Dr. Dharmendra Joshi (DJ)

Defibrillation & Cardioversion

• History• Case & Census• Definition• Types• Principles• Indications• Contraindications• Anaesthesia• Equipments• Positioning• Technique• Safety• Complications• Troubleshooting

Topics

History

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

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.

History

• 1947: First defibrillation on humans.

History

• 1966: Belfast Ambulance transported physicians performed first pre-hospital defibrillation.

• 1969: First pre-hospital defibrillation by non physicians.

• 1970’s: Diack, Wellborn and Rullman developed first AED’s.

Chain of Survival

• Early Recognition and Assessment• Early Access• Early CPR• Early Defibrillation

• Early Advanced Cardiac Life Support

Chain of SurvivalSudden cardiac arrest

survival rate:

• Pre-Hospital: 10%• In-Hopsital: 10%

• No record found about patient who was treated by defibrillation or cardioversion in KMCTH, Duwakot in last one month!!!

Case Scenario & Census

• Defibrillation is a non-synchronized delivery of energy during any phase of the cardiac cycle.

• Cardioversion is the delivery of energy that is synchronized to the large R waves or QRS complex.

Definition

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TYPES OF DEFIBRILLATORS

Internal External

DEFIBRILLATOR ELECTRODES Types of Defibrillator electrodes:-

a) Spoon shaped electrode

• Applied directly to the heart.

b) Paddle type electrode

• Applied against the chest wall.

c) Pad type electrode

• Applied directly on chest wall.

DEFIBRILLATOR ELECTRODES

Fig.- Pad electrode

DEFIBRILLATOR ELECTRODES

PRINCIPLE OF DEFIBRILLATION

Energy storage capacitor is charged at relatively slow rate from AC line.

Energy stored in capacitor is then delivered at a relatively rapid rate to chest of the patient.

Simple arrangement involve the discharge of capacitor energy through the patient’s own resistance.

PRINCIPLE OF DEFIBRILLATION

PRINCIPLE OF DEFIBRILLATION

The discharge resistance which the patient represents as purely ohmic resistance of 50 to 100Ω approximately for a typical electrode size of 80 cm2.

This particular waveform Fig 13.9(b) is called ‘ Lown’ waveform.

The pulse width of this waveform is generally 10 ms.

EXTERNAL DEFIBRILLATOR

power supply

energy storage

patient

ECG monitor

timing circuitry

gatecharge discharge

standby

switch is under operator control

applies shock about 20 ms after QRS complex, avoids T-wave

energy (joules)

charge (coulombs)

curr

ent (

amps

)

pulse duration

defibrillation occurs

no defibrillation

DEFIBRILLATOR STRENGTH DURATION CURVE

• Minimum defibrillation energy occurs for pulse durations of 3 - 10 ms (for most pulse shapes).

• Pulse amplitude in tens of amperes (few thousand volts).

STRENGTH DURATION CURVE

– intrinsic characteristics of patient – patient’s disease – duration of arrhythmia – patient’s age – type of arrhythmia (more energy required for v.

fib.)

• Operator selects energy delivered: 50-360 joules, depends on:

STRENGTH DURATION CURVE

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THE POWER OF DEFIBRILLATION• Higher voltages are required for external

defibrillation than for internal defibrillation.• A corrective shock of 750-800 volts is applied within

a tenth of a second.• That is the same voltage as 500-533 no. of AA

batteries!

NORMAL CARDIAC CONDUCTION

ECG tracingElectrical pattern

CARDIAC ARREST

Occlusion of the coronary artery leads to ischemia

Ischemia leads to infarct which causes interruption of normal cardiac conduction

Infarct = VF/VT

SHOCKABLE RHYTHMS

Ventricular Fibrillation Ventricular Tachycardia

• Indications for synchronized electrical cardioversion:

Supraventricular tachycardiaAtrial fibrillationAtrial flutterVentricular tachycardiaReentrant tachycardia with narrow or wide

QRS complex.

Indications

1. Pulse less ventricular tachycardia (VT)

2. Ventricular fibrillation (VF)

Indications: Defibrillation

• Dysrhythmias• Multifocal atrial tachycardia

Contraindications

• Cardioversion:– Almost always under induction or sedation. – Exceptions: hemodynamic instability or if

cardiovascular collapse is imminent. • Defibrillation

– is an emergent maneuver and performed promptly.

Anesthesia

• Defibrillators (automated external defibrillators [AEDs], semi-automated AED, standard defibrillators with monitors)

• Paddle or adhesive patch• Conductive gel or paste• ECG monitor with recorder• Oxygen equipment• Intubation kit• Emergency pacing equipment

Equipments

• Antero-lateral• Antero-posterior

Positioning

Fig. anterior –apex scheme of electrode placement (AED)

Anterior electrode pad

Apex electrode pad

– Emergent application– Elective cardioversion– Repetitive, futile attempts– Advanced cardiac life support (ACLS)

Technique

Waveforms Monophasic Biphasic

Charge Only one direction

Two direction (opposite)

Effectiveness Less effective More effective and at lower energies

Technique Contd…

Monophasic Defibrillation

• Delivers ‘shock’ in one phase• Adult: 200J, 300J, 360J, all subsequent shocks at 360J• Child: 2J/Kg, 2J/Kg, 4J/Kg, all subsequent shocks at

4J/Kg

Biphasic Defibrillation

• Two phases to the delivery of the ‘shock’• Adjusts ‘shock’ according to thoracic impedance• Adult: 150J, 150J, 150J• Child: 1– 2J/Kg

Energy selection:Cardioversion:• Begins with 25-50 J for atrial flutter.• 50-100 J (or the biphasic equivalent) to treat

atrial fibrillation.

Technique Contd…

Defibrillation:• Immediate• Rapid polymorphic ventricular tachycardia (rate

>150 bpm) >> 200-360 J (or biphasic equivalent [100-200 J).

• Monomorphic ventricular tachycardia >> 100-200 J (or biphasic equivalent [50-100 J]).

• Ventricular fibrillation >> 200-360 J (or biphasic equivalent [100-200 J]).

Technique Contd…

Classes of discharge waveform

Fig:- Generation of bi-phasic waveform

The biphasic waveform is preferred over monophasic waveform to defibrillate, WHY?????

• A monophasic type, give a high-energy shock, up to 360 to 400 joules due to which increased cardiac injury and it burns the chest around the shock pad sites.

• A biphasic type, give two sequential lower-energy shocks of 120 - 200 joules, with each shock moving in an opposite polarity between the pads.

Classes of discharge waveform

AUTOMATIC EXTERNAL DEFIBRILLATOR

Rhythm Analysis and the Defibrillator

Video Demonstration

SafetyGeneral Safety• Yourself, other staff

– Dry surface area– Oxygen

• Chest wall– GTN patch– Jewellery– Paddles / Pads not touching

• Technique– One Person– Two Person– Adhesive Pads

Safety

Operator Safety• Assertive• Announce:

– CHARGING, – ALL CLEAR / STAND CLEAR (Visual Check of Area), – SHOCKING

• Check rhythm• Discharge Shock• Continue as per algorithm

PRECAUTIONS IN DEFIBRILLATION PROCESS

The paddles used in the procedure should not be placed:-• on a woman's breasts.• over an internal pacemaker patients.

Before the paddle is used, a gel must be applied to the patient's skin.

Common:• Atrial, Ventricular and Junctional premature beats

Serious:• Ventricular fibrillation (VF)• Digitalis toxicity• Severe heart disease• Thromboembolization (1-3%)• Myocardial necrosis• Pulmonary edema• Painful skin burns

Complications

• Attach the external and internal paddles if the monitor reads, "No paddles."

• Check to ensure that the leads are securely attached if the monitor reads, "No leads."

• Connect the unit to AC power if the message reads, "Low battery."

• Verify that the Energy Select control settings are correct if the defibrillator does not charge.

TROUBLESHOOTING

• Change the electrodes and make sure that the electrodes adapter cable is properly connected if you receive a message of "PACER FAILURE." Restart the pacer.

• Close the recorder door and the paper roll if the monitor message reads, "Check recorder”.

TROUBLESHOOTING

Video Demonstration

‘’Success depends on delivery of current to the myocardium’’

Thank You!!!