17) Cardiac Arrhythmias Flashcards
Describe some abnormal impulse generations in the heart:
Delayed or early afterpolarisation
Ectopic focus
Describe some abnormal conduction that can occur in the heart:
Conduction block
Re-entry loops
What is circus movement (in terms of conduction)?
Part of conduction pathway is blocked so impulse travels in retrograde fashion, re-exciting some cells
Describe Wolf-Parkinson-White syndrome:
Accessory pathway between atria and ventricles (bundle of Kent), that doesn’t have rate slowing properties of AVN
What are the general actions of arrhythmia drugs on impulse generation and conduction?
Decrease funny current slope in pacemaker cells
Raise threshold to prolong action potential
Decrease conduction velocity
Increase refractory period
What are examples of class Ia anti-arrhythmics?
Quinidine and procainamide
What is the mechanism of action of class Ia anti-arrhythmics?
Decrease conduction, increase refractory period and increase AP threshold by sodium channel blocking
When are class Ia anti-arrhythmics indicated?
Prevent AF
Ventricular arrhythmias
What are the side effects of class Ia anti-arrhythmics?
Hypotension Proarrthymia Dizziness Confusion Lupus like syndrome (procainamide)
What are examples of class Ib anti-arrhythmics?
Lidocaine, mexiletine
What are examples of class Ic anti-arrhythmics?
Flecainide, propafenone
What are examples of class II anti-arrhythmics?
Propanolol, metoprolol, bisoprolol, esmolol
What are examples of class III anti-arrhythmics?
Amiodarone, sotalol
What are examples of class IV anti-arrhythmics?
Verapamil, diltiazem
What is the mechanism of action of class Ib anti-arrhythmics?
Sodium channel blockers (fast association) - decrease Na+ conduction in fast beating or ischemic tissue
When are class Ib anti-arrhythmics indicated?
Ventricular tachycardia
What are the side effects of class Ib anti-arrhythmics?
Dizziness, drowsiness, abdominal upset
What is the mechanism of action of class Ic anti-arrhythmics?
Sodium channel blockers (slow association) - decrease sodium entry, increase refractory period
When are class Ic anti-arrhythmics indicated?
Supraventricular arrhythmia (fib and flutter)
Premature ventricular contractions
WPW
What are the side effects of class Ic anti-arrhythmics?
Pro-arrhythmic
Sudden death in previous MI
CNS and GI effects
What is the mechanism of action of class II anti-arrhythmics?
Beta blockers
Decrease conduction through AVN
Decrease depolarisation
When are class II anti-arrhythmics indicated?
Tachycardia
Protect ventricles from high atrial rate
Convert re-entrant arrhythmias
What are the side effects of class II anti-arrhythmics?
Bronchospasm, hypotension
What is the mechanism of action of class III anti-arrhythmics?
Increase refractory period and prolong repolarisation by blocking K+ channels
When are class III anti-arrhythmics indicated?
Ventricular tachycardia
WPW
What are the side effects of class III anti-arrhythmics?
Amiodarone: pulmonary fibrosis, hepatic injury, thyroid disease, optic neuritis
General: pro-arrhythmic, fatigue, insomnia
What is the mechanism of action of class IV anti-arrhythmics?
Ca2+ channel blockers - slow conduction through AVN, increase refractory period
What are the side effects of class IV anti-arrhythmics?
Hypotension, decreased CO, GI problems
When are class IV anti-arrhythmics indicated?
Supraventricular tachycardia, convert re-entry
What is the mechanism of action of adenosine?
Activation of K+ channels in AVN and SAN causing hyperpolarisation and decrease HR
When is adenosine used?
Convert re-entrant supraventricular arrhythmias
What is the mechanism of action of vernakalant?
Blocks atrial specific K+ channels to slow atrial conduction
When is vernakalant used?
Convert AF to sinus
What is the mechanism of action of ivabradine?
Blocks the funny current in sinus node to slow HR
When is ivabradine used?
Sinus tachycardia, angina, heart failure
What is the mechanism of action of digoxin? And when is it used?
Decreases conduction at AVN, increases vagal activity
Reduce ventricular rate in AF
What is the mechanism of action of atropine? When is it used?
Selective muscarinic antagonist that blocks vagal activity to increase HR in vagal bradycardia
What are the principles of AF treatment?
Rate control
Rhythm control