Cardiac Conduction System & ECG (complete) Flashcards Preview

CV Unit I > Cardiac Conduction System & ECG (complete) > Flashcards

Flashcards in Cardiac Conduction System & ECG (complete) Deck (16):
1

Describe the relationship between ventricular APs of individual cardiac myocytes and the surface electrocardiogram

- R wave => phase 0
- ST segment => phase 2
- T wave => phase 3
- Segment after T wave => phase 4

2

What is the sequence of the activation of the cardiac electrical conduction system?

- Upper portion of septum is depolarized from left to right
- then depolarization downward in the septum to the apex
- Depolarization from endocardium to epicardium
- Depolarization moves upward from apex in the free walls of both ventricles
- Depolarization of the base of the ventricles

OVERALL GOAL: to help push the blood in the correct direction!

3

Describe the P wave

- Represents atrial depolarization

4

Describe the QRS complex

- Represents depolarization of ventricles

5

Describe the T wave

- Represents repolarization of ventricles
- When K+ channel takes over

6

Describe the PR interval

- Index of conduction time across the AV node
- Depolarization pauses at the bundle of His after depolarization of atria and before that of ventricles

7

Describe the QT interval

- Represents total duration of depolarization and repolarization

8

Describe the effects of left or right bundle branch block on cardiac conduction

Right: QRS widening w/ delayed conduction to RV

Left: QRS widening w/ delayed conduction to LV

9

What are the three major mechanisms by which disturbances in cardiac conduction cause tachyarrhythmias?

1) Abnormal reentry pathways
2) Ectopic foci
3) Triggered activity

10

Describe abnormal reentry pathways as a mechanism leading to arrhythmia

- Most common cause of severe tachycardias
- Reentry occurs w/ unidirectional block and slowed conduction

11

Describe ectopic foci as a mechanism leading to arrhythmia

- when cells outside conduction system acquire automaticity
- and if depolarization rate exceeds that of SA node => abnormal rhythm
- Can be isolated ectopic beats or sustained arrhythmias

12

Describe the concept of triggered activity as a mechanism leading to arrhythmia

- abnormal afterdepolarizations may be triggered by the preceding AP
- Early afterdepolarization before AP => tachyarrhythmia
- Delayed afterdepolarizations appear after an AP => also triggers arrhythmias

13

What are the three types of atrioventricular block?

1) First Degree
2) Second Degree
3) Third Degree

14

Describe first degree AV block

- Conduction is delayed
- BUT all P waves conduct to the ventricles

15

Describe second degree AV block

Some P waves conduct --- not all

16

Describe third degree AV block

- No P waves conduct
- Ventricular pacemaker now needed