The Coronary Arteries
The heart, though full of blood, still needs its own arteries to supply nourishment and oxygen to the heart muscle.These are the coronary arteries. They arise from the root of the aorta, the body’s main artery, and wind round the surface of the heart in the shape of an upside-down papal crown or corona – hence their name. The illustration above is a wax cast of the coronary arteries and you can see just how dense is the network of vessels involved.
Your heart beats at between about 60 and 200 times every minute of your life which comes to more than two billion heartbeats – it needs a lot of feeding.
Coronary Artery Disease
Coronary artery disease is the process of narrowing of one or more of the coronary arteries thus reducing the rate at which blood can flow through the artery. It is the most dangerous form of atheroma. Coronary artery disease, more usually referred to as Coronary Heart Disease (CHD), was until very recently the commonest cause of death in most developed societies (recently narrowly overtaken in the UK by dementia for women). In the UK approximately 2.3 million people have diagnosed CHD and the annual incidence of new cases is about 300,000. About 200 people in the UK die of CHD every day mainly from heart attacks – that is equivalent to a Boeing 757 crashing every day. It is also a cause of much morbidity – the symptoms and limitations resulting from the disease.
The Causes of CHD
Coronary artery disease does not have a single cause. A number of “risk factors” contribute to its development. Some are irreversible – age (the older you are the more susceptible you are), gender (men develop CHD on average 10 years younger than women) and family history (you are at greater risk if you have a close relative with the disease – and the younger that relative, the greater the risk to you). You can’t do anything about these risk factors.
Then there are the reversible risk factors – the ones which you can influence. These include cigarette smoking, high blood pressure, type 2 diabetes, high blood cholesterol and obesity (and their combination, as seen in metabolic syndrome). Overshadowing all of these, because it contributes to most of them, is lack of exercise.
Predicting your risk
There are several tools for predicting the risk of developing CHD in any individual. The best validated is the Q-Risk 3. Go on line at https://qrisk.org/three/. You will be asked to feed in your age, sex, height, weight, cholesterol/HDL ratio, blood pressure, presence or not of diabetes, ethnicity, smoking status, family history, deprivation, presence of rheumatoid arthritis or kidney disease, and post code. Don’t worry if you do not know all of these. The risk scoring system will fill in average values for missing data. From that information the tool will calculate your risk of developing both CHD and Cardiovascular Disease (CVD) over the next ten years.
How CHD harms or kills you
Narrowing and blockage of the coronary arteries is caused by atheroma or hardening of the arteries. As we grow older we develop patchy narrowing of the arteries due to fatty plaques composed of cholesterol. These are laid down in the arterial wall and compounded by overlying thin layers of blood clot. This gradually restricts the flow of blood to the heart muscle. A point may be reached when the artery is unable to supply the needs of the heart muscle during exercise. The muscle lacks a sufficient supply of oxygen to be able to continue to contract effectively and this produces pain during exertion, known as angina pectoris. This is a tight strangling pain across the centre of the chest, often radiating into the throat, jaws or left arm. It forces the sufferer to stop exercising and then settles over the next few minutes.
Atheroma plaques are delicate creatures and may break, crack or burst. If this happens the body’s repair mechanisms are set off and that usually means the formation of a clot. This is a coronary thrombosis and may be large enough to block the artery. The result is death of the area of heart muscle supplied by that artery. This is known as a myocardial infarction, usually referred to as a heart attack. The immediate danger is sudden death due to rhythm disturbance precipitated by the damage to the heart muscle. For those who survive to reach hospital the outlook is good.
The modern treatment of heart attacks is extremely effective in limiting the damage done. Even so, enough loss of heart muscle, particularly after more than one attack, can result in damage to the ability of the heart to perform its full function. This can result in breathlessness on exertion, fatigue, poor circulation and ultimately heart failure. Heart failure is not as bad as it sounds. The heart continues to work but just not as efficiently and as effectively as the undamaged heart. Modern treatment is very effective at improving the symptoms of heart failure.
Next week I will tell you about the effects of exercise in preventing and treating coronary disease.
PS Doctors’ priorities:
A recent survey of 137 US general practitioners found that they were less likely to recommend preventive treatments for their patients when pushed for time. When they did have time, recommending exercise was very unlikely to be included even though this would have been one of the most effective strategies. Oh dear…..