Mechanisms of Cardiac Arrhythmia

Question 1

Two general mechanisms of arrhythmias.

Answer 1

1. Alteration in Impulse Formation

2. Alteration in Impulse Conduction

Question 2

Ion and ion channel involved in phase 4 pacemaker depolarization.

Answer 2

Sodium
Funny channel (slow sodium channel)

Question 3

What are the 3 mechanisms of arrhythmia?

Answer 3

1. Automaticity
2. Triggered activity
3. Re-entry

Question 4

What are the two types of triggered activity that lead to arrhythmia.

Answer 4

1. Early Afterdepolarization (EAD)

2. Delayed Afterdepolarization (DAD)

Question 5

What is a complication of EAD?

Answer 5

Increase QT interval due to prolonged action potential (AP). Can lead to Torsades de Pointes (TdP)

Question 6

Causes of DAD

Answer 6

High intracellular calcium

Large catecholamine release or digoxin toxicity

Question 7

What is a complication of altered impulse conduction?

Answer 7

Arrhythmias can be caused by AV blocks or any type of delayed conduction. If the delay is a unidirectional block then Re-entry signals can be generated.

Question 8

What are the 3 requirements for re-entry?

Answer 8

1. Two Pathways
2. Unidirectional Block
3. Slowed Conduction thru the blocked area