Cardiovascular: ECGs & Arrhythmia Flashcards
What are the 6 leads in the coronal plane?
The limb leads
* aVR
* aVL
* aVF
* I
* II
* III
What are the 6 leads in the transverse plane?
The chest leads
V1-V6
Describe the colour of the limb electrodes
Right shouder - Red
Left shoulder - Yellow
Left leg - Green
Right leg - Black
Hint: start with red for right then work through the traffic lights clockwise
Where do each of the coronal leads lie on the QRS axis?
- I: 0’
- II: +30’
- aVF: +90’
- III: +120’
- aVR: -150’
- aVL: -30’
What is the normal QRS axis range, and what defines a left axis deviation and a right axis deviation?
Normal: -30’ - +90’
RAD: +90’ - +180’
LAD: -30’ - -90’
This is because the wave of propagation normally goes from SA node through bundle of hiss and down in right-left downward direction.
How would you use a QRS deflection in leads I,II&III to calculation deviation?
Is there any axis deviation here?
No, I&II are positive deflection and III is negative, this is normal QRS axis
Is there any axis deviation here?
Yes, I is positive deflection and II&III are negative, this is therefore a left axis deviation
Is there any axis deviation here?
Yes, II&III are positive deflection and I is negative, this is therefore a right axis deviation
What does the P wave correspond to?
With regards to electrical conduction
Atrial depolarisation
What does the QRS complex correspond to?
With regards to electrical conduction
Ventricular depolarisation
What does the T wave correspond to?
With regards to electrical conduction
Ventricular repolarisation
What does the PR segment tell us about with regards to electrical conduction?
What does deviations in a PR segment therefore hint at?
If P is depolarisation of the atria and QRS is depolarisation of the ventricles then PR segment is the conduction through the AVN/ bundle of hiss.
A prolonged PR segment can indicate conductive tissue dissorder
A shortened PR can indicate that conduction is bypassing the AVN
What does the QRS complex tell us about with regards to electrical conduction?
What does deviations in QRS complex therefore hint at?
Time for ventricular depolarisation
Deviations can indicate conductive tissue dissorders in the ventricles such as right bundle branch block or left bundle branch block
What does the ST segment tell us about with regards to electrical conduction?
What does deviations in a ST segment therefore hint at?
ST segment – start of
ventricular repolarisation
(should be isoelectric aka flat)
ST elevation acute infarction
ST depression ischaemia
What does the T wave tell us about with regards to electrical conduction?
Ventricular repolarisation
What time is one small box equivelent to?
0.04s
What is Wolff-Parkinson-White (WPW) syndrome?
A syndrome that causes the an extra path of conduction in the heart bypassing the AV node and is more rapid that AV/bundle of hiss conduction
What is this hinting at?
Wolff-Parkinson-White (WPW) syndrome
Shorter PR interval therefore AV node being bypassed
Why could Wolff-Parkinson-White (WPW) syndrome make AF worse?
If conduction between atria and ventricles bypassed and rapid conduction then AF could also lead to VF
What is this hinting at?
Left ventricular hypertrophy due to high blood pressure
QRS complex phatty on leads V5&V6 corresponding to depolarisation of a large muscle where the left ventricle is. Corresponding negative reflection on the opposite leads
What is this hinting at?
RSR in V1 is Right bundle branch block
What is this hinting at?
Left bundle branch block
Anything up here?
Nope
P wave is followed by a regular PR interval and QRS complex followed by a regular T wave
The change in rate is due to breathing, speeds up when you breath in, slows down when you breath out
What is this?
Sinus tachycardia
Increased heart rate however the increased rate is still coming from regular sinus node signalling therefore sinus tachycardia
What is up here?
Sinus bradycardia
What is sino-atrial disease
A degenerative condition affecting the atria,
including the sinoatrial (SA) and
atrioventricular (AV) nodes
Can lead to sinus tachycardia, sinus
bradycardia, atrial ‘ectopic’ beats, and atrial
fibrillation
What is this?
Atrial tachycardia
QRS doesn’t always follow P wave meaning somewhere in the atria is fireing itself
A consequence of sino-atrial disease
Sino-atrial disease - treatment?
permanent pacemaker to prevent slow rhythms
antiarrhythmic drugs to prevent or moderate
rapid rhythms
– beta blocker
– digoxin
– amiodarone
What is this?
1st degree AV block
PR interval extended indicating a delayed conduction time between atria and ventricles
What is this?
2nd degree AV block
Blockage at bundle of hiss
Some QRS complexes not fireing at all
If QRS doesn’t fire to long enough then results in passing out
What is this?
3rd degree AV block
P waves completely independent of ventricular depolarisation, none are getting through
Ventricles still contract on their own rythm as a backup but it is not ideal
Causes of AV nodal block
- sino-atrial disease
- coronary heart disease
- aortic valve disease
- damage during heart surgery
- drugs
– beta-blockers
– digoxin
– calcium channel blockers
What is this?
Atrial fibrillation
Atria activating rapidly therefore they can’t contract effectively (contractions can’t keep up with signals)
Can also appear on some leads as no P-wave present at all, just flat between each QRS complex with T wave
What is this?
Atrial flutter
Saw tooth - atrial flutter
Signal keeps going around atria triggering itself rapidly rather than moving down the atria
Different look of atrial fibrillation vs atrial flutter?
Atrial fibrillation - messy
Atrial flutter - sawtooth
Causes of atrial flutter / fibrillation
- sino-atrial disease
- coronary heart disease
- valve disease (esp. mitral valve)
- hypertension
- cardiomyopathy
- hyperthyroidism
- pneumonia, lung pathology
Treatments for atrial fibrillation/ atrial flutter
- drugs to block AV node and therefore limit
heart rate
– digoxin
– beta blocker
– calcium channel blocker - electrical cardioversion
- catheter ablation
What arrythmia could childhood pneumonia lead to?
Atrial fibrillation/ flutter
Untreated strep as a child can cause a mumour as a child which then makes the atria weakened and the damage effects kick in later in life
What is this?
Ventricular tachycardia
Short circuiting of impulses within ventricles - signal going round and round ventricles.
Diseased ventricles
No p wave - qrs firing on its ones
What is this?
Ventricular fibrillation
Carnage
Heart can’t really function
Treatment for ventricular fibrillation
ACUTE
* defibrillation
* IV antiarrhythmic drugs
* remove any triggering cause
LONG TERM
* oral antiarrhythmic drugs
* treat underlying heart conditions
* implantable defibrillator for some
patients
