Arrhythmias and Anti-arrhythmic drugs Flashcards Preview

Cardiovascular: pharmacology > Arrhythmias and Anti-arrhythmic drugs > Flashcards

Flashcards in Arrhythmias and Anti-arrhythmic drugs Deck (84)
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1

There are two main electrical dysfunction mechanisms. You can have defects in impulse ______ or impulse ______.

There are two main electrical dysfunction mechanisms. You can have defects in impulse formation or impulse conduction.

2

what are the two defects in Impulse formation?

1. SA node automaticity is interrupted or altered (missed beats, ectopic beats)
2. triggered activity

3

There are physiological ways that the SA node activity is modulated e.g. by the ANS (e.g. sinus tachycardia, sinus arrhythmia (this is quite common in _____ people)
However it is also pathological - for example ____ _______.

There are physiological ways that the SA node activity is modulated e.g. by the ANS (e.g. sinus tachycardia, sinus arrhythmia (this is quite common in young people)
However it is also pathological - for example latent pacemakers.

4

what are latent pacemakers?

these are pacemakers outwith the SA node which are just waiting to take over the pacemaking activity i.e overdrive suppression is lost.

5

which two circumstances allow latent pacemakers to activate?

1. when the SA node AP firing frequency is pathologically low or when there is a problem with the conduction of the SA node
2. might also occur if a latent pacemaker firs at a rate which is faster than the SA node firing rate.

6

with a low SA node firing frequency you get an ______ escape beat - latent pacemaker initiates the impulse e.g. the AP is not generated by SA node activity, it has escaped the normal overdrive.

escape beat - latent pacemaker initiates the impulse e.g. the AP is not generated by SA node activity, it has escaped the normal overdrive.

7

when might SA node firing frequency be low?

during intense vagal stimulation

8

with a fast latent pacemaker firing frequency you get an ____ beat

ectopic

9

give some causes of an ectopic rhythm

ischaemia, hypokalaemia, increased sympathetic activity, fibre stretch

10

what are the two kinds of triggered activity?

EAD, DAD

11

which part of the heart often causes EAD?

the purkinje fibres

12

during which two phases do EADs incite the AP?

phase 2 (terminal plateau) and phase 3 (repolarisation)

13

In phase 2 what is the EAD mediated by ?

Ca channels - the repolarisation happens quicker than it would normally

14

In phase 3 what is the EAD mediated by ?

Na channels - they recover from inactivation

15

what is EAD associated with?

prolongation of AP and drugs (e.g. sotalol) prolonging the QT interval (the interval between depolarisation and repolarisation).

16

what dangerous rhythm can EAD lead to?

ventricular fibrillation

17

when do DADs occur?

after complete repolarisation

18

what are DADs associated with?

Ca overload

19

what provokes the Ca overload in DAD?

catecholamines, digoxin, heart failure

20

what are the three mechanisms for defects in impulse conduction?

re-entry, conduction block, accessory tracts

21

what is re-entry?

a self sustaining electrical circuit (anatomically may be due to parallel conduction pathways) which stimulates an area of myocardium repeatedly/ rapidly

22

re-entry
1. normal conduction:
We have a conduction pathway in the heart (possibly the purkinje fibres) which divides into two branches. There is a ______ area between the two branches. APs will travel down both branch 1 and 2 and from these branches they will enter into a mass of _____. The APs try to negotiate their way around the ____ area and this is not normally a problem. The two APs from branch 1 and 2 then meet in the ____ and ______ each other

We have a conduction pathway in the heart (possibly the purkinje fibres) which divides into two branches. There is a non-excitable area between the two branches. APs will travel down both branch 1 and 2 and from these branches they will enter into a mass of ventricle. The APs try to negotiate their way around the non-excitable area and this is not normally a problem. The two APs from branch 1 and 2 then meet in the middle and extinguish each other

23

Re-entry
2. abnormal conduction:
There is _______ conduction block meaning that the AP in branch 1 is ____ but the AP in branch 2 _____ ____ forward - (anterograde conduct).

There is unidirectional conduction block meaning that the AP in branch 1 is fine but the AP in branch 2 cannot conduct forward - (anterograde conduct).

24

re-entry conditions are satisfied if
- the AP is not allowed to progress down its normal direction of branch i.e. unidirectional block - anterograde conduction ______
- the AP can go in the wrong direction but _____ slowly. The AP goes down branch 1, it then goes round the island of non-conducting tissue however, there is no _______ of AP. The AP will continue in a right hand direction but will also go up branch 2 very slowly in a ______ conduction.

- the AP is not allowed to progress down its normal direction of branch i.e. unidirectional block - anterograde conduction prohibited

- the AP can go in the wrong direction but abnormally slowly. The AP goes down branch 1, it then goes round the island of non-conducting tissue however, there is no extinguishing of AP. The AP will continue in a right hand direction but will also go up branch 2 very slowly in a retrograde conduction.

25

why is the slow retrograde in re-entry important?

if means that branch 1 is no longer refractory - ie has recovered from inactivation so the AP meets excitable tissue once more without an impulse having to come from the point before branching

26

what is the movement of APs in a circle called?

circus movement

27

what is first degree AV block?

the tissue conducts all impulses but more slowly than usual

28

what happens in intermittent block?

the tissue conducts some impulses but not others - example second degree AV block

29

accessory tracts - some individuals possess electrical pathways that bypass the _____. Conduction through accessory pathways is relatively ____-

some individuals possess electrical pathways that bypass the AV node
conduction through accessory pathways is relatively rapid

30

name a common accessory tract pathway

bundle of kent