Coronary heart disease is the leading single cause of death in both men and women in the UK, Northern Europe and North America. Women are not immune from it; going through the menopause increases the risk. Postmenopausal women are two and a half times more likely to die from heart disease than from breast cancer.
In many cases, coronary heart disease may be preventable.
Coronary heart disease risk increases with age, and is increased with certain metabolic disturbances and with diseases such as diabetes or high blood pressure (hypertension), and with certain lifestyle habits such as smoking and obesity. Inherited factors may also increase the likelihood of developing heart disease. The “metabolic syndrome” is a cluster of metabolic abnormalities, obesity and blood pressure, and predisposes to coronary heart disease and type 2 diabetes (see below).
Cholesterol is a type of fat (lipid) and high blood levels increase the risk of coronary heart disease. Cholesterol levels can be measured in the blood, but it is important to measure the two main types of cholesterol. LDL (low density) cholesterol is the “bad” type; high levels lead to “furring up” of the arteries (atheroma or atherosclerosis), and are therefore bad. HDL (high density) cholesterol is the “good” type; raised levels represent cholesterol being removed from the arteries, and are therefore good. Raised blood levels of triglycerides, another type of blood fat, also increase the risk for coronary heart disease; obesity, insulin resistance and diabetes are particularly associated with raised triglycerides.
Hypertension is often linked with abnormal cholesterol patterns, insulin resistance and obesity. High blood pressure also puts extra strain on the heart, leading to thickening of the heart muscle.
Insulin resistance develops when the body tissues become less responsive to the action of endogenous insulin. It is linked with various metabolic abnormalities and is a major feature of the metabolic syndrome.
Diabetes is a condition where there is loss of control of blood sugar levels, This may be due to a failure to produce insulin (the hormone which regulates blood sugar levels) by the pancreas, known as type 1 diabetes, or due to insulin resistance, and sometimes failure of insulin production due to exhaustion of the pancreas, known as type 2 diabetes. High blood sugar levels and high insulin levels both lead to furring up of the arteries.
Obesity is assessed by body mass index (BMI). It is calculated by dividing weight (in kg) by height (in metres) squared. A BMI between 18 and 25 is normal, between 25 and 30 is overweight, and above 30 is obese. Waist circumference measurement can assess central obesity. Central (abdominal) obesity is often linked to raised cholesterol and triglycerides, to insulin resistance, and to elevated blood pressure. It is a particular risk factor for coronary heart disease, and can also predispose to type 2 diabetes. It is a key feature of the metabolic syndrome.
Smoking causes damage to the linings of blood vessels which impairs their function, makes the blood more likely to clot, and lowers the protective HDL cholesterol levels.
A family history of coronary heart disease, shown by a close relative under age 70 years with the disease, may signify increased risk. In some cases, this can be due to inheritance of cholesterol or insulin problems and may thus be prevented. Ethnic origin may affect risk; people of South Asian ethnic origin have the highest risk in the UK.
Menopause increases coronary heart disease risk because of loss of the female hormone, oestrogen. Oestrogen helps to keep arteries functioning normally, lowers cholesterol, and improves insulin action.
Symptoms of coronary heart disease
Chest pain is the major symptom (angina). This is usually described as crushing or heavy pain in the centre of the chest, spreading across and down the arm or into the neck. It is usually brought on by physical exertion, but can be brought on by emotional stress or even by a cold wind blowing in the face. Prolonged or severe angina may signify a heart attack occurring.
Heart attack (myocardial infarction) occurs when an artery supplying the heart muscle with blood becomes blocked, and a part of the heart muscle may then be injured. If this part of the heart carries an important part of the electrical system of the heart, sudden death may occur. Or damage to the heart muscle may make the pumping action less effective, leading to heart failure (shortness of breath, swelling of the feet and legs).
Diagnosis and treatment
ECG (electrocardiogram) is a recording of the electrical activity of the heart. This will often show if someone is having a heart attack, but the ECG usually has to be done whilst exercising on a treadmill to show up narrowing of the coronary arteries. Exercise tests are done in people who get chest pain, and are less reliable just as a screening test for apparently healthy people.
Echocardiograhy uses sound waves to image the heart. This can show whether there is any thickening of the heart muscle, any narrowing or weakness of the heart valves, and whether the pumping action of the heart is normal. Combining this with either exercise or drugs to increase the heart rate (stress echocardiogram) can show whether there is any evidence of narrowing of coronary arteries preventing sufficient blood flow through the coronary arteries (ischaemia). This is a better test than ECG exercise tests.
Cardiac MRI (magnetic resonance imaging) is a more sophisticated means of imaging the heart and blood vessels. It can be used to assess heart structures, ischaemia and scarring.
Coronary angiography requires the insertion of a small plastic tube into an artery in the groin; the tube is passed up until it enters the coronary artery of the heart, and dye is then squirted through its which shows up any blockages on an X-ray screen. CT coronary angiography uses a CT (computed tomography) scan to image the coronary arteries and show any blockages. It is a non-invasive technique. CT can also measure coronary artery calcium and such calcium scores can show how much atheroma is present.
Angioplasty is a technique where a blockage in an artery is opened up by a small balloon. This is carried out during coronary angiography. Once the blockage is opened, a stent (metal mesh) may be put there to keep the artery open. Some stents are impregnated with a drug to help prevent further furring up.
Coronary artery bypass surgery is a major heart operation where the chest is opened and a piece of vein is used to bypass a blockage in an artery. This may be performed if angioplasty is not possible.
Drugs can be given to help relieve chest pain in patients who have extensive coronary disease which is not amenable to angioplasty or surgery. Such drugs include nitrates given as a spray or tablet under the tongue for acute episodes of angina, or as longer lasting tablets and skin patches. Beta-blockers slow the heart rate and help it work more efficiently, as do calcium antagonists. Newer drugs such as ranolazine and ivabridine can be very effective in treating angina. Drugs are also given as prevention to people at increased risk for coronary heart disease, and to those who have had a heart attack.
Prevention of coronary heart disease
Lifestyle measures, such as eating a balanced low-fat diet, correction of body weight, increasing physical activity and stopping smoking, are an important part of prevention.
Screening for risk factors is essential in anyone who may be at increased risk for coronary heart disease.
Blood pressure measurement will reveal any degree of raised blood pressure. Sometimes, a 24-hour recording of blood pressure, using a small portable machine, may be required to show if there is any blood pressure abnormality.
A fasting lipids blood sample is taken for measurements of various types of cholesterol and triglycerides, and a blood sugar is measured to help exclude diabetes. In patients who may have the metabolic syndrome, measurements of blood insulin may also be made, and a “glucose tolerance test” may need to be done (see under “Metabolic Syndrome” section).
Other blood measurements that can signify increased risk, such as homocysteine levels and C-reactive protein (CRP), may also be performed occasionally as necessary.
Occasionally other non-invasive tests, such as measurements of arterial function or arterial thickness, may occasionally be carried out.
Advice on diet and lifestyle and treatment with various drugs can then be given on an individual basis to correct any abnormalities that have been identified.
Microvascular angina (formerly known as cardiac syndrome X) is a condition in which chest pain occurs identical to angina, and tests for ischaemia are abnormal, but there is no evidence of blockage of the coronary arteries on angiography. It is thought to be due to either a dysfunction or a spasm of the tiny coronary artery branches (microcirculation) in the heart muscle. It occurs in both sexes, but is more common in women than men, and often arises around the time of menopause. Treatment is the same as for angina due to furred up coronary arteries, with long-acting calcium antagonists being particularly useful in this condition. In some women, the symptoms will respond to oestrogen treatment (HRT). Microvascular angina does not usually lead to heart attacks or sudden death, as may occur in patients with atheromatous coronary artery disease. Many patients with microvascular angina also have features of the metabolic syndrome.