Anti-Arrythmic Classes Flashcards
What are the 4 classes of anti-arythmic
Nasty boys kill cats
Class 1 : Na-channel blocker
Class 2: Beta blocker
Class 3 : K-channel blocker
Class 4 : Ca-channel blocker.
What is the effect off class 1A antiarrhytimichs
Example : procainamide, quinidine
Action : block fast sodium channels in the myocardium — > decrease the rate of phase 0 (depolarization) and phase 4 (repolarization)
Increase effective refractory period ** Difference with other types **
Decreases automaticity of the AV/conduction
What are the effects of class Ia anti arrhythmics
Ventricular arrythmias and refractory supraventricular tachycardia.
What are the side effects of class 1A anti-arrythmics
Hypotension and tachycardia
Can also cause GI signs including vomiting and diarrhea.
What are the effects of Class 1B anti-arrythmics
Example : lidocaine, mexiletine, tocainide.
Action
- Blocs sodium channels in the myocardium - decreases the rate of phase 0 depolarization and 4 repolarization.
- Decrease the effective refractory period ** Difference with 1A **
- Increase AV conduction ** bad for SVT
What are the indication for type 1B
Ventricular arrythmias
What are the side effects of lidocaine in cats
CNS toxicity
Cat - hemolysis, methemoglobin and sudden death.
What are the side effects of mexiletine in cats
Anorexia, vomiting
What is the mechanism of action of beta blockers
Example : atenolol, propranolol, esmolol
Action : beta blocker —> sympatholytic.
It will therefore decrease heart rate, heart contractility, decrease SA/AV node conduction and decrease SNS tone (cardio and reno-protective)
What are the indications of beta blockers
- Atenolol : decrease obstruction and myocardial oxygen demand in obstructive hypertrophic cardiomyopathy and stenosis (aortic or pulmonary)
- Systemic hypertension
- Supra ventricular tachycardia —> rate control
- Ventricular ectopy (atenolol alone in cats, in combination for dogs.)
What are the side effects of atenolol
Negative inotrope, can cause bradyarrythmias and hypotension.
Possible bronchospasm (B2 receptor)
N.B. Do an up titration and never stop all the sudden
What happens if you stop beta blocker abruptly
Reflex tachycardia
What are the effect of Class II/III anti arrythmics
Example : sotalol and amiodarone
Action :
- K+ channel blocker —> prolong AP duration by decreasing slope of the phase 3 depolarization.
- Non selective beta blocker —> prolongs AP and effective refractory period at the AV node, atrial and ventricular myocardium.
What are the indications for class II/III anti arythmic ?
- ventricular arythmias
What are the side effects of class II/III antihypertensive
Négative inotrope
Bradyarrythmias (1st degree AV block)
Hypotension
Bronchospasm (B2)
What are the side effects specifics to amiodarone
Vomiting, anorexia, hepatopathy, neutropenia, anaphylaxis (IV, not with new formulations)
What are is the mechanism of action of class IV anti-arrythmics
Eg. Diltiazem.
Action : calcium channel blocker *different from amlodipine —> non-dihydropyrimidine (heart specific)
Blocks the inward calcium movement into the voltage gated calcium channels from the SA/AV node.
Decreases heart rate and AV conduction
What are the indications for class IV
Atrial fibrillation and other SVT
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What are the negative side effects of class IV anti-arrythmics
Negative inotrope
Vasodilation/hypotension (rare)
Bradyarrythmias
Vomiting
