NBE lecture

1. Defibrillation and Cardioversion
Dr.Venugopalan P P
DA,DNB,MNAMS,MEM-GW
Director ,Emergency Medicine Aster DM healthcare
PG Teacher -EM NBE
Deputy Director -MIMS Academy

2. Defibrillation
• Defibrillation - is the
treatment for immediately
life-threatening
arrhythmias with which
the patient does not have
a pulse
• Ventricular fibrillation
(VF) or pulseless
ventricular tachycardia
(VT)

3. Cardioversion
Cardioversion - is any process that
aims to convert an arrhythmia back
to sinus rhythm.
Electrical cardioversion is used
when the patient has a pulse but is
either unstable, or chemical
cardioversion has failed or is
unlikely to be successful
Scenarios may be associated with
chest pain, pulmonary oedema,
syncope or hypotension.
Used in less urgent cases - eg,
atrial fibrillation (AF) - to try to
revert the rhythm back to sinus

4. The aim in both are to deliver electrical energy to the heart to stun the heart momentarily and thus
allow a normal sinus rhythm to kick in via the heart's normal pacemaker, ie the sinoatrial node.
Defibrillation and Cardioversion

5. When to defibrillate …
ASAP ……

6. Defibrillation- A bit of history
• 18th century two
physiologists, Prévost
and Batelli, performed
shock experiments on the
hearts of dogs.
• Applied electrical shocks
and discovered that small
shocks put the dogs'
hearts into VF and this
was successfully reversed
with a larger shock

7. Defibrillation-A bit of history
It was first used in humans
by Claude Beck, a cardio-
thoracic surgeon - on a boy
aged 14 years who was
undergoing cardio-thoracic
surgery for congenital heart
disease.

8. Defibrillation- A bit of history
1959-Bernard Lown
designed the modern day
monophasic defibrillator
This is based on the
charging of capacitors
and then delivering of a
shock by paddles over a
few milliseconds.

9. Defibrillation-A bit of history
1980s the biphasic
waveform was
discovered.
This provided a shock at
lower levels of energy
which were just as
efficacious as
monophasic shocks.

10. Mono phasic Vs Biphasic
Monophasic systems, the current travels only in one direction - from one paddle to the
other.
Biphasic systems, the current travels towards the positive paddle and then reverses and
goes back; this occurs several times
Biphasic shocks deliver one cycle every 10 milliseconds and they are associated with
fewer burns and less myocardial damage
Mono phasic shocks, the rate of first shock success in cardiac arrests due to a shockable
rhythm is only 60%, whereas with biphasic shocks, this increases to 90%.
However, this efficacy of biphasic defibrillators over mono phasic defibrillators has not
been consistently reported

11. Type of Defibrillators
• Automated External Defibrillators [AED]
• Semi- Automated AEDs
• Standard defibrillators with Monitor
• Trans-venous or Implanted defibrillators

12. AED
Does not require special medical
training to use
Found in public places - eg, offices,
airports, train stations, shopping
centres.
Analyse the heart rhythm and then
charge and deliver a shock if
appropriate.
It cannot be overridden manually
and can take 10-20 seconds to
determine arrhythmias.
Unsurprisingly ease of use and
speed of use are important factors
for success

13. Four steps of AED
operations
• Power on
• Attach paddle
• Analyse Rhythm -Stand clear
• Shock- Stand clear

14. Semi Automated AEDs
Similar to AEDs but can
be overridden and usually
have an ECG display.
They tend to be used by
paramedics.
They also have the ability
to pace.

15. Standard Defibrillators
• Monophasic
• Biphasic - Different
waveforms
• Biphasic Truncated Exponential
(BTE) waveform
• Rectilinear Biphasic Waveform
(RBW)

16. Implantable Cardiac
Defibrillators -ICD
• Trans-venous
• Implanted

17. Paddles versus Patches
Paddles were originally used but their
use is being superseded by adhesive
patches.
Adhesive patches are placed most
commonly antero-apically - the anterior
patch goes under the right clavicle and
the apical patch is placed at the apex.
Adhesive electrodes are better, as they
stick to the chest wall, so there is no
mess with gels.

18. Paddles versus Patches
Paddles require a significant level of
force, which is not needed with
adhesive electrodes.
Adhesive electrodes also allow good
ECG trace without interference.
Adhesive electrodes are also safer, as
no operator is required
Before discharging a shock, it is
important to ensure everyone is clear of
the patient.

19. Energy Level
Cardiac Arrest
Monophasic - Single
shocks started at and
repeated at 360 J.
Biphasic -Single and
repeated shock 200 J
Use maximum energy
available in your machine

20. COACHED
Continue Chest Compressions
Oxygen Away
All Else Clear
Charging
Hands Off
Evaluate the Rhythm -
Shockable vs Non-shockable
Defibrillate or Disarm

21. Cardioversion

22. Indications
• Unstable tachycardia
• Decompensated rapid AF with a rapid ventricular
response - eg, a hypotensive patient, not
responding to medical therapy
• VT with a pulse
• Supraventricular tachycardias including AF without
decompensation; not acutely urgent

23. Cardioversion the shock has to be properly timed, so that it does not occur during
the vulnerable period, ie during the T wave. If this occurs then VT can be triggered.
Synchronisation

24. Signs of Unstable
Tachycardia
• AMS
• Cold and clammy extremities
• Chest pain
• Dyspnea
• Diaphoresis
• Hypotension
• Rapid thready pulse
• Syncope

25. Atrial Fibrillation-Special
considerations
Cardioversion is used for rhythm
control.
Not all cardioversion is successful
and, at one year, 50% redevelop AF
Medical treatments and
cardioversion are of similar efficacy
(unless permanent AF).
Cardioversion of AF is associated
with increased risk of
thromboembolic disease (TED)
Anticoagulation is required for at
least three weeks before and at least
four weeks afterwards

26. Atrial Fibrillation-Special
considerations
Transoesophageal
echocardiogram-TEE- during the
procedure, in order to look for
thrombus
POC Echo to rule out Thrombus
Sotalol or amiodarone can be given
for at least four weeks prior to
cardioversion in patients who have
had a previous failure to cardiovert
or early recurrence of AF .
Others advocate the use of
medications such as sotalol and
amiodarone to maintain sinus
rhythm after cardioversion

27. How to Cardiovert ?
Cardioversions are performed under general anaesthesia or sedation.
Sedation decisions need to be made carefully
Get consent
Usually done in theatres or Cardiac ICU or Resuscitation bay with
the support of an anaesthetist , Cardiologist or Emergency physician
or Intensivist
The majority of cardioversions are elective procedures; however,
some are performed when patients are acutely unwell with
tachycardia - eg, chest pain, breathlessness.
Decisions regarding sedation will need to be made and in practice
this involves the anaesthetist.

28. How to Cardiovert ?
Get Crash cart ready
Turn on the machine and attach adhesive electrodes (efficacy may be better with anterior-
posterior electrodes)
Choose the energy level.
IV-O2 -Monitor - Get a clearly visible trace on the monitor - eg, using lead II.
Hit the 'sync' button - usually a blip or dot appears on the monitor, marking each QRS
complex. Higher starting energy is associated with better success and fewer shocks
Broad complex tachycardia and AF: monophasic - begin with 200 J, or biphasic - 120-150
J.
Atrial flutter and narrow complex tachycardia: monophasic - 100 J, or biphasic - 70-120 J.
Charge.

29. Synchronisation mark in Monitor

30. How to Cardiovert ?
Ensure all is clear around the bed including Oxygen
Discharge or shock - there may be a 1- to 2-second delay as the
machine ensures synchronisation
Check rhythm after the shock - if sinus rhythm, then stop; if not, then
you may need to deliver another shock at higher energy levels.
Look for burns afterwards and obtain a 12-lead ECG.
Sync may not be successful in tachycardias where the QRS complex
has a variable morphology.

31. Consider Nine C’s of
Cardioversion
• Consent
• Consult as needed
• Consider sedation
• Crash Cart
• Confirm Synchronization
• Confirm shock delivery
• Continuous monitoring
• Consider POC Echo and TEE
• Consider Anticoagulant in AF

32. Paediatric cardioversion/
Defibrillation
Supraventricular tachycardias synchronised
DC shocks are usually given at 1 J/kg.
Cardiac arrest situation with a shockable
rhythm, note the following: Manual
defibrillator should be used for children <1
year of age. Manual defibrillator energy levels
are 4 J/kg.
AED:
Child aged 1-8 years - either use paediatric
pads which reduce the energy delivered or
AED device with paediatric program to reduce
the energy delivered.
Child aged >8 years - same energy levels as
adult Advanced Life Support (ALS)
guidelines.
AED can be used in Infants also using infant
Pads

33. Thanks a lot for Patient listening
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