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supporting life > arrhythmias > Flashcards

arrhythmias Flashcards

1
Q

define an arrhythmia

A 
An arrhythmia (dysrhythmia) is a disturbance of the normal rhythmic
beating of the heart – usually due to an ectopic pacemaker
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2
Q

are all arrhythmia life threatening

A

no some can be asymptomatic

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3
Q

what are some broad symptoms of arrhythmia

A

palpitations, syncope, dizzy shortness of breathe

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4
Q

name four most common arrythmias

A

ventricle tachycardia, atrial fibrillation, ventricle fibrillation, complete heart block

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5
Q

what is the purpose of the effective refractory period

A

Cells cannot fire another AP during most of an

existing AP = effective refractory period

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6
Q

which part of conducting system in heart is the primary pacemaker

A

san

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7
Q

a part of the hearts conducting system fails what part will become the new primary conductor and why

A

the next most distal part and because all parts are capable of intrinsic pacemaking albeit at a slower rate than the part before it

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8
Q

what do you call an arrhythmia below 60 bpm

A

bradycardia

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9
Q

what do you call arrhythmia above 100

A

tachycardia

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10
Q

if arrhythmia origin is described as supra ventricular where is it

A

atrial or av nodes

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11
Q

if arrhythmia origin is described as ventricular where is it

A

ventricles

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12
Q

what ultimately are the two causes of an arrhythmia

A

disorder with conduction or impulse generation

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13
Q

what three criteria can you class an arrhythmia on

A

rate, location, cause

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14
Q

what generally causes bradycardia

A

slowing down of san impulse rate, or san fails distal pacemaker takes over

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15
Q

what generally causes tachycardia

A

Tachycardias
Disorders of impulse generation
Disorders of impulse conduction – re-entry

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16
Q

define 3rd degree heart block

A

electrical connection between atria and ventricles is blocked

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17
Q

what causes 3rd degree heart block

A

idiopathic fibrosis, atherosclerotic

coronary heart disease, dilated cardiomyopathy

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18
Q

how does 3rd degree heart block affect cardiac rhythm

A

slower most distal conduction system takes over from block, bradycardia. degree of slowing depends on location of block.
Heart rhythm driven by ‘escape beats’ originating from distal pacemaker just below the block.
A distal pacemaker represents a latent pacemaker in the conduction system becoming active

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19
Q

explain overdrive suppression in the heart

A 
of overdrive suppression by
the SAN (the fastest pacemaker dominates).
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20
Q

what is a latent pacemaker

A

capable of pacemaking due to intrinsic automaticity , because it has the ion channels required for phase four depolarisation

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21
Q

what are the symptoms of 3rd degree heart block

A

temporary syncope as heart stops, followed by recovery, with breathlessness,
fatigue and possible chest pain, especially with effort

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22
Q

what is the prognosis for 3rd degree heart block

A

Episodes of syncope tend to get longer and escape beats slow. Most patients die
within 2 months unless treated, some die immediately. Risk depends on location of block –
more distal block → slower rhythm → greater risk of asystole (heart stopping).

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23
Q

how do you treat 3rd degree heart block

A

Requires implantation of a permanent pacemaker to generate the cardiac rhythm
unless risk is low or block is likely to be temporary. If risk of asystole is high, may need
immediate temporary pacemaker

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24
Q

what is the hallmark(thing to look for) in an ecg of someone with 3rd degree heart block

A

p wave is dissociated with qrs complex, atria and ventricles beat independently of each other

25
Q

what normally causes tachycardia

A

re entry impulses

26
Q

explain the process of re entry pulses

A

part of the heart impulse is delayed, refractory period in adjacent part of the heart finishes and the delayed impulse can then re enter, causing contraction can start a vicious cycle

27
Q

based on the description of re entry impulses what two things are needed for this pathological state to occur

A

an in excitable core for the impulse to circle around and

refractory periods of vary lengths or different zones of conductivity

28
Q

in tissue with re entry currents what would you expect to see a unidirectional…

A

Unidirectional block
with slowed retrograde
conduction

29
Q

how do you stop re entries in heart

A

prolong refractory period,

Convert unidirectional block to
bidirectional block by suppressing
conduction

30
Q

how do rotors form and what is a rotor

A

rotor is a spiral of eletricsl conduction, can form when impulse meets an obstacle, dead tissue after MI, cause impulse to spread in different directions and potentially cause fibrillations

31
Q

what is Functional re-entry

A

e-entry can also occur without a defined anatomical pathway
This typically occurs during or after an MI, when cardiac conduction is slowed in some
regions of the heart and therefore becomes spatially heterogeneous, can lead to rotors

32
Q

what can cause delayed after depolarisations

A

Caused by excessive increases in [Ca2+]i due to e.g. catecholamines, digoxin

33
Q

what can cause early after depolarisations

A

Caused by stimuli that increase the Ca2+ current or AP duration
e.g. hypoxia, catecholamines, sotalol (an anti-arrhythmic!)

34
Q

what is Atrial fibrillation

A

Definition: Chaotic atrial rhythm with rapid and ‘irregularly irregular’ ventricular
rhythm

35
Q

what causes atrial fibrillation

A

Most often an ectopic focus located in the cardiac muscle layer surrounding a
pulmonary vein. Risk factors include atrial dilatation, heart failure, hypertension, excessive
alcohol intake, old age.

36
Q

what is effect of atrial fibrillation on cardiac rhythm

A

No organised atrial beating due to chaotic electrical activity.
Ventricular excitation occurs when atrial depolarisations are sufficient to be conducted
through the AVN

37
Q

symptoms of atrial fibrillation

A

Symptoms: Palpitations, breathlessness, dizziness, syncope.

38
Q

what is prognosis for atrial fibrillation

A

Prognosis: Typically progression is paroxysmal → persistent → permanent. This is
associated with progressive electrical and structural remodelling of the atria which
promotes more complex and refractory forms of re-entry. stroke risk!

39
Q

why is atrial fibrillation a major risk for stroke

A

no atrial pumping causes stasis of blood, thrombi can

form, esp. in the LA appendage, and then embolise to the cerebral circulation

40
Q

what is hallmark of atrial fibrillation on ecg

A

Hallmark: Lack of P waves due to chaotic atrial electrical activity. Baseline shows small
fibrillatory (‘f’) waves of varying amplitude. ‘Irregularly irregular’ high frequency QRS
complexes cause fast irregular tachycardia (>150 bpm).
With time, ‘f’ waves become smaller and QRS complexes occur less frequently, so HR
slows down.

41
Q

name the four classes of drugs to treat arrythmias and state an example

A

Class 1: Na+ channel blockers - suppress conduction e.g. flecainide
Class 2: β receptor blockers - reduce excitability, inhibit AVN conduction
e.g. bisoprolol
Class 3: drugs which prolong the AP and refractory period e.g. amiodarone
Class 4: Ca 2+ channel blockers - inhibit AVN conduction e.g. verapamil

42
Q

what is action of adenosine which lies outside these classes of drugs

A

Adenosine: slows AV nodal conduction

43
Q

what is action of digioxin which lies outside these classes of drugs

A

Digoxin: stimulates vagus, slows AV nodal conduction

44
Q

how can you target supraventricular tachycardias and AF

A
  1. Reduce proportion of impulses conducted thru the AV node = rate control (Class 2, Class 4, adenosine, digoxin)
  2. Target the source of the arrhythmia or the conduction of the impulse away from the
    source by blocking the re-entrant pathway = rhythm control(Class 3 or Class 1: These drugs suppress re-entry)
45
Q

what is Radiofrequency catheter ablation

and what does it treat

A

Ectopic pacemaker or site along a re-entrant pathway is destroyed,

Transvenous catheter is threaded into the heart, placed against the
endocardium, and radio-frequency energy is delivered to the tip.
This heats the tip, causing a lesion ~1 cm wide

46
Q

define Vtach

A

Definition: A run of rapid (typically 120-200 bpm) successive ventricular beats caused
by an ectopic site in one of the ventricles.

47
Q

what is cause of vtach

A

Cause: Varied. Most often due to cardiac scarring after MI or dilated cardiomyopathy.
Can be congenital (e.g. Brugada syndrome, LQT syndrome), or caused by some
anti-arrhythmic drugs(!). Almost always due to re-entry

48
Q

vtach Effect on cardiac rhythm

A

Effect on cardiac rhythm: Tachycardia. Rhythm may be regular (monomorphic VT) or
irregular (polymorphic VT).

49
Q

what are the symptoms of vtach

A

Chest pain, shortness of breath, syncope

50
Q

what is the prognosis of vtach

A

could lead to ventricle fibrillation, If persistent, may compromise cardiac pumping,
leading to heart failure and death.

51
Q

describe vtach ecg

A

Broad complex rapid rhythm. Complexes can be of regular (monomorphic) or
varied shape (polymorphic). Atria usually beat more slowly and independently of the ventricles
(AV dissociation). The P waves don’t ‘capture’ the ventricles because when they get through
the AV node the conduction system is usually refractory, since it’s being depolarised so
frequently by the ventricular ectopic pacemaker

52
Q

how can you treat vtach

A

Treatment: Implanted cardioverter defibrillator (AVID Trial)

Class I, Class 2, Class 3 anti-arrhythmic drugs, radiocatheter ablation

53
Q

what is an implantable defibrillator

A

The generator can sense and differentiate arrhythmias by rate and
location, and delivers an appropriate shock or shock sequence, causing
cardioversion (i.e. a return to sinus rhythm).
More successful than drug therapy in patients with serious ventricular
arrhythmias (AVID trial)

54
Q

what is ventricular fibrillation

A

Definition: Chaotic and disorganised electrical activity of the heart

55
Q

what causes ventricular fibrillation

A

Usually MI, ischaemic heart disease, cardiomyopathy, but can be idiopathic

56
Q

what is ventricular fibrillation effect on cardiac rhythm

A

Effect on cardiac rhythm: no organised ventricular beat so no cardiac output

57
Q

what is the prognosis for VF and symptoms

A

Symptoms and prognosis: Unconsciousness within seconds, death occurs rapidly

58
Q

what do you see on ecg for VF

A

CG hallmark: Disorganised electrical activity which fades as the heart dies

supporting life (20 decks)

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