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Cardiovascular Science > Cardiac arrhythmicity > Flashcards

Cardiac arrhythmicity Flashcards

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1
Q

List the cardiac pacemakers in order of fastest to slowest

A

Sinoatrial node
Atrioventricular node
Bundle of His
Purkinje fibres

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2
Q

What is the pace of the SA node?

A

60-100 beats/min

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3
Q

What is the pace of the AV node?

A

40-60 beats/min

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4
Q

What is the pace of the bundle of His?

A

40-60 beats/min

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5
Q

What is the pace of the Purkinje fibres?

A

20-40 beats/min

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6
Q

What three tracts come off the SA node?

A

Anterior: Bachman’s bundle
Middle: Weckenbach’s
Posterior: Thorel’s

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7
Q

Describe an SA node action potential

A 
4
0
3
4
Smooth
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8
Q

Describe a ventricular action potential

A 
4
0
1
2
3
4
Pointy
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9
Q

How is a signal propagated in the heart?

A

From cell to cell

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10
Q

What does the heart form?

A

A functional syncytium

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11
Q

What allows the passage of ions between cells?

A

Gap junctions

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12
Q

What is the effect of the sympathetic nervous system on SA node action potential?

A

Sympathetic nervous system speeds up action potential

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13
Q

What is the effect of the parasympathetic innervation of the SA node?

A

Slows down action potentials

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14
Q

What is happening at phase 4 in the SA node?

A

Spontaneous depolarisation
Slow influx leakage of Na+
Slow leakage of Ca2+

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15
Q

What is happening at phase 0 in the SA node?

A

Depolarisation
Influx of Ca2+
Through L-type channels

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16
Q

What is happening at phase 3 in the SA node?

A

Repolarisation
Efflux of K+
No Ca2+ comes in

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17
Q

What is happening at phase 0 in the AV node?

A

Rapid depolarisation

Influx of Na+

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18
Q

What is happening at phase 1 in the AV node?

A

Partial repolarisation
Na+ stops coming in
K+ efflux

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19
Q

What is happening at phase 2 in the AV node?

A

Plateau phase
K+ efflux
Ca2+ influx

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20
Q

What is happening at phase 3 in the AV node?

A

Repolarisation
K+ efflux
No movement of Ca2+

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21
Q

What is happening at phase 4 in the AV node?

A 
Ventricle diastole
Pacemaker depolarisation
Ions return to original location
Via Na+/K+ATPase
Na+/Ca2+ transporter
Ca2+ ATP pump
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22
Q

What is the absolute refractory period?

A

A second action potential cannot be generated

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23
Q

What is the PQRST complex?

A

A heart beat seen on the ECG

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24
Q

What is P to R?

A

Atrial systole

Ventricle diastole

25
Q

What is R to S?

A

Isovalemic contraction
AV valves close
Valves out of the heart are not open

26
Q

What is S to T?

A

Ventricle systole

Ejecting blood

27
Q

What is the T wave?

A

Isovalemic relaxation

Ventricles are relaxing but not filling with blood

28
Q

What is T to P?

A

Ventricles filling with blood

29
Q

What is R to T?

A

Ventricle contraction

30
Q

Define arrhythmia

A

A disturbance in the rate, rhythm, or pattern with which the heart contracts

31
Q

How many people in the UK have arrhythmias?

A

2 million

32
Q

What causes arrhythmia?

A

Coronary artery disease leading to myocardial ischemia or infarction
Structural changes that accompany heart failure
Drugs
Electrolyte imbalance
Congenital defects

33
Q

What are consequences of arrhythmias?

A

Produce vascular stasis (e.g. atrial fibrillation)

Reduce cardiac output

34
Q

What is the primary classification of arrhythmias?

A

Anatomical origin

35
Q

What are supraventricular arrhythmias?

A 
Originate higher up the conduction route than the ventricle
e.g. 
Sinus bradycardia
Sinus tachycardia
Atrial tachycardia
Atrial fibrillation
AV block
Wolff-Parkinson-White syndrome
36
Q

What are ventricular arrhythmias?

A 
Originate in the ventricle
e.g. 
Ventricular premature beats
Salvos
Bigemini
Ventricular tachycardia
Ventricular fibrillation
Torsades de Points
37
Q

What is an ECG

A

Electrocardiogram

Measures the change in electrical field during propagation of a cardiac action potential

38
Q

What does the PR interval tell us?

A

Time of conduction through the AV node

39
Q

What does the QT interval tell us?

A

Duration of ventricular action potential

40
Q

What are the two classifications of arrhythmia based on mechanisms?

A

Disturbances in conduction

Disturbances in impulse formation

41
Q

What is the most common conduction block?

A

Complete block of the forward movement of the action potential between the SA node and the ventricular myocardium

42
Q

What would be the result of a block in the Weckenbach’s bundle?

A

Reduced ventricular rate

43
Q

What would be the result of a block in the bundle of His?

A

Asystole (no ventricular contraction)

Bradycardia

44
Q

What would be the result of a block in either branch of the purkinje system?

A

No change in heart rate but reduced cardiac output

45
Q

What makes the heart more susceptible to re entry?

A

When conduction velocity is slow and the cardiac cells spend less time in a refractory state

46
Q

What makes re entry less likely?

A

Long wavelength

47
Q

What must happen for re entry to occur?

A

Presence of a unidirectional block within a conduction pathway
Critical timing
Refractory state of normal tissue that the wavefront encounters

48
Q

What might be the cause of slow conduction velocity?

A

Ischemia

49
Q

Are re entrant arrhythmias confined to one heart chamber?

A

No

50
Q

What shape do reentrant arrhythmias form?

A

Spiral

51
Q

What is ventricular tachycardia?

A

Ventricular rates generally around 100 to 200 beats per minute

52
Q

What is ventricular fibrillation?

A

Life threatening

Many small waves propagate throughout the ventricles

53
Q

What is atrial flutter?

A

Atrial rates of 250-350 beats per minute

Ventricular rate substantially slower

54
Q

What is atrial fibrillation?

A

Rapid atrial rate (350-600 beats per minute) not immediately life threatening

55
Q

What are the two kinds of disturbance in impulse formation?

A

Early delayed after depolarisations

Delayed after depolarisations

56
Q

What does triggered activity mean?

A

Refers to a situation where heart tissue is stimulated once but results in the production of more than one conducted beats

57
Q

What are early delayed after depolarisations?

A

Prolonged action potential duration is necessary for generation
Can contribute to initiation of arrhythmia syndrome, Torsades de pointes

58
Q

What is Torsades de Pointes?

A

Drug induced blockade of K+ channel leads to prolonged action potential depolarisation
If net inward currents are larger than outward currents during phase 3 this causes an EAD
Causes multifocal ventricular tachycardia

59
Q

What are delayed after depolarisations?

A

Cellular Ca2+ overload in the SR
Phasic release of Ca2+
Depolarising inward current

Cardiovascular Science (12 decks)

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