2. • Defibrillation is a non-synchronized
delivery of energy during any phase of the
cardiac cycle.
• Cardioversion the delivery of energy that
is synchronized to the large R waves or
QRS complex.
2
3. • The delivered shock in both defibrillation and
cardioversion causes electric current to go from the
negative to the positive electrode of the defibrillator,
passing the heart on its way.
• It causes all the heart cells to contract
simultaneously.
• interrupting and terminating the abnormal electrical
rhythm without damaging the heart, and thus
allowing the sinus node to resume normal
pacemaker activity.
3
4. Indications for defibrillation include the
following:
• Pulseless ventricular tachycardia (VT)
• Ventricular fibrillation (VF)
4
5. • At the end of the 18th century two physiologists, Prévost and Batelli,
performed shock experiments on the hearts of dogs. They applied
electrical shocks and discovered that small shocks put the dogs'
hearts in to VF and this was successfully reversed with a larger shock.
It was first used in humans by Claude Beck, a cardiothoracic surgeon -
on a 14 year-old boy undergoing cardiothoracic surgery for congenital
heart disease. Electrodes were placed across the open heart. Closed
chest defibrillation was not discovered until the 1950s in Russia. But it
was not until 1959 that 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. In the 1980s the biphasic
waveform was discovered. This provided a shock at lower levels of
energy which were just as efficacious as monophasic shocks.
5
6. • Automated external defibrillators (AEDs)
• Semi-automated AEDs
These are 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
• Standard defibrillators with monitor - may be monophasic
or biphasic Transvenous or implanted
6
7. • In monophasic systems, the current travels only in
one direction - from one paddle to the other.
• In 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.
7
8. • They are associated with fewer burns and less
myocardial damage.
• With monophasic shocks, the rate of first shock
success in cardiac arrestsdue to a shockable
rhythm is
• only 60%, whereas with biphasic shocks, this
increases to 90%
8
10. • The largest electrode or pad works best.
8-12 cm is acceptable. Smaller electrode
size may result in myocardial necrosis and
therefore be harmful.
10
13. Indications for synchronized electrical cardioversion
include the following:
• Supraventricular tachycardia SVT
• Atrial fibrillation
• Atrial flutter
• Any patient with reentrant tachycardia with narrow or wide
QRS complex (ventricular rate >150) who is unstable (eg,
chest pain, pulmonary edema, hypotension)
13
15. Sinus Tachycardia
• Rate above 100 beats/minute
• The rhythm is regular
• All intervals are within normal limits
• There is a P for every QRS and a QRS for every P
• The P waves all look the same
• Caused by fever, stress, caffeine, nicotine, exercise, or by
increased sympathetic tone
• Treatment is to take care of the underlying cause
16.
17. The source of the impulse is some
where above ventricles , but the
impulse then spread to the ventricles
so the heart beats faster than normal .
Wednesday, 3 July 2013 17
18. Supraventricular Tachycardia
(SVT)
• Rate is between 150 and 250 beats/minute
• The rhythm is regular
• QRS intervals can be within normal limits
• There can be a P wave, but more likely it will be
hidden in the T wave or the preceding QRS wave
• Starts and stops abruptly
• Treat with Valsalva maneuver or adenosine IV
20. Atrial Flutter
• Atrial rate is between 250 and 350 beats/minute.
Ventricular rate can vary
• The rhythm is regular or regularly irregular
• There is no PR interval. QRS may be normal
• 2:1 to 4:1 f waves to every QRS
• There are no P waves; they are now called flutter waves
• Problem: Loss of atrial kick and ventricular conduction is
too fast or too slow to allow good filling of the ventricles
22. Ventricular Tachycardia
• Rate is between 100 and 200 beats/minute
• The rhythm is regular, but can change to
different rhythms
• No PR interval; QRS is wide and aberrant
• There may be a P wave, but it is not related
to the QRS
23.
24. Ventricular Fibrillation
• Rapid, irregular rhythm made by stimuli
from many different foci in the ventricula
• Produces no pulse, blood pressure, or
cardiac output
• Can be described as fine or coarse
• Most common cause of sudden cardiac
death
