Defibrillator, Cardioversion, Critical care, Cardiology, Shocks, ICU, Resuscitation, Atrial flutter, Atrial fibrillation

1. Defibrillator & Cardioversion
in Critical Care
Dr Rajesh T Eapen
Burjeel Hospital
Muscat

2. Overview
• Defibrillation is non-synchronized random
administration of shock during a cardiac cycle.
• In 1956, alternating current (AC) defibrillation
was first introduced to treat ventricular
fibrillation in humans.
• Later in 1962, direct current (DC) defibrillation
was introduced.

3. Cardioversion- What is it?
• Cardioversion is a synchronized administration
of shock during the R waves or QRS complex
of a cardiac cycle.

4. History
• 1849: Ludwigg and Hoffa – VF induced by electrical
stimuli

5. History
• 1899: Prevost and Batelli - while a weak stimulus can
produce fibrillation, a stimulus of higher strength
applied to the heart could arrest ventricular
fibrillation and restore normal sinus rhythm.

6. History
• 1947: First defibrillation on humans

7. History
• 1966: Belfast Ambulance transport physicians
performed first pre-hospital defibrillation.
• 1969: First pre-hospital defibrillation by non
physicians.
• 1970’s: Diack, Wellborn and Rullman developed first
AED’s.

8. How does it work?
• During defibrillation and cardioversion,
electrical current travels from the negative to
the positive electrode by traversing
myocardium. It causes all of the heart cells to
contract simultaneously. This interrupts and
terminates abnormal electrical rhythm. This,
in turn, allows the sinus node to resume
normal pacemaker activity.

9. Indications
Indications for defibrillation include the following:
• Pulseless ventricular tachycardia (VT)
• Ventricular fibrillation (VF)
• Cardiac arrest due to or resulting in VF
Indications for electrical cardioversion include the following:
• Supraventricular tachycardia (atrioventricular nodal reentrant tachycardia
[AVNRT] and atrioventricular reentrant tachycardia [AVRT])
• Atrial fibrillation
• Atrial flutter (types I and II)
• Ventricular tachycardia with pulse
• Any patient with re-entrant tachycardia with narrow or wide QRS complex
(ventricular rate >150 bpm) who is unstable (e.g, ischemic chest pain, acute
pulmonary edema, hypotension, acute altered mental status, signs of shock)

10. Anesthesia
• Defibrillation is an emergent maneuver and,
when necessary, should be promptly performed
in conjunction with or prior to administration of
induction or sedative agents.
• Cardioversion is almost always performed under
induction or sedation (short-acting agent such as
midazolam). The only exceptions are if the
patient is hemodynamically unstable or if
cardiovascular collapse is imminent.

11. Equipment
Equipment to be ready:
• Defibrillators (automated external defibrillators [AEDs], semi-automated
AEDs, standard defibrillators with monitors)
• Paddle or adhesive patch
• Conductive gel or paste
• ECG monitor with recorder
• Oxygen equipment
• Intubation kit
• Emergency pacing equipment
• Blood pressure cuff (automatic or manual)
• Pulse recorder
• Oxygen saturation monitor
• Intravenous access
• Suction device
• Code Cart with ACLS (Advanced Cardiovascular Life Support) medications

12. • The use of hand-held paddle electrodes may
be more effective than self-adhesive patch
electrodes.
• The success rates are slightly higher for
patients assigned to paddled electrodes
because these hand-held electrodes improve
electrode-to-skin contact and reduce the
transthoracic impedance.

13. Positioning
• Paddle placement on the chest wall has 2 conventional positions:
anterolateral and anteroposterior.
• In the anterolateral position, a single paddle is placed on the left
fourth or fifth intercostal space on the mid axillary line. The second
paddle is placed just to the right of the sternal edge on the second
or third intercostal space.
• In the anteroposterior position, a single paddle is placed to the right
of the sternum, as above, and the other paddle is placed between
the tip of the left scapula and the spine.
• An anteroposterior electrode position is more effective than the
anterolateral position for external cardioversion of persistent atrial
fibrillation.
• The anteroposterior approach is also preferred in patients with
implantable devices, to avoid shunting current to the implantable
device and damaging its system.

14. Technique
• Emergent application, which may be life-saving, and elective cardioversion
should be used cautiously, with attention to patient selection and proper
techniques. Repetitive, futile attempts at direct current cardioversion
should be avoided.
• Advanced cardiovascular life support (ACLS) measures should be instituted
in preparing the patient, such as obtaining intravenous access and
preparing airway management equipment, sedative drugs, and a
monitoring device.
For elective procedures, prepare as follows:
• Nil per os (NPO) for 8 hours prior to the procedure
• Stop digoxin 48 hours prior to the procedure
• Continue medications on the morning of the procedure under the
direction of the physician
• After the procedure, do not drive, operate machinery, or sign important
documents for 24 hours and/or until sedation has worn off
• There is no patient preparation for emergency procedures.

15. Monophasic versus biphasic
waveforms
• Defibrillators can deliver energy in various waveforms
that are broadly characterized as monophasic or
biphasic.
• Monophasic defibrillation delivers a charge in only one
direction. Biphasic defibrillation delivers a charge in
one direction for half of the shock and in the
electrically opposite direction for the second half.
• Newer defibrillators deliver energy in biphasic
waveforms. Biphasic waveform defibrillators deliver a
more consistent magnitude of current. They tend to
successfully terminate arrhythmias at lower energies
than monophasic waveform defibrillators.

16. Energy selection for defibrillation or
cardioversion
• In 2010, the American Heart Association issued guidelines for initial
energy requirements for monophasic and biphasic waveforms.
Atrial fibrillation energy requirements are as follows:
• 200 Joules for monophasic devices
• 120-200 Joules for biphasic devices
Atrial flutter energy requirements are as follows:
• 100 Joules for monophasic devices
• 50-100 Joules for biphasic devices
Ventricular tachycardia with pulse energy requirements are as follows:
• 200 Joules for monophasic devices
• 100 Joules for biphasic devices
Ventricular fibrillation or pulseless ventricular tachycardia energy
requirements are as follows:
• 360 Joules for monomorphic devices
• 120-200 Joules for biphasic devices

17. ECG strip shows SVT terminated by a synchronized shock
(synchronization marks [arrows] in the apex of the QRS complex) to
normal sinus rhythm.

18. • Ventricular fibrillation terminated by an
unsynchronized shock (arrows) to normal
sinus rhythm.

19. Complications
• The most common complications are harmless arrhythmias, such as
atrial, ventricular, and junctional premature beats.
• Serious complications include ventricular fibrillation (VF) resulting
from high amounts of electrical energy, digitalis toxicity, severe
heart disease, or improper synchronization of the shock with the R
wave.
• Thromboembolization is associated with cardioversion in 1-3% of
patients, especially in patients with atrial fibrillation who have not
been anticoagulated prior to cardioversion. Current American
College of Cardiology (ACC)/American Heart Association (AHA)
guidelines recommend to anticoagulate for 3-4 weeks before and
after cardioversion. The presence of an intracardiac thrombus
should be excluded using transesophageal echocardiography prior
to cardioversion if therapeutic anticoagulation has not been
achieved.

20. Manual - Internal
• Same as manual external except pads are in direct
contact with the heart
Usually found
operating rooms

21. Automated External (AED)
• Uses computer to analyze
heart then suggest
whether a shock is
needed or not
• Usually found in public
places
• Made simpler for anyone
to use

22. Implantable Cardioverter
• Similar to pacemakers,
constantly monitor
patients heart and
administer shocks when
needed
• Limitation – cannot
distinguish when
heartbeat changes due to
exercise and other
activities

23. Types
23
360J 200J

24. 24
Sternum
Apex

25. 25
Automated AED

26. Wearable Cardiac defibrillator
• Portable defibrillator
that is worn as a vest,
monitors heart 24/7
• Not as common as
others

27. 27

28. Cardioversion
• Alive, unstable, tachyarrhythmia
• Unstable?
- Signs of low cardiac output: systolic hypotension <
90 mmHg, altered mental status
- Excessive rates >150/min
- Chest pain
- Heart failure
• Synchronized cardioversion is shock delivery
that is timed (synchronized) with the QRS
complex 28

29. Conditions Starting J (monophasic)
AF 200
Atrial flutter 100
VT 200
SVT 100
29

30. 30

31. 31
Defibrillation Cardioversion

32. 32

33. Types of Cardioversion
Chemical cardioversion
• Antiarrhythmic medications are used to alter flow of electrical activity through the
heart. Based on the clinical situation, chemical cardioversion can be performed in
the hospital in monitored setting or in an outpatient setting.
Electrical cardioversion
• This is also known as direct current (DC) cardioversion. Electrical shock is
synchronized (perfectly timed) to convert an abnormal rhythm to a normal sinus
rhythm. DC cardioversion is performed in the hospital in a monitored setting.
Internal cardioversion
• Internal cardioversion is performed less frequently nowadays, owing to the
presence of biphasic waveform defibrillators and intravenous ibutilide. It is
performed if external cardioversion fails. It is performed using preexisting
implantable cardioverter defibrillators (ICDs), epicardial wires during surgery, or
internal paddles applied to the epicardium in the presence of sternotomy wires.
Advantages of internal cardioversion are that this technique avoids the risk of a
skin irritation from external shock. Disadvantages are that it may damage ICD
systems, it consumes the battery of the ICD, and it does not always convert atrial
arrhythmias.

34. Safety
General Safety
• Yourself, other staff
– Dry surface area
– Oxygen
• Chest wall
– Pads not touching

35. Safety
Operator Safety
• Assertive
• Announce:
– CHARGING,
– ALL CLEAR / STAND CLEAR (Visual Check of Area),
– SHOCKING
• Check rhythm
• Discharge Shock
• Continue as per algorithm