Antidysrhythmics

Question 1

Class I

Answer 1

Na+ channel blockers; overall slow down conduction and decrease the slope of phase 0 depolarization

Question 2

Class Ia

Answer 2

Delay repolarization; moderate

Question 3

Class Ib

Answer 3

Accelerate repolarization; weak

Question 4

Class Ic

Answer 4

Reduce conduction velocity; strong

Question 5

Class II

Answer 5

Beta blockers

Question 6

Class III

Answer 6

K+ channel blockers

Question 7

Class IV

Answer 7

Ca++ channel blockers

Question 8

Quinidine, procainamide

Answer 8

Class Ia: Na+ channel blockers
Mechanism: increases AP, ERP, and QT interval
Indication: atrial and ventricular arrhythmias (SVTs and VTs)
Adverse Effects: cholinergic effects (increase HR, etc)

Question 9

Lidocaine

Answer 9

Class Ib: Na+ channel blocker
Mechanism: decreases AP, ERP, allowing for a more coordinated contraction
Indication: post-MI and other ventricular arrhythmias
Adverse Effects: toxicity at high doses

Question 10

Propanolol, metoprolol, esmolol

Answer 10

Class II: beta blockers
Mechanism: block b1 receptors to decrease HR, contractility, and AV conduction
Indication: afib, SVTs, VTs, post-MI (to improve O2 supply/demand and decrease cardiac modeling)

Question 11

Amiodarone

Answer 11

Class III: K+ channel blockers
Mechanism: block K+ exit, which delays depolarization, increases AP duration, and increases ERP
PK: long 1/2 life
Indications: ventricular tachycardias (vfib and vtach)
Contraindications: pregnancy, drug interactions
Adverse Effects: pulmonary fibrosis, prodysrhythmic (torsades, bradycardia, AV block)

Question 12

Verapamil, diltiazem

Answer 12

Class IV: Ca++ channel blockers
Nondihydropyridines
Mechanism: block Ca++ influx, which decreases HR, contractility, and AV node conduction (like beta blockers)
Indications: afib, SVTs
Contraindications: avoid concurrent admin of CCB and BB)
Adverse Effects: bradycardia, AV block, hypotension

Question 13

Adenosine

Answer 13

Mechanism: binds adenosine receptor in cardiac tissue, causing hyper polarization and basically stops the heart
PK: super short 1/2 life…must be given rapid IVP followed by flush
Indications: afib (supra-), SVT
Adverse Effects: flushing, transient hypotension, transient cessation of electrical activity

Question 14

Digoxin

Answer 14

Class: cardiac glycoside
Mechanism: potent Na+/K+ ATPase inhibitor, resulting in increase contractility (inotropy)
Indications: afib (supra-), SVT
Contraindications: heart block, hypokalemia (causes digoxin toxicity), WPW, advanced CKD

Question 15

Atropine

Answer 15

Class: anticholinergic
Mechanism: muscarinic receptor antagonism, causing increased HR
Indications: symptomatic bradycardia, complete heart block
Adverse Effects: anticholinergic s/s