Anti-Arrhythmics

Question 1

outline the MOA for the classifications

Answer 1

Question 2

Phase of Action Potential and properties of conduction:
Phase 0 influences conduction ____
Phases 2 and 3 influence the __ ___
Phase 4 determines the rate of ___ ___ (pacemaker rate)

Answer 2

Phase 0 influences conduction speed
Phases 2 and 3 influence the refractory period
Phase 4 determines the rate of spontaneous depolarization (pacemaker rate)

Question 3

What two drug classes act on the SA and AV node action potentials?

Answer 3

Class IV and class II: calcium and beta blockers

Question 4

what class acts on the atrial and ventricular myocytes?

Answer 4

class III: a K channel blocker. Will lengthen the muscle potential.

Question 5

in terms of phases, how would you:

1. slow a physiological pace maker (SA)
2. increase refractory period
3. increase the heart rate
4. slow down a re-entry circuit

Answer 5

Question 6

2 main mechanisms of brady cardia

Answer 6

1. a slow pacemaker (SA nodes)
2. Conduction block (junctional or ventricular pacemaker)

Question 7

how would you expect the action potential curve and the ECG to change if you aded a K+ channel blocker?

Answer 7

K+ blocker will slow down the refreactory period and thus the point to re-polarization will increase.

Question 8

how would you expect the action potential curve and the ECG to change if you aded a Na+ channel blocker?

Answer 8

the depolarizationQRS complex will be wider

Question 9

Note;

Question 10

Usually SINUS tachycardia is okay )Exercise, acute bleeding), but sometimes it is not: give examples

Answer 10

1. pain due to myocardial infarction
2. hyperthyroidism

Question 11

How can we slow down the SA node?

Answer 11

Lengthen phase 4 of the action potential.

• beta blockers
• Ca Channel blockers.

Question 12

The SA node is the pacemaker due to automaticity

-The AV node has this ability too, and maybe the purkinje fibers as well. But the AV node and purkinje are all SLOW

How do other locations with flat phase 4 AP’s become FAST pacemakers then?

Answer 12

Via Re-entry Circuits- they require a very delicate balance of conduction speed and refractory periods.

Question 13

for atrial tachycardia where the atrium is acting as the pacemaker instead of the SA node, we have to be worried about clots because poor contraction –> stasis of blood –> clot.

• we have to break the re-entry circuit with drugs or electricity.
• if this re-entry circuit cannot be broken, then decrease the heart rate by suppressing the AV node.
• What drugs might break the re-entry circuit

Answer 13

1. alter the conduction speed (class I (Na+ Channel blocker))
2. increase the referactory period : Class III (K+ channel blockers)

Question 14

tachycardia can be mediated by re-entry circuits from the AV node (rather than the normal SA node). What are the two AV node tachycardia

Answer 14

Question 15

what 3 drugs can be used to break the circuit in the AV node

Answer 15

1. beta blocker
2. calcium channel blockers
3. adenosine; veyr profound suppresion.
   - can also do carotid massafe, vagal maneuver

Question 17

SA and AV nodes:
___ blockers
__ channel blockers

Atrial or Ventricular
___channel blockers (most common)
____channel blockers (used more in the past)

Answer 17

SA and AV nodes:
BETA blockers
CALCIUM channel blockers

Atrial or Ventricular
K+channel blockers (treatment of refractory period) (most common)
Na+ channel blockers (used to reduce the initial depolarization) used more in the past)

Question 18

Tachycardia non pharmacological treatments

Answer 18

• cardioversion and defibrillation

Question 19

To suppress the AV node for a few hours, what drug class would you use?
1. Class I and III 2. Class II and IV 3. Class I and II 4. Digoxin 5. Adenosine

Answer 19

2. Class II and IV: Beta and Calcium Blockers

Question 20

For thie case, To try to convert back to sinus, what drug class would you use?
1. Class I and III

2. Class II and IV
3. Class I and II
4. Class III and IV
5. Adenosine

Answer 20

Ventriculat tachycardia treatment:

class I and III

• Na and K blockers