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MD3001 Cardiology > Pathophysiology of Arrhythmias > Flashcards

Pathophysiology of Arrhythmias Flashcards

1
Q

What are the important things to note about the conducting tissue of the heart?

A
  • the material between the atria and ventricles on both sides are known as the AV rings and do not conduct electricity
  • the only way electricity travels from atria to ventricles is through the AV node
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2
Q

What are the types of bradycardias?`

A
  • sinus bradycardia

- AV block

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3
Q

What can cause sinus bradycardia?

A
  • drugs (b-blockers, diltiazem)
  • vagal activity
  • hypothyroidism
  • sinus node disease
  • electrolyte abnormalities
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4
Q

What can cause AV block?

A
  • vagal activity
  • MI
  • electrolyte abnormalities
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5
Q

What are the types of AV block?

A
  • 1st degree: long PR interval
  • 2nd degree Mobitz type 1: progressive lengthening of PR interval until P wave blocked and it resets
  • 2nd degree Mobitz type 2: block after 2 or 3 conducted beats in regular pattern
  • 3rd degree: complete AV dissociation
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6
Q

What are the classes of tachycardias?

A
  • narrow complex/supraventricular tachycardias

- broad complex tachycardias/ventricular

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7
Q

What are the different types of narrow complex tachycardias?

A
  • atrial tachycardias
  • junctional tachycardias
  • AVNRT
  • AVRT
  • atrial flutter
  • atrial fibrillation
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8
Q

What are the types of broad complex tachycardias?

A
  • SVT with rate-dependent bundle-branch block

- SVT with pre-existing bundle-branch block morphology on ECG

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9
Q

What are the different mechanisms of tachycardias?

A
  • ectopic focus (tissue with pacemaker function)
  • re-entry/circus movement
  • fibrillation (independent wavelets of activity)
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10
Q

Describe circus movement

A
  • conduction coming down through cardiac tissue meets an island of non-conducting cells
  • the impulse can go one way or the other around the island
  • if a critically timed ectopic beat travels down through the cardiac tissue, one of the limbs may be refractory so it can only go down one way
  • by the time it has gone around the island, the limb is no longer refractory and so it can travel backwards
  • this can keep going and going
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11
Q

What is AVNRT?

A
  • AV nodal re-entrant tachycardia

- tachycardia where re-entry circuit is through juxtanodal material

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12
Q

What is AVRT?

A
  • AV re-entrant tachycardia

- tachycardia where re-entry is through an accessory pathway

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13
Q

What terminates tachycardias?

A

adenosine

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14
Q

Describe Wolff-Parkinson-White Syndrome?

A
  • pre-excitation of the ventricles
  • presence of anatomical atrio-ventricular bypass tract
  • shortened PR interval and wide QRS
  • forms basis for circus movement and AVRT
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15
Q

Describe the adenosine test in narrow complex tacycardias

A
  • bolus of adenosine given and wait for response
  • if no effect: wrong diagnosis (sinus tachycardia if narrow complex, VT if broad complex)
  • transient slowing with p waves: atrial flutter/tachycardia
  • transient slowing without p waves: AF
  • restoration of sinus rhythm: AVNRT/AVRT
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16
Q

What is atrial fibrillation and the symptoms of this?

A
  • irregular narrow complex tachycardia with no p waves

symptoms:

  • SOB, hypotension
  • dizziness and syncope
  • embolism of left atrial thrombus
17
Q

in AF you would use drugs to control the HR unless what?

A
  • the patient is symptomatic with high ventricular response rates refractory to treatment
  • the patient has acute presentation with a clear precipitating cause
18
Q

What are the rate control treatments for AF?

A

Drugs that slow AV conduction:

  • diltiazem
  • verapamil
  • b-blockers
  • digoxin

AV node ablation and permanent pacemaker

19
Q

What are the rhythm control treatments of AF?

A

cardioversion:

  • electrical DC cardioversion
  • chemical (flecainide, propafanone, amiodarone)

maintenance of sinus rhythm:

  • class 3 sotalol, amiodarone
  • class 1c flecainide
20
Q

How to distinct between VT/SVT

A
  • if history of LV damage it will be VT

- if right bundle-branch block its SVT

21
Q

How would you treat VT?

A

Acute:

  • DC synchronised cardioversion
  • amiodarone
  • lignocaine

then manage underlying cause and prevent it recurring (implanted cardioverter defribrillator/anti-tachycardia pacemaker/b-blockers)

22
Q

What are the mechanisms of ventricular tachycardia?

A
  • acute LV damage (ischaemia)
  • chronic LV damage (re-entry through fibrotic areas of non-conduction)
  • abnormalities in Na and K channels (long QT) polymorphic
23
Q

What is torsade de Pointes?

A

abnormal heart rhythm that can cause sudden death

24
Q

What are the mechanisms of torsade de pointes?

A

congenital:

  • ion channelopathy
  • catecholaminergic polymorphic VT
  • plus provocation

acquired:

  • drugs that inhbit inward rectifying K channel (antihistamines/erythromycin)
  • drugs that lengthen QT interval (amiodarone/sotalol)
25
Q

How would you treat LQT Syndrome?

A
  • identify risk
  • avoid precipitating events
  • b-blockers
  • pacemaker
  • ICD

MD3001 Cardiology (56 decks)

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