling that middle-aged spread significantly reduces not just the risk of heart attack and stroke but also of type 2 diabetes — with a reduction in the risk of cancer thrown in as a bonus.
The saturated fat debate has been brought into focus this year with the publication of a study suggesting that reducing saturated fat does not increase the risk of heart attack and that polyunsaturated fat does not reduce it. But as with so many statistics, it depends on your perspective. Replacing calories of saturated fat with the same number of calories of refined carbohydrates may well not protect you against heart disease. A heart-healthy diet which not only limits saturated fat but also red meat and cakes, pastries and carbonated drinks, and has more fruit, vegetables and fish along with regular intake of mono/polyunsaturated fat and nuts, indisputably does. During a groundbreaking project on a population group in North Karelia in Finland, levels of use of butter on bread dropped from almost 90 per cent to under 5 per cent and the use of mono/polyunsaturated cooking oils increased to 60 per cent of the group. In combination with other factors, including less salt and less smoking, the result was that over a 30-year period average cholesterol levels across the board dropped by 20 per cent and heart attack rates dropped by 85 per cent.
The overall message? Ignore the recent headlines which sought to turn traditional thinking about cardiovascular disease on its head. Exercise regularly, keep your weight down, limit intake of saturated fat and refined carbohydrates and focus on fruit, vegetables, unrefined carbohydrates and mono/polyunsaturated fat alternatives. Alcohol in small amounts is protective, but with increasing levels the risks outweigh any benefits. As for smoking — do you need to ask?