Antiarrhythmics Flashcards
Class IA MOA, Effect, and Uses
- MOA:
- Na+ and slight K+ channel blockade
- EFFECT:
- slows phase 0 depolarization
- prolongs repolarization/refractory period
- elevates resting membrane potential
- USES:
- Reentry
- ectopic supraventricular and ventricular tachycardias
Quinidine
- Class IA
- anticholinergic effects speed up AV conduction
- need to be combined with neg. inotrope
- alpha blockade causes hypotension
- used for: PACs, PVCs, AF/AF to NSR, Preventing SVT, WPW with atrial fibrillation
Quinidine adverse effects
- GI
- Dig toxicity
- Prolongs QT interval, which may cause Torsades
Procainamide
- Class IA
- DOC for WPW with Afib
- also used for: SVT (Afib, reentry)
- kidneys convert 50% of dose to NAPA
- Stop treatment until: rhythm suppressed, QT prolonged >50%, or you’ve reached maximum dose
Procainamide adverse effects
- lupus like syndrome
- agrunulocytosis
- fever
- QT prolongation
Class IB MOA, Effects, Uses
- MOA:
- Rapidly blocks and un-blocks Na+ channels (best when cells fire rapidly)
- EFFECT:
- shorten phase 3 repolarizaiton
- decrease AP duration
- Use:
- venricular arrhythmias
Lidocaine
- Class IB
- used to be DOC for ventricular arrhythmias
Lidocaine adverse effects
- mental status change
- arrhythmias (sinus arrest, AV block, asystole)
Class IC MOA, Effects, Uses
- MOA:
- potently blocks Na+ channels
- EFFECTS:
- markedly slows phase 0
- significantly prolongs AV refractory period
- USE:
- prevents supraventricular arrhythmias in structurally normal hearts
Flecainide
- Class IC
- used for SVT (Afib and paroxysmal SVT)
- only use in structurally normal hearts!!
Flecainide adverse effects
- aggravation of ventricular arrhythmias
- heart failure
- altered mental status
Class II MOA, Effects, Uses
- MOA:
- beta blockers
- EFFECTS:
- depresses automaticity
- prolongs AV conduction
- decreases heart rate and contractility
- USES:
- SVT
- Vtach
- thyrotoxicosis
- pheochromocytoma
- palpitation prophylaxis
- Vtach after MI prophylaxis
Caution using Class II with…?
- diabetes (masks signs of hypoglycemia)
- PVD (can cause vasospasm)
- Impotence (exaggerates)
- Asthma/COPD (bronchospasms)
- SSS (further depresses heart rate)
- AV blocks (can make block worse)
Class III MOA, Effects, Uses
- MOA:
- blocks K+ channels
- EFFECTS:
- prolongs phase 3, prolonging AP
Amiodarone
- Class III
- Also has Na+, Ca++, and Beta blockade
- Decreases conduction velocity, reentry, rate of fire, automaticity, and inotropy
- DOC for ventricular arrhythmias during resuscitation
- also used for supraventricular arrhythmias and reentrant tachycardia
- low dose for Afib/Aflutter suppression
- Long half-life!!!
Amiodarone toxicities
-pulmonary, hepatic, thyroid, cardiac, GI, and neuro toxicities
Ibutilide
- Class III
- affects the slow influx of Ca++ during phase 2, rather than K+ channels
- prolongs AP and increases atrial and ventricular refractoriness
- used for IV chemical cardioversion of Afib
Ibutilide toxicites
- can cause Torsades de Pointes, so you must check electrolytes (K and Mg) before drug administration
- short half-life
Sotalol
-Class III
-Also has nonselective Beta-blockade
prolongs AP, increases atrial/ventricular refractoriness, and inhibits conduction in accessory pathways
-Used for SVT and ventricular arrhythmias
Sotalol adverse effects
-prolongs action potential which can cause development of Torsades
Class IV MOA, Effects, Uses
- MOA:
- Ca++ channel blockade
- EFFECTS in nodal tissue:
- elevates threshold potential
- slows phase 0 depolarization
- decreases conduction velocity
- lengthens refractory period
- decreases HR
- terminates reentry rhythms through AV node
- Uses:
- AVNRT
- Afib/Aflutter
- MAT
Class IV side effects
- AVN delays
- bradycardia
- constipation
Verapamil
Class IV Calcium Channel blocker
Diltiazem
Class IV calcium channel blocker
Do not use Class IV in…?
- wide complex tachycardias of unknown origin
- Afib with WPW
- SSS
- AV blocks without a pacemaker
Adenosine
- MOA: K+ channel agonist
- EFFECT: rapid efflux of K+ hyperpolarizes the cells of the SA and AV nodes
- Net effect: slows SA firing and AV node conduction
- DOC for reentrant tachycardias
- DOC for SVT
- must slam and chase due to half-life of only 10 seconds!
- caffeine and theophylline are competitive antagonists - need to use higher dose
Adenosine toxicities
- facial flushing
- atrial arrhythmias
- nausea
- shortness of breath
- chest tightness
- caution with asthma and COPD because of bronchospasms
Digoxin
- blocks the Na+/K+ pump, increasing intracellular Na+
- Na+ competes with Ca++ for eflux from cell, so intracellular Ca++ is increased
- Used when there’s a slow ventricular response with Afib, Aflutter, and Atach
- 3rd choice for SVT
Digoxin toxicities
- can make a ladle ST segment depression
- arrhythmias
- GI
- ENT
- do not use with renal failure, hypokalemia, or Afib with WPW
DOC for Wolff-Parkinson-White syndrome
Procainamide
Old DOC for ventricular arrhythmias
Lidocaine
Current DOC for ventricular arrhythmias
Amiodarone
2nd DOC for SVT
Verapamil
DOC for SVT
Adenosine
DOC for reentrant tachycardias (although there are several ways to treat)
Adenosine
3rd DOC for SVT
Digoxin
Usually the 1st line drug for Afib/Aflutter ventricular rate control
Diltiazem
