Anti-Arrhythmic

Question 0

Propranolol, Esmolol

Answer 0

Class II agents, beta-blockers, negative chronotropic and dromotropic agents
Special note: antiarrythmic drug that has been shown to reduce mortality post-MI, other antiarrhythmic treatments take now secondary role to ICD in chronic management of arrhythmia.

Question 1

Quinidine, Lidocaine, Flecainide

Answer 1

Class I Agents: Na Channel Blockers
Class Ia (Quinidine, Procainamide, Dispyramide) prolongs conduction and repolarization (k blocker)
Class 1b (Lidocaine, Mexilitine) is weak Na blockade, used for VT only
Class 1c (Flecainide, Propafenone) is strong Na blockade

Question 2

Sotalol, Amiodarone, Dronedarone, Dofetilide

Answer 2

Class III agents: potassium channel blockade, delay repolarization (phase 3) and thereby increase effective refractory period.
Risk of Torsade de Pointed as a form of pro arrhythmia from early afterpolarization by significantly prolonging QT interval
*side effects of amiodarone: additive effects on slowing of AV nodal conduction when used with digoxin, interstitial pneumonitis, blue skin, glaucoma
*Ibutilide induces the slow inward Na current in phase 2, i.r. Pseudo Type III

Question 3

Diltiazem, Verapamil

Answer 3

Class IV agent: L-type calcium channel blocker, acts primarily on slow myocytes (SA and AV node), which are dependent on Ca influx for phase 0 of action potential.
*Nifidepine is Calcium Channel Blocker, but not indicated in arrhythmia because there is no negative chronotropic or dromotropic effect–vasodilation of arteries leading to possible reflex tachycardia. Could worsen angina.

Question 4

Adenosine

Answer 4

Class IV agent: blocks a1 (adenosine 1) receptor, prolong AV conduction by causing cell hyperpolarization (increasing outward ik) and attenuates catecholamine stimulation of i ca (L) and i f). Used for SVT only.