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
Is a 3rd degree heart block (complete heart block) always an emergency where a cardiologist needs to immediately come and pace the patient?
No
When does a pateitn with 3rd degree heart block need a cardiologist to come and immediately pace them? (EMERGENCY)
The escape rhythm of the ventricles is causing syncope
When is 3rd degree heart block not an immediate emergency and pacing can wait till the next day?
Escape rhythm is producing no symptoms like syncope
How does atrial fibrillation compared to atrial fibrillation with 3rd degree heart block look on ECG?
AFIb has a wiggly baseline with IRREGULAR rhythm of QRS complexes. (Absent p waves)
AFIb with 3rd degree heart block (absent p waves) but Regular QRS complexes
What are some questions you need to ask when thinking about a tachycardia?
Is it a regular or irregular rhythm?
Broad QRS or narrow QRS complex?
What are the atria doing?
What are the ventricles doing?
How is the atrial and ventricular activity related?
What are the 4 types of narrow QRS complex tachycardia?
Sinus tachycardia
Supraventricular tachycardia
Atrial fibrillation
Atrial flutter
Which 2 of the narrow complex tachycardia’s are regular rhythm?
Sinus tachycardia
Supraventricular tachycardia (SVT)
Which 2 of the narrow complex tachycardias are an irregular rhythm?
Atrial fibrillation
Atrial flutter
What are the 2 types of Supraventricular tachycardia which are narrow complex regular rhythm tachycardias?
AVRT (ORTHODROMIC)
AVNRT
What is orthodromic AVRT?
Pathophysiology?
A type of regular rhythm narrow complex tachycardia
AtrioVentricular Re-entry Tachycardia
When there is an accessory pathway between the atria and the ventricles where the electrical activity circulates in the normal direction (atria to ventricles not ventricles to atria)
What would happen to the characteristics of the ECG if a patietn had an antidromic AVRT?
Would lead to the ECG being regular and having a broad QRS complex tachycardia since the impulse would circulate the accessory pathway from the ventricles first then to the atria
What is a characteristic finding of a SVT that is an orthodromic AVRT?
Retrograde P waves showing the electrical impulse circulating back up from the ventricle into the atria in the accessory pathway
Narrow QRS
Regular rhythm
Why does a patient with orthodromic AVRT need managing by an electro physiologist?
The accessory pathway can lead to atrial fibrillation which can develop into life threatening ventricular fibrillation
Why may a SVT appear to be atrial fibrillation?
How can you distinguish this?
There may appear to be no P waves but this is because the P waves are buried in the T waves
You know its not atrial fibrillation since there is a regular rhythm of QRS complexes
How is orthodromic AVRT managed?
Catheter ablation once the accessory pathway is identified by the electrophysiologist
How is AVNRT managed?
Treated with adenosine and vagal manoeuvres
Catheter ablation is last resort if symptomatic
What is the pathophysiology of AVNRT?
Accessory pathway that runs through the AVN
There is normally a slow pathway and fast pathway and it normally runs slow-fast
What is the pathophysiology of atrial fibrillation?
Normally lots of small accessory pathways or ectopics in the atria
This unpredicatablitliy in atrial signalling means the ventricles receive impulses at random points (irregular rhythm)
How does atrial fibrillation look on ECG?
Absent p waves
Irregularly irregular QRS complexes/ventricular contractions
What is atrial flutter?
How does it appear on ECG?
Narrow QRS complex tachycardia with REGULAR rhythm of QRS
SAW TOOTHED PATTERN
The atria are rapidly contracting due to a re-entrant loop at the tricuspid valve, but the AVN can only conduct at a certain rate so you get a sort of block
Atria beat at 300bpm
Can have:
2:1 so get 150bpm (QRS complexes)
3:1 so get 100bpm
4:1 so get 75bpm
How is atrial fibrillation treated?
Rate control and rhythm control + Anticoagulation
(Beta blockers or CCB for rate)
Normally ALWAYS BISOPROLOL + APIXABAN
(Flecanaide or amiodarone for rhythm)
How is atrial flutter treated if it is causing Life threatening features like syncope or ischaemic chest pain?
Synchronised DC cardio version Under sedation or GA
IV amiodarone. If the cardio version doesn’t work
Radio frequency ablation long term of accessory pathway
How can a regular rhythm broad complex tachycardia be caused by a Supraventricular tachycardia?
Narrow. Complex tachycardia with Bundle Branch Block (aberrancy)
What is a cause of regular rhythm Broad complex tachycardia?
Ventricular tachycardia
Antidromic AVRT
Narrow complex tachycardia with. BBB
How can you determine ventricular tachycardia on an ECG?
Many unusual looking QRS complexes
QRS look unusual due to the p waves morphing into them. Since the atria is still in sinus (AVN dissociation) and the ventricles are working separately p waves are still generated just cant see them as well.
Some times you get a normal looking PQRS called a capture beat where the P waves are still. From the atria captures the ventricles at the right time to produce a normal QRS
What are the 2 shockable rhythms if in Cardiac arrest?
Ventricular tachycardia
Ventricular fibrillation
What is the treatment for ventricular tachycardia (broad complex regular rhythm tachycardia)?
IV amiodarone or defibrillation
What are some irregular broad complex tachycardia?
AF with abberrancy
AF with pre-excitation of ventricles
Torsades de pointes
VF (ventricular fibrillation)
Why do patients with wolf Parkinson’s white (accessory pathway) need treating?
Can lead to atrial. Fibrillation being conducted to the ventricles which can. Lead to ventricular fibrillation. Which will lead to death
What causes AF with pre-excitation of the ventricle/?
How does it look on ECG?
Accessory pathway. Leeds to broad fast. Irregular ventricle contraction
Delta waves (depolarisation of ventricles through the accessory pathway)
What cases Torsades de pointes?
Prolonged QT interval
Leads to repolarisation of the myocytes taking longer and longer until eventually after depolarisations happen where depolarisation occurs before a refractory period occurs
Polymorphic ventricular tachycardia
How does Torsades de pointes appear on ECG?
Ventricular tachycardia where the QRS are twisting around the baseline
What are some causes of a prolonged QT?
Long QT syndrome
Medications like flecanide, sotalol, amiodarone
Electrolyte imbalances (hypokalaemia, hypomagnesaemia and hypocalcaemia)
Macrolides
Hypothermia
Subarachnoid haemorrhage
SSRIs
How Do you manage Torsades de pointes?
Correct underlying. Cause (electrolyte imbalance)
IV MAGNESIUM SULPHATE INFUSION
DEFIBRILLATION IF IN VENTRICULAR TACHYCARDIA
Cardio version
What is bigeminy?
When every other beat is a ventricular ectopic
Normal PQRST then have a ventricular ectopic (broad. QRS)
How is bigeminy managed?
Reassurance in otherwise. Healthy people
Cardiologist help if underlying cardiac disease or family history
B blockers can be used to manage symptoms
How do you manage unstable patients at risk of asystole/(in peri arrest)?
First line ATROPINE 500mg IV
Inotropes like adrenaline
Temporary cardiac pacing
Permanent implantable pacemaker
How does atropine work?
Antimuscarinic inhibits the parasympathetic nervous system
What are some side-effects of atropine
Dry eyes
Dry mouth
Constipation.
Urinary retention
Pupil dilation
How does hyperkalaemia appear on an ECG?
Tall tented T waves
Flattened p waves
Broadened QRS
Prolonged pr
How is hyperkalaemia managed?
IV calcium gluconate 10% to protect the heart
Insulin + dextrose
Calcium resonium to clear K+
Haemofiltration required if K+ does not reduce
What changes can be seen on ECG with hypokalaemia?
U waves
T wave inversion
ST depression
Prolonged pr
How is hypokalaemia managed?
Sando K
Add K+ to fluid bags
What is the maximum amount of potassium you can give to a patient per hour?
10mmol K+ per hour
What heart rhythms are non shockable?
Asystole
Pulseless Electrical Activity (PEA)
What scoring system is used to assess a patients clot risk with atrial fibrillation?
CHADSVASC Score
What scoring systems are used to assess a patients bleed risk when assessing use of anticoagulants with Atrial fibrillation?
ORBIT
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