Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Yr 4 - ACC > Cardiology: Heart Block > Flashcards

Cardiology: Heart Block Flashcards

1
Q

What is atrioventricular (AV) block (heart block)?

A

The partial or complete interruption of impulse transmission from the atria to the ventricles.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the most common cause of AV block?

A

Idiopathic fibrosis & sclerosis of the conduction system.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What investigations are required in all patients presenting with AV block?

A

1) ECG: to help determine the subtype of AV block

2) Labs (e.g. FBC, U&Es, TSH, troponin): to rule out underlying causes

3) Echocardiogram: to rule out structural heart disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the 4 subtypes of AV block?

A

1) First-degree AV block

2) Second-degree AV block (type 1)

3) Second-degree AV block (type 2)

4) Third-degree (complete) AV block

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does first degree AV block involve?

A

The consistent prolongation of the PR interval (defined as >0.2 seonds) due to delayed conduction via the AV node.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What PR interval defines 1st degree heart block?

A

> 0.2 seconds i.e. >5 small squares

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the PR inverval on an ECG?

A

The PR interval represents the time between atrial depolarisation and ventricular depolarisation.

From the beginning of the P wave to the beginning of the QRS interval.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is every P wave is followed by in 1st degree heart block?

A

A QRS complex (i.e. there are no dropped QRS complexes, unlike some other forms of AV block).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are some causes of 1st degree heart block?

A

First-degree AV block is common and can often be an incidental finding.

1) Enhanced vagal tone: often seen in athletes (non-pathological)

2) Post myocardial infarction

3) Lyme disease

4) SLE

5) Congenital

6) Myocarditis

7) Electrolyte derangements

8) Drugs: particularly AV blocking drugs such as beta-blockers, rate-limiting calcium-channel blockers, digoxin and magnesium

9) Thyroid dysfunction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Who can first degree AV block often be seen in?

A

Athletes (non pathological)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

ECG findings in 1st degree AV block?

A

1) rhythm: regular

2) P wave: every P wave is present and followed by a QRS complex

3) PR interval: prolonged >0.2 seconds (5 small squares)

4) QRS complex: normal morphology and duration (<0.12 seconds)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Typical history & exam findings in 1st degree heart block?

A

Patients are usually asymptomatic.

Clinical examination is normally unremarkable.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What drugs can cause 1st degree heart block?

A

AV blocking drugs:

1) beta blockers

2) rate limiting calcium channel blockers e.g. diltiazem, verapamil

3) digoxin

4) magnesium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Complications of 1st degree heart block?

A

First-degree AV block does not usually progress to higher grade AV blocks.

Those with first-degree AV block may be at an increased risk of atrial fibrillation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the 2 types of 2nd degree heart block?

A

1) Type 1: Mobitz type 1 AV block or Wenckebach phenomenon.

2) Type 2: Mobitz type 2 AV block.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What occurs in Mobitz type 1 AV block?

A

There is progressive prolongation of the PR interval until eventually the atrial impulse is not conducted, and the QRS complex is dropped.

AV nodal conduction resumes with the next beat and the sequence of progressive PR interval prolongation and the eventual dropping of a QRS complex repeats itself.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Who is second-degree AV block (type 1) often seen in?

A

Often seen in athletes (non-pathological)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Causes of second-degree AV block (type 1)?

A

1) Increased vagal tone: often seen in athletes (non-pathological)

2) Drugs: beta-blockers, calcium channel blockers, digoxin, amiodarone

3) Inferior myocardial infarction

4) Myocarditis

5) Cardiac surgery (mitral valve repair, Tetralogy of Fallot repair)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What type of MI can cause econd-degree AV block (type 1)?

A

Inferior MI - as the RCA supplies the AV node.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

ECG findings in second-degree AV block (type 1)?

A

1) Rhythm: irregular

2) P wave: every P wave is present, but not all are followed by a QRS complex

3) PR interval: progressively lengthens before a QRS complex is dropped

4) QRS complex: normal morphology and duration (<0.12 seconds), but are occasionally dropped

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Clinical features & exam findings in patients with second-degree AV block (type 1)?

A

History:
- Usually asymptomatic
- Some can develop symptomatic bradycardia and present with symptoms such as pre-syncope and syncope.

Exam:
- Irregular pulse
- Bradycardia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Complications of second-degree AV block (type 1)?

A

The patient may become haemodynamically compromised, although this is rare.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Management osecond-degree AV block (type 1)?

A

Usually, no intervention is required if the patient is asymptomatic. If the patient is symptomatic a pacemaker may be considered.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What happens in second-degree AV block (type 2) (Mobitz type 2 AV block)?

A

There is a consistent PR interval duration with intermittently dropped QRS complexes due to a failure of conduction.

The intermittent dropping of the QRS complexes typically follows a repeating cycle of every 3rd (3:1 block) or 4th (4:1 block) P wave.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Cause of second-degree AV block (type 2)?

A

Mobitz type 2 AV block is always pathological:

1) MI

2) Idiopathic fibrosis of the conducting system (Lenegre’s or Lev’s disease)

3) Cardiac surgery (especially surgery occurring close to the septum such as mitral valve repair)

4) Inflammatory conditions (rheumatic fever, myocarditis, Lyme disease)

5) Autoimmune (SLE, systemic sclerosis)

6) Infiltrative myocardial disease (amyloidosis, haemochromatosis, sarcoidosis)

7) Hyperkalaemia

8) Drugs (e.g. beta-blockers, calcium channel blockers, digoxin, amiodarone)

9) Thyroid dysfunction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Where does the block typically occur in 2nd degree AV block (type 2)?

A

1) Bundle branches (80%)
2) Bundle of His (20%)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

PR interval in second degree heart block type 1 and 2?

A

Type 1: progressive prolongation of the PR interval until a dropped beat occurs

Type 2: PR interval is constant but the P wave is often not followed by a QRS complex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

ECG findings in second-degree AV (type 2)?

A

1) Rhythm: irregular (may be regularly irregular in 3:1 or 4:1 block)

2) P wave: present but there are more P waves than QRS complexes

3) PR interval: consistent normal PR interval duration with intermittently dropped QRS complexes

4) QRS complex: normal (<0.12 seconds) or broad (>0.12 seconds)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

When will the QRS complex be broad in second-degree AV block (type 2)?

A

The QRS complex will be broad if the conduction failure is located distal to the bundle of His.

30
Q

Symptoms & exam findings in second-degree AV block (type 2)?

A

Symptoms:
- palpitations
- pre-syncope
- syncope

Exam:
- ‘regularly irregular’ pulse

31
Q

Complications of second-degree AV block (type 2)?

A

1) Risk of progressing to symptomatic complete AV block, in which the escape rhythm is likely to be ventricular and thus too slow to maintain adequate systemic perfusion.

2) Patients are also at risk of developing asystole.

32
Q

Management of second-degree AV block (type 2)?

A

1) Patients should be placed on a cardiac monitor as soon as possible (due to risk of progression to complete AV block).

2) Investigate underlying cause

3) Temporary pacing or isoprenaline may be required if the patient is haemodynamically compromised due to bradycardia.

4) A permanent pacemaker is usually inserted if there are no reversible causes identified.

33
Q

What happens in third-degree (complete) AV block?

A

Occurs when there is no electrical communication between the atria and ventricles due to complete failure of conduction.

ECG will show P waves and QRS complexes that have no association with each other, due to the atria and ventricles functioning independently.

34
Q

Third-degree (complete) AV block can consist of:

1) Narrow-complex escape rhythms

2) Broad-complex escape rhythms

What are narrow-complex escape rhythms?

A

1) QRS complexes of <0.12 seconds duration

2) Originate above the bifurcation of the bundle of His

35
Q

Typical heart rate in narrow-complex escape rhythms in third degree heart block?

A

> 40 bpm

36
Q

What are broad-complex escape rhythms in 3rd degree heart block?

A

1) QRS complexes >0.12 seconds duration

2) Originate from below the bifurcation of the bundle of His

3) These escape rhythms produce slower, less reliable heart rates and more significant clinical features (e.g. heart failure, syncope).

37
Q

Desribe QRS complexes in narrow-complex escape rhythms

A

QRS complexes of <0.12 seconds duration

38
Q

Where do narow-complex escape rhythms in 3rd degree heart block originate from?

A

Above the bifurcation of the bundle of His

39
Q

Where do broad-complex escape rhythms in 3rd degree heart block originate from?

A

Originate from below the bifurcation of the bundle of His.

40
Q

Desribe QRS complexes in broad-complex escape rhythms

A

QRS complexes >0.12 seconds duration

41
Q

Describe HR in road-complex escape rhythms in 3rd degree heart block

A

These escape rhythms produce slower, less reliable heart rates and more significant clinical features (e.g. heart failure, syncope).

42
Q

Causes of third-degree (complete) AV block?

A

1) Congenital: structural heart disease (e.g transposition of the great vessels), autoimmune (e.g maternal SLE)

2) Idiopathic fibrosis: Lev’s disease (fibrosis of the distal His-Purkinje system in the elderly) and Lenegre’s disease (fibrosis of the proximal His-Purkinje system in younger individuals)

3) Ischaemic heart disease: myocardial infarction, ischaemic cardiomyopathy

4) Non-ischaemic heart disease: calcific aortic stenosis, idiopathic dilated cardiomyopathy, infiltrative disease (e.g. sarcoidosis, amyloidosis)

5) Iatrogenic: post-ablative therapies and pacemaker implantation, post-cardiac surgery

6) Drug-related: digoxin, beta-blockers, calcium channel blockers, amiodarone

7) Infections: endocarditis, Lyme disease, Chagas disease

8) Autoimmune conditions: SLE, rheumatoid arthritis

9) Thyroid dysfunction

43
Q

What are some iatrogenic causes of 3rd degree heart block?

A

1) post-ablative therapies

2) pacemaker implantation

3) post-cardiac surgery

44
Q

ECG findings in 3rd degree heart block?

A

1) Rhythm: variable

2) P wave: present but not associated with QRS complexes

3) PR interval: absent (as there is atrioventricular dissociation)

4) QRS complex: narrow (<0.12 seconds) or broad (>0.12 seconds) depending on the site of the escape rhythm (see introduction)

45
Q

Symptoms & exam findings in 3rd degree heart block?

A

Symptoms:
- palpitations
- pre-syncope/syncope
- confusion
- SOB (due to HF)
- chest pain
- sudden cardiac death

Exam:
- Irregular pulse
- Profound bradycardia
- Haemodynamic compromise (e.g. prolonged capillary refill time and hypotension)

46
Q

Management of 3rd degree heart block?

A

1) Place on cardiac monitor

2) Transcutaneous pacing/temporary pacing wire or isoprenaline infusion may be required. Some rhythms (particularly narrow-complex escape rhythms) may respond to atropine.

3) A permanent pacemaker is usually required.

47
Q

What is the main complication of 3rd degree heart block?

A

sudden cardiac death due to ventricular arrhythmias

48
Q

How do electrical impulses travel through the heart?

A

1) The sinoatrial node (SAN) acts as the initial pacemaker

2) The impulse spreads throughout the atria and towards the atrioventricular node (AVN)

3) The depolarisation wave travels through the heart’s septum via the Bundle of His and Purkinje fibres.

4) These then divide into the left and right bundle branches

5) The right bundle branch depolarises the right ventricle, and the left bundle branch depolarises the left ventricle simultaneously.

6) The septum is depolarised by the left bundle branch, resulting in the septum being depolarised from left to right.

49
Q

What is the septum depolarised by?

A

The LBBB

50
Q

What do the following ECG components represent:

1) p wave
2) PR interval
3) QRS complex
4) T wave

A

1) Atrial depolarisation

2) Conduction through the AVN to the ventricles

3) Ventricular depolarisation

4) Ventricular repolarisation

51
Q

Normal cardiac conduction:

A

1) The sino-atrial node acts as the initial pacemaker

2) Depolarisation reaches the atrioventricular node

3) Impulses travel simultaneously down the bundle of His via the left and right bundle branches. The septum is depolarised from the left.

4) Both the left and right ventricular walls are depolarised simultaneously.

52
Q

What is the main feature of bundle branch blocks?

A

The broadening of QRS complexes.

53
Q

Why are the P waves and PR intervals normal in bundle branch blocks?

A

As the problem is below the atria.

54
Q

What is the diagnostic criteria for RBBB?

A

1) Broad QRS complex: >120 ms (3 small squares)

2) RSR’ pattern in V1-V3: an initial small upward deflection (R wave), a larger downward deflection (S wave), then another large upward deflection (a second R wave, which is indicated as R’)

3) Wide, slurred S wave in lateral leads: I, aVL, V5-V6

55
Q

The WiLLiaM MaRRoW mnemonic can be used to quickly recognise left and right bundle branch blocks.

What leads are looked at?

A

V1 and V6

56
Q

What does ‘MaRRoW’ refer to in BBB?

A

Refers to the ECG appearance of right bundle branch block.

1) M: complexes in V1 resemble the letter M: initial small upward deflection (r wave), a larger downward deflection (S wave), then another large upward deflection (second R wave)

2) W: complexes in V6 resemble a W: initial small downward deflection (Q wave), then a larger upward deflection (R wave), and then a wide downward deflection (S wave)

57
Q

Pathophysiology in RBBB?

A

1) The SA node acts as the initial pacemaker

2) Depolarisation reaches the AV node

3) Depolarisation through the bundle of His occurs only via the left bundle branch. The left branch still depolarises the septum as normal.

4) The left ventricular wall depolarises as normal.

5) The right ventricular walls are eventually depolarised by the left bundle branch, this occurs by a slower, less efficient pathway.

58
Q

Cause of RBBB?

A

1) can be physiological

2) damage to the right bundle branch

59
Q

What are the causes of damage to the right bundle branch?

A

1) lung pathology:
- COPD
- pulmonary emboli
- cor pulmonale

2) Primary heart muscle disease (ARVC)

3) Congenital heart disease (e.g. ASD)

4) Ischaemic heart disease

5) Primary degeneration of the right bundle

60
Q

What is the diagnostic criteria for LBBB?

A

1) Broad QRS complex: >120 ms (3 small squares)

2) Dominant S wave in V1

3) Broad, monophasic R wave in lateral leads: I, aVL, V5-V6

4) Absence of Q waves in lateral leads

5) Prolonged R wave >60ms in leads V5-V6

61
Q

What does ‘WiLLiaM’ refer to in BBB?

A

W: complexes in V1 resemble the letter W: deep downward deflection (dominant S wave), which may be notched

M: complexes in V6 resemble the letter M: broad, notched or ‘M’ shaped R wave in V6

62
Q

Pathophysiology of LBBB?

A

1) The SA node acts as the initial pacemaker

2) Depolarisation reaches the AV node

3) Depolarisation down the bundle of His occurs only via the right bundle branch. The septum is abnormally depolarised from right to left.

4) The right ventricular wall is depolarised as normal.

5) The left ventricular walls are eventually depolarised by the right bundle branch, this occurs by a slower, less efficient pathway.

63
Q

Cause of LBBB?

A

LBBB is always pathological.

1) conduction system degeneration

2) myocardial pathologies e.g. ischaemic heart disease, cardiomyopathy and valvular heart disease.

3) may also occur after cardiac procedures

64
Q

What does the left bundle branch split into?

A

Anterior and posterior fascicles.

65
Q

Each branch of the left bundle branch may be damaged in isolation.

Is anterior or posterior fascicular block more common?

A

Anterior fascicle is much more common.

66
Q

What does anterior fascicle block result in?

A

Left axis deviation.

67
Q

What does posterior fascicle block result in?

A

Right axis deviation.

However, the posterior fascicle does much less work than the anterior fascicle, so it can be blocked without any obvious ECG changes.

68
Q

What is bifascicular block?

A

This involves both the RBBB and blockade of one of the fascicles of the left bundle branch.

69
Q

What is trifascicular block?

A

When a 3rd-degree heart block exists alongside bifascicular block.

70
Q
A

Yr 4 - ACC (73 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions