
6
Overview
Sudden Cardiac Arrest
Sudden cardiac arrest (SCA) is a condition in which
the heart suddenly stops pumping blood eectively
due to a malfunction of the heart’s electrical system.
Oen victims of SCA have no prior warning signs
or symptoms. SCA also can occur in people with
previously diagnosed heart conditions. Survival
from SCA depends on immediate and eective
cardiopulmonary resuscitation (CPR).
The use of an external debrillator within the rst
few minutes of a collapse can greatly improve
a patient’s chance of survival. Heart attack and
SCA are not the same, though sometimes a heart
attack can lead to an SCA. If you are experiencing
symptoms of a heart attack (chest pain, pressure,
shortness of breath, tight feeling in the chest or
elsewhere in the body), immediately seek medical
attention.
Sinus Rhythm and Ventricular Fibrillation
The normal heart rhythm, known as sinus rhythm,
creates electrical activity resulting in coordinated
contraction of the heart muscle. This generates
normal blood ow around the body.
Ventricular brillation (V-b or VF) is a condition
in which there is uncoordinated contraction of the
heart muscle, making it quiver rather than contract
properly. Ventricular brillation is the most
commonly identied arrhythmia in SCA patients. In
victims of SCA it is possible to re-establish normal
sinus rhythm by means of an electric shock across
the heart. This treatment is called debrillation.
Ventricular Tachycardia
Ventricular tachycardia (VT) is a type of tachycardia
(rapid heartbeat) that arises from improper
electrical activity of the heart. VT starts in
the bottom chambers of the heart, called the
ventricles. Although there are many dierent types
of VT, this arrhythmia can be potentially life-
threatening if the patient presents with no pulse
and is unresponsive. If not treated with immediate
debrillation VT may lead to other arrhythmias.
Treatment by AED
It is a common misconception that CPR alone
and calling emergency services is enough. CPR is
a temporary measure that maintains blood ow
and oxygen to the brain. CPR alone will not return a
heart to a normal rhythm during VF or VT. The key
to survival is debrillation – and the sooner
the better.
Debrillation is a common treatment for life-
threatening arrhythmias, mainly ventricular
brillation. Debrillation consists of delivering an
electrical shock to the heart with a device called
a debrillator. This restores normal heart muscle
contractions and allows normal sinus rhythm to
be restored by the body’s natural pacemaker in
the heart.