Brent Cornell

    
Blood pumped through the heart is at high pressure and cannot be used to supply the heart muscle with oxygen and nutrients

• Coronary arteries are the blood vessels that surround the heart and nourish the cardiac tissue to keep the heart working
• If coronary arteries become occluded, the region of heart tissue nourished by the blocked artery will die and cease to function

Causes of Coronary Occlusion

Atherosclerosis is the hardening and narrowing of the arteries due to the deposition of cholesterol

• Atheromas (fatty deposits) develop in the arteries and significantly reduce the diameter of the lumen (stenosis)
• The restricted blood flow increases pressure in the artery, leading to damage to the arterial wall (from shear stress)
• The damaged region is repaired with fibrous tissue which significantly reduces the elasticity of the vessel wall
• As the smooth lining of the artery is progressively degraded, lesions form called atherosclerotic plaques
• If the plaque ruptures, blood clotting is triggered, forming a thrombus that restricts blood flow
• If the thrombus is dislodged it becomes an embolus and can cause a blockage in a smaller arteriole

Consequences of Coronary Occlusion

Atherosclerosis can lead to blood clots which cause coronary heart disease when they occur in coronary arteries

• Myocardial tissue requires the oxygen and nutrients transported via the coronary arteries in order to function
• If a coronary artery becomes completely blocked, an acute myocardial infarction (heart attack) will result
• Blockages of coronary arteries are typically treated by by-pass surgery or creating a stent (e.g. balloon angioplasty)

Risk Factors for Coronary Heart Disease

There are several risk factors for coronary heart disease (CHD), including:

• Age – Blood vessels become less flexible with advancing age
• Genetics – Having hypertension predispose individuals to developing CHD 
• Obesity – Being overweight places an additional strain on the heart
• Diseases – Certain diseases increase the risk of CHD (e.g. diabetes)
• Diet – Diets rich in saturated fats, salts and alcohol increases the risk
• Exercise – Sedentary lifestyles increase the risk of developing CHD
• Sex – Males are at a greater risk due to lower oestrogen levels
• Smoking – Nicotine causes vasoconstriction, raising blood pressure

Mnemonic:  A Goddess