Anti-Arrhythmics

Question 1

Quinidine

Answer 1

Class: Class IA antiarrhythmic

Mech: Block inward K rectifying channel (slow rate) at normal concentrations; blocks sodium channels (fast rate) at high concentrations which prolongs prolongs effective refractory period and prolongs AP duration. Also has alpha-adrenergic blockade, M2 blockade, vagal inhibition

Thera: Chronic A-flutter/fib, SVT, VT

Tox: diarrhea, nausea, fever, hepatitis, QT prolongation (TdP)

Misc: Numerous drug interactions with CYP2D6

Question 2

Procainamide

Answer 2

Class: Class IA antiarrhythmic

Mech: Block inward K rectifying channel (slow rate) at normal concentrations; blocks sodium channels (fast rate) at high concentrations which prolongs prolongs effective refractory period and prolongs AP duration.

Thera: Chronic A-flutter/fib, SVT, V-fib

Tox: Drug-induced lupus, QT prolongation (TdP), hypotension

Question 3

Disopyramide

Answer 3

Class: Class IA antiarrhythmic

Mech: Block inward K rectifying channel (slow rate) at normal concentrations; blocks sodium channels (fast rate) at high concentrations which prolongs prolongs effective refractory period and prolongs AP duration.

Thera: Chronic A-flutter/fib, SVT, VT

Tox: Prominent anticholinergic action (constipation, dry mouth, glaucoma), QT prolongation (TdP)

Question 4

Lidocaine

Answer 4

Class: Class IB Antiarrhythmic

Mech: Block Na channel in inactivated state, no action on atrial tissue (therefore cannot be used for atrial arrhythmias

Thera: Emergency VT/VF, digitalis toxicity

Tox: Tremor, nausea, seizures

Question 5

Mexiletine

Answer 5

Oral version of lidocaine but has some renal toxicity

Question 6

Tocainide

Answer 6

Same as lidocaine except not available in the US bc of fatal bone marrow aplasia and pulmonary fibrosis

Question 7

Flecainide, Propafenone, moricizine

Answer 7

Class: Class IC

Mech: Most potent Na channel blocks (greatly prolonging Na recovery), IKr channel blockade as well

Thera: chronic A-fib/flutter, paroxysmal SVT due to structural heart disease

Tox: Worsened HF, MI, proarrhythmic in ischemic tissue(MI thing)
Flecainide=blurry vision
Propafenone=brady, bronchospasm

Question 8

Propanolol

Answer 8

Class: Class II (nonselective beta blocker)

Mech: Decrease SA, AV node activity (decrease phase 4 depolarizaiton)

Thera: A-fib/flutter, SVTs (exercise induced, digitalis induced), PVC, MI

Tox: Hypotension, bronchospasm, bradycardia

Misc: All beta blockers are contraindicated in WPW syndrome and avoid sudden withdrawal bc may cause an MI

Question 9

Carvedilol

Answer 9

Class: Class II (nonselective beta blocker)

Mech: Decrease SA, AV node activity (decrease phase 4 depolarizaiton)

Thera: A-fib/flutter, SVTs (exercise induced, digitalis induced), PVC, MI, CHF

Question 10

Metoprolol, Acebutolol,

Answer 10

Class: Class II B1 selective blocker

Same as above

Acebutolol has some sympathomimetic

Question 11

Esmolol

Answer 11

IV with short half life and is useful in treatment of SVT in acute setting where short duration is desired

Question 12

Class III antiarrhythmics

Answer 12

Mech: K channel blockade which prolongs refractoriness

Thera: A-fib/flutter, paroxysmal SVT, VT

Tox: Photosensitivity (blue-gray skin) numerous drug interactions, TdP, pulmonary fibrosis, peripheral neuropathy, hepatic dysfunction

Question 13

Sotalol

Answer 13

Class III

Mech: Blocks IKs, non-selective B-blocker

Thera: Preferred drug for A-fib over Quinidine

Tox: EADs, TdP, slow HR, decrease AV conduction

Question 14

Ibutilide

Answer 14

Class III

IV dose for Afib/flutter

Question 15

Dofetilide

Answer 15

Class III

Mech: IKr blocker, maintain sinus rhythm after cardioversion, and converts chronic AFib

DO NOT use for ventricular arrhythmias or paroxysmal AFib

Question 16

Amiodarone

Answer 16

Class III

Mech: Thyroxine analog that mimics all classes (decease Na, Ca, K, alpha, beta) with long half life of 80 days

Thera: Useful against almost all arrhythmias except digitalis toxicity and not during pregnancy.

Tox: QT prolongation (TdP), pulmonary fibrosis, peripheral neuropathy, hepatic dysfunction, corneal microdeposits, photosensitivity

Question 17

Dronedarone

Answer 17

Less effective but fewer side effects than amiodarone but still causes QT prolongation, nausea, diarrhea

Question 18

Verapamil

Diltiazam

Answer 18

Class: Class IV

Mech: Blockade of L-type calcium channels slowing the SA and AV node activity and prolonging AV refractoriness

Thera: Prevent or terminate reentrant SVTs, slow ventricular rate during a-flutter/fib

Tox: Hypotension, brady, constipation, dizziness, increased serum digoxin levels and becomes additive with digoxin and B blockers in terms of AV block

Contraindicated in WPW

Question 19

Adenosine

Answer 19

Mech: Adenosine receptors in atria, sinus node, AV node, activates K current, shortening AP hyperpolarizing tissue, and slowing down automaticity and AV conduction

Thera: A-fib, paroxysmal SVT

Tox: Sedation, dyspnea, hypotension

Question 20

Magnesium

Answer 20

Thera: Prevents recurrent TdP and some digitalis-induced arrhythmias

Misc: Alternative to amiodarone for shock-refractory cardiac arrest

Question 21

Cardiac glycosides (digoxin)

Answer 21

Mech: Na/K pump inhibitor which slows AVN conduction and activity

Thera: A-fib/flutter, chronic SVT

Tox: May cause DAD arrhythmias

Misc: low therapeutic index