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Year 3 - Medicine > Cardiology - Arrhythmias > Flashcards

Cardiology - Arrhythmias Flashcards

1
Q

What is bradycardia?

A

A heart rate of less than 60bpm.

Absolute bradycardia = HR < 40bpm

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2
Q

What are some causes of sinus bradycardia?

A
  • medications
  • hypothyroidism
  • hypothermia
  • sleep apnoea
  • rheumatic fever
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3
Q

What is first degree heart block?

A

Occurs where there is delayed atrioventricular conduction through the AV node, causing a prolonged PR interval (>0.20 seconds).

Despite delayed conduction, every atrial impulse leads to a ventricular contraction, meaning every p wave results in a QRS complex.

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4
Q

What are the types of second degree heart block?

A
  • Mobitz Type 1 (Wenckebach’s phenomenon)
  • Mobitz Type 2
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5
Q

What is Mobitz Type 1 heart block (Wenckenbach’s phenomenon)?

A

Occurs due to increasingly delayed atrioventricular conduction through the AV node, followed by failure of the atrial impulse to conduct to the ventricles.

On ECG, this shows as progressive lengthening of the PR interval, finally resulting in a QRS complex being dropped.

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6
Q

What is Mobitz Type 2 heart block?

A

Occurs when there is a constant PR interval, followed by a sudden failure of a P wave to be conducted to the ventricles.

Note there is a risk of asystole with Mobitz Type 2.

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7
Q

What is third degree (complete) heart block?

A

Characterised by no conduction from the atria to the ventricles, meaning there is no relationship between the P waves and QRS complexes.

Note there is a significant risk of asystole with complete heart block.

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8
Q

What are some common causes of third degree (complete) heart block?

A
  • digoxin toxicity
  • inferior STEMI
  • severe hyperkalaemia
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9
Q

How should a stable bradycardia / AV node block be treated?

A

Observe

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10
Q

How should unstable bradycardia / AV node block with risk of asystole be treated?

A
  • Atropine 500mcg IV
  • noradrenaline
  • transcutaneous cardiac pacing (using a defibrillator)

Definitive management includes placing a permanent implantable pacemaker.

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11
Q

What is the most common cardiac arrhythmia encountered in clinical practice?

A

Atrial fibrillation (AF)

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12
Q

What is atrial fibrillation?

A

Occurs when contraction of the atria is uncoordinated, rapid and irregular due to disorganised electrical activity that overrides the normal, organised activity from the SA node.

On ECG there will be absence of p waves.

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13
Q

What are the consequences of atrial fibrillation?

A
  • irregularly irregular ventricular contractions
  • tachycardia
  • heart failure (due to poor filling of ventricles during diastole)
  • risk of stroke*

*As there is haemostasis within the atria, thrombosis can occur and result in emboli. The emboli can travel to the brain and block the cerebral arteries, causing an ischaemic stroke.

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14
Q

Presentation of atrial fibrillation.

A
  • asymptomatic
  • palpitations
  • dyspnoea
  • syncope
  • symptoms of associated conditions (e.g. stroke, sepsis)
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15
Q

What are the differential diagnoses for an irregularly irregular pulse?

A
  • atrial fibrillation
  • ventricular ectopics

These can be differentiated using an ECG. An ECG should be performed on everyone with an irregularly irregular pulse.

Ventricular ectopics disappear when the heart rate gets over a certain threshold. Therefore a regular heart rate during exercise suggests a diagnosis of ventricular ectopics.

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16
Q

What is meant by valvular and non-valvular atrial fibrillation?

A

Valvular AF is defined as patients with AF who also have moderate or severe mitral stenosis, or a mechanical heart valve.

Non-valvular AF without valve pathology, or with other valve pathology such as mitral regurgitation or aortic stenosis, is classed as non-valvular AF.

In valvular AF, the assumption is that the valvular pathology has led to AF.

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17
Q

What are the most common causes of atrial fibrillation?

A

AF affects mrs SMITH:

Sepsis
Mitral valve stenosis
Ischaemic heart disease
Thyrotoxicosis
Hypertension

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18
Q

What is paroxysmal atrial fibrillation?

A

Intermittent atrial fibrillation, where the AF comes and goes in episodes, lasting no longer than 48 hours.

Short term cardiac monitoring with a 24 hour cardiac monitor is considered the first line investigation.

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19
Q

What are the principles to treating atrial fibrillation?

A
  • rate control
  • rhythm control
  • anticoagulation to prevent stroke
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20
Q

NICE guidelines (2014) suggest all patients with atrial fibrillation should have rate control as first line unless:

A
  • there is a reversible cause for their AF
  • their AF is of a new onset (<48 hours)
  • their AF is causing heart failure
  • they remain symptomatic despite being effectively rate controlled
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21
Q

What are the options for rate control in atrial fibrillation?

A
  • beta blocker first line
  • calcium channel blocker (not preferable in heart failure)
  • digoxin (only in sedentary people, needs monitoring and risk of toxicity)
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22
Q

Rhythm control can be offered to patients with atrial fibrillation where:

A
  • there is a reversible cause for their AF
  • their AF is of new onset (<48 hours)
  • their AF is causing heart failure
  • they remain symptomatic despite being effectively rate controlled
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23
Q

Outline the principles behind rhythm control in atrial fibrillation.

A

Cardioversion events can put a patient back into sinus rhythm, or long term medical rhythm control can sustain normal rhythm.

24
Q

When considering cardioversion for rhythm control of atrial fibrillation, there is a choice between immediate cardioversion and delayed cardioversion.

A

Immediate cardioversion if the AF has been present for <48 hours or they are severely haemodynamically unstable.

Delayed cardioversion if the AF has been present for >48 hours and they are haemodynamically stable.

Note in delayed cardioversion, the patient should be anticoagulated for a minimum of 3/52 prior to cardioversion.

Anticoagulation is essential because during the 48 hours prior to cardioversion they may have developed a blood clot in the atria and reverting them back to sinus rhythm carries a high risk of mobilising that clot and causing a stroke.

25
Q

How can cardioversion be delivered to a patient with atrial fibrillation?

A

Pharmacological cardioversion:
- flecanide
- amiodarone (pts with structural heart disease)

Electrical cardioversion - sedation or general anaesthetic, and using a cardiac defibrillator, to deliver controlled shocks to restore sinus rhythm.

26
Q

What is the treatment of paroxysmal atrial fibrillation?

A

“Pill in the pocket” approach - take a pill to terminate AF only when they feel the symptoms of AF to start.

Flecanide is the usual treatment for a “pill in the pocket” approach.

27
Q

Give the respective risk of stroke for a patient with atrial fibrillation who:

a) takes anticoagulation

b) does not take anticoagulation

A

a) 1%

b) 5%

28
Q

Which scoring system is used to decide whether a patient with atrial fibrillation should be started on anticoagulation?

A

CHA2DS2-VASc

Score:

0: no anticoagulation
1: consider anticoagulation
>1: offer anticoagulation

29
Q

CHA2DS2-VASc mnemonic:

A

C - congestive heart failure
H - hypertension
A2 - age >75yrs (+2)
D - diabetes
S2 - stroke or TIA previously (+2)

V - vascular disease
A - age 65-74yrs
S - sex (female)

30
Q

Which scoring system is used to assess bleeding risk for a patient commenced on anticoagulation?

A

ORBIT tool, based upon:

  • low Hb or haematocrit
  • age (>74yrs)
  • previous bleeding
  • GFR <60ml/kg/1.73m2
  • antiplatelet medication

https://www.mdcalc.com/calc/10227/orbit-bleeding-risk-score-atrial-fibrillation

ORBIT score can be compared to CHA2DS2-VASc score to inform decision on whether anticoagulation therapy is started in patients with AF.

31
Q

Outline the mechanism of action of warfarin in atrial fibrillation.

A

Warfarin is a vitamin K antagonist, blocking the functioning of several clotting factors and prolonging the prothrombin time.

32
Q

What is measured when commencing a patient on warfarin?

A

International normalised ratio (INR) to assess how anticoagulated the patient is by warfarin.

INR is a calculation of how the prothrombin time of the patient compares with the prothrombin time of a normal health adult:

INR of 1: normal prothrombin time
INR of 2: prothrombin time twice that of a normal adult
INR of 0.5: prothrombin time is half that of a normal adult

The target INR for AF is 2-3.

33
Q

What is the mechanism of action of apixaban in atrial fibrillation?

A

DOACs that inhibit factor Xa, preventing the conversion of fibrinogen to fibrin. This prevents thrombogenesis.

34
Q

What are the advantages of DOACs over warfarin?

A
  • no monitoring required
  • no major interaction problems
  • slightly better than warfarin at preventing strokes in AF
  • slightly less risk of bleeding than warfarin
35
Q

What is atrial flutter?

A

A re-entrant rhythm in either atrium, whereby the electrical signal re-circulates in a self-perpetuating loop due to an extra electrical pathway.

This stimulates atrial contraction at 300bpm - the signal makes its way to the ventricles every second lap due to the long refractory period to the AV node, causing 150bpm ventricular contraction.

Gives a ‘sawtooth’ pattern on ECG.

36
Q

What are the causes of atrial flutter?

A
  • hypertension
  • ischaemic heart disease
  • cardiomyopathy
  • thryotoxicosis
37
Q

What is the treatment of atrial flutter?

A

As per atrial fibrillation:
- rate and rhythm control
- treat underlying condition
- anticoagulation based upon CHA2DS2-VASc & ORBIT score
- radiofrequency ablation of the re-entrant rhythm

38
Q

What is supraventricular tachycardia?

A

Ventricular tachycardia caused by the electrical signal re-entering the atria from the ventricles, resulting in fast narrow complex tachycardia.

39
Q

What is atrioventricular nodal re-entrant tachycardia?

A

Supraventricular tachycardia caused by a re-entry point back through the AV node.

40
Q

What is atrioventricular re-entrant tachycardia?

A

Supraventricular tachycardia caused by a re-entry point through an accessory pathway (Wolff-Parkinson-White syndrome).

ECG Changes:

Short PR interval (< 0.12 seconds)
Wide QRS complex (> 0.12 seconds)
“Delta wave” which is a slurred upstroke on the QRS complex

41
Q

What is atrial tachycardia?

A

Supraventricular tachycardia caused by an ectopic signal originating in the atria somewhere other than the SA node (ectopic electrical activity).

42
Q

What is the acute management of patients with supraventricular tachycardia?

A
  1. Valsava manoeuvre
  2. Carotid sinus massage
  3. Adenosine
  4. Direct current cardioversion
43
Q

What is the mechanism of action of adenosine in the treatment of supraventricular tachycardia?

A

Anti-muscarinic blocking vagal input to the AV node, resetting the heart to normal sinus rhythm.

It will cause a brief episode of asystole or bradycardia, however it is quickly metabolised and so sinus rhythm should return quickly.

44
Q

What is the long term management of patients with paroxysmal supraventricular tachycardia?

A
  • medication (beta blockers, CCBs)
  • radiofrequency ablation
45
Q

What is radiofrequency ablation?

A

Catheter ablation is performed in a electrophysiology laboratory, often called a “cath lab”. It involves local or general anaesthetic, inserting a catheter in to the femoral veins and feeding a wire through the venous system under xray guidance to the heart.

Once in the heart it is placed against different areas to test the electrical signals at that point. This way the operator can hopefully find the location of any abnormal electrical pathways. The operator may try to induce the arrhythmia to make the abnormal pathways easier to find.

Once identified, radiofrequency ablation (heat) is applied to burn the abnormal area of electrical activity. This leaves scar tissue that does not conduct the electrical activity. The aim is to remove the source of the arrhythmia.

46
Q

Radiofrequency ablation can be curative for which cases of arrhythmia?

A
  • atrial fibrillation
  • atrial flutter
  • supraventricular tachycardia
  • Wolff-Parkinson-White syndrome
47
Q

What are ventricular ectopics?

A

Premature ventricular beats caused by random electrical discharges from outside of the atria. Patients often present complaining of random, brief palpitations.

They can be diagnosed by ECG.

48
Q

What is the management of ventricular ectopics?

A
  • FBCs (anaemia)
  • U&Es (electrolyte disturbances)
  • TFTs (hyperthyroidism)

Reassure and no treatment in healthy patients; if patient has a background of heart disease, seek expert advice.

49
Q

What are the four cardiac arrest rhythms?

A
  • ventricular tachycardia
  • ventricular fibrillation
  • pulseless electrical activity (PEA)
  • asystole
50
Q

What are pacemakers?

A

Devices that deliver controlled electrical impulses to specific areas of the heart to restore the normal electrical activity and improve the heart function.

The box is implanted under the skin in the left anterior chest wall or axilla, and the wires are implanted into the relevant chambers of the heart.

51
Q

Give some indications for a pacemaker.

A
  • symptomatic bradycardias
  • Mobitz Type 2 AV block
  • third degree (complete) heart block
  • severe heart failure
  • hypertrophic obstructive cardiomyopathy
52
Q

What is a single chamber pacemaker?

A

Have leads in a single chamber:

Right atrium if the AV conduction in the patient is normal and the issue is with the SA node. They stimulate depolarisation of the right atrium, which spreads into the left atrium, and the ventricles via the AV node.

or

Right ventricle if the AV conduction in the patient is abnormal, allowing the pacemaker to directly stimulate the ventricles.

53
Q

What is a dual chamber pacemaker?

A

Dual chamber pacemakers have leads in both the right atrium and right ventricle, allowing the pacemaker to synchronise the contractions of both atria and ventricles.

54
Q

What is a biventricular (triple) pacemaker?

A

Leads in the right atrium, right ventricle and left ventricle allow the pacemaker to synchronise the contractions in these chambers, to optimise heart function.

Commonly used in heart failure. AKA cardiac resychronisation therapy (CRT) pacemakers.

55
Q

What are implantable cardioverter defibrillators (ICDs)?

A

Devices that continually monitor the heart and apply a defibrillator shock to cardiovert the patient back to sinus rhythm if they identify a shockable arrhythmia.

56
Q

ECG changes with pacemakers.

A

The pacemaker intervention can be seen as a sharp vertical line on all leads on the ECG trace. A line before each p-wave indicates a lead in the atria. A line before each QRS complex indicates a lead in the ventricles. Therefore:

A line before either the P or QRS but not the other indicates a single-chamber pacemaker
A line before both the P and QRS indicates a dual-chamber pacemaker

Year 3 - Medicine (33 decks)

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