Arrhythmias Flashcards
Cardiac causes of arrhythmias
IHD
Structural change
atrial dilatation due to MR
cardiomyopathy
Percarditis/Myocarditis
Non-cardiac causes of arrhythmias
Caffeine
Smoking
Alcohol
Pneumonia
Electrolyte disturbance
Drugs (Beta-2 agonist/digoxin/levodopa/tricyclics/doxorubicin)
Name 3 regular tachycardias
Sinus Tachycardia
Focal atrial tachycardia (outpacing SA node)
Atrial Flutter
AV re-entrant tachycardia (eg WPW)
Junctional tachycardia (AVN becomes pacemaker)
Name 3 irregular tachycardias
Sinus arrhythmia - freq. ectopics
Atrial Fibrillation
Flutter with variable block (3:1, 2:1)
Multifocal atrial tachycardia (assoc. COPD)
Management of sinus tachycardia and multifocal atrial tachycardia?
Sinus tachycardia - treat cause (e.g. dehydration with IVF)
Multifocal atrial tachycardia - correct hypoxia/hypercapnia in COPD
Tx of AV nodal re-entrant tachycardia (AVNRT) and AV re-entrant tachycardia (AVRT)?
consider transiently blocking AV node to break circuit
1. Valsalva manoeuvre - carotid sinus massage, blow into syringe
2. IV adenosine
What will happen if you transiently block the AV node and the tachycardia is atrial in origin?
Blocking AVN removes ventricular activity and should reveal the underlying abnormal atrial rhythm
E.g. flutter or fibrillation
Define a broad complex tachycardia
> 100bpm
QRS >120ms
If you are unsure if a tachyarrhythmia is an SVT or VT, how should you treat it?
Treat for VT first
Giving AV block in VT can be dangerous
Name at least 3 broad complex tachycardias
Ventricular Tachycardia (VT)
Ventricular Fibrillation (VF)
Torsades de Pointes
*Narrow complex tachycardias with a bundle branch block can appear like broad complex tachycardias!
How can you differentiate VT from SVT with a bundle branch block?
IHD = increased likelihood of ventricular arrhythmia
ECG findings only present in VT:
- All chest leads have same concordance (i.e. all positive or all negative)
- QRS >160ms
- Left Axis deviation
- ‘Northwest Axis’ QRS +ve in AvR
- AV dissociation or 2:1,3:1 Mobitz II heart block
- Fusion beats
- Capture beats (normal complex)
- Rsr pattern (first R wave larger, whereas in RBBB its rsR)
Management of broad complex tachycardias
If compromise (chest pain, HF, shock, syncope):
- DC cardioversion
If uncompromised:
- correct electrolytes
- amiodarone 300mg IV
- if unsuccesful, sedate and cardiovert
Management of narrow complex tachycardias
Compromise?
- DC Cardioversion
Uncompromised:
Regular rhythm =
- vagal manoeuvres
- adenosine 6mg IV
Irregular rhythm = AF most likely
Rate control
- beta blocker
- verapamil
- digoxin
Rhythm control
- amiodarone
- flecainide
Describe what happens to the rate and cardiac output in Atrial Fibrillation and flutter
Atrial rate between 300-600bpm
ventricles conduct some signals in AF => irregular
in flutter they conduct in divisions of 300
cardiac output reduces by 10-20%
Causes of AF/Atrial Flutter
Heart failure
HTN
IHD/MI
PE
Mitral Valve disease
Pneumonia
Hyperthyroid
Post-operative complication
Caffeine/Alcohol
Low K+, Mg2+
