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CVS > Arrhythmias and Conduction Defects > Flashcards

Arrhythmias and Conduction Defects Flashcards

1
Q

What is the pathway for the normal conduction of electrical activity in the heart?

A

Electrical activity is generated at the SAN, where it spreads over the two atria. From the SAN and atria, the electrical activity reaches the AVN, where there is a slight delay. This delay allows the ventricle time to fill with blood. Following the delay, conduction moves down the Bundle of his to Purkinge Fibres, and moves up the ventricles causing ventricular contraction from bottom up

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2
Q

How can you identify a sinus rhythm on an ECG?

A

There is a P wave before every QRS complex

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3
Q

What are the types of arrhythmias and conduction defects

A 
Atrial Fibrillation (AF) - most common
Atrial Flutter
Complete Heart Block
Ventricular Tachycardia
Supraventricular Tachycardia (SVT)
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4
Q

What are the causes of Atrial Fibrillation?

=> Mnemonic - SMITH

A 
S - Sepsis
M - Mitral Valve Pathology
I - Ischaemic Heart Disease
T - Thyrotoxcosis
H - Hypertension
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5
Q

What are the clinical features of AF?

A

=> Often asymptomatic

  • Dyspnoea
  • Chest pain
  • Palpitations
  • Syncope
  • Irregularly irregular pulse
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6
Q

Why is there a coagulation risk in AF?

A

As atria are not contracting properly, there is stasis of the blood. Stasis is one of the factors in Virchow’s triad, and therefore results in the formation of blood clots. These blood clots may embolise, travelling up the Left Carotid Artery and entering the Circle of Willis. This can cause an ischaemic stroke

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7
Q

How is AF categorised?

A
  • First detected episode
  • Recurrent episodes - 2 or more
  • Permanent AF - AF lasting 7 days or more
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8
Q

What are the investigations carried out in suspected AF?

A

=> ECG

  • P waves missing
  • Irregularly irregular pulse
  • Narrow QRS complex tachycardia

=> Blood tests

  • U&E
  • Cardiac enzymes
  • TFTs

=> Echocardiogram which may show:

  • Left atrial enlargement
  • Mitral Valve disease
  • Poor LV function
  • Other structural abnormalities
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9
Q

What is the management of AF?

A

=> Principles of treatment:

  • Rate or rhythm control
  • Anticoagulation to prevent stroke

=> All patients should have rate control as first line UNLESS:

  • Younger than 65
  • Reversible cause of AF
  • AF < 48 hours
  • AF is causing heart failure
  • Remain symptomatic despite effective rate control
  • First presentation

=> Options for rate control:

  • First line: B blockers
  • Ca blockers
  • Digoxin

=> Rhythm control offered to following patients:

  • Age < 65
  • History of ischaemic heart disease
  • Reversible cause of AF
  • AF < 48 hours
  • AF causing heart failure
  • Remain symptomatic despite effective rate control
  • First presentation

=> Options for rhythm control

  • Pharmacological cardioversion
  • Electrical cardioversion

=> Cardioversion - immediate or delayed?

  • Immediate if AF < 48 hours or haemodynamically unstable
  • Delayed if AF > 48 hours and stable. For delayed cases, patient should be anti-coagulated for 3 weeks before cardioversion

=> Pharmacological cardioversion:

  • Flecanide
  • Amiodarone in cases of structural abnormalities
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10
Q

How is the risk of coagulation determined?

A

CHA2DS2VASc score:
Score 0 - no risk
Score 1 - If man then start treatment. Female not started as they have only reached a score of 1 because of their gender
Score 2 or more - start treatment regardless of gender

HAS BLED score also used

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11
Q

What is the main cause of Atrial Flutter?

A

Due to re-entry circuit in the right atrium around tricuspid. This results in blood stasis hence there is a coagulation risk. Overtime the ventricle decompensate

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12
Q

What is the main investigation in cases of Atrial Flutter?

A

ECG - Leads I and II show a tooth like shape

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13
Q

What is the management of Atrial Flutter?

A

Controlling rate and rhythm as with Atrial Fibrillation

RATE : B blockers
RHYTHM: Cardioversion and drugs - flecainide

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14
Q

What are the causes of heart block?

A
  • Coranary Artery Disease
  • Cardiomegaly
  • AV node blocking agent
  • Anti-arrhythmic drugs

A block can occur anywhere in the conduction pathway, at the AVN or the bundle branches in the interventricular septum

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15
Q

What are the different types of Heart Block?

A
  • Atrioventricular Block - first degree, second degree, third degree
  • Right Bundle Branch Block (RBBB)
  • Left Bundle Branch Block (LBBB)
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16
Q

What are the categories of AV Block?

A

First degree - prolonged PR interval. There is no change in HR therefore no treatment is required

Second degree - There are 2 types:

MOBITZ TYPE 1 - Gradually increasing PR interval and dropped QRS complex

MOBITZ TYPE 2 - Fixed prolonged PR interval and dropped QRS complex

Third Degree - Atria and ventricles completely out of sync. PR interval and QRS complex completely dissociated

17
Q

What is the management of second degree heart block?

A

Pacemakers and monitoring

18
Q

What are the clinical features of Heart Block?

A
  • Bradycardia
  • Syncope
  • Fatigue
  • Chest Pain
  • Dyspnoea
19
Q

What is the management of Heart Block in general?

A

If acute and rate VERY low, IV atropine

20
Q

What are the causes of Right Bundle Branch Block?

A
  • PE
  • RV hypertrophy
  • Ischaemic Heart Disease
  • Congenital Heart Disease
21
Q

What can be seen on the ECG of Right Bundle Branch Block?

A

M pattern on V1 - MaRRow

M for M pattern and R indicating RBBB

22
Q

What are the causes of Left Bundle Branch Block?

A
  • Ischaemic Heart Disease
  • LV hypertrophy
  • Aortic Valve Disease
  • Cardiac Surgery
23
Q

What can be seen on the ECG of Left Bundle Branch Block?

A

W pattern on V1 - WiLLiam

W for W pattern and L for LBBB

24
Q

What is Ventricular Tachycardia and what are its causes?

A

VT is very fast HR originating form the ventricles

Causes:

  • Re-entry pathways
  • Ventricles begin to control HR as opposed to SAN
25
Q

What are the clinical signs of VT?

A

Occur as ventricles fail to relax and fill with blood, reducing CO and decreasing perfusion

  • Tachycardia
  • Dyspnoea
  • Hypotension
  • Weak Pulse
  • Dizziness/ light headedness
  • Chest pain
  • Irregular HR
26
Q

What does an ECG show in VT?

A

Wide complex tachycardia

27
Q

What is the management of Acute VT?

A

Is the patient haemodynamically stable?

YES - Immediate cardioversion

NO - Antiarrhythmic drugs (Amiodarone or lidocaine). If thse fail then electrical cardioversion

=> If drug therapy fails:

  • EPS
  • Defibrillator
28
Q

What is the management of long term VT?

A

Defibrillator

29
Q

What are the adverse signs?

A
  • Shock (systolic BP<90)
  • Syncope
  • MI
  • Heart Failure

If any of these signs are seen in a patient, emergency management is needed depending on whether tachycardia or bradycardia

=> In cases of tachycardia:
- synchronised DC shock

=> In cases of bradycardia:
- IV atropine

30
Q

What are the NICE guidelines for AF post-stroke?

A
  • Warfarin, direct thrombin or factor Xa inhibitor
  • In acute stroke patients in the absence of a bleed, anticoagulation therapy should be commenced post 2 weeks
  • Antiplatelets, eg Aspirin, are only given is cases of comorbidities
31
Q

What is the CHADSVASc Score?

A

C - Congestive Heart Failure - 1

H - Hypertension - 1

A - Age ≥ 75 - 2
or Age 65 to 74 - 1

D - Diabetes - 1

S - Prior to Stroke or TIA - 2

V - Vascular Disease - 1

S - Sex (Female) - 1

This score determines whether there is a need to anti-coagulated a patient long term, not the same as delayed cardioversion where they are only anti-coagulated for 3 weeks

32
Q

What is an ECG with absent P waves and narrow complex bradycardia indicative of?

A

Atrial Fibrillation with a slow ventricular response

33
Q

What drug is contraindicated in VT?

A

Verapamil

34
Q

What is the main characteristic of Supraventricular Tachycardia on an ECG?

A

Narrow Complex Tachycardia

35
Q

What is the management of SVT?

A
  • Vagal manouvers
  • IV Adenosine
  • Electrical cardioversion
36
Q

What are the medications taken to prevent episodes of SVT?

A
  • B blockers

- Radio frequency ablation

37
Q

What is Torsades de Pointes?

A

Polymorphic VT associated with a long QT, which can progress into a VF and cause sudden death

38
Q

What are the causes of a long QT interval?

A

=> Congenital causes:

  • Jervell-Lange-Nielsen syndrome
  • Romano-Ward syndrome

=> Anti-arrhythmics:

  • Amiodarone
  • Sotalol
  • Class 1a antiarrhythmic drugs

=> Other drugs:

  • Tricyclic antidepressants
  • Antipsychotics
  • Chloroquines
  • Tefenadine
  • Macrolides (Erythromycin)

=> Electrolyte imbalances:

  • Hypocalcaemia
  • Hypokalaemia
  • Hypomagnesia

=> Other causes:

  • Subarachnoid haemorrhage
  • Hypothermia
  • Myocarditis
39
Q

What is the management of Torsades de pointes?

A

IV magnesium sulphate

CVS (12 decks)

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