Chest pains Flashcards
Risk factors for MI
Diabetes
High blood pressure
High weight
High cholesterol/ triglycerides
What are the steps of investigating cause of chest pain?
Triage nurse determines the severity of condition
Attending A&E doctor does full work on the patient to determine the underlying cause
What happens to the patients in the resuscitation unit?
Attached to cardiac monitor - able to observe patient continuously
IV access
FBC, blood glucose, urea and electrolytes, lipids, ALT, AST and troponin
ECG - look at dynamic changes, indicating acute ischaemia.
Chest X-ray - to rule out other pathologies
What is an important marker for MI?
Troponin
In what other conditions are troponin levels elevated?
Heart failure
Renal failure
Pericarditis
What happens if the ECG shows ST elevation?
The patient would need urgent assessment by the cardiologist
Transfer to the CATH lab
For percutaneous coronary intervention
To unblock the affected artery
What is the treatment for suspected coronary syndrome?
ROMANCE
What does ROMANCE stand for?
Reassurance
Oxygen
Morphine
Aspirin
Nitrates
Clopidogrel
Emoxiprin (low molecular weight heparin)
What is the effect of nitrates?
Release nitric oxide
Induce vasodilation
What is the effect of clopiodogrel?
Antiplatelet agent used to inhibit blood clots in coronary artery disease
Inhibits purinergic P2y receptors
What are the steps to determine the type of chest pain the patient is experiencing?
SOCRATES
S - site (where?)
O - onset (is it constant, does it get better?)
C - character (is it sharp, dull or grabbing?)
R - radiation (does the pain permeate anywhere else in the body?)
A - associated symptoms (shortness of breath, palpitation, lightheadedness and syncope)
T - time (does the pain stay and go, is it constant, how long does it last?)
E - Exacerbating and alleviating (is it positional?)
S - severity (how bad is the pain from 1-10?)
Why is SOCRATES important?
Knowing these factors about the pain will allow appropriate diagnosis
What are possible causes of pain in the chest area?
Acute coronary syndrome
Pneumothorax - most important to exclude
Pulmonary embolism
Aortic dissection
Gastro-oesophageal reflux
Anxiety
Inflammation of rib joint and muscle injuries
What does ACS cause chest pains?
Causes chest pains due to significant blockage of the coronary arteries
Why does pneumothorax cause chest pains?
Air leaks in space between lung and chest wall causing them to collapse
Chest x-ray needs to be done when patient enters A&E to rule this out
What two tests are essential in the diagnosis of ACS?
ECG
Troponin levels
What is a STEMI?
ST segment elevation myocardial infarction
Most severe type of MI
Long interruption of the heart’s blood supply
Extensive damage to a large area of the myocardium
What is a NSTEMI?
Non-ST segment elevation myocardial infarction
An NSTEMI results from a partial interruption of blood supply to the heart
Smaller region of damage to the myocardium compared to STEMI
ST depression or T wave inversion
What is an unstable angina?
Least serious form of ACS
Still a medical emergency
Blood supply is seriously restricted
There is no permanent damage to the myocardium
Negative troponin levels but may have some changes to the ECG
What are the three types of ACS?
STEMI
NSTEMI
Unstable angina
What are the two main diagnostic tests for acute MI?
12-lead ECG
Troponin
When should the ECG performed?
Within 10 minutes of being admitted to hospital with chest pains
Provides key information to help confirm what level and type of damage has been inflected upon the myocardium
What is troponin used for?
Primary test to look for myocyte damage/ death
To confirm diagnosis
When should troponin be measured?
High sensitivity troponin test can detect raised troponin 3 hours after onset of chest pain
Where are the leads in a 12-limb ECG placed?
6 on the chest
One on each limb
How many leads make up the 12-lead ECG?
10
Obtain 12 electrical views of the heart
Why is it important to place the leads correctly?
Angles at which the electrodes look at the heart and the direction of the heart’s electrical depolarisation
Important to place leads accurately so the tracing is accurate
Which are the limb leads?
aVR
aVL
aVF
Which are the chest leads?
V1-V6
What does lead II indicate?
Rhythm strip
Shows trends in heart rate and basic rhythm
Why is it important to understand which lead corresponds to which position?
In order to localise the pathology to a particular heart region
What does ST elevation in V3 and V4 indicate?
Anterior MI
What does ST elevation in V2, V3 and aVF indicate?
Inferior MI
What does ST elevation in V1, aVL, V5 and V6 indicate?
Lateral MI
What does ST elevation in V1 and V2 indicate?
Septal MI
Anterior MI
ST elevation in V3 and V4
Inferior MI
ST elevation in V2, V3 and aVF
Lateral MI
ST elevation in V1, aVL, V5 and V6
Septal MI
ST elevation in V1 and V2
What does the P wave indicate?
Atrial depolarisation
What does the QRS complex indicate?
Ventricular depolarisation
What does the PR interval indicate?
Time interval between the first deflection of the P wave and the first deflection of the QRS complex
Transit time for the electrical signal to travel from the SAN to the ventricles
What does the T wave represent?
Ventricular repolarisation
What does the ST segment represent?
Period of zero potential between ventricular depolarisation and repolarisation
Provides information about the blood supply to the heart
If elevated = blood supply is significantly compromised
When is ST elevation significant?
When there is more that 1 mm elevation from the baseline in at least 2 adjacent limb leads
Or more than 2 mm of elevation in 2 adjacent chest leads
Or a new onset left bundle branch block
What are characteristics of the ECG in NSTEMI?
Lack specificity
Must be interpreted within the context of the clinical scenario
Pathological Q wave - indicate MI has happened at some point
Characteristics of pathological Q waves
Downward deflection wider than 2 small squares or greater in height than 1/3 of the subsequent T wave
How long do pathological Q waves take to develop?
Takes hours to develop
How long do pathological Q waves last?
Rarely goes away once developed
Absence of pathological Q wave means that MI has not happened
TRUE or FALSE
FALSE
Absence of pathological Q wave does not eliminate the diagnosis of MI
What happens if MI is suspected in patient?
MI is medical emergency
When suspected in patient, initial treatment will begin before some tests are carried out to confirm diagnosis
What are tests used for diagnosis and monitoring?
Troponin
FBC
Arterial blood gases
Renal function
Blood glucose
Why is a FBC ordered in MI patients?
Anaemia may precipitate an MI in angina patients
Why are arterial blood gases measured in MI patients?
Determine levels of
- hypoxia
- pH
- lactate
- glucose
- haemoglobin
Why are renal function tests ordered in MI patients?
Urea and electrolytes may be dysregulated or worsen due to poor renal perfusion in cardiogenic shock
Hypokalaemia may predispose to arrhythmias
Why is blood glucose measured in MI patients?
Diabetes must be controlled aggressively after an MI
With intravenous insulin infusions
What happens after diagnosis of MI?
Admission to cardiac care units
Treatments given
What causes ST elevation?
Total occlusion of the coronary circulation supplying an area of the heart causes necrosis of the whole wall of the heart
This causes the area to depolarise as the ion movements cannot be controlled
Electrodes measure the movement of electricity through the heart
Depolarisation of the necrosed area travels to the neighbouring areas of the heart
This is picked up by the electrodes and causes a negative deflection of the baseline of the ECG rather than a true baseline
When positive vector travels away from the electrode it is represented as a negative deflection on the ECG
During ST it is back to true baseline - but this is perceived as elevated as initially the potential is affected by the necrosed area
Differences in affected areas of the heart in STEMI and NSTEMI
STEMI - transmural infarct
NSTEMI - subendocardial infarct as most distal to coronary arteries
How can we differentiate NSTEMI from unstable angina?
Cardiac markers
Troponin is positive in NSTEMI due to infarct but negative in unstable angina due to ischaemia
What is the reason behind the positive deflection in NSTEMI?
NSTEMI is also characterised by infarct area
This is depolarised
This time the positive vector is travelling towards the electrode
This results in positive deflection in the ECG
Causes an abnormal positive baseline compared to true baseline
So the ST segment reflecting a voltage of 0 appears depressed
Why are ST changes acute?
ST changes are acute and disappear over time
Infarct tissue
Fibrosis does not have ionic leakage as in infarct tissue
So there is no baseline shift
