Year 3: Cardiovascular > Heart block (Complete*) > Flashcards

Heart block (Complete*) Flashcards

(29 cards)

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1
Q

Define heart block

A

Impaired electrical conduction between atria and ventricles

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2
Q

Heart block is also known as?

A

AVN block

N.B. Sinoatrial node block rarely leads to syndrome as AVN acts as secondary pacemaker

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3
Q

What are the main types of heart block?

A

First degree heart block

Second degree heart block: Type I (AKA Mobitz Type I)

Second degree heart block: Type II (AKA Mobitz Type II)

Third degree heart block

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4
Q

What are the characteristic features of first degree heart block on ECG?

A

Consistent prolonged PR interval

  • PR interval >0.20s [200ms] (>5 small squares)

No dropping of QRS complex

N.B. PR segment is end of P wave to start of Q wave

N.B. PR interval = start of wave to start of Q wave. (number of small squares x 0.04s)

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5
Q

What are the main causes of first degree heart block?

A

High vagal tone (normal variant)

  • Young healthy adults
  • Athletes

Acute inferior MI

  • RCA supplies AVN

Drugs (especially in elderly patients)

  • Beta-blockers
  • Rate limitting CCBs (Non-DHBs)
  • Cholinesterase inhibitors
  • Digoxin
  • Magnesium

Electrolyte abnormalities (e.g. hyperkalaemia)

Myocarditis

Lyme disease

SLE

Valvular abscess (infective endocarditis)

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6
Q

List examples of drugs which can cause first degree heart block.

A

Beta-blockers

Digoxin

Cholinesterase inhibitors (e.g. rivastigmine used to treat Alzheimer’s)

Non-DHP CCBs (e.g. fendilline, verapamil)

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7
Q

How is first degree heart block managed?

A

Stop AVN blocking drugs and manage reversible causes

Benign treatment so no treatment needed

N.B. Can consider pacemaker in some symptomatic cases

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8
Q

What are the ECG features of second degree heart block type I (Mobitz type I)/Wenckebach?

A

Characterised by increasing PR interval prolongation followed by failure of P wave to conduct a QRS complex.

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9
Q

What are causes of mobitz type I?

A

Inferior MI (most common cause)

Professional athletes due to high vagal tone (normal variant)

Drugs

Myocarditis

Cardiac surgery (e.g. CHD repair)

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10
Q

What is the most common cause of second-degree heart block type I?

A

Inferior MI

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11
Q

What is the management plan for Mobitz type I?

A

Generally assympyomatic and does not require management as risk of complete heart block is low.

Stop AVN blocking drugs

If symptoms do arise:

Cardiac monitoring ECG

Consider atropine if bradycardia (anticholinergic)

N.B. My rarely be considered for pacemaker if symptomatic

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12
Q

How does second-degree heart block type I differ to SA node block type I?

N.B. Both called wenckebach for some reason so better to just call them by second-degree type I/ SAN block type I respectively.

A

Normal PR interval

Progressively shortening P-P interval

N.B. Dont mistake P-P interval with PR interval

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13
Q

What is second degree heart block type II (Mobitz type II)?

A

Normal PR interval + intermittent non-conducted P waves

Unlike Type I, the PR interval isnt increasingly prolonged

Unlike first-degree, causes non-conducted P waves

N.B. Caused by failure in the bundle of his/purkinje system

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14
Q

Which type of second-degree heart block is almost always pathological?

A

Mobitz type II

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15
Q

Which conducting structures are most likely to be affected in mobitz type II?

A

Bundle branches (80%)

Bundle of His (20%)

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16
Q

What are causes of Mobityz type II?

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A

Idiopathic fibrosis (Lenegre’s disease)

  • Most common, especially in older adults

Anterior MI

  • Damages bundle of His

Medications

Inflammatory/autoimmune disease

  • Rheumatic heart disease
  • SLE
  • Myocarditis
  • Systemic sclerosis

Infiltration

  • Amyloidosis
  • Sarcoidosis
  • Haemochromatosis

Surgery: Mitral repair or septal ablation (used in treatment of hypertrophic cardiomyopathy).

17
Q

What is the most common cause of mobitz type II?

Study These Flashcards
A

Lenegres disease (Idiopathic fibrosis)

18
Q

Which type of MI causes mobitz type II?

Study These Flashcards
A

Anterior MI

N.B. LAD supplies bundle of his and branches

19
Q

Which type of cardiac surgery most commonly causes mobitz type II?

Study These Flashcards
A

Mitral valve repair

Septal ablation

  • Used in management of HCOM
20
Q

What is the management plan for patients with Mobitz type II?

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A

Conservative:

Continous cardiac monitoring

Acute management: IF BRADYCARDIA or haemodynamically unstable

Follow bradycardia management algorithm

  • Treat regardless of symptoms for mobitz type II block due to high risk of asystole

Surgical:

Definitive: Permament pacemaker

N.B. Need to be on pacemaker as there is a high risk of complete heart block

21
Q

Pacemaker ECG

22
Q

What is complete heart block? (aka third degree)

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A

Type of heart block characterised by:

Severe bradycardia

Desynchronisation between P waves and QRS complex

23
Q

What are the main signs/symptoms of complete heart block?

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A

Syncope

Cardiac arrest

Bradycardia (30-50bpm)

Wide pulse pressure

JVP canon waves

S1 variable intensity

ECG findings: Severe bradycardia, diassociation of P and QRS complex

24
Q

What signs on cardiac examination may be seen in patients with complete heart block?

Study These Flashcards
A

Bradycardia (30-50bpm)

Wide pulse pressure

  • Difference between SBP and DBP >100 mmHg

JVP canon waves

S1 variable intensity

25
JVP canon A waves ## Footnote [https://www.youtube.com/watch?v=c71OwG91fF8](http://)
N.B. Can be seen as right atrium contracts against a closed tricuspid valve. This happens in situations where atria and ventricles are not coordinated
26
What are causes of complete heart block?
Myocardial infarction (especially inferior MI) Drugs: Beta-blockers, CCB Idiopathic fibrosis (aka Lenegre's disease)
27
What is the management plan for patients with complete heart block?
**_Acute management_**: Follow bradycardia management algorithm * If assymptomatic, treat if complete heart block with **broad QRS complex** **_Long-term management_**: Permament pacemaker This is due to high risk of sudden cardiac death
28
Patients should be advised not to drive how long after pacemaker insertion?
Group 1 drivers (Cars, motorcyles): 1 week Group 2 driver (Bus,lorries): 6 weeks
29
When would you start with 3 shocks followed by compressions during cardiac arrest?
Monitored, immediately witnessed cardiac arrest in following areas if a defibrillator is immediately available: Cath lab Critical care area Coronary care unit After cardiac surgery | In normal cases its 1 shock followed by compressions
Year 3: Cardiovascular
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