Cardiovascular Disease & Treatments | Biology for Grade 10 PDF Download

Development of cardiovascular disease

Coronary heart disease

• The heart is a muscular pump. Like all muscles, it needs oxygen for aerobic respiration to contract. The coronary arteries supply blood, and therefore oxygen, to the heart muscle.
• The coronary arteries may become blocked by a build-up of fatty material, caused by certain kinds of 'bad' cholesterol. As the fatty material increases, one or more coronary arteries narrow, and can become blocked.

• If a blockage builds up, the amount of oxygen reaching the heart muscle is reduced. A person will develop chest pain, and if left untreated, a heart attack is the result. This can cause damage to, or death of the heart muscle. Part of the heart muscle, or the whole heart, will die.

Ways of treating cardiovascular disease

Coronary heart disease

• Drugs and surgery can help to control coronary heart disease.

Statins

• Statins are drugs that help to lower cholesterol in the blood. They do this by lowering its production in the liver.
• Statins are prescribed for people with heart disease or who have a high risk of developing it. They need to be taken long-term. Cholesterol levels will rise again if a person stops taking them.
• Some studies have raised concerns regarding the side effects of statin use, while others believe they can bring additional positive benefits.
• Statins are not suitable for everyone - they should not be prescribed for people with liver disease, or pregnant or breast feeding women.
• Some patients taking statins often experience side-effects such as headaches and memory loss. There have been reports of statins being linked with type 2 diabetes and liver damage.
• Other people argue that statins should be used more widely. They may protect against other conditions such as Alzheimer's disease, but further research is needed.

Stents

• Coronary arteries that are blocked or have become narrow can be stretched open and a stent inserted to restore and maintain blood flow.

• They can be used in instances where drugs are less effective, and offer a longer term solution. Stents are made from metal alloys and do not lead to an immune response in the patient.
• Around 75 000 operations are carried out each year. Risk factors depend on the patient's:
  • age
  • general health
  • whether they have had a heart attack
• The operation is safe as it does not involve surgery, but there is a risk of bleeding, heart attack or stroke.

Heart transplants

• A heart transplant is required in cases of heart failure. Coronary heart disease can lead to heart failure. The heart fails to pump sufficient blood and organs are starved of oxygen. There are different degrees of severity of heart failure.
• A consultant assesses the patient's condition. If other treatments are not managing the heart condition, a transplant may be recommended and a patient will be put on a waiting list. A transplant puts major strain on the body, and the benefits and risks will be evaluated including whether the patient's condition is sufficiently severe and other health factors.
• There is a shortage of donor hearts in the UK. Only around 200 transplants are carried out each year in a small number of hospitals.
• Artificial hearts are plastic devices used occasionally to keep patients alive whilst waiting for a heart transplant. They can also be used to allow a patient's heart to rest to help it recover.

After the transplant, the patient will:

• need time to heal, recover and build up strength
• have to take drugs called immunosuppressant drugs for the rest of their life - this prevents the person's immune system from rejecting the donor heart
• have an increased risk of infection because of these drugs

Evaluation of different treatment methods

• Drugs used alongside heart conditions and transplants prolong life.
• NHS data shows the life expectancy of heart transplant patients:

Evaluating the treatment methods

Taking pulses and calculating blood flows

The pulse

• The simplest way of checking heart rate is to measure your pulse. As the heart beats, a pulse can be felt in locations where an artery passes over a solid structure, such as bone. Locations include wrist, neck and upper arm.
• The pulse rate is expressed in beats per minute.

• To measure your pulse rate, count the number of beats in a set period of time, eg 30 seconds, or a minute.
• In healthy people, generally, the lower the resting pulse rate, the fitter they are.
• Pulse rates increase during and after exercise, as more oxygen must be provided to the muscles, and carbon dioxide removed.

Flow rates of blood

• Scanning techniques such as MRI can be used to measure blood flow in the body.
• The blood flow from the heart is called cardiac output. It is the volume of blood pumped by the heart per minute. Stroke volume is the volume of blood pumped out of the heart per beat.

Cardiac output in cm³ per minute = heart rate in beats per minute × stroke volume in cm³ per beat.

• An increase in heart rate or stroke volume will increase cardiac output.
• So, if a person has a resting heart rate of 70 beats per minute and a resting stroke volume of 75 cm³ per beat, the cardiac output for this person at rest is:
• Cardiac output in cm3 per minute = 70 × 75 = 5250 cm³ per minute.

Example: An athlete is exercising. If their maximum heart rate is 130 beats per minute, and stroke volume is 150 cm³, what is their cardiac output in dm³?

Calculation:

• Cardiac output in cm3 per minute = heart rate in beats per minute × stroke volume in cm3 per beat.
• Cardiac output in cm3 per minute = 130 × 150 = 19 500 cm³ per minute = 19.5 dm³ per minute.