45 Arrhythmias

Question 1

In the SA node is there fast action Na channels?

Answer 1

No–Inward funny current cause low slope then inward Ca does upslope

Question 2

What is ohm’s law?

Answer 2

current= voltage / resistance

Question 3

Does the the extracellular current and intracellular current run in the same direction in cell to cell conduction?

Answer 3

No–opposite direction

Question 4

What are the 2 factors that effect the voltage difference in cell to cell conduction ?

Answer 4

1. The amplitude and rate of rise of the action potential

2. The resting membrane potential

Question 5

What 2 factors that effect the resistance include in cell to cell conduction?

Answer 5

1. Gap junctions

2. Myocyte anatomy

Question 6

What reflects sinus node automaticity?

Answer 6

Heart Rate

Question 7

What reflects AV nodal conduction time?

Answer 7

PR-interval

Question 8

What reflects conduction time in ventricles?

Answer 8

QRS duration

Question 9

What reflects ventricular action potential duration?

Answer 9

QT interval

Question 10

What is the time from the beginning of an action potential until cell is able to conduct another action potential?

Answer 10

effective refractory period (absolute)

Question 11

What is the time from end of effective refractory period until cell regains normal excitability?

Answer 11

Relative refractory period

Question 12

All cardiac arrhythmias occur because of what? 6 examples

Answer 12

perturbed ion channel function

[mutation, ischemia, electrolyte abnormalities, abnormal autonomics, drugs, lightning!]

Question 13

What is diastolic depolarization? what types of cells can do this?

Answer 13

1. automaticity - altered in pathology

2. any cardiac myocyte is capable of it

Question 14

What type of depolarization occurs before end of previous action potential?

Answer 14

Early afterdepolarization

Question 15

What type of depolarization occurs after previous action potential is completely finished?

Answer 15

delayed after depolarization

Question 16

A prolonged action potential can cause what type of abnormal depolarization? How? what can it lead to?

Answer 16

EAD through reactivation of Ca channels

run of spontaneous activity

Question 17

What specific type of arrhythmia can EAD lead to?

Answer 17

torsades de pointes

Question 18

Are EAD induced arrythmias more common with fast heart rate?

Answer 18

slow heart rate

Question 19

K channel genetic mutations lead to? What are these patients predisposed to?

Answer 19

1. congenital long QT syndrome 2

2. EADs, arrhythmias, syncope, and sudden cardiac death

Question 20

What is the main cause of delayed afterpolarizations?

Answer 20

abnormal intracellular Ca handling

Question 21

Are delayed afterpolarizations more common with slow heart rate?

Answer 21

Fast heart rate–also associated with ischemia

Question 22

cardiac arrhythmias are due to what?

Answer 22

abnormal impulse conduction

Question 23

What are the three requirements for re-entry?

Answer 23

1. geometry for a conduction loop
2. unidirectional conduction block
3. slow conduction (the effective refractory period must by less than propagation time around loop)