Main Types Of Cardiovascular Disease Biology Essay


Cardiovascular disease is arguably the biggest killer in developed countries, in the U.K alone there are 82000 deaths a year from coronary heart disease. CHD costs the country billions in direct patient treatment and care, not to mention the lost work days, it is estimated that there are 2.7 million suffering from CHD and 2 million of those have chest pains (angina). Over this paper I will discuss coronary heart disease in detail with emphasis on the causes and risk factors, symptoms, diagnosis and modern treatments. Firstly I will give an overview on how CHD affects the heart and the implications for the rest of the body.

The heart is a muscular pump, it requires blood for oxygen and nutrients just like every other muscle in our body and that blood is supplied to the heart through the coronary arteries (shown in the diagram below). In a healthy heart the blood flows through the arteries into the capillaries then into the muscle cells unrestricted and unobstructed. In a heart suffering from CHD the coronary arteries have become coated with a fatty deposit of cholesterol and triglycerides in a process called atherosclerosis, this stiffens them and restricts the blood flow to the heart muscles, the heart in turn has to work harder to force the blood through the narrow channel. Eventually the atherosclerotic plaque can build up so much that a thrombus (blood clot) occurs completely cutting off supply to the heart muscle cells which then begin to die of oxygen starvation, this in turn causes myocardial infarction (heart attack) which is often fatal even if treated as soon as possible.

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Some people have a higher risk of developing CHD than others; those more at risk are people with diabetes, obesity, a poor diet high in saturated fats, smokers, living more sedentary lifestyles with little exercise and possible genetic predisposition. The key to preventing heart disease lies in minimalizing these factors by proper treatment diabetes, and lifestyle change. Diet is incredibly important in minimalizing the risk of CHD, high blood cholesterol has been linked to up to 47% of deaths from CHD. Cholesterol not a triglyceride, it is made from fats generally found in animal cells and is an essential part of the diet as it is used for the construction of our own hormones and cell membranes. Cholesterol is a fat therefore it is not soluble in water, so the body needs to convert it so it can transport it in the blood lumen, this conversion happens in the liver where the cholesterol is converted into 2 different lipoproteins: high density lipoprotein (HDL) and low density lipoprotein (LDL). HDL is made from a formation of cholesterol, protein and unsaturated fats, it is thought of as being beneficial to health because it transports cholesterol back to the liver where it is broken down or used to make bile, this reduces the levels of blood cholesterol and thus reduces the risk of heavy atherosclerotic plaque build-up in turn reducing ones risk of CHD. LDL is made from cholesterol, protein and saturated fats, it is these that deposit on the coronary artery walls. Saturated fats in the blood can decrease the effectiveness of LDL receptors in the liver so even less LDL is processed further increasing the amount in the blood stream; therefore LDL is viewed as the unhealthy cholesterol. There are certain foods that can reduce the amount of LDL in our blood, such as polyunsaturated fats that are found in foods like in fish and nuts. Monounsaturated fats found in foods like red meat and olive oil can increase the activity of LDL receptors that binds the LDL for processing in the liver. In general eating a low fat diet will reduce the amount LDLs in our bloodstream and keep the LDL receptors working. The amount of salt we eat also effects our rick of CHD, blood with elevated salt levels has decreased water potential which leads to increased blood pressure (hypertension). When hypertension is combined with atherosclerosis; more blood is being forced through a narrow coronary artery increasing the risk of rupturing the plaque coating the artery releasing the highly thrombogenic material contained within.

The extra strain on the heart can have a variety of symptoms. One of the most common is the pain response the heart sends to the brain when its blood flow is being restricted, this chest pain is called angina. Angina is bought on usually from physical activity or stress that naturally increases the rate the heart beats, it has been described by sufferers as a tightening sharp pain that can travel up the neck and down the arms. Heart failure is another symptom of C.H.D, this is when the heart cannot adequately meet the blood transportation need for the body resulting in a sudden (acute) or prolonged (chronic) loss of blood to the extremities resulting in death of tissue. Another symptom of CHD a higher risk of an Ischaemic stroke, a stroke is when the blood supply to the brain is interrupted resulting in death of brain tissue. Strokes are serious and can result in serious brain damage or death even if treated quickly. A stroke can be the result of the release of thrombogenic material being transported to the brain or the result of atrial fibrillation, this is when the electrical impulse that triggers the depolarisation and hence the contraction is interrupted causing an irregular inefficient heartbeat. If it where to happen to the ventricles of the heart atrial fibrillation could instantly become fatal, if it happens in the atria the compressed blood can clot and be transported to the brain causing a cut off of oxygen and a stroke.

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Diagnosis of CVD can be done in a number of ways, one of which is an electro cardiogram (ECG/EKG). An ECG is performed by connecting numerous electrical sensor nodes to certain points on the body to measure the hearts contractions then a continuous measurement is then produced for analysis, here is how an ECG reading of a healthy heart looks:






Using these ECG results we can see the electrical impulse that travels through the heart in a normal healthy cardiac cycle, the different stages in the results are labelled PQRST. Notice how the two beats are identical and the lines between the beats are smooth and event free. We can use a healthy ECG reading to compare and identify an abnormality suggesting a form of CVD.

In this ECG reading we can see a 'jittering' or fibrillating making the P wave unclear indicating that this person is suffering from atrial fibrillation. Different types of CVD give different ECG readings, for example; a patient having a heart attack would have massively elevated S and T waves. Early detection of CVD can be lifesaving, an ECG can pick up early signs of problems before symptoms or complications arise meaning patients receive treatment sooner.

Treatment of CVD has become increasingly effective According to the NHS 'since (year) 2000, there has been a 40% reduction in deaths from heart disease in people under 75'. This has been attributed to: technological advantages in treatment, patients being diagnosed and treated sooner and faster, understanding of the diseases and prevention concentrated on higher risk individuals. Treatments themselves vary from prescribed lifestyle changes, operations such as a heart transplant to prescribed medication. Percutaneous transluminal coronary angioplasty (PTCA) can now be performed at specialist cardiac centres; this operation involves inserting a small inflatable device into the coronary arteries, the device is then inflated pushing the fatty deposits against the artery wall to allow blood to flow more freely. The results are a reduced risk of a thrombus developing and relief from angina, PTCA can be performed in about half an hour and the patient is usually able to go home the next day, though the NHS recommend avoiding driving for a week. There is also a multitude of drug treatments available for different factors minimalizing the risk of complications caused by CVD. Drug treatments include 'statins' that increase the number of LDL receptors in the liver, beta blockers that slow the heart beat to reduce the risk of a thrombus developing, nitrates that dilate the blood vessels reducing blood pressure.

There is no 'cure' for CVD; it is more prevalent in developed countries because of the availability of effortless transport and abundance of foods high in saturated fat, this combined with an aging population not being ravaged by diseases like malaria or AIDS and high child survival rate and CVD will become common. With advances in treatment we can alleviate symptoms and minimalize fatalities or serious complications using drugs and surgery, but the biggest weapon we have against CVD is prevention