Class IA antiarrhythmic

Sodium channel blockade

Prolong the APD and dissociate from the channel with intermediate kinetics

Treatment: Atrial and ventricular arrhythmias, long term therapy is avoided due to side effects

Side effects: AP and QT interval prolongation, induction of torsades de pointes, arrhythmia and syncope; disopyramide and quinidine have antimuscarinic effect; Procainamide causes syndrome resembling lupus erythematosus

Class IB antiarrhythmics

Sodium channel blocker

Shorten the APD in some tissues of the heart and dissociate from the channel with rapid kinetics

Treatment: Termination of ventricular tachycardia and prevention of v-fib after cardioversion of acute ischemia. IV lidocaine administered for arrythmias.

Side-effects: Hypotension, parathesias, tremor, nausea of central origin, light-headedness, hearing disturbances, slurred speech, and convulsions. Well tolerated below 9mcg/mL

Class 1C antiarrhythmic

Sodium channel blockade

Minimal effects on the APD and dissociate from channel with slow kinetic; Inc QRS in EKG

Treatment: SVT in patients with normal hearts

Side-effects: Provocation or exacerbation of potentially lethal arrythmias (dangerous), acceleration of ventricular rate in patients with flutter, increased freq of REVT

Propanolol and esmolol

Sotalol

Class 2

Sympatholytic 

Sotalol is nonselective and prolongs AP (class 3 action); Reduction in cAMP causing reduction of both Na and Ca currents and suppression of abnormal pacemakers. AV node is sensitive. PR interval prolonged

Propanolol is non-selective antagonist, Esmolol is B-1 selective blocker

Treatment: Control ventricular rate in a-fib or flutter and terminate/prevent PSVT; Suppresses PVCs

Side-effects: Contraindicated in patients with WPW because they can exacerbate ventricular response

Class 3

Prolongs the APD (inc QT interval). Blocks the rapid component of the delayed rectifier potassium current (amiodarone is a Na channel blocker) thus prolonging refractory period. 

Treatment: Ventricular arrythmias and maintaining sinus rhythm in patients with a-fib. Supraventricular and ventricular arrythmias in children

Side-effects: Bradycardia, Asthma, Torsades-de-Pointes

Class 4

Blockade of the cardiac calcium current

Slows conduction in regions where the action potential upstroke is calcium dependent, like SA and AV nodes

Class 3 with wide capacity to block inactivated sodium, weakly calcium, potassium channels and weakly beta-adrenoceptors. Prolongs QT by K blockade. Effects last 1-3 months after discontinuation.

Treatment: all arrythmias (adjuvant)

Side-effects: microcrystalline deposits in cornea and skin, thyroid dysfunction (hyper/hypo), paresthesias, tremor, and pulmonary fibrosis

Class 4 blocks both activated and inactivated L-type calcium channels. Decreases conduction velocity and increases effective refractory period. PR interval is increased. Also causes peripheral vasodilation.

 Treatment: terminates SVT in patients with normal heart, prevents nodal arrythmias

Side-effects:Dose-related AV block, sinus arrest, constipation, lassitude, nervousness, and peripheral edema; contraindicated in WPW

Activator of inward rectifier K current and inhibition of calcium current=marked hyperpolarization and suppression of calcium-dep APs=inc AV nodal refractory period; less effective in presence of adenosine receptors such as theophyline or caffeine

Treatment: Conversion of PSVT to sinus rhythm