Arrhythmias Flashcards
Treatment of VT - Haemodynamically Compromised
Emergency DC Cardioversion
Treatment of VT - Haemodynamically Stable
IV lidocaine or IV amiodarone
May need DC cardioversion if unsuccessful
Treatment of Bradycardia - Rate >40bpm and Asymptomatic
No treatment needed
Look for a cause and stop any drugs which could be contributing
Presentation of Sick Sinus Syndrome
Sinus node dysfunction Bradycardia +/- arrest Sinoatrial block SVT alternating with bradycardia/asystole AF and thromboembolism may occur
Treatment of Symptomatic Sick Sinus Syndrome
Pacing
Acute Management of SVT
Vagotonic manoeuvres
IV adenosine or verapamil
DC shock if compromised
Maintenance Therapy of SVT
Beta blockers or verapamil
Maintenance Therapy of AF/flutter
Beta blocker or verapamil
Alternatively, digoxin or amiodarone
Flecanide for pre exited AF
Causes of First and Second Degree Heart Block
Normal variant Athletes Sick sinus syndrome Ischaemic heart disease Acute myocarditis Drugs (beta blockers, digoxin)
Treatment of First Degree Heart Block
None needed
Follow up recommended to monitor development to ore advanced block
Causes of Mobitz Type I Block
Vagal in origin
Usually block in AV node
Treatment of Mobitz Type I Block
Generally only requires monitoring
Causes of Mobitz Type II Block
Block at infranodal level (e.g. Bundle of His)
Treatment of Mobitz Type II Block
Permanent pacing due to higher risk of progression to complete heart block
Causes of Third Degree Heart Block
Ischaemic heart disease Idiopathic (fibrosis) Congenital Digoxin toxicity Aortic valve calcification Cardiac surgery/trauma Infiltration
Treatment of Third Degree Heart Block
Dependant on cause, but ventricular pacing generally needed
Treatment for Bradycardia - Symptomatic or Rate below 40bpm
IV Atropine
No response = temporary pacing wire
If needed = Isoprenaline infusion, or external cardiac pacing
What is the most common childhood arrhythmia?
Supraventricular re-entry tachycardia
How does IV Adenosine slow the heart rate?
Block the secondary circuit at the AV node to return the heart to sinus rhythm
What are the two main mechanisms of arrhythmia production?
Defects in impulse formation
Defects in impulse conduction
How does pathological altered automaticity lead to arrhythmias?
A latent pacemaker subverts the SA node’s function as the heart’s normal pacemaker
How does triggered activity lead to arrhythmias?
Afterpolarisations are triggered by a normal AP
Can get early after depolarisation or late depolarisation
When do Early Afterdepolarisations occur?
During the inciting AP within Phase 2 and Phase 3
Associated with prolongation of AP and drugs prolonging QT interval
When do Late Afterdepolarisations occur?
After complete depolarisation
Associated with Ca2+ overload provoked by catecholamines, digoxin, heart failure
What defects in impulse formation lead to arrhythmias?
Altered automaticity
Triggered activity
What defects in impulse conduction lead to arrhythmias?
Re-entry
Conduction block
Accessory tracts
How does re-entry lead to arrhythmias?
Re-entry occurs when a self sustaining current occurs which stimulates and area of myocardium repeatedly/rapidly
Re-entrant circuits require:
Unidirectional block
Slowed retrograde conduction velocity
How do accessory tract pathways lead to arrhythmias?
Electrical pathways that bypass AV node (e.g. Bundle of Kent)
Ventricles receive impulses from both normal and accessory pathways
Sudden onset tachycardia with recovery of normal sinus rhythm after carotid sinus massage or adenosine is characteristic of which arrhythmia?
Paroxysmal Supraventricular Tachycardia
What is the most common cause of Paroxysmal Supraventricular Tachycardia?
Atrioventricular nodal reentrant tachycardia
What are the three kinds of atrial fibrillation?
Paroxysmal
Persistent
Permanent
What is paroxysmal atrial fibrillation?
Episodes of AF terminate spontaneously
What is persistent atrial fibrillation?
Episodes are non self terminating
What is permanent atrial fibrillation?
Continuous AF which cannot be cardioverted
Treatment centres on rate control and anticoagulation
