2.2.4 Coronary heart disease

• Explain the cause of coronary heart disease (CHD)

  
  

  1. Layers of fatty material build up inside coronary arteries (vessels supplying blood to heart muscle)

  2. This narrows coronary arteries, reducing blood flow

  3. Resulting a lack of oxygen / glucose for heart muscle
• Explain how CHD can cause a heart attack

  1. Restricted blood flow through coronary arteries so not enough oxygen reaches heart muscle

  2. So not enough aerobic respiration / energy released
• Describe how coronary heart disease can be treated

  1. Stent (metal mesh tube) inserted into coronary artery to keep it open so blood continues to flow

  ✘ Risk of surgery / infection / blood clots

  2. Statins (drugs) - reduce blood cholesterol, slowing deposit of fatty material in arteries

  ✘ Effects take time, may be side effects
• Explain the consequences of faulty heart valves

  Healthy heart valves prevent backflow of blood in the heart

  1. Valve doesn't open fully → restricts blood flow

  OR valve develops a leak → back flow of blood occurs

  2. So less blood containing oxygen pumped around body

  3. So less aerobic respiration and less energy released

  4. So more anaerobic respiration which produces lactic acid

  5. Causing tiredness / muscle fatigue / increased breathing rate
• Describe how faulty heart valves can be treated

  1. Biological valve replacement - from animals or human donors

  ✘ Wear out / stiffen over time so may need to be replaced, ethical issues

  2. Mechanical valve replacement - artificial, longer lasting

  ✘ May cause clots so anti-clotting drugs required
• Describe how heart failure (failure to pump enough blood) can be treated

  ● Transplant of a donor heart, or donor heart and lungs

  ✘ Takes time to find a donor, risk of rejection by immune system so take immunosuppressant drugs

  ● Artificial heart occasionally used to keep patients alive while waiting for a transplant, or to allow heart

  to rest as an aid to recovery

  ✘ Expensive, does not last long, can cause blood clots so take blood thinning drugs
• why is this statement wrong?

  “When coronary arteries are blocked,

  less blood flows to the body.”

  The aorta carries blood away from the heart to the body. Coronary

  arteries branch off this to supply the heart muscle with blood. If

  blocked, the heart muscle receives less blood.
• why is this statement wrong

  “Biological valves can be rejected.”

  Biological valves are treated with chemicals to prevent this.
• Advantages of statins

  ● Decrease blood cholesterol; slows down build-up of fatty material in arteries

  ● Maintain blood flow to heart muscle cells

  ● Not invasive / easy to take

  ● Low cost (compared to stent operation)
• Disadvantages of statins

  ● Might be side effects of drug eg. muscle pain

  ● Effects take time to happen

  ● Drug will need to be taken long term

  ● Might forget to take drug
• Advantages of stents

  ● Blocked artery held open so blood flow to heart muscle cells increased

  ● Remains in place for a long time

  ● Effect is immediate / rapid recovery from operation
• Disadvantages of stents

  ● Risk of infection from operation

  ● Risk of surgery eg. heart attack / bleeding

  ● Risk of blood clot
• artificial heart.

  Advantages

  ● Prolongs patients life when waiting for heart transplant

  ● Heart not rejected by body's immune system / no need for

  immunosuppressant drugs
• artificial heart.

  Disadvantages

  ● Do not work as well as natural hearts / parts can wear out

  ● Blood clots can occur so blood thinning drugs need to be administered

  ● Battery needs regular charging

  ● Surgery can cause complications / infection