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Dr Diana R Holdright

Consultant Cardiologist

Dr Diana Holdright

Cardiac Conditions - Hypercholesterolaemia

Cholesterol is an essential component of body cells and structures.  However, high blood cholesterol levels are associated with an increased risk of cardiovascular disease, the most common cause of death in the Western world.  There are several components that together make up the blood cholesterol level, the two major components being LDL (low density lipoprotein) and HDL (high density lipoprotein) cholesterol.  High levels of LDL cholesterol increase the risk of cardiovascular disease, whereas high levels of HDL cholesterol are protective, and as such people often refer to LDL as the “bad” cholesterol, and HDL the “good”. 

Patients frequently ask what a normal cholesterol level is, but the ideal cholesterol level varies from person to person and depends largely on whether the patient is already known to have vascular disease in the form of angina, a prior heart attack, TIA or stroke, or documented atheroma in the arteries supplying the heart, brain, or legs. These patients fall into the category of “secondary prevention”, where the risk of further heart attack, stroke or death is reduced by about one fifth for each 1 mmol/L the LDL cholesterol is lowered with statin therapy* and changes in lifestyle. In particular, they “stabilise” plaque within the blood vessel wall, particularly in lipid-rich plaques, rendering them less prone to rupture, the mechanism behind a heart attack.  Some statins are particularly potent and may actually halve the risk of future cardiovascular problems.

High levels of HDL cholesterol are protective to the cardiovascular system, and women in particular tend to have higher levels. Some women have especially high levels such that the total cholesterol is high, but primarily due to the “good” HDL cholesterol, and as such, the total cholesterol level should never be looked at in isolation since this may be misleading. The ratio of HDL to total cholesterol is a useful way of analysing the profile.  HDL increases modestly with regular exercise and sensible eating habits, and progress is being made to find drugs which raise the HDL cholesterol and produce cardiovascular benefit, analogous to statins which lower the LDL cholesterol and improve outcome over time.

Cholesterol levels increase gradually with age, but obesity, lack of exercise, poor diet and diabetes mellitus are also known culprits. Some patients, however, have a purely genetically determined high cholesterol level, so called familial hypercholesterolaemia, where there are mutations in the genes which regulate the clearance of LDL cholesterol from the blood.  Familial hypercholesterolaemia causes premature atherosclerosis and heart disease, and as it is due to an abnormal dominant gene first degree relatives (siblings, parents and children) have a 50% chance of inheriting it. It greatly increases the risk of heart attack at a young age, and so screening is important; the advent of genetic testing and developments in screening tools have improved our ability to detect carriers of the gene at a young age and begin treatment early to reduce their risk of future heart problems.

* Cholesterol Treatment Trialists’ (CTT) Collaborators. Efficacy and safety of more intensive lowering of LDL cholesterol.  Lancet 2010; 376: 1670-81

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