arrhythmias

Question 1

define an arrhythmia

Answer 1

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

Question 2

are all arrhythmia life threatening

Answer 2

no some can be asymptomatic

Question 3

what are some broad symptoms of arrhythmia

Answer 3

palpitations, syncope, dizzy shortness of breathe

Question 4

name four most common arrythmias

Answer 4

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

Question 5

what is the purpose of the effective refractory period

Answer 5

Cells cannot fire another AP during most of an

existing AP = effective refractory period

Question 6

which part of conducting system in heart is the primary pacemaker

Answer 6

san

Question 7

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

Answer 7

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

Question 8

what do you call an arrhythmia below 60 bpm

Answer 8

bradycardia

Question 9

what do you call arrhythmia above 100

Answer 9

tachycardia

Question 10

if arrhythmia origin is described as supra ventricular where is it

Answer 10

atrial or av nodes

Question 11

if arrhythmia origin is described as ventricular where is it

Answer 11

ventricles

Question 12

what ultimately are the two causes of an arrhythmia

Answer 12

disorder with conduction or impulse generation

Question 13

what three criteria can you class an arrhythmia on

Answer 13

rate, location, cause

Question 14

what generally causes bradycardia

Answer 14

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

Question 15

what generally causes tachycardia

Answer 15

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

Question 16

define 3rd degree heart block

Answer 16

electrical connection between atria and ventricles is blocked

Question 17

what causes 3rd degree heart block

Answer 17

idiopathic fibrosis, atherosclerotic

coronary heart disease, dilated cardiomyopathy

Question 18

how does 3rd degree heart block affect cardiac rhythm

Answer 18

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

Question 19

explain overdrive suppression in the heart

Answer 19

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

Question 20

what is a latent pacemaker

Answer 20

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

Question 21

what are the symptoms of 3rd degree heart block

Answer 21

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

Question 22

what is the prognosis for 3rd degree heart block

Answer 22

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).

Question 23

how do you treat 3rd degree heart block

Answer 23

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

Question 24

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

Answer 24

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

Question 25

what normally causes tachycardia

Answer 25

re entry impulses

Question 26

explain the process of re entry pulses

Answer 26

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

Question 27

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

Answer 27

an in excitable core for the impulse to circle around and refractory periods of vary lengths or different zones of conductivity

Question 28

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

Answer 28

Unidirectional block with slowed retrograde conduction

Question 29

how do you stop re entries in heart

Answer 29

prolong refractory period, Convert unidirectional block to bidirectional block by suppressing conduction

Question 30

how do rotors form and what is a rotor

Answer 30

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

Question 31

what is Functional re-entry

Answer 31

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

Question 32

what can cause delayed after depolarisations

Answer 32

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

Question 33

what can cause early after depolarisations

Answer 33

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

Question 34

what is Atrial fibrillation

Answer 34

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

Question 35

what causes atrial fibrillation

Answer 35

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.

Question 36

what is effect of atrial fibrillation on cardiac rhythm

Answer 36

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

Question 37

symptoms of atrial fibrillation

Answer 37

Symptoms: Palpitations, breathlessness, dizziness, syncope.

Question 38

what is prognosis for atrial fibrillation

Answer 38

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!

Question 39

why is atrial fibrillation a major risk for stroke

Answer 39

no atrial pumping causes stasis of blood, thrombi can | form, esp. in the LA appendage, and then embolise to the cerebral circulation

Question 40

what is hallmark of atrial fibrillation on ecg

Answer 40

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.

Question 41

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

Answer 41

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

Question 42

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

Answer 42

Adenosine: slows AV nodal conduction

Question 43

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

Answer 43

Digoxin: stimulates vagus, slows AV nodal conduction

Question 44

how can you target supraventricular tachycardias and AF

Answer 44

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)

Question 45

what is Radiofrequency catheter ablation | and what does it treat

Answer 45

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

Question 46

define Vtach

Answer 46

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

Question 47

what is cause of vtach

Answer 47

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

Question 48

vtach Effect on cardiac rhythm

Answer 48

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

Question 49

what are the symptoms of vtach

Answer 49

Chest pain, shortness of breath, syncope

Question 50

what is the prognosis of vtach

Answer 50

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

Question 51

describe vtach ecg

Answer 51

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

Question 52

how can you treat vtach

Answer 52

Treatment: Implanted cardioverter defibrillator (AVID Trial) | Class I, Class 2, Class 3 anti-arrhythmic drugs, radiocatheter ablation

Question 53

what is an implantable defibrillator

Answer 53

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)

Question 54

what is ventricular fibrillation

Answer 54

Definition: Chaotic and disorganised electrical activity of the heart

Question 55

what causes ventricular fibrillation

Answer 55

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

Question 56

what is ventricular fibrillation effect on cardiac rhythm

Answer 56

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

Question 57

what is the prognosis for VF and symptoms

Answer 57

Symptoms and prognosis: Unconsciousness within seconds, death occurs rapidly

Question 58

what do you see on ecg for VF

Answer 58

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