Myocardial Infarction & Acute Coronary Syndromes Flashcards
What is “acute coronary syndrome”?
a term used to describe a range of conditions associated with sudden, reduced blood flow to the heart
this results in ischaemia (and sometimes infarction) of the myocardium
it is a medical emergency and requires immediate hospital admission
What are the 3 different types of ACS?
- STEMI - ST elevation MI
- NSTEMI - non-ST elevation MI
- unstable angina - ischaemia, without infarction
What is the difference in the way that STEMIs and NSTEMIs are usually diagnosed?
- STEMI is diagnosable on the basis of classical ECG changes
-
NSTEMI is usually diagnosed on the basis of a suggestive history with positive biochemical markers
- e.g. positive / raised troponin
How is unstable angina usually diagnosed?
Why is it significant to identify?
- there are no obvious ECG changes
- biochemical markers (troponin) are negative
- history is suggestive of ACS
- unstable angina is significant as there is a high risk (50%) of MI in the subsequent 30 days
Why are NSTEMI, STEMI and unstable angina all grouped together?
they all share a common mechanism
this is rupture or erosion of the fibrous cap of a coronary artery plaque
they can be thought of as a spectrum with unstable angina being the least severe and STEMI being the most severe
What is the “textbook presentation” of ACS?
STEMI, NSTEMI and unstable angina can all have a similar clinical presentation
- acute onset of central or left-sided chest pain
- the pain often comes at rest, in the morning, and gradually increases in intensity over a period of minutes
- pain radiates down the left arm
- pain is associated with diaphoresis (sweating), pre-syncopal or syncopal symptoms
- 30% of patients present without pain
What is the difference in how much the coronary arteries are occluded in the different types of acute coronary syndromes?
- STEMI is associated with complete or almost complete occlusion of one or more of the coronary arteries
- NSTEMI and unstable angina are associated with partial occlusions
What % of cases of MI are fatal?
How many deaths occur within 2 hours of symptom onset?
15% of cases of MI are fatal
50% of deaths occur within 2 hours of onset of symptoms
What is the incidence of coronary heart disease?
300,000 cases per year
coronary artery disease accounts for 3% of admission to UK hospitals each year
What are the non-modifiable risk factors for ACS?
- advancing age
- male gender
-
family history of IHD
- only significant if symptoms presented before the age of 55 in the relative
What are the modifiable risk factors for ACS?
- smoking
- hypertension
- diabetes
- obesity
- hyperlipidaemia
- sedentary lifestyle
What are the controversial risk factors for ACS?
- stress
- having a Type A personality
- left ventricular hypertrophy (LVH)
- cocaine use
- increased fibrinogen
How can cocaine use increase the risk of ACS?
- acutely it can cause coronary vasospasm which causes MI
- chronically it increases the risk of MI from a traditional atherosclerotic disease process
What are the symptoms of ACS?
- chest pain
- diaphoresis (sweating)
-
breathlessness
- in many cases this may be the only symptom
- syncope (fainting)
- tachycardia
- vomiting and sinus bradycardia
- distress (also sometimes a “feeling of impending doom”)
- sudden death
infarction can occur in the absence of any physical signs
Where does the chest pain radiate to in ACS?
Where does it radiate to if it is more predictive of MI?
- radiates down the inside of the left arm and into the neck and jaw
- can also radiate to the epigastrium and the back
- it is more predictive of MI if it radiates to the RIGHT arm or BOTH arms
- contrary to the classical textbook definition of radiating down the left arm
What type of pain is present in ACS?
How long does it last and how severe is it?
- it is a “crescendo pain” that increases in severity over a period of minutes after onset
- pain typically lasts up to a couple of hours
- typically a “mid-range” pain - i.e. 5-7/10
Why might syncope occur in ACS?
syncope occurs as a result of severe hypotension or severe arrhythmia
Why might vomiting and sinus bradycardia occur in ACS?
What might make this worse?
occurs as a result of excessive vagal stimulation, which is most common in inferior MI
nausea and vomiting can be aggravated by opiates given for pain relief
Why can sudden death occur in ACS?
When do most of these deaths occur?
sudden death is usually the result of ventricular fibrillation or asystole
most deaths occur within the first hour
Why is it important to get help as soon as possible for patients with ACS?
if the patient survives the first hour, the likelihood of severe arrhythmias still remains, but diminishes with each subsequent hour
cardiac failure is the major cause of death in those that survive the first few hours
whether or not this develops depends on the extent of myocardial damage
Why are MIs and strokes more common in the morning?
- the blood pressure lowers overnight
- BP then rises again when the person wakes up
- the higher BP is thought to dislodge any thrombus that has formed overnight
What factors are particularly significant for the likelihood of ACS compared to other causes of chest pain?
- pain lasting for > 15 minutes
- pain that radiates to the arms or jaw
- diaphoresis
- vomiting
- exertional chest pain
What features suggest non-ACS chest pain?
-
reproducible chest pain
- e.g. tender chest wall or positional pain
- pleuritic chest pain
What features of chest pain are NOT useful to predict the likelihood of ACS?
- the severity of the pain
- response to GTN spray
- response to PPIs or antacids
