1.2 Broad defintions of cardiovascular diseases
The following are broad definitions that may be useful in familiarising yourself with the range of CVDs and are here for you to return to at any time during the course to use as a reminder. You will undoubtedly come across variations as you read about them on the internet and in other texts.
Atherosclerosis (hardened or furred-up arteries) is due to the accumulation of fatty material within the blood vessel wall, which can lead to narrowing of the vessel and restriction of blood flow.
Ischaemia is a restriction in the blood supply within the blood vessels, with resultant tissue damage.
Coronary heart disease (CHD) is the most common form of heart disease, which involves a reduction in the blood supply to the heart muscle by narrowing or blockage of the coronary arteries. It is often characterised by atherosclerosis in the coronary arteries, angina pectoris and myocardial infarction, leading to acute heart failure.
Myocardial infarction (MI) occurs when the blood supply to part of the heart is cut off. If the blood flow to the heart is not restored, that part of the heart will die, causing disability or death. Myocardial infarction is the main cause of acute heart failure.
Heart failure is a medical condition resulting from heart disease and is often misunderstood. It describes when the organ cannot pump efficiently and is unable to generate blood flow sufficient to meet the demands of the body, either at rest or during exercise. Congestive heart failure is the term generally used when there is peripheral swelling due to fluid build-up.
Heart attack is the common name for acute heart failure, which is most often due to myocardial infarction following blockage of a coronary artery, but which also may be caused by other events that disturb the organised spread of electrical activity in the heart (e.g. arrhythmia, electrocution).
Arrhythmia is an uncontrolled, disordered or irregular heart beat. It can be faster or slower than normal.
Palpitations are when a distinct heart beat can be felt, and may be normal, faster or slower than usual. This is not necessarily a problem; for example, they can be caused by certain medications or simply by drinking too much caffeine in a short space of time!
Blood pressure is a measure of the force generated by the beating of the heart pressing blood against the walls of the arteries as it is pumped around the body. A blood pressure measurement shows the higher systolic pressure – when the heart contracts – and the lower diastolic pressure – when the heart relaxes.
Normal adult blood pressure should be less than about 140/90 mmHg (systolic/diastolic), as in the first pale pink zone in the bottom left-hand corner of Figure 2. If your blood pressure is consistently measured by medical staff as over 140/90 mmHg (the pink central zone or red outer zone of Figure 2), or over 140/80 mmHg if you have diabetes, you will be considered to have elevated or high blood pressure, known as hypertension. Consistently high blood pressure is a risk factor for many cardiovascular diseases. The excess pressure can damage the lining of an artery, allowing blood clots to form and cause blockages.
Strokes are caused by either blocked or burst blood vessels in the brain. By reducing high blood pressure to within the normal range, nearly half of all strokes can be prevented. Strokes are not covered in this course in detail – they vary according to the area of brain affected and there is not the space to cover the required brain anatomy or neuroscience. Strokes can kill or cause major disability, although full recovery is possible after a minor stroke.
Other rarer forms of heart disease are those that some people may be born with, known as congenital heart defects. Examples include problems with the heart valves or heart beat rhythm, and these are more likely to be encountered in younger people. They can cause long-term problems and even death (if undiagnosed) for people with these conditions. Sometimes you hear news stories about previously healthy children or young adults dying suddenly, especially following strenuous sports activities such as football matches (see Box 2).
Box 2: Sudden heart death in the young
SADS is another acronym that is used interchangeably, but this time for two descriptions of the same condition: Sudden Arrhythmic Death Syndrome and Sudden Adult Death Syndrome. The first is more accurate because SADS can affect children too.
There are a number of different causes of sudden heart death in young people, but sometimes no cause is found when a young person dies. This happens in about 1 in 20 cases in the UK (up to 500 per year). It is thought that a proportion of cases may be caused by a fast, uncontrolled heart beat (arrhythmia). One identified arrhythmia has been called long QT syndrome, which describes a lengthening of the time it takes the heart's electrical system to recharge, leaving the individual susceptible to an abnormal heart beat rhythm.
If the condition is diagnosed in time, a miniature defibrillator (to restart the heart) may be fitted or drugs can be taken (for the rest of the individual's life) to slow down the heart rate. Without treatment, the brain becomes deprived of oxygen, causing fainting – or, rarely, collapse and death.
As long QT syndrome can be genetically inherited and may be brought on by exercise, it has been suggested that all young athletes should be screened for the condition (Cardiac Risk in the Young, 2003).