Cardiology: Arrhythmias Flashcards

1
Q

What are the 4 possible rhythms in a pulseless patient?

A

1) ventricular tachycardia
2) ventricular fibrillation
3) pulseless electrical activity
4) asystole

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2
Q

Cardiac arrest rhythms can be shockable or non-shockable.

Which rhythms are shockable? Which are unshockable?

A

Shockable:
- ventricular tachycardia
- ventricular fibrillation

Non-shockable:
- pulseless electrical activity
- asystole

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3
Q

What is pulseless electrical activity?

A

All electrical activity except VF/VT, including sinus rhythm without a pulse.

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4
Q

What is asystole?

A

When there is no significant electrical activity.

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5
Q

What is a narrow complex tachycardia?

A

A fast heart rate with a QRS <0.12 seconds.

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6
Q

What are the four main differentials of a narrow complex tachycardia?

What does the treatment for each focus on?

A

1) Sinus tachycardia: treatment focuses on the underlying cause

2) Supraventricular tachycardia: treated with vagal manoeuvres and adenosine

3) Atrial fibrillation: treated with rate control or rhythm control

4) Atrial flutter: treated with rate control or rhythm control, similar to atrial fibrillation

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7
Q

What is a broad complex tachycardia?

A

A fast heart rate with a QRS complex >0.12 seconds.

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8
Q

What are the 4 groups of broad complex tachycardia?

A

1) Ventricular tachycardia of unclear cause

2) Polymorphic ventricular tachycardia, such as torsades de pointes

3) Atrial fibrillation with bundle branch block

4) Supraventricular tachycardia with bundle branch block

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9
Q

VT can be divided in monomorphic VT and polymorphic VT.

What is the difference?

A

Monomorphic: characterised by a single, stable QRS morphology with no beat-to-beat variation.

Polymorphic: has beat-to-beat variation in QRS shape and multiple QRS morphologies.

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10
Q

What is monomorphic VT most commonly caused by?

A

Myocardial infarction.

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11
Q

How is ventricular tachycardia of unclear cause treated?

A

IV amiodarone

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12
Q

How is atrial fibrillation with bundle branch block treated?

A

Treated as AF

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13
Q

How is supraventricular tachycardia with bundle branch block treated?

A

Treated as SVT

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14
Q

How is polymorphic ventricular tachycardia, such as torsades de pointes treated?

A

Treated with IV magnesium.

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15
Q

What is the QT interval?

A

From the start of the QRS complex to the end of the T wave.

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16
Q

What is the corrected QT interval (QTc)?

A

This estimates the QT interval if the heart rate were 60 beats per minute.

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17
Q

What is a prolonged QTc?

A

Men: >440 milliseconds

Women: >460 milliseconds

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18
Q

What does a prolonged QT interval represent?

A

Prolonged repolarisation of the myocytes after a contraction.

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19
Q

What can prolonged repolarisation result in?

A

Waiting a long time for repolarisation can result in spontaneous depolarisation in some muscle cells.

These abnormal spontaneous depolarisations before repolarisation are known as afterdepolarisations.

These afterdepolarisations spread throughout the ventricles, causing a contraction before proper repolarisation.

20
Q

What is torsades de pointes?

A

A form of polymorphic ventricular tachycardia associated with a long QT interval.

Aterdepolarisations spread throughout the ventricles, causing a contraction before proper repolarisation. This leads to recurrent contractions without normal repolarisation.

21
Q

Complications of torsades de pointes?

A

1) Will terminate spontaneously and revert to sinus rhythm

OR

2) Will progress to ventricular tachycardia (can lead to cardiac arrest)

22
Q

What are some causes of a prolonged QT?

A

1) Long QT syndrome (inherited)

2) Medications, such as antipsychotics, citalopram, flecainide, sotalol, amiodarone and macrolide antibiotics

3) Electrolyte imbalances: hypokalaemia, hypomagnesaemia and hypocalcaemia

4) Myocarditis

5) Hypothermia

6) SAH

23
Q

What medications can cause a long QT interval?

A

1) Antiarrhythmics: amiodarone, sotalol, class 1a antiarrhythmic drugs

2) Tricyclic antidepressants

3) Antipsychotics

4) Citalopram

5) Chloroquine

6) Erythromycin

24
Q

What electrolyte abnormalities can lead to a long QT interval?

A

Hypocalcaemia, hypokalaemia, hypomagnesaemia

25
Q

Management of torsades de pointes?

A

IV magnesium sulphate

26
Q

Acute management of a prolonged QT interval?

A

1) If the patient has adverse signs (systolic BP < 90 mmHg, chest pain, heart failure) –> immediate cardioversion is indicated

2) In the absence of such signs –> antiarrhythmics

3) If these fail –> electrical cardioversion may be needed with synchronised DC shocks

27
Q

General management of a prolonged QT interval?

A

1) Stopping and avoiding medications that prolong the QT interval

2) Correcting electrolyte disturbances

3) Beta blockers (not sotalol)

4) Pacemakers or implantable cardioverter defibrillators

28
Q

What antiarrythmics are indicated in prolonged QT interval?

A

1) amiodarone (ideally administered through a central line)

2) lidocaine

3) procainamide

29
Q

Who should lidocaine be used with caution in?

A

Severe left ventricular impairment

30
Q

Why are dilitazem and verapamil contraindicated in patients with ventricular tachycardia?

A

IV administration of a calcium channel blocker can precipitate cardiac arrest in such patients.

31
Q

What are ventricular ectopics?

A

Ventricular ectopics are premature ventricular beats caused by random electrical discharges outside the atria.

32
Q

Who are ventricular ectopics common in?

A

1) They are relatively common at all ages and in healthy patients

2) More common in patients with pre-existing heart conditions (e.g. IHD, HF)

33
Q

How may ventricular ectopics appear on an ECG?

A

Ventricular ectopics appear as isolated, random, abnormal, broad QRS complexes on an otherwise normal ECG.

34
Q

What is bigeminy?

A

Refers to when every other beat is a ventricular ectopic.

The ECG shows a normal beat (with a P wave, QRS complex and T wave), followed immediately by an ectopic beat, then a normal beat, then an ectopic, and so on.

35
Q

Management of ventricular ectopics?

A

1) Reassurance and no treatment in otherwise healthy people with infrequent ectopics

2) Seeking specialist advice in patients with underlying heart disease, frequent or concerning symptoms (e.g., chest pain or syncope), or a family history of heart disease or sudden death

3) Beta blockers are sometimes used to manage symptoms

36
Q

What are some causes of bradycardia?

A

1) medicattions e.g. beta blockers

2) heart block

3) sick sinus syndrome

4) hypothyroidism

5) anorexia nervosa

6) raised ICP

etc etc

37
Q

What is sick sinus syndrome?

A

This encompasses many conditions that cause dysfunction in the SA node.

38
Q

What is sick sinus syndrome often caused by?

A

Idiopathic degenerative fibrosis of the SA node.

39
Q

What can sick sinus syndrome result in?

A

1) sinus bradycardia
2) sinus arrhythmias
3) prolonged pauses

40
Q

There is a risk of asystole in which heart conditions?

A

1) Mobitz type 2

2) Third-degree heart block (complete heart block)

3) Previous asystole

4) Ventricular pauses longer than 3 seconds

41
Q

What does management of unstable patients and those at risk of asystole involve?

A

1) IV atropine (1st line)

2) Inotropes (e.g. isoprenaline or adrenaline)

3) Temporary cardiac pacing

4) Permanent implantable pacemaker, when available

42
Q

What are 2 options for temporary cardiac pacing?

A

1) Transcutaneous pacing, using pads on the patient’s chest

2) Transvenous pacing, using a catheter, fed through the venous system to stimulate the heart directly

43
Q

What is atropine?

A

An antimuscarinic medication and works by inhibiting the parasympathetic nervous system.

44
Q

1st line medical management of asystole (or severe bradycardia)?

A

IV atropine

45
Q

Side effects of atropine?

A

Inhibiting the parasympathetic nervous system leads to side effects of pupil dilation, dry mouth, urinary retention and constipation.

46
Q
A