Cardiac Rhythms (Monitoring III)

Question 1

MOA of Class I Antiarrhythmic drugs?

Answer 1

Sodium (Na) Channel Blockers, this includes IA, IB, IC.

Question 2

Explain the difference between the three classes of Class I antiarrhythmic drugs?

Answer 2

Class I = Na channel Blockers

IA = Moderate depression of phase 0 with prolongs phase 3 repolarization (K+ channel block leads to increased QT interval.)

IB = Weak depression of phase 0 with shortened phase 3 repolarization.

IC = Strong depression of phase 0 with little effect on phase 3 repolarization.

Question 3

Examples of Class 1A antiarrhythmic drugs?

Answer 3

quinidine
procainamide
disopyramide

Question 4

Examples of Class 1B antiarrhythmic drugs?

Answer 4

lidocaine

phenytoin

Question 5

Examples of Class 1C antiarrhythmic drugs?

Answer 5

Flecainide

Propafenone

Question 6

MOA of class II antidysrhythmic

Answer 6

class II are beta blockers and they slow phase 4 depolarization in the SA node

Question 7

Examples of Beta blockers?

Answer 7

Class II antidysrhythmic are Esmolol, Metoprolol, Atenolol, Propranolol

Question 8

MOA of class III antidysrhythmic drugs

Answer 8

Class III antidysrhythmic drugs are Potassium channel Blockers.
They prolong phase 3 repolarization (increased QT) and increase effective refractory period.

Question 9

Examples of class three antidysrhythmic drugs

Answer 9

K+ channel blockers would be Amiodarone, Bretylium

Question 10

MOA of class IV antidysrhythmic drugs?

Answer 10

Class IV dysrhythmic drugs would be calcium channel blockers which decrease conduction velocity through AV node.

Question 11

How can a reentry pathway be broken? (2)

Answer 11

1. slowing conduction velocity through the circuit

2. increasing the refractory period of the cells at the location of the unidirectional block

Question 12

What are three reasons or causes of a reentry pathway? (give examples with the cause)

Answer 12

conduction occurs over a long distance. Ex. left atrial dilation due to mitral stenosis

conduction velocity is too slow. Ex. ischemia and hyperkalemia

refractory period is shorter. Ex. epinephrine and electric shock from alternating current

Question 13

Common characteristics observed on EKG if you have WPW?

Answer 13

Delta wave

Short PR interval

Wide QRS complex

Possible T wave inversion

Question 14

Explain the reentry conduction pathway of orthodromic vs antidromic AVNRT?

Answer 14

Orthodromic - atrium, AV node, Ventricle, accessory pathway, atrium

Antidromic - Atrium, accessory pathway, ventricle, AV node, atrium

Question 15

What medications would you NOT want to use with antidromic AVNRT and why?

Answer 15

DO NOT use AV nodal blocking drugs with a patient who has antidromic AVNRT (wide QRS).

Adenosine
Digoxin
Calcium Channel Blockers 
Beta blockers
Lidocaine