Cardiovascular System and Conditions

Describe the size, position and orientation of the heart

• About the size of a fist
• Within the mediastinum in the thoracic cavity, 2/3 of which sits to the left of body's midline
• Cone shaped with it's apex pointed anteriorly and inferiorly to the left, and its flat base facing posteriorly and superiorly to the right

Describe the pericardium and the layers of the heart wall

• Heart is covered by the pericardium, which protects the heart but allows for its vigorous contractions
• The pericardium is made up of the outer fibrous layer, inner parietal layer, pericardial cavity and the inner visceral layer (also known as the Epicardium)
• The heart wall is made up of the: Epicardium (also known as the visceral layer of the pericardium) Myocardium (heart muscle, makes up bulk of heart) Endocardium (smooth inner lining)

Describe the flow of blood through the heart and each of its components

• Deoxygenated blood from the body enters the right atrium via the vena cava inferior and vena cava superior
• This blood is pumped from the right atrium into the right ventricle via the tricuspid valve
• The blood is then pumped into the pulmonary trunk via the pulmonary valve
• The pulmonary trunk then splits into the left and right pulmonary arteries into the lungs, where it is oxygenated through external respiration
• Oxygenated blood is pumped from the lungs into the left atrium via the pulmonary veins
• This blood is pumped from the left atrium into the left ventricle via the bicuspid/mitral valve
• The blood is then pumped into the aortic arch via the aortic valve, and pumped to the rest of the body via the aorta

What are the different divisions of the cardiovascular system?

• Pulmonary (lungs)
• Systemic (muscles and other organs)
• Hepatic (liver)
• Coronary (heart)

What are the main functions of the cardiovascular system?

• transport blood and nutrients
• remove waste
• hormonal control
• temperature regulation
• host defence
• reproduction

What is the basic composition of "blood"?

55% liquid plasma, 45% solids

• Erythrocytes (red blood cells)
• Leukocytes (white blood cells)
• Thrombocytes (platelets)

What are the different types of blood vessels and what sort of blood do they carry?

• Arteries (oxygenated)
• Arterioles (oxygenated)
• Capillaries (both)
• Venules (deoxygenated)
• Veins (deoxygenated)

Describe the structure of a blood vessel

• Tunica adventitia (protective layer, elastic and collagen fibres)

• Tunica media (smooth muscle and elastic fibres)

• Tunica intima (smooth endothelial layer)

• Lumen (empty inner space)

• Veins have one way valves that resist gravity and ensure one way blood flow

Describe the coronary arteries

They supply the cardiac muscle with oxygenated blood and branch off from the aorta. Consist of:

• Right coronary artery
• Left coronary artery
• Circumflex artery
• Left anterior descending artery

Describe the electrical conduction pathway in the heart

• The Sinoatrial Node (SA node), the main pacemaker for the heart, located in the right atrium near its junction with the vena cava, sends electrical impulses across the atria causing them to contract
• These impulses travel to the Atrioventricular Node (AV node), located in the right atrial wall near the base of the interatrial septum. Here there is a slight delay, to allow the atria to fully contract and blood to flow into the ventricles
• After a slight delay, the AV node sends the electrical impulses down the Bundle of His, which travels down the interventricular septum and branches out into the right and left bundle branches
• The left and right bundle branches innervate the left and right ventricles respectively via the Purkinje fibres
• All compartments eventually relax, allowing blood to flow back into the atria

Explain the cardiac cycle and how long it takes (for normal sinus rhythm at 75bpm)

• Atrial Systole (0.1 secs): SA node depolarises (- to +), depolarising of atrial cardiac muscles and contraction. Impulses travel to the AV node and pause, allow full contraction of atria, signal travels down BoH to purkinje causing ventricular depolarisation.
• Ventricular Systole (0.3 secs): Atrial muscles repolarise (- to +) and relax (atrial diastole). Ventricular depolarisation causes contraction. Pressure in ventricles increases and AV valves close, causing brief period where all 4 valves shut (isovolumetric contraction [0.05 secs]). Ventricular contraction overcomes pressure causing semilunar valves to open. Meanwhile, ventricular muscles cells repolarise (+ to -).
• Relaxation period (0.4 secs): Longest period, both atria and ventricles relaxed. When HR increases this period is most shortened. Ventricular repolarisation relaxes ventricles. Again, brief period all 4 closed (iso relaxation). Pressure keeps falling, AV valves open, passive ventricular filling begins (to 75%).

Describe Coronary Artery Disease (I.e. CAD or ischaemic heart disease) and the process of atherosclerosis

CAD almost always caused by atherosclerosis of coronary arteries. Tears in the Tunica intima create build up in lipids and cholesterol in Tunica media (plaques). White blood cells create fibrous caps around the plaques. Causes narrowing of artery lumen (stenosis) leading to ischaemia.

Describe Stable Angina include signs, symptoms and management

Stable Angina: insufficient oxygen reaching myocardium from significant stenosis of at east one coronary artery due to coronary artery disease.

Signs/symptoms: Chest pain (can radiate) relieved at rest, dib, sob, increased WOB, indigestion like, belching, nausea, sweating

Management: Will usually self administer own glyceryl trinitrate (GTN). Place pat at rest, avoid walking moving excessively, analgesia as required, ECG.

Describe Acute Coronary Syndrome (ACS) including how it occurs and the three conditions

Includes: Unstable Angina, non-ST-segment elevation myocardial infarction (NSTEMI), ST-segment elevation myocardial infarction (STEMI)

• Rupture of fibrous cap from atherosclerosis leads to platelet aggregation
• Thrombus (blood clot) expands the plaque (intraplaque thrombus) or thrombus itself expands (intraluminal thrombus) and can occlude artery if large enough. This causes death of heart tissue.

Above process exacerbated by vasoconstricting substances associated with platelet aggregation, constricting and narrowing vessels.

Describe ACS signs, symptoms and management

Signs and symptoms: Chest pain not relieved at rest, nausea and vomiting, sweating, dib, pallor, impending sense of doom. 1/3 pats present atypically - watch out for sob, abdo pain and collapse/faint especially in the young (25-40), elderly (>75), unwell diabetics and unwell female pats

Management: 12 lead ASAP, correction of major ABC problems, administer medication (O2, entonox), rapid transport to nearest appropriate hospital

Explain the Pathophysiology of Heart Failure

Abnormality in cardiac structure or function, meaning the heart cannot deliver O2 at the rate the body needs. Can be acute or chronic (stable in last month).

Can be caused by previous MI, chronic hypertension, arrhythmias, genetic heart conditions.

L Ventricular Failure: Inefficient pumping of blood out of the heart to the body causes a backlog in the L ventricle, Mitral valve, L Atrium and pulmonary vein to the lungs.

R Ventricular Failure: Blood continues to back up from the lungs, pulmonary artery, R ventricle, R atrium, Vena cava, rest of body.

Describe Heart Failure signs, symptoms and management

Signs and symptoms include SOB, DIB, Tachypnoea, Tachycardia, Crackles, Fatigue, Haemoptysis, Congestion, Peripheral oedema

Management: Management of ABCs, pat at rest, full set of obs, o2 if required (<94%), ECG

Describe Sickle Cell, signs and symptoms, and management

Genetic disease where red blood cells are shaped like sickles. Reduced oxygen carrying capacity and can create blockages leading to hypoxia and pain.

Pats usually have UCPs with treatment plans and specific hospitals.

Signs and symptoms: Pyrexia, DIB, low saturations, coughs chest pain, pallor, fatigue. Dehydration, headache, priapism

Triggers for crisis: Exercise, altitude, infection, pregnancy, dehydration, stress, cold

Management: follow UCP, pain relief, repeat obs, ECG, consider fluids, put pat at rest and use chair, convey to specialist unit unless primary survey problems take precedence (e.g. HAC, HASU)