Cardiac Conduction System and ECG Flashcards Preview

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Flashcards in Cardiac Conduction System and ECG Deck (26)
1

Initial rapid upward deflection of R wave corresponds to ____ of the action potential

Phase 0 = fast inward INa current

2

____ corresponds to Phase 0 = fast inward INa current of the action potential

Initial rapid upward deflection of R wave

3

Which part of ECG is isolectric?

ST segmeent is isolectric

4

What does ST segment correspond to on action potentiaL?

phase 2 plateau (when Ca2+ influx and K+ efflux balanced)

5

What does phase 2 plateau correspond to on ECG

ST segment

6

What does T wave on ECG correspond to on action potential

phase 3 of AP (rapid decrease in voltage as K+ efflux continues)

7

What does isoelectric segment after T wave correspond to?

phase 4 of the action potential

8

There must be Concordance between ____ and ___ on ECG

QRS and T wave in every ekg lead

9

Why is there concordance between QRS and T? is there difference with an individual myocyte?

ventricular myocytes depolarize earliest must repolarize latest

discordance with individual myocyte

10

what if there is no concordance between QRS and T

ischemia
ventricular hypertrophy

11

Why is T wave longer than QRS segment?

repolarization requires more time than depolarization

12

How does depolarization spread from cell to cell?

via gap junctions (formed by connexins that allow ions to pass from cell to cell)

13

Path of electrical transmission in the heart...

1) SA node (where SVC enters the heart) = spontaneously depolarizes (automaticity)

2) travel from RA and then LA generating P wave

3) when reach AV node --> delay
4) pass to Bundle of His (extension of AV node)
5) Splits into left and right bundle for LV and RV
6) pass to purkinje fibers --> ventricles

14

Valves on either side of AV _____ conduct electrical signal

DO NOT

15

Why does signal delay when it reaches AV node?

allows atria time to contract before ventricles contract

16

mean what?

P wave
QRS
T wave

atrial depol
ventricular depol
ventricular repol

17

PR interval means

index of conduction

time across AV node

18

QT interval means

total duration of depol & repol

19

1st degree AV block

conduction delay but all P waves conduct to ventricles

PR prolonged

20

2nd degree AV block

some P waves conduct but others don't

21

3rd degree AV block

complete block
no P waves conduct & ventricular pacemaker takes over

22

Three mechanisms by which cardiac conduction cause tachyarrhythmias

abnormal reentry pathways

ectopic foci

triggered activity --> abnormal afterpolarizations

23

abnormal reentry pathways present where

atria
ventricles
junctional tissue

24

when does abnormal reentry pathway occur

unidrectional block and slowed conduction through reentry pathway
after slow reentry, previously depol tissue recovered

MOST COMMON MECHANISM OF SERIOUS TACHY

25

ectopic foci

area of myocardium outside conduction system acquires automaticity

if rate of depol > SA node --> abnormal rhythm occurs

26

triggered activity

abnormal afterpolarizations by preceding AP

early afterpolarization before AP fully repol --> tachyarrhythmia

delayed afterpol appear after AP is complete --> arrhythmia