Introduction

Each year, tobacco smoking accounts for around approximately 20% of all heart disease deaths.

What is Coronary Heart Disease (CHD)?

CHD has two principal forms - angina and heart attacks. Both occur because the arteries carrying blood to the heart muscle become blocked or narrowed, usually by a deposit of fatty substances, a process known as atherosclerosis. Angina is a severe pain in the chest brought on by exertion and relieved by rest. A heart attack is due to obstruction of a coronary artery either as a result of atherosclerosis or a blood clot: part of the heart muscle is deprived of oxygen and dies.

Risk factors for Coronary Heart Disease

Cigarette smoking, raised blood cholesterol and high blood pressure are the most firmly established, non-hereditary risk factors leading to CHD with cigarette smoking being the "most important of the known modifiable risk factors for CHD", according to the US Surgeon General. A cigarette smoker has two to three times the risk of having a heart attack than a non-smoker. If both of the other main risk factors are present then the chances of having a heart attack can be increased eight times. At least 80% of heart attacks in men under 45 are thought to be due to cigarette smoking. At this age, heavy smokers have 10 to 15 times the rate of fatal heart attacks of non-smokers. Even light smokers are at increased risk of CHD: a US study found that women who smoked 1-4 cigarettes a day had a 2.5-fold increased risk of fatal coronary heart disease.

The role of smoking in Coronary Heart Disease

Inhaling tobacco smoke causes several immediate responses within the heart and its blood vessels. Within one minute of starting to smoke, the heart rate begins to rise: it may increase by as much as 30 percent during the first 10 minutes of smoking. Smoking also raises blood pressure: blood vessels constrict which forces the heart to work harder to deliver oxygen to the rest of the body. Meanwhile, carbon monoxide in tobacco smoke exerts a negative effect on the heart by reducing the blood's ability to carry oxygen.

Smoking and arterial disease

Smoking tends to increase blood cholesterol levels. Cigarette smokers also have raised fibrinogen levels and platelet counts which make the blood more sticky. Carbon monoxide attaches itself to haemoglobin much more easily than oxygen does. This reduces the amount of oxygen available to the tissues. All these factors make smokers more at risk of developing various forms of atherosclerotic disease. As the atherosclerotic process progresses, blood flows less easily through rigid and narrowed arteries and the blood is more likely to form a thrombosis (clot). This sudden blockage of an artery may lead to a fatal heart attack, a stroke or gangrene of the leg.

Aneurysm

Is a ballooning of the wall of an artery which leads to risk of bursting or clotting, which may lead to catastrophic results. Smokers are very much more likely to die from a ruptured aneurysm of the abdominal aorta than non-smokers.

Peripheral vascular disease (PVD)

Smokers have a 16 times greater risk of developing peripheral vascular disease (blocked blood vessels in the legs or feet) than people who have never smoked. Smokers who ignore the warning of early symptoms and continue to smoke are more likely to develop gangrene of a leg.

Cigarette smoking combines with other factors to multiply the risks of atherosclerosis. Patients who continue to smoke after surgery for PVD are more likely to relapse, leading to amputation, and are more likely to die earlier.10

Thromboangiitis Obliterans (Buerger's Disease)

This is a rare form of PVD, and is virtually always due to heavy cigarette smoking. It consists of an inflammatory condition of small vessels that leads to blocking of the arteries and gangrene. Few sufferers are able to stop and many of them end up with multiple amputations.

Stroke

Smokers are more likely to develop a cerebral thrombosis (stroke) than non-smokers. A form of cerebral haemorrhage (subarachnoid) is more common in smokers, especially among women who also take the contraceptive pill.

The benefits of stopping smoking

Whatever age a person is, it is never too late to give up smoking. Blood is less likely to clot, the heart can pump more blood (and therefore oxygen) around the body with less effort. Giving up smoking reduces the risk of a heart attack and is particularly important for those who have other risk factors such as high blood pressure, raised blood cholesterol levels, are overweight or diabetic. Some studies have shown that, within five years of giving up, the risk is reduced almost to that of a non-smoker. Giving up smoking after a coronary attack can halve the chance of a recurrence. Stroke risk decreases significantly in two years and is about the same as for non-smokers after five years.

Passive smoking

Recent research has shown that exposure to environmental tobacco smoke can cause heart disease in non-smokers. The Government appointed Scientific Committee on Tobacco and Health found a relative risk of 1.23, ie an excess risk of 23 per cent in non-smokers exposed to passive smoking compared to those not exposed. A major review in the USA also confirmed an increased risk of heart disease as a result of passive smoking.