Antiarrhythmics Flashcards
Class IA antiarrhythmic drugs
- Quinidine
- Procainamide
- Disopyramide
Class IA antiarrhythmic mechanism of action
- Block Na+ and K+ channels (phase 0 and phase 3)
- Intermediate dissociation rate (secs)
- Inc QRS and QT intervals
Class IB antiarrhythmic mechanism of action
- Block Na+ channels
- Rapid dissociation rate (<1 sec)
- Shortened QT interval
Class I antiarrhythmics block phase _
0
Class IC antiarrhythmic mechanism of action
- Block Na+ channels
- Slow dissociation rate (>10 sec)
- Inc QRS duration
Side effects with procainamide
- Rash, myalgia, vasculitis, Raynauds
- Fever, hypotension, bradycardia
- QT prolongation, Torsades de Pointes
- Drug induced lupus (oral)
Uses for procainamide
IV only
- Sustained vtach
- unmasking brugada syndrome
- AF in WPW
Class IB drugs
- lidocaine (IV)
2. mexiletine (oral)
Class ___ antiarrhythmics have increased potency in ischemic tissue
IB
Indications for class IB antiarrhythmics
- Vtach
- Vfib
* *not useful for atrial arrhythmias
Side effects of Class IB antiarrhythmics
Mainly CNS
lidocaine: visual disturbances, tremors, seizures, hallucinations, coma, asystole, hypotension, N/V
Mexiletine: GI: N/V/D, constipation, blurred vision, ataxia, HA, tremor, confusion
Class IC drugs
Flecainide
Propafenone
Indications for class IC antiarrhythmics
- Afib in patients without CAD or HF
2. SVT
Adverse effects of class IC antiarrhythmics
Flecainide: VT/VF in pts with CAD, aflutter, dizziness, dyspnea, HA, blurred vision, nausea, tremor, fatigue, HF exacerbation, AV block
Propafenone: unusual taste, dizziness, HA, nausea, fatigue, constipation, diarrhea, HF, blurred vision, bradycardia, palpitations, bronchospasms
Class II antiarrhythmic drugs
Beta blockers:
- Metoprolol
- Propranolol
- Esmolol
Mechanism of action of Class II antiarrhythmics
- Reduction in intracellular cAMP concentration
- Reduction of the funny current
- Slows and limits Ca++ influx
- Inc PR interval
- Dec slope of phase 4 depolarization
- Prolonged repolarization at AV node
Indications for class II antiarrhythmics
- Treat/prevent supraventricular and ventricular arrhythmias
- Afib/flutter: control ventricular rate
- Paroxysmal SVTs: terminate and prevent ventricular arrhythmias
- Ventricular arrhythmias: raise threshold for ventricular fibrillation in ischemic myocardium
- Reduce ventricular arrhythmias and cardiac arrest after ACS and in pts with HF
- Reduce DADs by reducing increases in Ca++ influx
Adverse effects of class II antiarrhythmics
- fatigue
- bronchospasm
- hypotension
- impotence
- depression
- HF exacerbation
- masking of symptoms of hypoglycemia in DM
Mechanism of action of class III antiarrhythmics
- Block K+ delayed rectifier current (phase 3)
- prolonged repolarization period
- prolonged QT interval
Class III antiarrhythmic drugs
- Dronedarone
- Amiodarone
- Sotalol
- Ibutilide
- Dofetilide
Mechanism of action of amiodarone
- K+ channel blocker (class III), prolongs action potential duration/phase 3
- Na+ channel blocker (class I), blocks inactivated Na+ channels, relatively rapid rate of recovery
- L-type Ca++ blocker (class IV), slows sinus and AV node conduction
- B1, B2, a1 receptor blocker (class II), slows sinus and AV node conduction
True/false: amiodarone works best at high HRs
True
Pharmacokinetics of amiodarone
- Highly lipophilic (large volume of distribution)
- Delayed onset of action (need loading dose 10g total)
- T1/2 of 2months
- Hepatic metabolism CYP3A4 and 2C8 to active metabolite
- Inhibits CYP3A4, CYP2C9 and P-glycoprotein (drug interactions with digoxin, warfarin, statins)
Contraindications for amiodarone
- known hypersensitivity to amiodarone, including iodine
- Cardiogenic shock
- marked sinus bradycardia
- 2nd or 3rd degree AV block w/out pacemaker
Amiodarone black box warning
- pulmonary toxicity (10-17%)
- Liver injury
- Worsening cardiac dysrhythmias
Which drug is rarely prorhythmic?
Amiodarone
Warnings for amiodarone
- hypotension (IV)
- bradycardia/AV block
- Liver enzyme elevations
- Proarrhythmia
- Pulmonary disorders
- Thyroid abnormalities
- Surgery needs close monitoring
- Acute photosensitivity/blue discoloration
- CNS effects
Mechanism of action class IV antiarrhythmics
- Non-dihydropyridine calcium channel blockers
2. State dependent inhibition of L-type Ca++ channels
Class IV antiarrhythmic drugs
Verapamil
Diltiazem
IV and PO
Indications for Class IV antiarrhythmics
- supraventricular tachycarrhythmias
- afutter/afib
- SVTs
Adverse effects of class IV antiarrhythmics
hypotension, bradycardia, AV block, negative inotropy
Digoxin mechanism
- enhances central and peripheral vagal tone (sensitization of baroreceptors, inc paraympathetic tone, prolongs AV node refractory and decreases SA node automaticity)
- Inhibits Na/K ATPase pump (inc intracellular Ca++, Inc contractility and proarrhythmic potential)
Indications for digoxin
-Afib/aflutter, control of ventricular rate (only reduces RESTING HR, good w/BB or CCB, HFrEF)
Therapeutic window of digoxin
Narrow- 0.5-2.0 ng/ml (<1.0 in HF)
Adverse effects of digoxin
GI, halo vision, malaise, bradycardia, AV block, vtach/vfib
Mechanism of action for adenosine
- Activates acetylcholine-sensitive K+ current in the atrium and sinus and AV nodes
- hyperpolarization and suppression of calcium dependent APs
- Inc ERP of AVN
- Blocks conduction through the AV node
- Terminates PSVTs
Half life of adenosine
1-6 seconds
Adverse effects of adenosine
Transient flushing, dyspnea, bronchospasm, chest pressure/fullness
Class, MOA and limitation of Procainamide
- Class Ia
- Na+ and K+ channel blockers
- Risk of Torsades de Pointes, possible inc risk mortality
Class, MOA and limitation of lidocaine
- Class Ib
- Na+ blocker (fast kinetics)
- No efficacy in atrial arrhythmias
Class, MOA and limitation of Mexiletine
- Class Ib
- Na+ blocker (fast kinetics)
- No efficacy in atrial arrhythmias
Class, MOA and limitation of Flecainide
- Class Ic
- Na+ blocker (slow kinetics)
- contraindicated in CAD and structural heart disease
Class, MOA and limitation of B blockers
- Class II
- Beta adrenergic receptor competitive antagonist
- Hypotension and bradycardia
Class, MOA and limitation of Amidarone
- Class III
- Multichannel blocker
- Extra-cardiac side effects
Class, MOA and limitation of Dofetilide
- Class III
- K+ channel inhibition
- Risk of Torsades de Pointes, dependent on renal clearance
Class, MOA and limitation of Sotalol
- Class III
- K+ channel blocker
- RIsk of Torsades de Pointes, dependent on renal clearance
Class, MOA and limitation of DHCCB’s (verapamil, diltiazem)
- Class IV
- L-type Ca++ blocker
- Hypotension and bradycardia
