OzEMedicine - Wiki for Australian Emergency Medicine Doctors

see also: cardiology; Atherosclerosis - risk factors and molecular genetics

• Hypercholesterolaemia is a major risk factor along with smoking, hypertension and diabetes for developing atherosclerosis and primary prevention.
• Coronary heart disease is almost entirely due to atherosclerosis in the coronary arteries.
• atherosclerosis in the carotid arteries also plays a major role in stroke (CVA).

• the serum lipids are cholesterol and triglycerides which transported in the blood as large molecules known as lipoproteins.
• There are five major classes of lipoprotein:
  • triglyceride-rich and atherogenic:
    • chylomicrons
    • very low density (VLDL)
    • intermediate density lipoprotein (IDL)
  • cholesterol-rich and atherogenic:
    • low density lipoprotein (LDL)
  • cholesterol-rich and anti-atherogenic:
    • high density lipoprotein (HDL)

• A meta-analysis of randomised trials of statins showed that for each 1 mmol/L reduction of LDL cholesterol (which generally equates to a 20% reduction of LDL cholesterol) there is a 20–30% relative risk reduction of coronary heart disease events.
• Lowering the LDL a further 30% or so, or an extra 1 mmol/L, reduces coronary heart disease events by a further 20–30%.
• Reducing LDL cholesterol to below appropriate targets is more important than the method or specific drug used to achieve the reduction.

• LDL cholesterol < 4 mM
• triglycerides < 2 mM
• HDL > 1 mM
• total cholesterol < 5.5 mM

• LDL cholesterol < 2.5 mM (< 2mM if very high risk of future cardiovascular event)
• triglycerides < 2 mM
• HDL > 1 mM
• total cholesterol < 5.5 mM

• replacing saturated fat with either carbohydrate or foods rich in mono- or polyunsaturated fats and high fibre foods is effective in lowering LDL cholesterol.
• avoid baked foods containing trans fatty acids, such as pies, pastries, cakes and biscuits.
• response to diet can vary considerably and is usually seen in 4−6 weeks
• some patients are very responsive and can have up to 30% lowering of LDL cholesterol
• diets to consider:
  • Mediterranean-type diets, as found in Greece, Italy and Spain.
    • vegetarian-like, high in nuts and olive oil, vegetables and pasta which was cooked al dente. Fruit was eaten frequently along with some cheese, wine and nuts.
    • after a myocardial infarction, a Mediterranean-type diet compared to a usual low fat diet is associated with a 50% relative reduction in mortality. This is independent of any change in serum cholesterol.
  • low in total fat such as in Japanese cuisine
  • high intake of fish, particularly fish rich in marine omega-3 fatty acids

• For every kilogram decrease in body weight, LDL cholesterol decreases by 0.02 mmol/L, triglycerides decrease by 0.015 mmol/L and HDL cholesterol increases by 0.14 mmol/L.
• losing 5–10 kg is achievable and can make a difference to the risk profile.

• regular aerobic exercise (moderate effort of half an hour of intentional exercise most days of the week) improves the lipid profile independent of diet and drugs, and decreases LDL cholesterol by 10% and increases HDL cholesterol by 5%.

• On average plant sterols reduce LDL cholesterol by 10%, but this may vary from 0 to 30%. They have an additive effect to drug therapy.
• A dose of 2–4 g of plant sterols is needed, which equates to at least four teaspoons of plant-enriched margarine per day.

• A tablespoon or two of soluble fibre (eg. psyllium) each day, lowers LDL cholesterol by approximately 5%.

• in 2018, the Cochrane review found that there is little evidence to support these supplements as benefiting reducing cardiovascular disease

• If diet and nutraceuticals do not adequately reduce the LDL cholesterol and the patient remains at high risk of a cardiovascular event, drug therapy is indicated.

• HMGCoA reductase inhibitors, 'statins', are the first drugs to use. They are extremely efficacious and more than 90% of patients can tolerate them with negligible or no adverse effects.
• see statins
• In approximately 75% of the patients who cannot tolerate even half the usual dose of statins, ezetimibe can be effective.
  • Ezetimibe 10mg/d inhibits the absorption of dietary cholesterol.
  • in patients on maximal statins without adequate effect, adding ezetimibe can often lead to a synergistic lowering of LDL cholesterol by an extra 20–25%.

• diet rich in mono- and polyunsaturated fat and low glycaemic index carbohydrate food
• caloric restriction (leading to weight reduction) and exercise.
• consideration of marine omega-3 fatty acids (fish oil) and fibrates.

• Aust Prescr 2008; 31:119-22; How to treat hypercholesterolaemia; David Colquhoun
• Aust. Heart Foundation - Reducing risk in coronary heart disease
• Aust. Heart Foundation - Prevention of heart disease