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A2. Respiratory system > Arrhythmias - Pathophysiology, presentation and investigation > Flashcards

Arrhythmias - Pathophysiology, presentation and investigation Flashcards

1
Q

Learning Outcomes for arrhythmias

A
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2
Q

What is meant by normal sinus rhythm?

A

Normal heart rhythm with electrical activation beginning in the SA node

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3
Q

Which lead is the best to assess rhythm?

A

Whichever lead that shows the P wave most clearly, usually limb lead 2 or V1

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4
Q

What is the PR interval?

A

The time taken for the wave of depolarisation to travel from the SA node to the ventricular muscle (usualy no longer than 220 ms (6 boxes))

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5
Q

What is meant by first degree heart block?

A

When there is a delay in the conduction pathway from the SA node to the ventricles

There is therefore a characteristic prolonged PR interval

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6
Q

What are the casues of first degree heart block?

A

May be a sign of coronary artery disease, acute rheumatic carditis, digoxin toxicity or electrolyte disturbances.

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7
Q

What is meant by second degree heart block?

A

When on intermittant occasion, excitation completely fails to pass through the AV node or the bundle of His

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8
Q

What are the three different types of second degree heart block?

A

Mobitz type 1

Mobitz type 2

2:1 / 3:1 / 4:1 conduction

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9
Q

What is mobitz type 1 heart block?

A

Progressive lengthening of the PR interval and then failure of conduction of an atrial beat, followed by a conducted beat with a shorter PR interval and then a repetition of this cycle

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10
Q

What is mobitz type 2 heart block?

A

Most beats are conducted with a constant PR interval, but occasionally there is atrial depolarisation without a subsequent ventricular depolarization

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11
Q

What is meant by 2:1 / 3:1 / 4:1 conduction?

A

There may be alternate conducted and nonconducted atrial beats (or one conducted atrial beat and then two or three nonconducted beats), giving twice (or three or four times) as many P waves as QRS complexes. This is called ‘2:1’ (‘two to one’), ‘3:1’ (‘three to one’) or ‘4:1’ (‘four to one’) conduction

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12
Q

What is meant by third degree heart block?

A

Complete heart block (third degree block) is said to occur when atrial contraction is normal but no beats are conducted to the ventricles. When this occurs the ventricles are excited by a slow ‘escape mechanism’ from a depolarizing focus within the ventricular muscle.

No relationship between P waves and QRS complexes

Abnormally shaped QRS complexes,

because of abnormal spread of depolarization from a ventricular focus

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13
Q

What causes third degree heart block?

A

Complete heart block may occur as an acute phenomenon in patients with myocardial infarction (when it is usually transient) or it may be chronic, usually due to fibrosis around the bundle of His. It may also be caused by the block of both bundle branches.

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14
Q

What are the common causes of heart block?

A
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15
Q

Where does mobitz 1 and mobitz 2 take place?

A
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16
Q

What causes third degree heart block?

A

Complete heart block is caused by the aging process, medicines, heart attacks, infiltrative heart diseases (amyloidosis, sarcoidosis), and infectious diseases (endocarditis, Chagas disease). It may also occur after heart surgery and can be present from birth (congenital)

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17
Q

What are the presentations of third degree heart block?

A

Fainting, light headedness

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18
Q

When is heart rhythm said to be arrhythmia?

A

When the depolarisation sequence begins somewhere outwith the SA node

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19
Q

What can control the rhythm of contraction in the ventricles?

A

Most parts of the heart can depolarize spontaneously and rhythmically, and the rate of contraction of the ventricles will be controlled by the part of the heart that is depolarizing most frequently.

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20
Q

What makes up suprventricular rhythm?

A

Sinus rhythm, atrial rhythm and junctional rhythm

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21
Q

Which rhythms have narrow/wide QRS complexes?

A
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22
Q

What is the rate of contraction in supraventricular / ventricular rhythm?

A

The atrial muscle or the area around the AV node (the junctional region) have spontaneous depolarization frequencies of about 50/min. If these fail, or if conduction through the His bundle is blocked, a ventricular focus will take over and give a ventricular rate of about 30/min.

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23
Q

Why are escape rhythms called escape rhythms?

A

These slow and protective rhythms are called ‘escape rhythms’, because they occur when secondary sites for initiating depolarization escape from their normal inhibition by the more active SA node.

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24
Q

What does atrial flutter look like on an ECG?

A

Atrial rate is greater than 250/min, and there is no flat baseline between the P waves, ‘atrial flutter’ is present

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25
Q

What is meant by fibrillation?

A

When individual muscle fibres contract independently

26
Q

Explain why there are irregular QRS complexes present in atrial fibrillation

A

Depolarization spreads at irregular intervals down the His bundle. The AV node conducts in an ‘all or none’ fashion, so that the depolarization waves passing into the His bundle are of constant intensity. However, these waves are irregular, and the ventricles therefore contract irregularly.

27
Q

What is meant by supraventricular tachycardia?

A

Involves, atrial tachycardia, atrial flutter and nodal tachycardia

28
Q

Why are some of the P waves not followed by a QRS complex in atrial tachycardia?

A

In atrial tachycardia, the atria depolarize faster than 150/min

The AV node cannot conduct atrial rates of discharge greater than about 200/min. If the atrial rate is faster than this, ‘atrioventricular block’ occurs, with some P waves not followed by QRS complexes

29
Q

Explain the relationship between the P wave and the QRS complex in nodal tachycardia?

A

If the area around the AV node depolarizes frequently, the P waves may be seen very close to the QRS complexes, or may not be seen at all. The QRS complex is of normal shape because, as with the other supraventricular

arrhythmias, the ventricles are activated via the His bundle in the normal way.

30
Q

What is the diffrence between atrial tachycardia and heart block?

A

AV node working properly vs AV node and possible HIS bundle not working properly

31
Q

What is meant by the Wolff–Parkinson–White syndrome?

A

There is an ‘accessory’ conducting bundle, which forms a direct connection between the atrium and the ventricle, usually on the left side of the heart, and in these bundles there is no AV node to delay conduction. A depolarization wave therefore reaches the ventricle early, and ‘pre-excitation’ occurs. The PR interval is short, and the QRS complex shows an early slurred upstroke called a ‘delta wave’. The second part of the QRS complex is normal, as conduction through the His bundle catches up with the pre-excitation.

32
Q

What is meant by ventricular tachycardia?

A

If a focus in the ventricular muscle depolarizes with a high frequency the rhythm is called ‘ventricular tachycardia’

33
Q

What is seen on an ECG of ventricular tachycardia?

A

Excitation has to spread by an abnormal path through the ventricular muscle, and the QRS complex is therefore wide and abnormal.

Wide and abnormal complexes are seen in all 12 leads of the standard ECG

34
Q

What is meant by sinus tachycardia?

A

Sinus tachycardia (also colloquially known as sinus tach or sinus tachy) is asinus rhythm with an elevated rate of impulses, defined as a rate greater than 100 beats/min (bpm) in an average adult.

Three or less large squares between QRS complexes represents tachycardia on the ECG sheet usually

35
Q

How do you calculate heart rate in a patient with irregular qrs complexes?

A

Count the number of QRS complexes over 30 large squares (this correspondst o 6 seconds) then multiply by 10 to give the number of beats over a minute.

36
Q

Define sinus bradycardia

A

Sinus bradycardia is a sinus rhythm with a rate that is lower than normal. In humans, bradycardia is generally defined to be a rate of under 60 beats per minute.

This means a QRS complex is present every 5 boxes or more

37
Q

Define sinus arrest

A

Sinoatrial arrest is when the sinoatrial node of the heart transiently ceases to generate the electrical impulses. It is defined as lasting from 2.0 seconds to several minutes. Since the heart contains multiple pacemakers, this interruption of the cardiac cycle generally lasts only a few seconds before another part of the heart, such as the atrio-ventricular junction or the ventricles, begins pacing and restores the heart action

38
Q

What is meant by extrasytole or ectopic beat?

A

A premature contraction of the heart that is independent of the normal rhythm of the heart and that arises in response to an impulse in some part of the heart other than the normal impulse from the sinoatrial (SA) node. The extrasystole is followed by a pause, as the heart electrical system “resets” itself and the contraction following the pause is usually more forceful than normal. These more forceful contractions are frequently perceived as palpitations.

39
Q

What is an atrial extrasystole seen as?

A

Looks similar to the atrial escape beat whereby an abnormal P wave is seen because excitation of the atrium has begun somewhere other than the SA node. The difference is that an extrasystole comes early and an escape beat comes late.

40
Q

What do junctional extrasystoles look like?

A

In a junctional extrasystole there is no P wave at all, or the P wave appears immediately before or immediately after the QRS complex

41
Q

Describe ventricular extrasystole

A

Ventricular extrasystoles have abnormal QRS complexes, which are typically wide and can be of almost any shape.

Ventricular extrasystoles are common, and are usually of no importance. However, when they occur early in the T wave of a preceding beat they can induce ventricular fibrillation and are thus potentially dangerous.

42
Q

Discuss the prevalence of af in england

A

It is estimated that 1.36 million people in England have AF. This is equal to 2.4% of the population. AF prevalence is higher in men than in women, 2.8% versus 2.0%. AF prevalence increases with age; 2.9% of the total estimated AF in the population is likely to occur in people aged under 45, 16.6% in people aged 45-65 and 80.5% in people aged over 65.

43
Q

What are the signs and symptoms of AF?

A

Atrial fibrillation (AF) usually causes the heart’s lower chambers, the ventricles, to contract faster than normal.

When this happens, the ventricles can’t completely fill with blood. Thus, they may not be able to pump enough blood to the lungs and body. This can lead to signs and symptoms, such as:

Palpitations (feelings that your heart is skipping a beat, fluttering, or beating too hard or fast)

Shortness of breath

Weakness or problems exercising

Chest pain

Dizziness or fainting

Fatigue (tiredness)

Confusion

44
Q

What is thetreatment for atrial fibrilaltion?

A

Rule out over active thyroid, medication to treat overactive thyroid may stop af

Medicines to control af (sub divided into medication that can either restore heart rhythm or control the rate at which the heart beats.

Anticoagulation to prevent the risk of stroke (warfarin or a newer type of anticoagulant, such as dabigatran, rivaroxaban, apixaban or edoxaban)

Cardioversion (It involves giving the heart a controlled electric shock to try to restore a normal rhythm.)

Catheter ablation (a procedure that very carefully destroys the diseased area of your heart and interrupts abnormal electrical circuits.)

(Catheters (thin, soft wires) are guided through one of your veins into your heart, where they record electrical activity. When the source of the abnormality is found, an energy source, such as high-frequency radiowaves that generate heat, is transmitted through one of the catheters to destroy the tissue.)

Pacemaker

45
Q

What medications are able to restore normal rhythm?

A

Flecainide

beta-blockers, particularly sotalol

amiodarone

dronedarone (only for certain people)

46
Q

What drugs are used to control the rate of heart beat?

A

Beta blocker (bisoprolol or atenolol)

Calcium channel blocker (verapamil, diltiazem)

A medicine called digoxin may be added to help control the heart rate further. In some cases, amiodarone may be tried.

47
Q

WHat can cardioversion be used to treat?

A

Ventricular tachycardia

Supraventricular tachycardia due to reentry

Atrial fibrillation

Atrial flutter

Atrial tachycardia

Monomorphic VT with pulses

48
Q

f you’ve had atrial fibrillation for more than two days, cardioversion can increase the risk of a clot forming, how is clot formation avoided?

A

anticoagulant for three to four weeks before cardioversion, and for at least four weeks afterwards

49
Q

What are the indications for ICD therapy (implantable cardioverter-defibrillator)?

A

Cardiac arrest due to VF/VT not due to transient or

reversible cause eg early phase of acute MI

Sustained VT causing syncope or significant compromise

Sustained VT with poor LV function

50
Q

What are the indications for temporary pacing?

A
  • Intermittent or sustained symptomatic bradycardia, particularly syncope
  • Prophylactic when patient at high risk for development of severe bradycardia eg 2nd or 3rd degree AV block, post anterior MI, even when asymptomatic

(basically if there is bradycardia or risk of bradycardia)

51
Q

What are the indications for permanent pacing?

A
  • Symptomatic or profound 2nd/3rd degree AV block, particularly when cause unlikely to disappear
  • Probably Mobitz type II 2nd/3rd degree AV block even if asymptomatic
  • AV block associated with neuromuscular diseases after (or in preparation for) AV-node ablation
  • Alternating RBBB/LBBB
  • Syncope when bifascicular/trifascicular block and no other explanation
  • Sinus node disease associated with symptoms
  • Carotid sinus hypersensitivity/malignant vasovagal syncope
52
Q

What is meant by bifasicular block?

A

Bifascicular block – The term bifascicular block most commonly refers to conduction disturbances below the atrioventricular (AV) node in which the right bundle branch and one of the two fascicles (anterior or posterior) of the left bundle branch are involved

53
Q

Define trifasicular block

A

Prolongation of the PR interval (first degree AV block)

Right bundle branch block

Either left anterior fascicular block or left posterior fascicular block.

54
Q

What is a bundle branch block?

A

When there is abnormal conduction through either the right or left bundle branches.

There is a delay in the depolarization of part of the ventricular muscle. The extra time taken for depolarization of the whole of the ventricular muscle causes widening of the QRS complex.

In the normal heart, the time taken for the depolarization wave to spread from the interventricular septum to the furthest part of the ventricles is less than 120 ms, represented by three small squares of ECG paper. If the QRS complex duration is greater than 120 ms, then conduction within the ventricles must have occurred by an abnormal, and therefore slower, pathway.

55
Q

What is the approach to assess ECG?

A

ARIBAR

A - Any electrical activity

R - Rate

I - Irregular or regular

B - QRS complexes Broad or Narrow

A - Atrial activity?

R - Relationship between atrial acivity and ventricular activity?

56
Q

What are the four main types of supraventricular tachycardia?

A

atrial fibrillation, paroxysmal supraventricular tachycardia (PSVT), atrial flutter, and Wolff-Parkinson-White syndrome

57
Q

What is the disease mechanism behind paroxysmal supraventricular tachycardia?

A

The underlying mechanism typically involves an accessory pathway that results in re-entry.

58
Q

How is diagnosis of paroxysmal supraventricular tachycardia achieved?

A

Diagnosis is typically by an electrocardiogram (ECG) which shows narrow QRS complexes and a fast heart rhythm typically between 150 and 240 beats per minute

59
Q

What is the initial treatment of paroxysmal supraventricular tachycardia?

A

Vasalva manouvre

60
Q
A

A2. Respiratory system (77 decks)

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