Coronary Thrombosis and Myocardial Infarction.
Coronary thrombosis is the blockage of a coronary artery by a thrombus. If a coronary artery becomes blocked by a thrombus or embolus, heart muscle will become starved of oxygen leading to myocardial infarction (heart attack). The area deprived of blood, hence oxygen will become damaged and die.
Severe damage to the heart results in a reduced cardiac output (less blood is pumped out in a given time) and a build up of blood in the veins increasing their blood pressure. When the heart does not pump out blood as fast as it arrives heart failure is said to occur - the heart is not working as efficiently. Infarction on the left side of the heart causes a build up of blood in the pulmonary veins, fluid leaves the blood and enters the lungs causing difficulty in breathing and poor oxygenation of blood. Infarction on the right side causes build up of blood in the veins of the body causing oedema due to back pressure on the capillaries.
Prevention of CVD
CVD is a long term degenerative disease and people must be made aware of the complications of an unhealthy lifestyle early to try and educate them towards a healthy lifestyle. It has long been considered that CVD is a self inflicted disease because the lifestyle led by sufferers has influenced the onset of the disease.
The main risk factors that can lead to CVD are as follows:
Diet
A diet that is high in saturated fats causes a rise in blood cholesterol. In countries such as Japan where CVD is relatively rare, lower fat intakes and lower blood cholesterol are found than is typical of people in Britain. The amount of blood cholesterol is influenced mainly by the amount of saturated fats in the diet rather than the amount of cholesterol. This increases the deposition of cholesterol in the arteries leading to the formation of atheromatous plaques which are the underlying cause of CVD.
Hypertension
Hypertension, or high blood pressure, is associated with stress, smoking, obesity, excessive alcohol consumption and lack of exercise.
Long term hypertension places an extra strain on the heart and cardiovascular system making it work harder, speeds up the development of atheromatous plaques and increases the chances of suffering from angina, myocardial infarction or stroke. Hypertension may lead to heart failure, which occurs when heart muscles weaken and are unable to pump properly.
A blood pressure of 170/100 increases the chance of dying from CHD twofold compared to that of men with a normal blood pressure of 120/80.
Smoking
Smoking cigarettes has both a harmful effect on the respiratory system as the cardiovascular system.
Carbon Monoxide and nicotine are both toxic to the endothelium of arteries and therefore make the penetration of cholesterol plaques easier causing atheromatous plaques.
Carbon monoxide reacts irreversibly with haemoglobin to form carboxy-haemoglobin. This decreases the volume of oxygen carried in the blood and will therefore induce angina attacks.
Nicotine causes a higher concentration of fibrinogen which stimulates the clotting of platelets thus increasing the chance of developing a thrombus in an artery as the platelets are stimulated to stick to the surface of the endothelium.
Nicotine increases blood pressure and heart rate, but also constricts the blood vessels. This increases the chances of thrombosis especially stokes if the carotid arteries are effected as well as putting the heart under extra strain.
Atherosclerosis of peripheral arteries supplying the legs (also known as Beurger's Disease) causes crippling pain on walking and may lead to the death of tissues, subsequent gangrene which leads to amputation. More than 90% of sufferers of this condition have smoked at least 20 cigarettes a day for more than 20 years.
Physical Exercise
A lack of exercise will lead to a weak heart with a low cardiac output as the heart muscle is rarely exercised. Like any other muscle, exercise will increase the strength of the heart muscle and will enable a larger stroke volume to occur, therefore the heart doesn't need to beat as fast to pump as much blood around the body.
Lack of exercise will increase the risk of CVD because the heart is working much harder to pump blood around the body, therefore is being put under extra strain as with hypertension.
Gender
Men are twice as likely to suffer from CVD than women. Testosterone has a harmful effect on the cardiovascular system and pre-menopausal women produce oestrogen which protects against CHD. Post menopausal women tend to have an increase in blood fat levels, so the risk of developing CVD increases, but treatment with hormone replacement therapy will protect the body again from CVD. Although men cannot help their gender, to lower their risk they should make extra considerations about diet, exercise and smoking.
Stress
Leading a stressful lifestyle may increase the risk of heart attacks and angina attacks. Stressful lifestyles are also often coupled with lack of exercise (sedentary jobs in offices), smoking, excessive alcohol intake and poor diet.
Genetic factors
Heart disease has an inherited component, the more close relatives you have who develop heart disease, the more likely you are to suffer too. The main reasons that CVD runs in families is that it has a genetic component - such as certain genes that may increase the risk of developing atheromatous plaques. The second reason is that families share a common environment such as diet and being in an environment with smoke from cigarettes.
