Peri-arrest arrhythmias

Question 1

What does an arrhythmia occuring after initial resuscitation from cardiac arrest suggest?

Answer 1

That the patients condition is still unstable and there is a risk of further cardiac arrest

Question 2

Wat are the 3 main classifications of arrhythmias ?

Answer 2

Tachycarrhytmias
Bradyarrhythmias
Arrhythmias with normal heart rates e.g. hypokalaemia.

Question 3

What should be your general approach to all arrhythmias?

Answer 3

• ABCDE - assess for life-threatening features
• ECG monitoring
• 12-lead ECG
• IV access
• If hypoxic give Oxygen.
• Document heart rate and nature of the arrhytmia

Question 4

What features suggest an arrhythmia is life-threatening ?

Answer 4

• Shock
• Syncope
• Heart failure
• Myocardial ischaemia - chest pain &/or ECG changes
• Extremes of HR

Question 5

When heart rate increases what happens to dialstole and systole ?

Answer 5

Both are decreased but diastole is shortened to a greater degree

Question 6

Consider what happens to diastole and systole as heart rate increases and how this might affect cardiac output in a extreme tachycarrhythmia

Answer 6

• Particularly in very fast heart rates >150bpm
• As HR increases there is a reduction in cardiac output (as diastole is shortened and the heart does not have enough time to fill ==> decreased SV)
• Aditionally there will be decrease coronary blood flow potentially causing ischaemia

Question 7

When does the majority of coronary blood flow occur ?

Answer 7

Because these vessels traverse the myocardium, myocardial contraction during systole compresses arterial branches and prevents perfusion. Therefore, coronary perfusion occurs more during diastole rather than systole

Question 8

Regarding bradycardia, HR below what is generally poorly tolerated ?

Answer 8

<40bpm

Question 9

Why do patients with pre-existing heart disease tolerate bradycardia less well ?

Answer 9

They cannot compensate for bradycardia by increasing stroke volume (CO = HR x SV).

Question 10

What are the 4 general tx options for an arrhythmia?

Answer 10

1. No treatment
2. Simple clinical intervention e.g. vagal manoeuvres, percussion pacing
3. Drug treatment
4. Electrical - cardioversion for tachyarrhythmias and pacing for bradycarrhythmias.

If arrhythmia develops due to an underlying condition e.g. AMI, infection, heart failure etc. Make sure to afterwards tx the underlying condition.

Question 11

Why is electrical mx of an arrhytmia the preferred option over drugs if the patient is unstable ?

Answer 11

Because drug tx usually works more slowly and less reliably

Question 12

Life-threatening signs associated with a tachycarrhythmia are uncommon under what HR?

Answer 12

<150bpm

Note - if underlying heart disease or co-morbid they might be unstable with HR’s <150bpm.

Question 13

If a patient has life-threatening signs associated with a tachyarrhytmia what should you do ?

Answer 13

Synchronised cardioversion (upto 3 attempts)

Question 14

If synchronised cardioversion fails to terminate an arrhythmia and adverse features persist what should you do?

Answer 14

• Give IV amiodarone 300mg over 10-20mins
• Then attempt further synchronised cardioversion

Question 15

Why is it important to ensure when cardioverting a tachyarrhythmia it is set to deliver a synchronised shock?

Answer 15

So that it coincides with an R-wave. Otherwise there is a risk of coinciding with a T-wave and causing VF.

Question 16

What should be given to the patient when carrying out synchronised cardioversion?

Answer 16

• Concious sedation e.g. midazolam
• Or GA.

Question 17

What energy should be selected for broad complex tachyarrythmias ?

What energy should be selected for narrow complex tachyarrythmias ?

Answer 17

Broad complext - start with 120-150J
Narrow complex - start with 70-120J. Except AF start with max defibrillator output.

Question 18

If cardioversion is attempted for AF or atrial flutter what defib pad positions should be used? (if feasible)

Answer 18

Antero-posterior

Question 19

If a patient has a tachyarrythmia with no life-threatening features and you want to treat it what will you do ?

Answer 19

Drug therapy - choice depends on arrythmia type.

Question 20

A regular broad complex tachycardia could be ventricular or supraventricular with bundle branch block in origin. What is the safest approach to treating these arrythmias?

Answer 20

To treat all regular broad complex tachycardia as VT unless there has been a prev. diagnosis of SVT with bundle branch block.

Treat with amiodarone 300mg IV over 20-60mins then 900mg over 24hrs. If tachycardia persists after initial 300mg consider DC cardioversion.

Question 21

What is the most likley cause of an irregular broad complex tachycardia?

What are the other potential causes of irregular broad complex tachycardia?

Answer 21

AF with bundle branch block.

Others - AF with ventricular pre-exitation (WPW syndrome) or polymorphic VT (TdP)

Question 22

If someone is stable with TdP what is the treatment ?

Answer 22

• IV Mg2+ 2g over 10mins + correct hypokalaemia and stop QT prolonging drugs.
• Obtain expert help.

Note - often they are unstable and will need cardioversion or usual defibrillation if no pulse.

Question 23

List the potential causes of a regular narrow complex tachycardia ?

Do the same for irregular narrow complex tachycardias.

Answer 23

• Regular narrow complex tachycardias - Sinus tachy, paroxysmal SVT, atrial flutter with reg AV conduction
• Irregular narrow complex tachycardias - Most likely AF, sometimes atrial flutter with irregular AV conduction.

Question 24

Would you attempt to correct ‘treat’ sinus tachycardia ?

Answer 24

NO - this is a physiological response in sick patients, correcting it will usually make them worse.

Question 25

Is paroxysmal SVT usually life-threatening ?

Answer 25

No even in WPW patients, but often causes frightening symptoms. It might be if underlying structural heart disease or coronary disease.

Question 26

What is the typical atrial flutter 2:1 block heart rate?

Answer 26

Usually 150bpm (atrial rate is 300bpm ==> ventricular is 150bpm).

Question 27

In the absence of life-threatening features what is the treatment of regular narrow complex tachycardias?

Answer 27

1. Attempt vagal manoeuvres (carotid sinus massage or valsalva manoeuvre) + record a 12-lead ECG during each manoeuvre. Look out for this revealing atrial flutter waves as the HR slows. 2. If no response then give a rapid bolus of adenosine 6mg IV. 3. If no response repeat with 12mg IV adenosine and then if needed 18mg. 4. If adenosine is contraindicated or fails to terminate rhythm then consider giving verapamil 2.5mg IV or a beta-blocker e.g. metoprolol 2.5mg IV. 5. If narrow complex tachycardia persists then consider sync cardioversion.

Question 28

Vagal manoeuvres or adenosine will terminate almost all paroxysmal SVT's, what does failure to terminate a regular narrow complex tachycardia with there use suggest?

Answer 28

* It suggests an atrial tachycardia i.e. atrial flutter. * Exception to this is if the adenosine wasnt give quick enough or into a peripheral vein.

Question 29

If someone has life-threatening features and a irregular narrow complex tachycardia you would carry out sync cardioversion, what wold you start alongside this but not delay cardioversion in order to give?

Answer 29

Anti-coagulation either LMWH or unfractionated heparin.

Question 30

If there are no life-threatening features and someone has a irregular narrow complex tachycardia what tx could you give ?

Answer 30

Either: * Rate control - with beta-blocker, CCB or digoxin * Chemical cardioversion - propafenone or flecanide (more effective options but cant use if LVSD, IHD or prolonged QTc), amiodarone 300mg IV then 900mg over 24hrs. * Sync cardioversion.

Question 31

What is the general cut-off time for immediately (on presentation) treating someone with chemical or electrical cardioversion for AF and why?

Answer 31

If in AF >48hrs do not cardiovert them until anticoagulated for >= 3weeks or had a trans-oesophageal echo to rule out atrial thrombus. If life-threatening features however then crack on and cardiovert then anticoagulate for >= 4weeks.

Question 32

If someone with known or undiagnosed WPW presents with pre-exitation AF what should you avoid ?

Answer 32

* Adenosine, diltiazem, verapamil or digoxin. * These drugs block AV node and may make exitation worse.

Question 33

What are the causes of bradycardia ?

Answer 33

* Physiological e.g. athletes, sleep * Cardiac - AV block or sinus node disease * Non-cardiac; vasovagal, hypothermia, hypothyroidism, hyperkalaemia * Drug-induced; Beta-blockers, diltiazem, digoxin, amiodarone

Question 34

What is the treatment of bradycardia with life-threatening features?

Answer 34

1. Atropine 500mcg IV can be repeated upto 3mg, given every 3-5mins 2. If inadequate response consider cardiac pacing. If pacing cannot be achieved promptly consider 2nd line drugs (isoprenaline, adrenaline or dopamine (2.5-10mcg/kg/min).

Question 35

When should you consider using aminophylline instead of atropine for bradycardia tx ?

Answer 35

In bradycardia complicating acute MI, spinal cord injuries, or cardiac transplantation. Do not use atropine for cardiac transplant patients (this is because their hearts are denervated and will not respond to vagal blockade by atropine which may cause paradoxical sinus arrest or high-rade AV block).

Question 36

In life-threatening bradycardia with no response to atropine or atropine is contraindicated what should you do ?

Answer 36

* Transcutaenous pacing. * Can do percussion pacing at 50-70bpm whilst setting up cardiac pacing.

Question 37

When should you consider temporary transvenous pacing or early PPM insertion?

Answer 37

* Documented asystole (ventricular standstill >3s) * Mobitz type II AV block * CHB