Arrhythmias

Question 1

Bradycardia

Answer 1

HR is slow (

Question 2

Tachycardia

Answer 2

SHR is fast (>100 bpm)

More likely to be symptomatic when arrhythmia is fast and sustained

Subdivided into supra ventricular tachycardias (SVTs) and ventricular tachycardias (VTs)

Question 3

What is the normal cardiac pacemaker?

Answer 3

the sinus node

Question 4

What controls the sinus node?

Answer 4

Autonomic nervous system with parasympathetic predominating, resulting in slowing of the spontaneous discharge rate

Question 5

When is sinus bradycardia normal?

Answer 5

During sleep and in well-trained athletes

Question 6

Causes of sinus bradycardia that are intrinsic to the heart

Answer 6

Acute ischaemia + infarction of sinus node (from MI)

Chronic degenerative changes e.g. fibrosis from atrium and sinus node (sick sinus syndrome) - elderly

Question 7

What 2 things can sick sinus syndrome be caused by?

Answer 7

Sinus arrest

SA block

Question 8

What would an ECG show for sick sinus syndrome?

Answer 8

Intermittent pauses between consecutive P waves (>2s, dropped P waves) and bradycardia

Question 9

What is the normal PR interval?

Answer 9

0.12 - 0.20 seconds

Question 10

Aetiology of heart block

Answer 10

Coronary artery disease
Cardiomyopathy
Fibrosis of the conducting tissue (esp. elderly)

Question 11

What causes an atrioventricular block?

Answer 11

Block in the AV node or His bundle?

Question 12

What does a block inferior to the AV node/His bundle in the conduction system cause?

Answer 12

Bundle branch blocks (right or left)

Question 13

What is a 1st degree AV block?

Answer 13

Delayed AV conduction
Prolonged PR interval (>0.22 s) on the ECG
No change in the HR and Tx unnecessary

Question 14

Whats a 2nd degree AV block?

Answer 14

Some atrial impulses fail to reach ventricles

Intermittent failure of AV impulse

Question 15

What is Wencheback block phenomenon also called?

Answer 15

Type I block (in second degree AV block)

Question 16

What happens in type I second degree AV block?

Answer 16

Progressive PR interval prolongation until a P wave fails to conduct (i.e absent QRS after the P wave)

PR wave then returns to normal + cycle repeats itself

Question 17

What happens in type II 2nd degree AV block?

Answer 17

Dropped QRS complex isn’t proceeded by progressive PR interval prolongation. Usually QRS complex is wide

Question 18

what type of heart block is this:

When every 2nd or 3rd P wave conducts the ventricles
e.g. 2 P waves to each QRS complex

Answer 18

2:1 or 3:1 (advanced) type of second degree AV block

Question 19

What heart block is it when P waves and QRS complexes occur independently of teach other on the ECG

Answer 19

Third degree AV block/ complete heart block

All atrial activity fails to reach the ventricles

Question 20

In complete atrioventricular heart block how are ventricular contractions maintained?

Answer 20

By a spontaneous escape rhythm originating below the site of the block in either the His bundle or the His-Perkinje system

Question 21

In bundle branch block, what does the shape of the QRS complex depend on?

Answer 21

Whether the right or left bundle is blocked

It will be wide though as its always a complete block

Question 22

RBBB - what happens and what kind of patients does it occur in?

Answer 22

The 2 ventricles dont contract simultaneously
Sequential spread of an impulse –> secondary R wave

Healthy pts, PE, RV hypertrophy, IHD and congenital

Question 23

LBBB indicates what?

Answer 23

underlying pathology

IHD, LVH, aortic valve disease + after cardiac surgery

Question 24

Where do supra ventricular tachycardias arise from?

Answer 24

The atrium or the atrioventricular junction

Conduction is via the His-Purkinje system

Question 25

Sinus tachycardia cause

Answer 25

Physical response during exercise + excitement Also occurs with: fever, anaemia, HF, thyrotoxicosis, acute PE, hypovolaemia and drugs

Question 26

Tx sinus tachycardia

Answer 26

Treat underlying cause | BBs may be used to slow sinus rate

Question 27

Whats a tachycardia? and the 2 types?

Answer 27

>100 bpm SV ones - from the AV node Ventricular ones - from bundle of His

Question 28

3 cellular mechanisms for cardiac arrhythmias

Answer 28

1. abnormal conduction/re-entry 2. abnormal automaticity: depolarisation-induced automaticity 3. triggered activity: - EAD - DAD Early (EAD) and delayed (DAD) after depolarizations

Question 29

How can non-pacemaker sites result in enhanced automaticity and therefore an arrhythmia?

Answer 29

``` Depolarised tissue e.g. ischamia, scar Metabolic/electrolyte imbalance Relatively 'depolarised' MP Reduced threshold potential Increased Ca2+ current ```

Question 30

What are AV junctional tachycardias a result of?

Answer 30

re-entry circuits in which there are 2 separate pathways for impulse conduction

Question 31

What is AVNRT? | Whats it a result of

Answer 31

Atrioventricular nodal re-entry tachycardia Most common SVT Due to a ring of conducting pathway in AV node. 'Limbs' have differing conduction times + refractory periods Re-entry circuit. Impulse --> circus movement tachycardia

Question 32

What would the ECG of AVNRT show?

Answer 32

discrete P waves not visible | QRS complex usually normal shape as ventricles are activated in the normal way, down BoH

Question 33

Whats AVRT?

Answer 33

AV reciprocating tachycardia. NOT NODAL Due to presence of accessory pathway that connects the atria and the ventricles

Question 34

What is the delta wave a feature of?

Answer 34

Wolff-PArkinson-White syndrome - a congenital abnormality (a type of AVRT)

Question 35

ECG of Wolff-Parkinson-White syndrome

Answer 35

Path allows some of the atrial depolarisation to pass quickly to the ventricle before it gets through AV node Early depolarisation of part of the ventricle --> shortened PR interval and a slurred start to the QRS (delta wave) QRS is narrow

Question 36

What does the magnitude of the delta wave depend on?

Answer 36

how much of myocardium is affected by the accessory pathway

Question 37

Symptoms of AV junctional tachycardias

Answer 37

rapid regular palpitations usually with abrupt onset and sudden termination other: dizzy, dyspnoea, central chest pain + syncope

Question 38

Acute management of AV junctional tachycardia

Answer 38

Aim: to restore + maintain sinus rhythm | - emergency cardioversion

Question 39

Acute Mx for AV junctional tachycardia if haemodynamically stable?

Answer 39

Increase vagal stimulation of the sinus node by Valsalva mechanism Adenosine

Question 40

What is adenosine and what's its mechanism of action?

Answer 40

short-acting AV nodal-blocking drug that will terminate most junctional tachycardias Increases AV node refractoriness, breaking the re-entry circuit --> cardioversion

Question 41

Features of atrial fibrillation?

Answer 41

1. irregularly irregular 2. varying rate 3. absent p waves

Question 42

Presentation of atrial fibrillation?

Answer 42

usually incidental finding but we worry about CLOTS (associated with 5 fold increase in stroke) no clear p waves on ECG

Question 43

the 3 aspects to atrial fibrillation management

Answer 43

a. rate control b. rhythm control c. thromboprophylaxis

Question 44

How would you control the rate therapeutically for AF?

Answer 44

BB or calcium antagonists

Question 45

Rhythm control management for AF?

Answer 45

Electrical direct current (DC) cardioversion and then administration of BBs to suppress the arrhythmia

Question 46

Symptoms of ventricular ectopic premature beats

Answer 46

asymptomatic. or extra beats/ missed beats/ heavy beats

Question 47

What happens in ventricular ectopics ECG

Answer 47

beat isn't conducted to ventricles through the normal conducting tissue QRS complex on ECG is widened with bizarre configuration

Question 48

Tx for ventricular ectopics

Answer 48

beta blockers if symptomatic e.g. atenolol

Question 49

ECG for sustained ventricular tachycardia

Answer 49

>30 seconds. rapid ventricular rhythm with broad abnormal QRS complexes

Question 50

What is non-sustained ventricular tachycardia?

Answer 50

VT >/= 5 consecutive beats but lasting

Question 51

How is recurrence of sustained ventricular tachycardia prevented?

Answer 51

beta-blockers or implants bel cardiac defibrilator

Question 52

What's long QT syndrome?

Answer 52

ventricular depolarisation is greatly prolonged

Question 53

Causes of long QT syndrome?

Answer 53

congenital electrolyte disturbances variety of drugs

Question 54

Symptoms of long QT syndrome

Answer 54

palpitations, syncope (from polymorphic VT which normally stops spontaneously but may degenerate into VF)

Question 55

Tx of long QT syndrome

Answer 55

underlying cause + IV isoprenaline

Question 56

What natural hormone is isoprenaline similar to?

Answer 56

epinephrine/adrenaline

Question 57

What would no effective CO cause?

Answer 57

cardiac arrest!!!

Question 58

Atrial flutter rate?

Answer 58

Atrial rate is typically 300 bpm and AV node usually conducts every second flutter beat, giving ventricular rate of 150 bpm

Question 59

Atrial flutter ECG

Answer 59

'sawtooth' flutter waves (F waves)