Cholesterol is a waxy, fat-like substance found in every cell of the body. It has essential functions: it is a component of cell membranes, helps produce vitamin D, bile acids (for digestion), and hormones including oestrogen and testosterone. The body makes cholesterol in the liver, and additional cholesterol is absorbed from food.
Cholesterol is transported in the blood by lipoproteins, which are particles made of fat and protein. The two most clinically important types are low-density lipoprotein (LDL, often called ‘bad cholesterol’), which carries cholesterol to the arteries where excess amounts can accumulate in the artery wall as atherosclerotic plaque, narrowing the vessel and increasing the risk of heart attack and cardiac arrest; and high-density lipoprotein (HDL, often called ‘good cholesterol’), which helps remove cholesterol from the arteries and transport it back to the liver for processing.
High blood cholesterol (particularly high LDL) is a major modifiable risk factor for coronary artery disease. It usually causes no symptoms and is detected only through a blood test (lipid profile). In the UK, a total cholesterol above 5.0 mmol/L is considered elevated, but risk is assessed on the whole lipid profile and in combination with other cardiovascular risk factors.
For cardiac arrest survivors with coronary artery disease, achieving a very low LDL (below 1.4 mmol/L) is a key goal of secondary prevention, primarily through high-intensity statin therapy. Cholesterol levels are routinely checked at cardiac rehabilitation and cardiology follow-up appointments.
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