If you find this website useful, please consider a small donation here! Atherosclerosis- Hardening of arteries
- Tunica intima thickens with deposits of
- Cholesterol
- Fibrous (scar) tissue
- Dead muscle cells
- Blood platelets
- Arteries become less elastic and partially narrowed
- ↑BP which in turn accelerates atherosclerosis
- Leads to endothelium damage and weak walls
- Mechanism
- Excess cholesterol leaks from lipoproteins (LDLs)
- Deposited on arterial walls
- Macrophages (white blood cells) are trapped within cholesterol
- Release free radicals which damage the arterial wall
- Activates blood platelets which stick to damaged areas releasing clotting factors (thromboxanes)
- Forms a plaque which may rupture to produce a thrombus
- Circulating thrombus is called an embolus
- Embolus may lodge elsewhere in the circulation (brain, heart arteries)
- NB: healthy arteries produce anti-clotting factors (prostaglandins) → don't form clots
- Factors that aggravate atheroma formation / atherosclerosis:
- Hypertension (↑BP)
- Smoking (release of free radicals)
- High LDL and low HDL
- NB: they all cause endothelial damage
Aneurysm- Weak arterial walls may burst leading to severe loss of blood (haemorrhaging)
- Brain aneurysm is called a stroke
Deep Vein Thrombosis- Clots are formed by
- Endothelial damage (see atherosclerosis)
- Altered blood components (dehydration, too many platelets)
- Altered blood flow (stasis of veins) → this is what causes DVT
- Prolonged immobility
- Such as paralysis, long-distance flights, lying down for weeks after surgery
- Thrombus often originates in calf veins
- Inflammation of vein walls → destroys vein valves
- Causes leg pain, swelling, and redness
- Elastic support stockings required for life
- Prevented by taking aspirin or warfarin which inhibit blood clotting
Coronary Heart Disease- Atherosclerosis causes arteries to become narrowed
- More force required to move blood through narrowed vessels
- Blood pressure increases
- Stable angina
- ↑exercise leads to ↑oxygen requirements by heart
- Narrowed arteries prevent more blood to pass through
- Shortage of blood to heart muscle causes chest pain
- Cells do not die as some blood can still pass through
- Pain only occurs during activity but not at rest
- Myocardial infarction (MI)
- Coronary artery is totally blocked by a thrombus/embolus
- No blood supply to heart muscle and cells die
- Irreversible if not treated within 90min
- Heart failure
- Prolonged blockage of artery causes damage to heart muscle
- ↓contractions / ↓cardiac output / ↓pressure generated / less blood leaves heart
- More blood is stored:
- on the right side of the heart → enlarged heart
- in veins → swollen legs and enlarged liver
LifestyleCholesterol- Needed for
- Vitamin D production in skin
- Sex hormone production in gonads and adrenal glands
- Making cell membranes
- Produce bile acid (salts)
- Has properties similar to fats → soft, waxy, and insoluble (difficult to remove if deposits form)
- Transported in blood from liver to tissues
- Safe transport is needed due to its insolubility
- Achieved by lipoproteins, which are soluble fatty proteins
- These are wrapped around cholesterol
- Normally, only small amounts of free cholesterol escape
LDL- Low density lipoproteins
- Carries cholesterol from liver to tissues
- Normally, some cholesterol 'leaks' from the lipoprotein and is absorbed to build cell membranes
- Excess LDL/cholesterol → too much cholesterol leaks out and causes atherosclerosis
HDL- High density lipoprotein
- Picks up cholesterol from arterial walls and carries it away from tissues
- Travels to liver where cholesterol is removed with bile
Smoking - ↓antitoxidants (vitamins), more damage due to release of free radicals by phagocytes
- [exam] Nicotine constricts arteries causing platelets to stick together → vasoconstriction → heart must work harder to force blood through → increases BP
- [exam] ↑BP causes damage to blood vessel lining / endothelium / collagen
- Leads to rise on blood platelets and makes them more sticky / form a plug / adhere to collagen fibres
- Release of thromboplastin/thrombokinase
- Fibrinogen converted to insoluble fibrin
- Platelet plug trapped by fibrin mesh
- Raises conc. of fibrinogen (in blood) → increased risk of clotting
- ↑LDL causes more cholesterol to leak out in blood
- Carbon monoxide reduces the efficiency of the blood in terms of carrying oxygen
- Haemoglobin combines with CO more readily than with oxygen → forms carboxyheamoglobin
- Associated with plaque formation
- Principle CHD = heart muscle receives inadequate amount of blood or oxygen/(coronary) blood supply reduced
Treatment- Medication
- Beta blockers reduce heart rate and reduce oxygen required by heart
- Aspirin prevents blood clotting and thrombosis formation
- ACE inhibitors stabilize plaques → prevent thrombus to break off
- Statins reduce LDL and increase HDL
- Angioplasty
- Deflated balloon-like device is passed up to the heart via the aorta
- Guided into damaged coronary artery and inflated to stretch the artery
- Heart by-pass graft
- Leg veins and arteries from chest are used to by-pass the blocked region of the coronary artery
- Involves open heart surgery
- Reperfusion therapy after a myocardial infarction
- Angioplasty done within 90 minutes of onset of chest pain
- May prevent irreversible damage to the heart muscle
Prevention - 1. Screen population for
- High BP
- High cholesterol
- Uncontrolled diabetes
- Smoking? Unhealthy diet? No exercises?
- Men over 55 and women over 65 are at highest risk
- 2. Monitor the behaviour of the heart during exercise
- Difficult but encouraging the population to adopt a more healthy lifestyle from an early age is important
- Often leads to changes in diet and weight management
- 3. Giving up smoking and reducing alcohol intake
- Reduces blood pressure
- Coronary heart disease is a long-term degenerative disease, starts at birth
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Latest Comments
Unknown User wrote on Tue, 08 Jan 2008 20:27:
hi as well as studdying as level human biology i work as an ambulance technician.pre-hospitally we can give drugs to help break down any clots that form within blood vessels, initially we administer aspirin 300mg which thins the blood allong with a drug called GTN which is a spray given to angina patients under the tongue which has the same effect as the aspirin, paramedics and hospitals administer clot busting drugs in a process called thrombylisis which acts to break down any clots directly. the ultimate treatment is then carried out in hospital during which a catheter is inserted into the site of the MI and a baloon is inflated to widen the gap and if neccessary a metal stent inserted to maintain the width of te vessel.hope i got that right and it was helpfuladeChanged by admin on 29 Dec 2008 13:53:25
Unknown User wrote on Sun, 06 Jan 2008 19:59:
Hello,Does anyone know how to treat a heart attack?Thanks!Danny!
Unknown User wrote on Thu, 20 Dec 2007 17:37:
Double post - message deleted.Changed by admin on 20 Dec 2007 17:41:57
Simon wrote on Wed, 19 Dec 2007 21:36:
Thanks for your post Geo! You have written a good introduction for MI, which saves me from writing one :-) There are a lot of risk factors which could cause a MI. To tackle the problem, it is probably best to keep it simple and start from the beginning. Always remember that a MI is caused by ischaemic heart disease, and therefore, atherosclerosis.
Smoking produces a lot of free radicals, which damage the endothelial cell layer of the artery. A damaged endothelium accelerates the effects of atherosclerosis. Fruits contain a lot of antioxidants and prevent free radical formation.
Anastomosis means that one area is supplied by more than one artery. If one of them is obstructed, the other artery will become bigger and take over the main blood supply. Therefore, you are right in saying that all arteries supplying that area have to be blocked to cause a MI. But as far as I know, anastomosis in the heart is not very common. However, surgeons use this principle to revasculate an obstructed area of the heart.
Hypertension accelerates atherosclerosis and also directly affects the heart. High pressure in the arteries means that the heart must pump stronger to open the aortic valves and to overcome the strong resistance in the arteries. If this is a chronic problem, the heart muscle enlarges (left ventricular hypertrophy) to provide the heart with a stronger contraction force (increases cardiac output). An enlarged heart muscle needs more oxygen. If an artery is blocked, it cannot provide the muscle with as much oxygen and you get angina, which is eventually followed by a MI. Atherosclerosis is accelerated by the shear stress on the arteries caused by the hypertension. Again, the endothelium is damaged which favours cholesterol deposition. Accelerated atherosclerosis and an increased oxygen demand by the heart, both caused by hypertension, increase your risk of developing a MI.
Diabetes is associated with high glucose levels. The mechanism is poorly understood, but it does accelerate atherosclerosis. It also predisposes to infection, renal failure, and damages the arteries in the eye. It is believed that the high glucose levels also attack the nerve ends which causes reduced sensation of pain. This is why some diabetics may not feel their heart attack or the pain is felt at different places (not down the left arm).
Exercise reduces hypertension. It has been shown that 30 minutes of exercise per day reduces the systolic blood pressure (SBP) by 10mmHg! Weight reduction can reduce the SBP by 20 mmHg and a change in diet by 14 mmHg! Hope this help! Any questions please feel free to ask. Simon
Changed by Simon on Sun, 09 Aug 2009 17:51
Unknown User wrote on Wed, 19 Dec 2007 19:11:
Myocardial Infarction is a sudden death of some heart tissues (myocardium) that have been deprived of blood flow - ischemia. This occurs when a coronary artery becomes blocked by a blood clot or fatty deposite - artherosclerosis. The portion of the myocardium that has been obstructed die of oxygen deficiency - hpoxia. MI is also caused by cigaratte smoking; I think this is because the blood will carry very little oxygen in the presence of the smoke, hence causing the heart tissues to be oxygen deficient. Obesity and hypertension also cause MI, it could also be common among people with a family history of heart disease. How does diebetes mellitus and hypertension cause MI?If the heart has a defense against artherosclerosis by anastomoses, does it mean that both passages will have to be blocked to cause MI?Exercise, I know is good for both healthy and MI patients, what about hypertension patients, since hypertension is known to cause MI? How does exercise help reduce or check MI?
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