ischaemia and infarction

Question 1

define ischaemia

Answer 1

an inadequate supply of blood to a tissue, resulting in an insufficient supply of oxygen and other metabolic needs for that tissue

Question 2

define infarction

Answer 2

an insufficient supply of blood carrying oxygen and other metabolic needs leading to cell/tissue necrosis

Question 3

name the types of occlusion in ischaemia

Answer 3

partial complete - more severe and often leads to infarction

Question 4

what factors make tissues more susceptible to ischaemia?

Answer 4

1. previous damage to organ/tissue 2. single blood supply 3. onset of blood supply affected 4. type of tissue affected

Question 5

what is the most common cause of ischaemia?

Answer 5

occlusion of blood flow - tissue isn’t getting enough oxygen to meet its metabolic demands

Question 6

what are the main causes of occlusion?

Answer 6

atheroma thrombosis embolus spasm

Question 7

name types of venous ischaemia

Answer 7

strangulated hernia volvulus - bowel twists around itself, blocking off its own venous supply

Question 8

name examples of capillary ischaemia

Answer 8

frostbite diabetic microangiopathy disseminated intravascular coagulation

Question 9

name the 2 non-vascular (not occlusion of a blood vessel) causes of ischaemia

Answer 9

1. decrease in oxygenated blood flow 2. increased tissue demand

Question 10

what can cause a decrease in oxygenated blood flow?

Answer 10

1. Hypotension
2. Anaemia – there are fewer red blood cells in the blood so fewer cells with oxygen carrying capacity
3. Carboxyhaemoglobinaemia – i.e. carbon monoxide poisoning

Question 11

what can cause increased tissue demand?

Answer 11

1. Thyrotoxicosis – overactive thyroid
2. Tachyarrhythmias – the heart is beating faster so needs more oxygen to meet its demands
3. Marked Myocardial Hypertrophy – the heart is larger so needs more oxygen to maintain its contractile force

Question 12

which clinical syndromes cause gradual occlusion?

Answer 12

• angina
• hypertensive renal disease
• claudication
• ischaemic colitis - blood vessels supplying large intestine

Question 13

which clinical syndromes cause sudden onset of ischaemia/infarction?

Answer 13

• myocardial infarct
• renal infarct
• gangrene
• brain infarct
• gut infarct

Question 14

describe the pathophysiology of hypoxic damage

Answer 14

1. narrowing/blockage of artery means not enough oxygen can get to the heart (inadequate perfusion)
2. lack of oxygen (hypoxia) means heart cells shift to anaerobic metabolism, producing less ATP but more lactic acid
3. this leads to a rise in sodium, calcium and water levels in the cell as pumps require ATP
4. this leads to cell oedema and activation of degenerative lipases and proteases, which leads to cell death
5. myocardial function is decreased within 2 mins dye to lack of ATP impairing contractile function

Question 15

what are the non-modifiable risk factors for ischaemic heart disease?

Answer 15

• increasing age
• male (prior to age 60)
• ethnicity (south asians who live in UK)
• family history
• social deprivation
• type 2 diabetes

Question 16

what are modifiable risk factors for ischaemic heart disease?

Answer 16

• smoking
• diet
• sedentary
• overweight/obesity
• HBP
• high cholesterol levels
• excessive stress or alcohol consumption

Question 17

what are the two divisions of ischaemic heart disease?

Answer 17

• chronic ischaemic heart disease
• acute coronary syndrome

Question 18

name the 3 divisions of chronic ischaemic heart disease

Answer 18

• stable angina
• variant angina
• silent angina

Question 19

name the 3 divisons of acute coronary syndrome

Answer 19

• unstabke angina
• NSTEMI
• STEMI

Question 20

describe the pathophysiology of stable angina

Answer 20

• narrowed coronary arteries due to build-up of atherosclerotic plaques
• when patient does activity that puts stress on the heart, metabolic demands of the heart increase
• due to narrowed coronary arteries, not enough blood can reach heart to meet its metabolic demands
• leads to build-up of metabolites, causing chest pain (which can be releived by rest or GTN spray (causes vasodilation)

Question 21

what are the symptoms of stable angina?

Answer 21

• central precordial chest pain, which may raidate to arms/jaw
• pain can be ‘heavy, gripping, tight’
• dyspnoea
• palpitations
• chest pain occurs on exertion and subsides after rest

Question 22

describe the pathophysiology of variant angina

Answer 22

• caused by spasms of the coronary artery
• can occur without provocation (i.e. at rest)
• due spasm, coronary arteries are narrowed and metabolic demand of the heart can’t be met
• build-up of metabolites, causing chest pain

Question 23

what is the difference between stable and variant angina?

Answer 23

stable = upon exertion

variant = at rest

Question 24

name possible reasons for lack of chest pain in silent angina

Answer 24

• autonomic neuropathy - nerves are damaged
• may not be enough myocardium involved to produce pain

Question 25

describe the pathophysiology of silent angina

Answer 25

same as the other types of angina, minus the chest pain

Question 26

describe the management of angina

Answer 26

lifestyle management medications * to improve blood flow by dilating blood vessels * slow heart rate or reduce contractility to redyce demands from the heart/tissue for oxygen * secondary medication to reduce platelet aggregation, BP and blood cholesterol surgery * cardiac revascularation (e.g. stenting) * improves passage of blood through arteries affected by occlusion

Question 27

why are the acute coronary syndromes grouped together?

Answer 27

all caused by acute disruption of a coronary artery plaque which leads to sudden occlusion of the artery via platelet aggregation

Question 28

list the types of acute coronary syndrome in order of severity (least to most)

Answer 28

* unstable angina * NSTEMI * STEMI

Question 29

describe the pathophysiology of acute coronary syndrome

Answer 29

1. atherosclerotic plaque within coronary artery ruptures due to blood flow, exposing soft material inside 2. soft material is thrombogeneic (likely to form clots), leading to thrombus formation 3. this leads to partial or complete occlusion of coronary arteries

Question 30

what are the symptoms of acute coronary syndrome?

Answer 30

* dyspnoea * nausea * central chest pain - not all patients (some have a silent MI - more common in females, the elderly and diabetics)

Question 31

how can you diagnose acute coronary syndrome?

Answer 31

blood marker - troponin T * troponin is released when there is cardiac muscle damage due to necrosis * marker is taken multiple times during an admission and a significatn rise is diagostic of a myocardial infarction (NSTEMI or STEMI - no rise in unstable angina as there is no necrosis) ECG changes * differentiate between STEMIs, NSTEMIs and unstable angina * e.g. in STEMIs, there is an elevation of the ST segment

Question 32

what are the ECG findings for unstable angina and NSTEMI?

Answer 32

* can be normal * potential ECG changes = ST depression, T wave inversion * no ST elevation

Question 33

how is ACS managed?

Answer 33

**immediate management** * oxygen, vasodilator and analgesia (painkillers) **acute management - revascularation** * improves passage of blood through arteries affected by occlusion * insertion of a stent into coronary arteries * bypass graft (attaching a vessel which bypasses the area of blockage within the artery) **longer term management** * controlling modifiable risk factors * medication to reduce platelet aggregation, control BP and reduce/control blood cholesterl level

Question 34

name the possible complications following a myocardial infarction

Answer 34

**D**eath **A**rrhythmias – e.g. ventricular tachycardia/ventricular fibrillation. **R**upture – of ventricular septum (i.e. between the 2 ventricles), papillary muscles **T**amponade – accumulation of fluid within the pericardium (sac-like tissue surrounding the heart) leading to compression of the heart **H**eart Failure – damage to the heart muscle due to the necrosis **V**alve Disease – mitral regurgitation **A**neurysm – of the ventricle **D**ressler’s Syndrome – pericarditis (inflammation of the pericardium i.e. sac like tissue surrounding the heart) thrombo**E**mbolism – mural thrombus = adhering to blood vessel wall **R**ecurrence – further MI

Question 35

name the symptoms of variant angina

Answer 35

* central precordial chest pain, which may raidate to arms/jaw * pain can be 'heavy, gripping, tight' * dyspnoea * palpitations * chest pain at rest usually, rather than exertion * more common in women

Question 36

what are the ECG findings for STEMIs?

Answer 36

ST elevation