ECG Arrhythmias Flashcards
What ECG leads is atrial activity best seen on?
V1 and Lead II
What leads is ventricular activity best seen on?
Chest leads(V1-V6)
What is a sinus bradycardia?
What are its characteristics?
Heart rate below 60bpm
P before every QRS and QRS is narrow
What can cause sinus bradycardia?
B blockers
Being an athletes
Can have sinus disease
What are some examples of Bradycardias due to SAN disease?
Sick sinus syndrome:
Inappropriate sinus bradycardia
Sinus node exit block
Sinus arrest
What is sick sinus syndrome?
Range of diseases that cause dysfunction in the SAN usually due to idiopathic degenerative fibrosis of the SAN
When do patients with sick sinus syndrome require a pacemaker?
When in asystole for 3 secs when awake
Asystoles for 5s while asleep
Asystole of 4 seconds in AF or symptomatic
When a patient has a Bradycardia, what are the 2 structures that could have a pathology which causes it?
SAN
AVN
What are the conditions that affect the AVN that can lead to bradycardia?
1st degree heart block
2nd degree heart block
3rd degree heart block
What is considered a normal PR interval?
120-200ms (3-5 small boxes)
When do we consider a prolonged PR interval in a non athlete to be an AVN issue/pathological?
When 280-300ms or more (7 boxes or more)
When is a PR interval deemed to be pathological? (3)
Very long PR interval (7 boxes or more)
Other conduction disease
Infective endocarditis on aortic valve
Why is an infective endocarditis on the aortic valve able to cause a bradycardia?
An abscess can form in the area where the AV node is
What is a first degree heart block and its characteristics on an ECG?
There is a prolonged PR interval (all equal in length) which all have a QRS following them
What are the 2 types of second degree heart block?
Mobitz I (Wenckebach)
Mobitz II
What is Mobitz I (Wenckebach) second degree heart block?
PR interval gets increasingly longer and longer until a QRS gets dropped
What is Mobitz II second degree heart block?
PR interval is long but fixed (all equal) but a QRS complex randomly gets dropped
What is 3rd degree heart block?
Complete heart block
There is no association between the p waves from the atria and the QRS complexes from the ventricles
What heart blocks (bradycardias) involving impaired conduction via the AVN require cardiac pacing?
Mobitz II
Any non reversible 3rd degree heart block
What are some reversible causes of complete heart block (type 3 heart block)?
Hypothyroidism
Hypokalaemia
Hypocalcaemia
Beta blockers
Amiodarone
When and when doesn’t Mobitz I need treating?
Fine in people under 70 (>70 needs treating)
When and when doesn’t Mobitz I need treating?
Fine in people under 70 (>70 needs treating)
What causes Mobitz I when it’s benign?
Increased vagal tone
This is why athletes keep running after finishing a race to slowly increase their parasympathetic drive rather than suddenly increasing it. If they suddenly increase it, HR will massively drop and they will pass out
What is the pathophysiology of a 3rd degree heart block?
There is complete block in conduction between the atria and the ventricles (AVN is blocked)
This leads to the ventricles producing their own escape rhythm.
When conduction is completely blocked between the atria and the ventricles, what is the heart rate like and the QRS complex like?
Slower heart rate
Broader QRS complex
How does position of where the ventricular escape rhythm arises affect the heart rate and QRS Breadth?
The closer and higher up the escape rhythm arises to the AVN, the narrower the QRS and closer to normal heart rate the patient will. Have
The lower down the. Bundle branches/ventricles the escape arises, the slower the. Heart rate and the broader the QRS complexes