Introduction to Cardiovascular Disease

• Cardiovascular disease is to do with the blood vessels and heart, but not the blood itself.
• • Blue blood vessels = deoxygenated blood
  • Red blood vessels = oxygenated blood
  • When left ventricle squeezes, blood is squeezed through the aortic valve and sends it into the aorta
  • Aorta takes the blood around the body (systemic arteries)
  • High pressure blood vessels with a thick wall
  • Split into more arteries, then arterioles, then capillaries (width of just 1 red blood cell)

  
• Red blood blood cells move through the capillaries, exchanging oxygen as they go, and come out the other side in a deoxygenated state in the veins, which eventually become the inferior vena cava, which comes from the bottom half of the body, and the superior vena cava, which comes from the top half of the body

  
• The inferior and superior vena cava veins drain deoxygenated blood into the right atrium of the heart, the right atrium then squeezes the blood through the tricuspid valve, which takes the blood into the right ventricle of the heart. When the right ventricle squeezes, the tricuspid valve closes and opens the pulmonary valve, which sends the blood into the pulmonary artery, which takes the deoxygenated blood to the lungs.

  
• Pulmonary veins bring the oxygenated blood into the left atrium, when the left atrium contracts the blood moves through the mitral valve into the left ventricle, when the left ventricle contracts the mitral valve closes and the aortic valve opens, which brings us back to the beginning.

  
• • Arteries have thick walls; high pressure
  • Veins are thinner; low pressure
  • Capillaries = single cell layer of endothelium to allow for maximum exchange
  • Veins have some valves
  • Endothelium lines the inner layer of the blood vessels - smooth, allows blood to flow through it and prevents clotting
  • If other layers are exposed because the endothelium is damaged then the blood clots to stop bleeding

  
• Atria are contracting at this point in time, but the ventricles are about to contract, because mitral valve is open but blood is about to flow through aortic valve. Aorta has 3 branches coming off it that go off to the arms and head, before the rest of it goes down to the lower half of the body.

  
• Coronary arteries are important; they're the arteries that supply the blood to the heart muscle itself (because like any other muscle in the body, it needs its own supply of oxygen, glucose, nutrients, etc). Right and left coronary arteries come off just above the aortic valve - the very first branches of the aorta.

  
• When the heart contracts it stops blood from flowing through these arteries, so the main blood flow is when the heart muscle is relaxed. Circumflex artery goes around the back of the heart. Right coronary artery supplies the inferior part of the heart. They are end arteries, so if one is blocked then there's no other way for blood to get to that part of the heart, meaning it will die as a result of damage due to lack of blood flow.

  
• The contraction of the atria and the ventricles is stimulated by electricity - the flow of ions across membranes of the various cells. The rhythm of the heart is governed by the sinoatrial node (high up in the right atrium).

  
• The rhythm of the heart is governed by the sinoatrial node (high up in the right atrium) - part 1:

  • When the sinoatrial node depolarises, the walls of the right and left atria contract
  • The depolarisation and electrical aspect of the contraction is picked up by the atrioventricular node, which is in the middle of the heart, at the bottom of the right atrium - the atrioventricular node then sends a message down to the ventricles through the Bundle of His
• The rhythm of the heart is governed by the sinoatrial node (high up in the right atrium) - part 2:

  • The Bundle of His puts in a slight pause so that the ventricles don't contract straight away, but then sends a message down to the ventricles via the right and left bundle branches that go to the right and left ventricles (left gets anterior and posterior division because the wall is thicker)
  • The bundle branches divide into smaller fibres (Purkinje fibres), which help the ventricles to contract in a very well-coordinated fashion at the right time after the atria have contracted
• Electrocardiogram:

  • P wave = atria are depolarising, and therefore physically contracting
  • PR interval = gap where the Bundle of His is putting in the pause
  • QRS complex = when the ventricles contract (the left ventricle is the biggest ventricle, and therefore has the biggest influence on these deflections)
  • ST segment = not much going on lol
  • T wave = ventricles are repolarising again

  
• Atherosclerosis:

  • Narrowing of arteries due to thickening of endothelium by lipids and fibrous tissue - atherosclerotic plaques
  • 3 main sites:
  • Coronary arteries - ischaemic heart disease
  • Carotids and cerebral circulation - cerebrovascular disease/strokes
  • Legs - peripheral vascular disease
• Reversible risk factors for atherosclerosis:

  • Hypertension
  • Hyperlipidaemia
  • Diabetes mellitus
  • Smoking
• Irreversible risk factors for atherosclerosis:

  • Age
  • Male sex
  • Post-menopausal status
• Aneurysms:

  • Weakening of blood vessel wall resulting in ballooning
  • Fusiform or saccular
  • Fusiform aneurysm is spindle-shaped - the whole artery dilates
  • Saccular aneurysm is like a little sac on the side of the artery
  • Complications:
  • Bursting, causing internal haemorrhage
  • Blood clots causing thrombosis or embolism

  
• Thrombosis:

  • Thrombus = blood clot within the circulation
  • Leg veins - deep vein thrombosis (DVT)
  • Can cause pain and swelling from the vein being blocked - but can also be completely asymptomatic
  • Coronary thrombosis (heart attack)
  • Cerebral thrombosis (stroke)
• Embolism:

  • Embolus = something (usually a blood clot) moving round in the circulation
  • Pulmonary embolus (from DVT)
  • Blocks pulmonary arteries because further on after that the vessels get smaller, so the embolus would get stuck
  • Cerebral embolus (from heart or carotid vessels) - could cause stroke
  • Peripheral embolus (usually legs from aorta)
• Infarction = death of tissue due to interruption of the blood supply

  • Heart attack: myocardial infarction due to coronary thrombosis
  • Stroke: cerebral infarction due to cerebral thrombosis or embolism
  • Can also be caused by cerebral haemorrhage from a burst blood vessel/aneurysm
  • Gangrene: peripheral infarction, eg leg, from atherosclerosis/thrombosis/embolism
• Ischaemic heart disease - spectrum of heart disorders caused by coronary atherosclerosis and thrombosis:

  • Angina - reversible ischaemia due to narrowed coronary arteries - chest pain in exertion
  • Myocardial infarction - irreversible damage due to blocked coronary artery - chest pain at rest
  • Heart failure - can result from permanent damage by myocardial infarction
• Heart failure = failure of the heart to pump strongly enough. May be due to...

  • Valve stenosis (narrowed) or regurgitation (leaky)
  • Hypertension causing damage to heart muscle
  • Cardiomyopathy - specific heart muscle disorder
  • Ischaemic heart disease - damage from MI
  • Sustained arrhythmia - usually atrial fibrillation
• Tachycardia is too fast.
• Bradycardia is too slow
• Atrial fibrillation is the commonest sustained arrhythmia - uncoordinated atrial activity results in irregular ventricular contraction, often too fast
• The most important tests for arrhythmias (atrial fibrillation, tachycardia, bradycardia) is ECG.
• Angina and MI (myocardial infarctions) can be precipitated by stress (going to the dentist can be stressful for some people) - know what to do.
• Most pts with cardiovascular diseases are on anticoagulant treatment - increase bleeding dental procedures. Epinephrine in local anaesthetics is a vasoconstrictor, so might aggravate high blood pressure or arrhythmias too.