CPT1: Dysrhythmias 1

Question 1

What is dysrhythmia?

Answer 1

An abnormality in the physiolocical rhytm of the heart

Question 2

What are the statics relating to dysrhythmia?

Answer 2

• 15% of stroke patients have dysrhytmia
• 2-8% of patients with transient ischaemic attacks
• 2-year incidence increases with age:
  
  • 0.1% (30-39 YO)
  • >1% (70-79)
• Prevalance ~10% in males >70’s
• 7% of all hopsital admissions have an arrythmia

Question 3

What are Aetiologies (CAUSES) of dysrhytmias?

hint: unspecific

Answer 3

1. Infarcation
2. Conduction disorder (fibrosis)
3. Changes in autonomic nervous output (Stress, anxiety, exercise, smoking)
4. Electroylte imbalance (hypo/hyperkalaemia)
5. Circulating drugs (antiarrhythmias, caffeine, alcohol)

Question 4

What are causes of dysrhythmias?

Hint: Specific

Answer 4

• Hypoxia myocardium - pumlomary embolus, chronic pulmonary disease
• Ischaemia myocardium - acute MI, expanding MI, angina
• Bradycardia - Slow HR predisposes one to dysrhytmias
• Enlargement of atria or ventricles - producing stretch in the pacemakers

Question 5

Describe the ECG of the heart

Answer 5

• P - atrial depolarization
  
  • P-R ~120-200ms
• QRS complex - ventricular depolarization
  
  • QRS ~120ms
• T - ventricular repolarization
  
  • Q-T ~3-400ms
• P-R - interval -slowing through AV node

Question 6

Describe electrical flow through the heart

Answer 6

1. Depolarisation begins at the SA node and spreads rapidly across the atria through internodal conductin fibres/ pws
2. It slows at the AV node to allow time for the atria to complete contraction before starting ventricular contraction
3. Electrical singal enters the ventricular conducting system (his and purkinje fibres) and first goes to the apex of the ventricles before spreading upwards (ventircular contraction)

Question 7

Arrhythmia or dysrhytmia?

Answer 7

• Dysrhythmia accurate, arrhythmia most widely used
• Arrhythmia is generally the name for the anatomical site or chamber of origin

Question 8

What are terms used to describe the location of the origin of the arrhytmia?

Answer 8

• Supraventricular: Origin above the ventricles e.g. SA, atrial AV or HIS origin
• Ventricular origin: Origin is in the ventircles

Question 9

How sereve are cardiac arrhymias

Answer 9

• May be bengin or life-threatening
• Mat be paraoxysmal (sudden outbursts) or continous and may cause sudden death, heart failure, syncope (tempory loss of conciousness), light headedness, palpatations or no symptoms at all

Question 10

What does the description of dysrhytmia depend on?

Answer 10

• The rate, pattern, origin
• All descriptions depend on ECG
• BUT - this does not refer to how well the heart functios as a pump. Other parameters important (BP, pulse)

Question 11

What are 2 dysrhymia termomologies based on rate?

Answer 11

Trachycardia - more than 100 bpm

Bradycardia - less than 60 bpm

Question 12

What are 2 causes of Trachycardia?

Answer 12

• Increased automacity:
  
  • sustained by repeated spontanreous depolaisations of an ectopic focus or single cell
• Re-entery:
  
  • When it is initated by a ectopic beat and sustained by a closed loop circuit or re-entery circuit. Most common cause.

Question 13

What are the potential causes of bradycardia?

Answer 13

• Reduced automacity (e.g. sinus bradycardia)
• Abnormally slow conduction (e.g. AV block)

Question 14

What do the following terms mean:

1. Sinus
2. Atrial
3. Nodal
4. Supraventricular
5. Ventricular
6. Re-entrant

Answer 14

1. SA node
2. Atrial tissue but not SA node
3. AV node
4. Usually, but not necessarily, from the AV node
5. Ventricular tissue
6. Circuit involving retograde conduction. Also accessory pws e.g. Wolff-Parkinsons White Syndrome

Retograde conduction - backwards conduction of the heart

Question 15

Where might the follwing re-entry circuit be seen?

Answer 15

• Tissues with these type of circuits may exist:
• • in microscopic size in the SA node, AV node, or any type of heart tissue
• • in a “macroscopic” structure such as an accessory pathway in WPW

Question 16

Describe what happens during re-entry conduction

Answer 16

1. An arrhythmia is triggered by a premature beat
2. The beat cannot gain entry into the fast conducting pathway because of its long refractory period and therefore travels down the slow conducting pathway only
3. The wave of excitation from the premature beat arrives at the distal end of the fast conducting pathway, which has now recovered and therefore travels retrogradely (backwards) up the fast pathway
4. On arriving at the top of the fast pathway it finds the slow pathway has recovered and therefore the wave of excitation ‘re-enters’ the pathway and continues in a ‘circular’ movement. This creates the re-entry circuit

Question 17

Re-entery picture 2

Answer 17

Re-entery Picture 3

Question 18

Give some examples of specific types of Re-entry conditions

Answer 18

• Atrial Re-entry
  
  • Atrial flutter
  • Atrial fibrililation
  • Atrial trachycardia
• AV nodal re-entry
  
  • Supraventricular Trachycardia
• AV Re-entry
  
  • Supraventricular trachycardia
• Ventrical Re-entry
  
  • Ventricualar trachycardia

Question 19

What is Wolf Parkinons White Syndrome

Answer 19

• An abnormal band of atrial tissue connects the atria and ventircals and can electrically by pass the AV node
• ECG shows shorted PR interval and slurred QRS complex called delta wave
• As AV node and bypass tract have different conduction speeds and refractory periods, a re-entry circuit can develop causing bursts of trachycardia events

Question 20

What do the ECG waves for:

1. Atrial fibrillation
2. Atrial Flutter
3. Ventricular fibrillation
4. Ventricular premature beats

Answer 20

Question 21

What are do the following terms mean?

1. Paroxysmal
2. Fibrillation
3. Flutter
4. Block
5. Torsades de pointes
6. Electromechanical dissociation

Answer 21

1. Paroxysmal = Occurs in bursts
2. Fibrillation = Rapid chaotic rhythm. Multiple foci
3. Flutter = Rapid regular rhythm. Single focus
4. Block = delay or absence of conduction via AV node
5. Torsades de pointes = complex ventricular tachycardia
6. Electromechanical dissociation = ECG recording not reflected in mechanical activity (pulse)

Question 22

So what is paroxysmal supraventricular trachycardia?

Answer 22

A fast rhythmic burst (> 100 bt/min) originating within either the AV node, the SA node or the atrial tissue itself.

Question 23

What is the danger with arhythmias?

Answer 23

Increases risk of mortality and morbidities

Mortality = death

Morbidity = predisposition to disease

Question 24

What are the increased risks with atrial fibrillation?

Answer 24

• 2x more likely to have stroke
• 3x more likely to have Heart failure
• 2x mortality risk

Question 25

What are the symptoms of arrhythmias?

Answer 25

• Pain (including Angina)
• Shortness of breath
• Dizziness/ Syncope
• Palpatations (awareness of Heart beat)

Question 26

What is the difficulty with diagnosis?

Answer 26

Symptoms not unique to arrhytmias and intermittant arhythmias difficult to diagnosis. Therefore use 24hr ECG.

80% of CO from ventricular output regardless of atrial discoordination therefore may be unaffected or only slightly

Question 27

What does:

1. Slow Atrial fibrillation and effective AV block
2. Fast AF and ineffective AV block mean?

Answer 27

With slow AF + effective AV conduction block = small conduction of fibrillative events in the atria stimulate the ventricles.

With fast AF + ineffective AV conduction block = rapid and irregular heart beat, poor filling of ventricles prior to contraction and so inefficient circulation.

Question 28

What is the treatment criteria?

Answer 28

1. The arrhythmia causes poor circulation (haemodynamic failure)
2. Haemodynamic failure has not occurred BUT arrhythmia is a predictor of more serious arrhythmia.
   e. g. After MI, ventricular tachycardia increases risk of dying within 1 year by 30%.
3. Patient distress (palpitation awareness).

Question 29

What are aims of treatment?

Answer 29

1. Restore satisfactory circulation
2. Prevent further episodes of haemodynamic failure and palpitations.

Question 30

NOTE

Answer 30

Arrhythmia implicated in sudden death

However,

Much of the evidence comes from patients having ECG monitored continuously. These may NOT be representative of general population. Evidence DOES support notion that ventricular tachyarrhythmia is a more common cause of death than bradyarrhythmia

Question 31

What are hazzards of treatmetn

Answer 31

Arrhythmia may occur with no symptoms.

\ Presence does NOT automatically require treatment.

Antiarrhythmic drugs may make condition WORSE!!