Cardiovascular diseases Unit 4 Option C Section 3 CSE November 2006

Coronary Heart Disease A disease of the arteries supplying blood to the muscle forming the walls of the heart A blockage of a coronary artery is called a coronary thrombosis or heart attack causing extreme gripping chest pains Part of the heart muscle does not receive any blood, therefore no oxygen and it dies Damaged tissue replaced by non-contractile tissue so the heart loses some of its strength

CHD Size of attack depends on size and position of coronary artery blocked Heart attack also called myocardial infarction If a large artery is blocked, the whole heart may stop beating = cardiac arrest CHD major killer (27%) in developed countries

Hypertension Increased blood pressure Heart works harder Atheroma and blood clots more likely BP measured by a sphygmomanometer Cuff inflates till blood stops flowing in artery Air released until some blood squeezed through when ventricle contracts = systolic BP (120mm Hg) Air released allowing blood through more freely = diastolic BP produced by elastic recoil of arteries when ventricles relaxed (80mm Hg) High BP – above 120 / 80 Top figure increases with age

Hypertension Can cause kidney damage and blindness Increases risk of stroke and CHD Causes: - smoking - overweight so more capillaries supply adipose tissue - too much salt in diet which affects water balance and increases blood volume - Insufficient exercise so narrower vessels and more resistance to blood flow

Hypertension treatment Diuretics – increase excretion of salt and water in urine, reducing blood volume and pressure Beta blockers – slows heart rate and decrease its output so less blood forced through vessels Calcium antagonists – dilate arteries and arterioles by preventing calcium ions moving into smooth muscle cells Angiotensin converting enzyme inhibitors – prevent formation of angiotensin hormone which constrics arteries Drugs to dilate arteries

Atherosclerosis The main cause of CHD Is a process in which yellowish fatty substances are deposited in the walls of arteries in response to certain stimuli = plaque Stimuli include - diet rich in saturated fats and cholesterol - high cholesterol in blood - carbon monoxide from smoking - nicotine - hypertension

Possible sequence Stimulus causes damage to arterial endothelium Atheromas are deposits (plaques) of cholesterol and fibrous tissue which narrow arteries Blood flow reduced Artery walls less elastic

Effects 1 - Angina Reduction of blood flow to heart muscle causes angina – symptoms include gripping pain in chest, pains in left arm and breathlessness. Is a warning that a complete blockage of a coronary artery (a thrombosis) may occur Final blockage of the artery is usually caused by a blood clot or thrombus

Effects 2 – blood clots The atheroma deposits make artery lining, endothelium, rougher Roughness triggers formation of blood clots These clots can be in any artery Clots can travel in blood to heart If coronary arteries are narrower due to atheromas blood clots likely to get stuck and completely block the artery

Effect 3 –aneurysm and stroke If a blood clot forms a blockage in an artery, it can weaken the wall and cause it to swell = aneurysm The swelling can burst and if this happens near the brain it leads to a stroke This may cause some brain damage and depends on the amount of tissue damaged Commonly the middle cerebral artery is affected causing some paralysis down one side Damage to the right hand side of the brain causes speech problems Strokes can kill and are the main cause of disability in the UK

Risks 1 - diet High cholesterol diet as cholesterol main component of atheroma but some is needed for membranes Saturated fats increase blood cholesterol High fibre diets lower blood cholesterol by influencing absorption of fat Obesity and overweight are triggers, probably raise blood pressure High salt intake raises BP

Risks 2 - smoking Nicotine diffuses into blood and increases BP, heart rate, narrows blood vessels and raises fat levels in blood. All increase chance of arteries being blocked Nicotine and carbon monoxide damage endothelium lining so easier for fats to deposit Tobacco smoke makes platelets stick to endothelium so speed up formation of a blood clot

Other risks Stress Age - older Gender – male Heredity Body mass - high Exercise - low Diabetes Alcohol - high Social class – low????

Treatment Diet – unsaturated fat, low cholesterol Encourage healthy lifestyle - exercise Use of drugs to reduce blood pressure – calcium antagonists dilate blood vessels and beta blockers reduce heart rate Beta blockers stop adrenaline binding to receptors on cardiac muscle surface. Stop heart rate speeding up (used to combat stress too) Glyceryl trinitrate causes rapid dilation of blood vessels so improving oxygen supply to cardiac muscle (angina treatment)

Treatment 2 Decrease risk of blood clotting Reduce fluid retention Angioplasty to open up artery– stent can be left in Coronary artery by-pass using artery from elsewhere in body Heart transplant. Pioneered 1960s by Christiaan Barnard

SO …….. To reduce the risks of atherosclerosis Exercise Eat a healthy diet Don’t smoke Don’t drink Try not to get stressed