Arrhythmias

Question 1

What are the causes of abnormal automaticity?

Answer 1

lack of cardiac blood supply (reflecting myocardial damage induced by cardiac ischaemia, which can make the resting membrane potential unstable)

hypokalaemia

catecholamine activity (involving excessive cardiac β1-adrenoceptor signalling in response to noradrenaline and adrenaline)

Question 2

What is required for Re entry

Answer 2

Central inexcitable region

Zone of slowed conduction

Zone of unidirectional block

Question 3

The myocardial cell absolute refractory period (RP) is typically an effective barrier to a _______________

Answer 3

Re-entrant impulse and inappropriate re-excitation.

Question 4

Explain what happens at each stage during heart block.

3rd degree

2nd degree

1st degree

Answer 4

complete heart block (no conduction)

fraction of impulses conducted

abnormally slow impulse conduction

Question 5

During heart block partial or complete failure of conduction by ___ of impulses from _______

Answer 5

AVN

SAN to ventricles

Question 6

what is arrhythmais?

Answer 6

Abnormalities in heart rate/rhythm

Question 7

another name for automaticity?

Answer 7

impulse generation

Question 8

Abnormalities in heart rate/rhythm caused by disorders of what?

Answer 8

*Impulse generation
Abnormal automaticity
Triggered automaticity

*Impulse conduction
Re-entry circuits
Heart block

Question 9

what drives normal or sinus rhythm and acts as the normal pacemaker in the acts?

Answer 9

sinoatrial node (SAN)

Question 10

abnormalities in heart rate or rhythm (abnormal automaticity, leading to departures from normal or sinus rhythm can lead to either _________ or _______________–

Answer 10

increase (tachyarrhythmia) or decrease (bradyarrthythmia) in pulse rate

Question 11

On some occasions, arrhythmias can lean to ______________

Answer 11

atrial or ventricular fibrillation (AF or VF), where cardiac contractions become chaotic and uncoordinated.

Question 12

explain the problems with atrial or ventricular fibrillation (AF or VF)?

Answer 12

This means the heart stops working as a single functional unit and this has immediate, lethal consequences for maintaining cardiac output in VF; while AF poses a major risk of stroke owing to atrial-centred thromboembolism. These rhythm abnormalities are underpinned by disorders either in the generation or conduction (i.e. transmission) of cardiac electrical impulses.

Question 13

what is abnormal automaticity?

Answer 13

Occurs when sinoatrial node (SAN) activity is overridden by abnormal (latent) pacemaker activity in cells of conduction system or myocardium
due to spontaneous impulse generation

Question 14

what is triggered automaticity?

Answer 14

Associated with extra depolarisation events arising during non-nodal cardiac action potential (afterdepolarisations), either at the end of phase 2, commencement of phase 3 (early afterdepolarisations (EADs)) or in phase 4 (delayed afterdepolarisations (DADs))

Question 15

What are the causes of triggered automaticity

Answer 15

excessive net inward depolarising current (in the case of EADs);

and intracellular calcium accumulation (in the case of DADs)

Question 16

Impulse generation may go awry in respect of what?

Answer 16

the establishment of re-entry circuits (where impulses are maintained in a perpetual circus movement)

the development of heart block (where impulses are delayed or not conducted at all between the atria and ventricles).

Question 17

what is re-entry

Answer 17

due to a circuit within the myocardium, re-entry occurs when a propagating impulse fails to die out after normal activation of the heart and persists as a result of continuous activity around the circuit to re-excite the heart after the refractory period has ended

Question 18

explain myocadiac cell absolute refractory period

Answer 18

The absolute refractory period of the cardiac muscle action potential refers to the time interval when the voltage gated sodium channels are inactivated

Question 19

The cause after-depolarizations is linked to what and what

Answer 19

is linked to excessive net inward depolarising current (in the case of EADs);

and intracellular calcium accumulation (in the case of DADs)

Question 20

what causes abnormal automaticity

Answer 20

spontaneous impulse generation

Question 21

AF poses a major risk of stroke because__________

Answer 21

due to atrial-centred thromboembolism

Question 22

what type of after depolarization for each phase

phase 2

phase 3

phase 4

Answer 22

phase 2- EADs

phase 3 - EADs

phase 4 - DADs