USMLE Step 1 Antiarrhythmics
Class IA drugs
Quinidine, Procainamide, Disopyramide
Class IA mechanism
- INCR AP duration
- INCR effective refractory period
- INCR QT interval
- Acts on PHASE 0
Class IA use
- Atrial and ventricular arrhythmias
Drugs used in WPW
Procainamide and Amiodarone
Quinidine toxicity
Cinchonism
Procainamide toxicity
Reversible SLE-like syndrome
Dysopyramide toxicity
Heart failure
Class IA, Soltalol, Ibutilide toxicity
Torsades de pointes
Class IB drugs
Lidocaine, Mexiletine, Tocainide
Class IB mechanism
- DECR AP duration
- Preferentially affects ischemic or depolarized PURKINJE and VENTRICULAR tissue
- Acts on PHASE 0
Class IB use
, - Acute ventricular arrhythmia (ESP POST MI)
- DIGITALIS induced arrhythmia
Class IB toxicity
- CNS stimulation/depression
- Cardiovascular depression
- Hyperkalemia can INCR TOXICITY of these drugs
Class IC drugs
Flecainide, Propafenone
Class IC mechanism
- Significantly INCR ERP in AV NODE and accessory bypass tracts
- NO effect on ERP in PURKINJE and VENTRICULAR tissue
- Minimal effect on AP duration
- Acts on PHASE 0
Class IC use
- SVTs (including A. FIB)
- LAST RESORT in refractory VT
Class IC toxicity
- Proarrhythmic
Class II drugs
B-blockers: Metoprolol, Propranolol, Esmolol, Atenolol, Timolol, Carvedilol
Class II mechanism
- DECR SA and AV nodal activity
- DECR cAMP
- DECR Ca2+ currents
- Surpress abnormal pacemakers
- DECR slope of phase 4
- INCR PR interval
Class II use
- SVT
- Ventricular rate control for A. FIB and A. FLUTTER
Class IA drugs
Quinidine, Procainamide, Disopyramide
Class IA mechanism
- INCR AP duration
- INCR effective refractory period
- INCR QT interval
- Acts on PHASE 0
Class IA use
- Atrial and ventricular arrhythmias
Drugs used in WPW
Procainamide and Amiodarone
Quinidine toxicity
Cinchonism
Procainamide toxicity
Reversible SLE-like syndrome
Dysopyramide toxicity
Heart failure
Class IA, Soltalol, Ibutilide toxicity
Torsades de pointes
Class IB drugs
Lidocaine, Mexiletine, Tocainide
Class IB mechanism
- DECR AP duration
- Preferentially affects ischemic or depolarized PURKINJE and VENTRICULAR tissue
- Acts on PHASE 0
Class IB use
, - Acute ventricular arrhythmia (ESP POST MI)
- DIGITALIS induced arrhythmia
Class IB toxicity
- CNS stimulation/depression
- Cardiovascular depression
- Hyperkalemia can INCR TOXICITY of these drugs
Class IC drugs
Flecainide, Propafenone
Class IC mechanism
- Significantly INCR ERP in AV NODE and accessory bypass tracts
- NO effect on ERP in PURKINJE and VENTRICULAR tissue
- Minimal effect on AP duration
- Acts on PHASE 0
Class IC use
- SVTs (including A. FIB)
- LAST RESORT in refractory VT
Class IC toxicity
- Proarrhythmic
Class II drugs
B-blockers: Metoprolol, Propranolol, Esmolol, Atenolol, Timolol, Carvedilol
Class II mechanism
- DECR SA and AV nodal activity
- DECR cAMP
- DECR Ca2+ currents
- Surpress abnormal pacemakers
- DECR slope of phase 4
- INCR PR interval
Class II use
- SVT
- Ventricular rate control for A. FIB and A. FLUTTER
