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1ST YR CARDIO > Cardiac Arrhythmias > Flashcards

Cardiac Arrhythmias Flashcards

1
Q

What kind of abnormal anatomy can cause an arrhythmia?

A
  • Left ventricular hypertrophy - Accessory pathways - Congenital Heart Disease
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2
Q

What can be causes of arrhythmias in relation to the autonomic nervous system?

A
  • Sympathetic stimulation (stress, exercise, hyperthyroidism) - Increased vagal tone (parasympathetic system - causes bradycardia)
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3
Q

What metabolic factors can cause arrhythmias?

A
  • Hypoxia (chronic pulmonary disease, PE) - Ischaemia Myocardium (acute MI or angina) - Electrolyte imbalances (K+, Ca2+, Mg2+)
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4
Q

What type of inflammation can cause arrhythmias?

A

Viral myocarditis

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5
Q

How can drugs cause arrhythmias?

A

Direct electrophysiological effects or via the ANS

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6
Q

What genetic factors can cause arrhythmias?

A

Mutations of genes encoding cardiac ion channels (e.g. congenital long QT syndrome)

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7
Q

What are the two electrophysiological mechanisms?

A
  • Ectopic Beats
  • Re-entry
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8
Q

What are ectopic beats?

A

When the heart skips a beat or adds an extra beat

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9
Q

How are ectopic beats caused?

A

Beats / rhythms originating in places other than the SA node - Altered automaticity - Triggered activity

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10
Q

What is altered automaticity?

A
  • The cell depolarising itself - So accelerated generation of action potential by either normal pacemaker tissue or abnormal tissue within the myocardium
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11
Q

Give two examples of when altered automaticity occurs?

A
  • Ischaemia (when cardiac cells lack oxygen they become depolarized) - Catecholamines (i.e. adrenaline)
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12
Q

What is triggered activity?

A

Impulse initiation that depend on afterdepolarisations (Oscillations in membrane potential after an action potential)

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13
Q

What are two examples that cause triggered activity?

A
  • Digoxin (increases automaticity in His-purjinke system) - Long QT syndrome (affects repolarisation)
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14
Q

What is Re-entry?

A

Continuous circulating activity, where an impulse re-enters and continuously excites a certain region of the heart

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15
Q

What are three examples of conditions related to re-entry?

A
  • Accessory pathway tachycardia (extra pathway between hearts atria and ventricles) - Previous myocardial infarction (scarring) - Congenital heart disease
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16
Q

What causes re-entry?

A

Ectopic beats (premature)

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17
Q

How does an increase in phase 4 slope of the action potential affect the heart?

A

Increase heart rate

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18
Q

What causes an increase in phase 4 of the action potential?

A

Hyperthermia Hypoxia Hypercapnia Cardiac dilation Hypokalaemia (prolongs repolarisation)

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19
Q

How does a decrease in phase 4 slope of the action potential affect the heart?

A

Slowed conduction - bradycardia - heart block

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20
Q

What causes the decrease in phase 4 slope of the action potential?

A

Hypothermia Hyperkalaemia

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21
Q

What is the mechanism of triggered activity?

A
  • In phase 3 of the action potential an afterdpolarisation occurs - This afterdepolarisation may reach a depolarisation threshold - This can lead to a sustained train of triggered depolarisations
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22
Q

What is the mechanism of re-entry?

A

There is a slow depolarisation and fast depolarisation on one circuit. - Fast depolarisation leaves behind a long refractory period - When a premature beat occurs the slow action potential goes along the circuit and finishes the circuit when the refractory period wears off. - After this it splits at the end and one half goes back round and splits at the start - The whole thing starts again

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23
Q

What are the two characteristics of the fast action potential?

A
  • fast depolarisation - long refractory period
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24
Q

What are the two characteristics of the slow action potential?

A
  • slow depolarisation - short refractory period
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25
Q

What are the main symptoms of arrhythmias?

A

Palpitations SOB Dizziness Syncope Faintness (presyncope) Sudden cardiac death Angina Heart Failure

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26
Q

What are the usual investigations carried out to determine an arrhythmia?

A
  • 12 lead ECG - CXR - Echocardiogram - Stress ECG - 24 Hour ECG - Event recroder - Electrophysiological (EP) study
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27
Q

What is an ECG used for?

A
  • Assess rhythm - Shows signs of… - Previous MI (q waves) - Pre-excitation (wpw syndrome)
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28
Q

What is an exercise ECG used for?

A
  • Assess ischaemia - Shows exercise induced arrhythmias
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29
Q

What is the purpose of 24 hour Holter ECG?

A
  • assess for paroxysmal arrhythmia - link symptoms to underlying heart rhythm
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30
Q

Purpose of an echocardiography?

A

Assesses for structural heart disease e.g. - enlarged atria in AF - LV dilation - Previous MI scar - Aneurysm

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31
Q

Purpose of an EP study?

A
  • Triggers the arrhythmia to study its mechanism - May be able to treat by delivering radiofrequency ablation to the extra pathway (destroys the tissue)
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32
Q

What is a normal sinus arrhythmia?

A
  • Variation in heart rate due to changes in vagal tone from the respiratory cycle - on inspiration vagal tone is reduces so heart rate increases
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33
Q

What are common extrinsic causes of sinus bradycardia?

A

Hypothermia

Hypothyroidism

Raised intracranial pressure

Drug Therapy (BETA BLOCKERS, DIGOXIN etc.)

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34
Q

What are common intrinsic causes pf bradycardia?

A

Acute ischaemia/ infarction of the sinus node

Chronic Degenrative changes (e.g. fibrosis and shock sinus syndrome)

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35
Q

What heart rate is required to be classed as bradycardia?

A

Under 60 beats/min

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36
Q

What mechanisms could cause bradycardia?

A
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37
Q

What is the treatment for bradycardia?

A

Atropine (if acute e.g. acute MI)

Pacing if haemodynamic compromise (i.e. hypotension collapse)

38
Q

What heart rate is required to be classed as sinus tachycardia?

A

Heart rate over 100 beats/min

39
Q

What cause cause sinus tachycardia?

A

Anxiety

Fever

Hypertension

Anaemia (heart compensates for lack of red blood cells)

Drugs

40
Q

What is the treatment for sinus tachycardia?

A

Treat te underlying cause

Beta-adrenergic blockers

41
Q

What are symptoms of atrial ectopic beats?

A

Can be asymptomatic

Palpitations

42
Q

What is the treatment for atrial ectopic beats?

A

Generally no treatment

Beat blockers may help

Avoid stimulants e.g. coffee

43
Q

What are the three main causes of regular supraventricular tachycardia

A
  • AV nodal re-entrant tachycardia (AVNRT)
  • AV re-entrant tachycardia (via accessory pathway) (AVRT)
  • Ectopic atrial tachycardia (EAT)
44
Q

What is AV nodal re-entrant tachycardia (AVNRT)?

A

There are two different pathways within the AV node, one with slow conudction and fast refarctory period the other with fast conduction and long refarctory period

  • In sinus rhythm the impulse normally conducts through the fast pathway
  • If atrial impusle is premature when fast pathway is still refractory, slow pathway takes over
  • then travels back through fast pathway which has already recovered its excitability causing the “slow-fast”
  • Thus AVRNT
45
Q

What is atrioventricular re-entrant tachycardia?

A

Atrial activation occurs after ventricular activation

  • SO P wave is seen between the QRS and T wave
  • Re-entry occurs outside of AV node through an accessory pathway made of myocardial fibres from ventricles back to the atrium (multiple pathways can occur)
46
Q

What are AVRT patients more prone to?

A

Atrial fibrillation

47
Q

What do AVRT patients show on their ECG?

A
  • P wave is seen between the QRS and T wave
  • Narrow QRS complexes
  • Short PR interval
  • Delta wave: slurred beggining of the QRS complex
48
Q

What is AVRNT the most common cause for?

A
49
Q

What is seen on an AVNRT patients ECG?

A
  • Narrow QRS complexes
  • P waves cannot be seen
50
Q

What are the three types of AVRT?

A
  • Pre-excitation
  • Orthodromic AVRT
  • Antidromic AVRT
51
Q

What is pre-excitation AVRT?

A

Premature conduction through accessory pathways

  • Short PR interval
52
Q

What is orthodromic AVRT?

A

Forward moving conduction through the atrioventricular node

  • No delta wave
  • Retrograde P-wave after QRS
53
Q

What is antidormic AVRT?

A

Retrograde conduction through atrioventricular node

  • Wide QRS complex with delta wave
  • P wave rarely seen
54
Q

What is the management for acute supraventricular tachycardia?

A

Increase vagal tone

Slow condcution in the AVN

  • IV adenosine
  • IV verapamil (calcium channel blockers)
55
Q

What is the management for chronic supraventricular tachycardia management?

A
  • Avoid stimulants
  • EP study and radiofrequency abltation
  • Beta blockers
  • Antiarrhythmic drugs (i.e. sodium channel blockers, beta blockers, potassium channel blockers and calcium channel blockers)
56
Q

What are some causes of heart block?

A
  • Age
  • Acute MI
  • Myocarditis
  • Drugs (beta blockers, calcium channel blockers
  • Aortic valve disease
  • Post-aortic valve surgery
  • Genetic
57
Q

What is a first degree heart block?

A
  • PR interval longer than normal
  • Conduction follows each P wave so not really a block
  • More advanced block could form so long term follow up is required
58
Q

What is a 2nd degree heart block?

A

Some P waves conduct, others do not (intermittent block at AV node)

  • Two types; Mobitz I and Mobitz II
59
Q

What is Mobitz I?

A
  • Progressive lengthening of the PR interval
  • Eventually results in a dropped beat
  • Vagal tone is usual origin
60
Q

What is Mobitz II?

A
  • Pathological
  • Could develop into complete heart block
  • QRS is wide
  • Dropped QRS complex is not preceded by progressive PR intrverval prolongation
  • Only every second or third P wave conducts to the ventricle
  • Permanant pacemaker required
61
Q

What is 3rd degree AV heart block (complete heart block)?

A
  • Complete heart block
  • All atrial activity fails to conduct to the ventricles
62
Q

What are the causes of ventricular ectopics?

A
  • LVH
  • Herat failure
  • Myocarditis
  • Ischaemic heart disease
  • Inherited cardiac condition
  • Exercise
  • Beta-blockers
63
Q

What are some features of ventricular tachycardia?

A
  • Life threatening but may be haemodynamically stable
  • Most patients have significant heart disease
  • Cardiomyopathy can be a rare cause
  • Brugada and long QT syndrome could also be rare causes
64
Q

What are some ECG characteristics that help define VTs?

A
  • Rapid, wide and distorted QRS
  • Large T waves
  • Regular rhythm
  • P waves not usually visible
  • PR interval not measureable
65
Q

What is the treatment used to treat acute VT?

A
  • Direct current cardioversion (DCCV)
  • If stable use antiarrhythmic drugs whilst preparing for DCCV
  • Consider adenosine to make diagnosis if unsure
66
Q

What is the long term treatment for VT

A
  • Correct ischaemia
  • Optimise CHF therapies
  • Anti-arrhythmic drugs CAUSE WORSE OUTCOMES
  • If life threatening use implantable cardiovertor defibrillators (ICD)
  • VT catheter ablation
67
Q

What is the most serious arrhythmia?

A

Ventricular tachycardia

68
Q

What can ventricular fibrillation lead to?

A

Heart attack

69
Q

What effects can supraventricular tachycardia have?

A
  • Syncope
  • Severe SOB
70
Q

What is more serious?

  • supraventricular arrhythmias

OR

  • Ventricular arrhythmias
A

Ventricular arrhythmias

71
Q

What is supraventricular tachycardia?

A
  • Where the heart occasionally breats around 150-250 beats per minute
  • more commonly occurs in young people
  • can be caused by caffeien, stress and alcohol
72
Q

What is atrial fibrillation a big cause of?

A

Stroke

73
Q

How can atrial fibrillation cause strokes?

A
  • Causes pools of blood to form in the upper chambers of the heart
  • Can lead to blood clots
  • These blood clots can travel up to the brain
74
Q

What is Wolff-Parkinson White syndrome?

A
  • Extra muscle pathways between atria and ventricles
  • Thse pathways cause electrical signals to arrive at the ventricles too soon
  • So signal is sent back too soon
  • Causes a very fast heart rate
75
Q

WPW syndrome can predispose someone to what other arrhythmia?

A

Supraventricular tachycardia

76
Q

What is atria flutter?

A

Atria beat very fast affecting the efficiency of the ventricles to pump blood

77
Q

What is postural orthostatic tachycardia syndrome?

A
  • When standing up the blood vessels to do not contrsict in some people to keep the blood flow moving to the brain
  • The heart tries to make up for this by pumping faster
  • iIf the heart cannot pump fast enough, less blood is pumped to the brain
  • Causing lightheadedness, syncope and blurry vision
78
Q

How do heart blocks occur?

A

When the SA node sends the signal correctly but it is not sent through the AV node or lower electrical pathways as quickly as it should be

79
Q

What can be the cause of heart block?

A
  • Ageing
  • Swelling/scarring of the heart caused by coronary artery disease
  • Cardiac amyloidosis (protein deposits take the place of cardiac muscle)
80
Q

What is sick sinus syndrome?

A
  • SA node isnt sending inpulses properly
  • Heart rate alternates between bradycardic and tachycardic
  • Can be caused by scarring along the sinus node
81
Q

What arrhythmia is this ECG indicative of?

  • Heart rate <60bpm
  • Normal P wave before every QRS
A

Sinus Bradycardia

82
Q

What arrhythmia is this ECG indicative of?

  • PR interval >200ms
A

First Degree AV block

83
Q

What arrhythmia is this ECG indicative of?

  • Progressive lengthening of the PR interval until a beat is dropped
A

Second degree AV block Mobitz I

84
Q

What arrhythmia is this ECG indicative of?

  • Irregular dropped beats
A

Second degree AV block Mobitz II

85
Q

What arrhythmia is this ECG indicative of?

  • No relationship between P waves and QRS complexes
A

Third degree AV block

86
Q

What arrhythmia is this ECG indicative of?

  • Regular rhythm
  • Tachycardic
  • P waves occur before every QRS
  • Sawtooth appearance of P waves in II, III and aVF
  • Narrow QRS complex
A

Atrial FLutter

87
Q

What arrhythmia is this ECG indicative of?

  • Rhythm irregularly irregular
  • Rate is 350-450 bpm
  • Unclear P waves
  • Narrow QRS complex
A

Atrial Fibrillation

88
Q

What arrhythmia is this ECG indicative of?

  • Abrupt onset
  • Regular rhythm
  • Rate 150-250
  • Inverted P wave
  • P wave occurs after the QRS complex
  • May contain a delta wave (slurred QRS and short PR interval)
A

Atrioventricular Reentry Tachycardia (AVRT)

89
Q

What arrhythmia is this ECG indicative of?

  • Regular rhythm
  • Rate 150-250
  • P waves either not visible or after QRS complex
  • Narrow QRS complex
A

Atrioventricular Nodal Reentry Tachycardia (AVRNT)

90
Q

What arrhythmia is this ECG indicative of?

  • Regular, rapid rhythm
  • Wide QRS complexes
  • AV dissociation (P waves may not be visible)
A

Ventricular Tachycardia

91
Q

What arrhythmia is this ECG indicative of?

  • Associated with long QT syndrome
  • Rapid, irregular QRS complexes twisting around the baseline
A

Torsade de Pointes

92
Q

What arrhythmia is this ECG indicative of?

  • Heart rate >300bpm
  • Arrhythmic fibrillatory baseline
  • Erratic undulations with non visible QRS complexes
A

Ventricular Fibrillation

1ST YR CARDIO (6 decks)

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