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Year 2 > Rhythm Of The Heart > Flashcards

Rhythm Of The Heart Flashcards

1
Q

What is the conducting system of the heart?

A

Electrical impulses begin in the SAN and travels to the AVN. This is transferred from the bundle of His to the left and right bundle branches and this travels along the ventricles to reach the myocardium and transmit along the Purkinje fibres to the ventricular muscles.

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2
Q

What is the septum of the ventricle?

A

Contains the Bundle of His. The left side of the septum is stimulated first by the Bundle of His, and initially there is an intermittent depolarisation from the left bundle of His to the right ventricle, but there is a large depolarisation of the left ventricle which spreads to the right across the septum.

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3
Q

What is the role of the SAN?

A

Pacemaker cells which responds to neural and hormonal stimuli to establish heart rate at 60-100bpm.

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4
Q

What is the role of the AVN?

A

Ensures there is a delay between impulse transmission between the atria and ventricles for efficient ventricular filling. If SAN fails, it can establish 40-60bpm heart rate.

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5
Q

What is the role of the His-Purkinje system?

A

Spread of electrical impulses rapidly and synchronously into the cardiomyocytes of the ventricles for contraction.

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6
Q

What is the P wave?

A

Atrial depolarisation.

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7
Q

What is the QRS complex?

A

Ventricular depolarisation and atrial depolarisation.

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8
Q

What is the T wave

A

Ventricular depolarisation.

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9
Q

What does a delay of the PR interval mean?

A

Delay in atrioventricular condition through AV node.

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10
Q

What does a delay in the QRS mean?

A

Slow conduction through the ventricular myocardium.

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11
Q

What does a delay in the QT interval indicate?

A

Issue with depolarisation of the ventricular myocardium.

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12
Q

How can rhythm of heart be determined?

A

Space between the R waves.

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13
Q

How to determine heart rate on graph?

A

Regular rhythm: no of large squares between 2 R intervals

Irregular rhythm: no of QRS complexes on a rhythm strip multiplied by 6

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14
Q

What is the effect of the parasympathetic system on heart rate?

A

Slows heart rate for sleep, vasovagal syncope and in fitter people, they have a lower resting heart rate.

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15
Q

What is the effect of the sympathetic nervous system on heart rate?

A

Increases heart rate in first minutes after exercise, fear, adrenaline , and salbutamol use.

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16
Q

What causes a decrease in parasympathetic control of the heart?

A

Falling arterial pressure during syncope
Heart failure
First few seconds of exercise
Use of muscarinic blocking agents.

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17
Q

What causes a decrease in sympathetic control of the heart?

A

Rest and sleep
During vasovagal syncope
Use of beta blockers

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18
Q

How can we use an ECG to determine sinus bradycardia?

A

Sinus bradycardia is when the SAN node impulses results in a heart rate less than 60bpm. An ECG trace will show greater distance between the PQRS waves, with a normal P wave in front of each complex.

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19
Q

How do electrical impulses reach the left atrium?

A

Travel from the SA node along Bachmann’s bundle.

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20
Q

What are the features of the Bundle of His?

A

Bundle of His receives impulses from the SAN and splits into a left bundle branch and right bundle branch.
The left bundle branch gives off an anterior and posterior branch.

Bundle branch blocks cause a wide QRS complex.

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21
Q

What is heart block?

A

Electrical impulses that generate contraction of the heart are interrupted due to issues with the AV node. Heart block has 3 degrees of severity, with 3rd degree heart block being complete heart block and is a medical emergency.

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22
Q

What is 1st degree heart block?

A

Longer PR interval over 200 M/s due to disruption of electrical impulses to the AVN node.

This is normal in younger patients and athletes due to greater vagal tone.

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23
Q

What are the causes of 1st degree heart block?

A

It can be caused by
-> normal vagal tone in athletes and elderly
->acute rheumatic carditis
—>fibrosis in elderly
-> electrolyte imbalances with hypokalemia and hypomagesaemia
-> mitral valve surgery
-> coronary artery disease.

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24
Q

Which drugs can cause 1st degree heart block?

A

Beta blockers and digoxin which block the AV node. This can also cause other degrees of heart block.

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25
Q

What is acute rheumatic carditis?

A

Rheumatic fever is an inflammatory condition which can cause permanent damage to the heart valves, with greater risk for those with undertreated/untreated strep infections.

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26
Q

What is 2nd degree heart block?

A

Intermittent failure of electrical impulse conduction of the AVN to the Bundle of His, and impulses received from the SAN.

Generally, it is caused by increased vagal tone or myocardial infarction or may be a normal variant. The two types of 2nd degree block are Mobitz and Wenckebach.

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27
Q

What is a Mobitz II Arrythmia?

A

Type of 2nd degree heart block where there is a greater number of P wave to the number of QRS complexes and normal PR interval.

There may be a set ratio of PR to QRS complexes.

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28
Q

What is the significance of Mobitz II Arrythmia?

A

Patients are typically symptomatic with syncope, chest pain and fatigue so treatment with atropine or pacemaker is importantly due to high risk of progression.

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29
Q

What is the effect of ECG when Mobitz II Arrythmia occurs below the Bundle of His?

A

Wide QRS complex.

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30
Q

What is the effect of ECG when Mobitz II Arrythmia occurs within the Bundle of His?

A

Narrow QRS complex.

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31
Q

What is a Wenckebach arrythmia?

A

AKA Mobitz I, where there is a cyclical cycle of
1) PROGRESSIVE lengthening of PR interval in each QRS complex
2) intermittent failure of atria conduction
3) Following complex has a shorter PR interval

It is typically benign and does not usually require treatment but can cause bradycardia and hypotension so atropine can be given.

32
Q

What are the causes of Mobitz I arrythmia?

A

Normal variance
Increased vagal tone
Mitral valve surgery
HYPERkalemia
AV blocking drugs like digoxin and beta blockers

33
Q

What is a 3rd degree heart block?

A

Complete failure of electrical conduction, with no associations between the atria and ventricles due to a non-functional AV node, so ventricles rely on their own pacemaker.

This results in a ventricular escape rhythm, where depolarisation originates from the ventricles when there is a long pause in cardiac rhythm to prevent cardiac arrest.

34
Q

What is the cause of 3rd degree heart block?

A

Myocardial infarction
Degeneration of the conducting system.
Fibrosis around bundle of His
Block of both bundle branches

35
Q

How is 3rd degree heart block managed?

A

Acutely, administering dopamine and adrenaline for temporary support prior to a
Transcutaneous pacemaker

36
Q

What does an ECG show for 3rd degree heart block?

A

Wide and abnormally shaped QRS complexes due to ventricular focus of depolarisation, with no associations to P waves that are more frequent .

37
Q

How is sinus bradycardia treated?

A

Conservative treatment by investigating the causes of sinus bradycardia to remove it such as:
Hypothyroidism due to decreased cardiac output

Use of beta blockers or digoxin

Rate limiting calcium channel blockers

38
Q

How is heart block generally treated?

A

Investigating the causes of myocardial infarction to remove it such as:
Inferior myocardial infarction
Use of digoxin, beta blockers or rate limiting calcium channel blockers
Use of atropine

It can be treated using isoprenaline, a Beta-agonists.

39
Q

How is 2nd or 3rd degree heart block treated?

A

Pacemaker to

40
Q

Why does mitral valve surgery cause arrythmia?

A

Causes cardiac damage which induces an inflammatory response during the healing process post-surgery, disturbing electrical impulse conduction.

41
Q

Why does atropine cause heart arrythmia?

A

Atropine is a muscarinic antagonists which results in increased heart rate. However, it can result in an imbalance in control of heart rate that leads to arrythmia.

42
Q

What is the role of the bundle branches?

A

Carries signals from the AV node and Bundle of His to the walls of the ventricles for ventricular contraction. Consists of a left bundle branch with an anterior and posterior division and a singular right bundle branch.

43
Q

How can the bundle branches be assessed?

A

Bundle branches can be assessed with the:
V1 lead providing an anterior right view of the heart.
V6 lead providing a left view of the heart.

44
Q

What are the general causes of bundle branch block?

A

Typically due to fibrosis when remodelling occurs with conditions like:
-> Acute conditions like Ischaemia and myocarditis
-> Chronic conditions like hypertension, coronary artery disease and cardiomyopathies

45
Q

What is a left bundle branch block?

A

Issue with conduction of the heart from the AV node to the left bundle of His. This results inin the right ventricle compensating and contracting first.

The anterior branch of the left bundle branch tends to be blocked because depolarisation travels along the anterior fascicle. A block of the posterior fascicle is rare

Left bundle branch block is always an indicator of hear disease in the left ventircle

46
Q

What are the features of a left bundle branch block on ECG?

A

There will be a wider QRS complex and the right Bundle of His will have to compensate, so wave of depolarisation begins in right ventricle and goes toward the the left ventricle.

This causes V1 to become more negative as electrical signal is directed toward the left, creating a W.

V6 will become more positive but notched and have an M shape, due to late depolarisation of the left ventricle.

47
Q

What is a right bundle branch block?

A

Issue with conduction of the heart from the AV node to the right bundle branch, which typically occurs in lung conditions that affect the right side of the heart ONLY or right ventricular strain. The left bundle branch will compensate and the left ventricle will contract first.

48
Q

How does a right bundle branches block present?

A

M wave on V1

W wave on V6

Widening of the QRS complex due to delay of conduction of ventricular muscle from bundle branch block

-> Right bundle branch block pattern with a normal QRS complex is a normal variation in healthy people

49
Q

How does a right bundle branch block appear on an ECG?

A

Direction of depolarisation begins in the left towards the right, causing:
The V1 lead for the right side will show a large M wave due to right direction of current flow

The V6 lead for the left side will show a W wave, that has a slurred S wave and QRS complex is wider due to right direction current flow

50
Q

How does a left bundle branch block show on an ECG?

A

Direction of depolarisation begins in the right towards left, causing:
The V1 lead for the right side will show a W wave due to direction of current away from right to left

The V6 lead for the left side will show an M wave due to left direction of flow towards left

51
Q

What is sinus tachycardia?

A

SAN nodes fires electrical impulses that results in a heart rate between 120-140bpm at rest. It has no known cause but may be due to over-sensitivity to adrenaline or abnormal SAN. It can lead to narrow QRS complexes.

Sinus tachycardia is not an arrhythmia, and treatment is focused on targeting the underlying cause such as sepsis.

52
Q

What is supraventricular tachycardia?

A

Resting heart rate of 140bpm, caused by abnormality above the AV node that overstimulates of the AVN node. This leads to a narrow QRS complex on ECG.

This is caused by:
AVRT
AVNRT

53
Q

What is atrial tachycardia?

A

Heart rate greater than 140bpm due to abnormal electrical impulses generated from a region in the atria other than the SAN or enhanced automaticity of the SAN node. It is a type of supraventricular tachycardia

54
Q

What is ventricular tachycardia?

A

Occurs following ventricular damage, such as ischaemia where there is more than 3 consecutive premature ventricular contractions BEGINNING from the ventricles, that severely reduces cardiac output.

This causes a very fast heart rate, with regular wide QRS complexes. It is a medical emergency that can cause sudden death or progress onto ventricular fibrillation.

55
Q

What is the cause of ventricular tachycardia?

A

Focal automaticity in the ventricles that exceeds the rate of the SA node

AVNRT, with re-entry of signals

—> THis leads to a wide QRS complex.

56
Q

How to differentiate between supraventricular tachycardia and ventricular tachycardia?

A

Injection of adenosine, which blocks conduction through the AV node. In supraventricular tachycardia, there will be a very slow heart rate, but ventricular tachycardia will be unaffected.

57
Q

What is atrial fibrillation?

A

Chaotic electrical signals commonly originating in the left atria near the pulmonary veins that causes an irregular and fast heart rate.

ECG shows irregularly-regular narrow QRS complexes and absent P waves due to issues with atrial contraction. Patient will have an irregular pulse.

Higher risk of stroke due to thrombus.

58
Q

What are the risk factors for atrial fibrillation?

A

Cardiovascular disease such as hypertension and atherosclerosis
Genetics
Older Age
Drug use like caffeine

59
Q

What are the risk factors for thrombus formation?

A

Hypercoagubility
Blood stasis
Endothelial damage

60
Q

What is atrial flutter?

A

Atrial rate is 300bpm and there is a 2:1 ratio of P waves to a narrow QRS complex.

There is a regular heart rate but it is very fast rate and a saw tooth isoelectric line due to atria contracting faster than ventricles.

61
Q

What is the cause of atrial flutter?

A

Abnormal re-entrant circuit from the left or right atria which overrides the SAN node. This typically occurs in the right atria and causes a very high heart rate and reduced filling of the heart.

62
Q

How is ventricular tachycardia treated?

A

Synchronised cardioversion using a defibrillator: this is where the heart rate is monitored to deliver electric shocks during R waves

Correcting hypokalemia or hypomagnesaemia

Intravenous administration of amiodarone, an anti-arrythmia medication.

63
Q

What is AVNRT?

A

Atrioventricualr nodal re-entrant tachycardia is a type of supraventricular tachycardia, where there is an internal short circuit loop that increases stimulation down to the AV node, causing increased nodal firing.

This occurs due to a premature beat travelling down the slow pathway while the fast pathway is in recovery. The fast pathway recovers and the signal also travels along the fast pathway and there is an internal loop of firing from the fast and slow pathway down to the AV node, resulting in tachyarrythmia.

64
Q

What is AVRT?

A

Atrioventricular re-entrant tachycardia

This is a type of supraventricular tachycardia where there is an accessory electrical pathway in the heart that allows atrial impulses to travel to the ventricles and bypass the AV node, and impulses to go up from the ventricles to the atria. This causes an abnormal loop of electrical activity.

The AV node slows conduction from the atria to the ventricles but the accessory pathway does not regulate speed of conduction, therefore there is double stimulation of electrical activity.

In a genetic condition called Wolf-Parkinson-White syndrome, the re-entrant circuit is located in the ventricles.

65
Q

What is the epidemiology of atrial fibrillation?

A

More prevalent in older patients and atrial fibrillation increases the risk for stroke due to pooled blood causing thrombosis. It is the most common type of arrhythmia in adults.

66
Q

How is atrial fibrillation treated?

A

Electrical or pharmacological cardioversion
Anti-thrombotic agents such as warfarin
Drugs to reduce ventricular rate, such as digoxin and beta blockers

67
Q

Why can’t aspirin be given to people with atrial fibrillation?

A

Aspirin is an anti-platelet drug which prevents platelets clumping, and has limited effectiveness in atrial fibrillation. Instead, anti-thrombotic agents are given which slow down clotting and fibrin formation.

68
Q

How can risk of stroke be deterimined in Afib patients?

A

CHADS2-VASC score, which can also determine who will benefit most from anti-coagulation.

69
Q

How is sinus tachycardia treated?

A

Conservative treatment to investigate and remove the cause such as:
Hyperthyroidism
Anxiety
Heart failure
Hypovolaemia
Sepsis

70
Q

How is supraventricular tachycardia treated?

A

Supraventricular tachycardia can self-reverse but alternatively:
IV adenosine is given to block AV conduction for slower rate
Vagotonic manoeuvres to increase parasympathetic control of heart rate

71
Q

What is Torsades de pointes?

A

Also known as polymorphic ventricular tachycardia. It is characterised by a prolonged QT interval due to an issue with ventricular repolarisation and greater heart rate, causing the QRS complexes to twist around the isoelectric line.

This may ooccur due to genetic mutations with ion channels.

72
Q

What is sick sinus syndrome?

A

Impaired functioning of the SA node which results in long pauses on ECG where no contraction of the heart occurs, and can lead to dizziness, shortness of breath and fatigue. Can occur naturally with aging or due to other heart pathologies.

73
Q

What is bradyarrythmia?

A

Slow heart rate caused by an irregular heartbeat. This can occur due to:
—>Heart block where there is an inability to propogate electrical impulses: 1st degree, 2nd degree or complete heart block
—>Issue with the SAN node in Sick sinus syndrome and Sinus bradycardia

74
Q

What is tachyarrythmia?

A

Heart rate over 100bpm, accompanied by an irregular heart rate. This can occur due to:
—>Re-entry of electrical impulses into the AV nodes in AVNRT or AVRT

—>Issues with the automaticity of the heart

—>Trigger activity

75
Q

How can automaticity of the heart be disrupted in tachyarrhythmias?

A

Disorders of the SAN in sinus tachycardia

Metabolic causes which trigger higher heart rate such as hypoxia, ischaemia, high sympathetic tone from the use of sympathomimetics.

76
Q

What is triggered activity?

A

Caused by leakage of positive ions to cardiac cell that leads to abnormal depolarisation which is depolarisation in phase 2,3 or 4 of an action potential in a cardiac myocyte which initiates impulses that cause tachyarrythmia.

—>Early afterdepolarisation is in phase 2/3.
—>Delayed afterdepolarisation is when this occurs during or close to repolarisation.

Year 2 (247 decks)

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