Cardiac Arrhythmia Pharm Flashcards
Class 1A drugs and their MOA
Na channel blockers (also block K channels)
*Quinidine, Procainamide, Disopyramide
Class 1B drugs and their MOA
Na channel blockers (do not block K channels)
*Lidocaine, Mexiletine
Class 1C drugs and their MOA
Na channel blockers (also block some K channels) *block Na channels stronger than other class 1
*Flecanide, Propafenone
Class 2 drugs and their MOA
Beta blockers
*Esmolol, Propanolol
Class 3 drugs and their MOA
K channel blockers
*Amiodarone, Sotalol, Dofetilide, Ibutilide
Class 4 drugs and their MOA
Cardioactive (non-dihydropyradine; L-type) Ca channel blockers
*Verapamil, Diltiazem
Where in the heart are fast action potentials?
Artial/ventricular cardiomyocytes, purkinje fibers
*targets of class 1 and 3 drugs
Where in the heart are slow action potentials?
SA node and AV node
- targets of class 2 and 4 drugs
- ventricular rate control
Fast action potential phases in the heart (atria and ventricles)
0- Na influx 1- Na close, K efflux 2- plateau, K efflux and Ca influx 3- Ca close, K efflux 4- Na/K and Na/Ca ATPases restore RMP
Slow action potential phases in the heart (SA and AV nodes)
4- funny channels (If) and T-type Ca channels slowly depolarize
0- Rapid Ca influx through L-type Ca channels
3- Ca channels close, rapid K influx, repolarization
Class 1A drugs indication
*Quinidine, Procainamide, Disopyramide
Disopyramide most commonly used, treats ventricular arrhythmias
*all class 1A prolong QT interval and AP
Class 1B drugs indication
*Lidocaine and Mexiletine
- Lidocaine (VTach in acute MI)
- Mexiletine (ventricular arrhythmias, chronic pain)
*all class 1B do NOT prolong AP or QT interval
Class 1C drugs indication
Flecainide, Propafenone
- Flecanide (supraventricular arrhythmias, ventricular arrhythmias refractory to other treatment)
- Propafenone (supraventricular arrhythmias)
- all class 1C do not prolong AP or QT interval
- prolong QRS interval
- contraindicated in pt with any structural heart disease
Class 2 drugs indication
Propanolol, Esmolol
- Propanolol (Afib, Aflutter, supraventricular arrhythmias)
- Esmolol (short acting, supraventricular arrhythmias)
Class 3 drugs indication
Amiodarone, Sotalol, Dofetilide, Ibutilide
Amiodarone (Afib and Vtach)
Sotalol (Afib and Vtach)
Dofetilide (Afib, maintain sinus in pt after cardioversion)
Ibutilide (Afib)
*all class 3 drugs block K channels, prolong QT, prolong refractory period, prolong AP
Amiodarone adverse effects
Has qualities of Class 1, 2, 3, 4 drugs
- AV block and bradycardia
- Torsades de pointes due to QT prolongation
- Pulm fibrosis
- Hepatitis
- Photodermatitis
- Corneal deposits
- Hypo or hyperthyroidism
Class 4 drugs indication
Verapamil, Diltiazem
Verapamil, Diltiazem (superventricular tachys, afib, aflutter)
*block L-type Ca channels in SA/AV nodes, slowing phase 0
Adenosine indication and MOA
Clinical use: conversion to sinus rhythm in PSVT
- MOA: activates A1 adenosine receptor (Gi), enhances K current and inhibits Ca current and funny current
- Hyperpolarizes pacemaker cells, slowing conduction
Class 1A and 3 drugs are proarrhythmic, causing…
excesive slowing of repolarization and torsades du pointes
*class 1A causes slowed repolarization and conduction
Class 1A and 1C drugs are proarrhythmic, causing…
excesive slowing of conduction and persistent ventricular tachycardias
*class 1A causes slowed repolarization and conduction
Drugs to treat atrial fibrillation
No HF and LVEF >40%
Class 1C or Class 3 drugs
*first try direct current cardioversion (DCC)
Drugs to treat atrial fibrillation
No HF and LVEF <40%
Class 3 drugs
*first try direct current cardioversion (DCC)
Drugs to treat atrial fibrillation in patient with structural heart disease or former ischemic disease
Class 3 drugs
*Class 1C contraindicated in this situation
Goal of pharmacologic treatment in patient with atrial fibrillation
restoration of sinus rhythm
Drugs to treat paroxsymal supreventricular tachycardia (PSVT)
Most common type is atrioventricular nodal reentrant tachycardia (AVNRT)
Class 2 and 4 drugs
Reversal of torsades de pointes
If hemodynamically unstable:
- Correct electrolyte abnormalities
- Magnesium sulfate
- Transvenous temporary pacemaker or isoproterenol