Sudden Cardiac Arrest
(Sudden Cardiac Death)
Medical Author: Benjamin C. Wedro, MD, FAAEM
Medical Editors: Daniel
Kulick, MD, FACC, FSCAI, and Melissa Conrad Stöppler, MD
Cardiac Arrest Symptoms and Causes
Medical Author: Melissa Conrad Stoppler, MD
Medical Editor: Dennis Lee, MD
Singer Michael Jackson died on June 25, 2009, after being rushed to a hospital suffering from cardiac arrest.
Cardiac
arrest is the sudden loss of cardiac function, when the heart abruptly stops
beating. A person whose heart has stopped will lose consciousness and stop
normal breathing, and their pulse and blood pressure will be absent.
Unless resuscitative efforts are begun immediately, cardiac arrest leads to
death within a few minutes. This is often referred to by doctors as "sudden
death" or "sudden cardiac death (SCD)."
Ventricular fibrillation is the most common cause of cardiac arrest. Ventricular
fibrillation occurs when the normal, regular, electrical activation of heart
muscle contraction is replaced by chaotic electrical activity that causes the
heart to stop beating and pumping blood to the brain and other parts of the
body. Permanent brain damage and death can occur unless the flow of blood to the
brain is restored within five minutes. Heart attack is the most common cause of
ventricular fibrillation. Less common causes of cardiac arrest include
respiratory arrest (loss of breathing function), choking, trauma, electrocution,
and drowning.
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Introduction to sudden cardiac arrest
A natural disaster hits, the power goes off and the lights go out. It's a
common scene that plays out during hurricane and tornado seasons, and it's very
similar in trying to explain sudden cardiac arrest. The heart sustains an insult,
the electricity is short circuited, the heart can't pump, and the body dies.
The heart is an electrical pump, where the electricity is generated in
special pacemaker cells in the upper chamber, or atrium, of the heart. This
electrical spark is carried through pathways in the heart so that all the muscle
cells contract at once and produce a heart beat. This pumps blood through the
heart valves and into all the organs of the body so that they can do their work.
This mechanism can break down in a variety of ways, but the final pathway in
sudden death is the same: the electrical system is irritated and fails to
produce electrical activity that causes the heart to beat. The heart muscle
can't supply blood to the body, particularly the brain, and the body dies.
Ventricular fibrillation (V Fib) is the most common reason
for sudden
death in patients. Without a coordinated electrical signal, the bottom chambers of the heart
(ventricles) stop beating and instead, jiggle like Jello. Ventricular
Fibrillation is treated with
electrical shock, but for it to be effective, the shock usually needs to happen
within less than four to six minutes, not only for it to be effective, but also to
minimize brain damage from lack of blood and oxygen supply.
Automatic external
defibrillators (AEDs) are commonly available in public places to allow almost anybody
to treat sudden death. Less commonly, the heart can just stop beating. The
absence of a heart beat is known as asystole (asystole: a=no + systole=beat).
What are the causes of sudden cardiac arrest?
Sudden death is most often caused by heart disease. When blood vessels
narrow, the heart muscle can become irritated because of lack of blood supply.
In heart attack (acute
myocardial infarction), a blood vessel becomes
completely blocked by a blood clot, and there is enough irritability of the
muscle to cause ventricular fibrillation. In fact, the reason many people with
chest pain are admitted to the hospital is to monitor their heart rate and
rhythm for signs that might lead to ventricular fibrillation. Sudden death may
also be the first presentation of heart disease.
Congestive heart failure and heart valve problems, like aortic stenosis
(narrowing of the aortic valve) also increase the risk of sudden cardiac arrest.
Cardiomyopathy is a broad category of heart disease where the heart muscle
does not contract properly for whatever reason. Often it is ischemic, where part
of the heart muscle doesn't get an adequate blood supply for a prolonged period
of time and no longer can efficiently pump blood. People whose ejection
fractions (the amount of blood pumped out of the heart with each heart beat) is
less than 30% are at greater risk for sudden death (a normal ejection fraction
is above 50%). In some people, cardiomyopathy may develop in the absence of
ischemic heart disease.
Inflammation of the heart muscle, known as myocarditis (myo=muscle +
card=heart + itis= inflammation), can also cause rhythm disturbances. Diseases
like sarcoidosis, amyloidosis, and infections can cause inflammation of the
heart muscle.
Some people are born with electrical conducting systems that are faulty,
which place them at higher risk for rhythm disturbances. Some are due to the
wiring, or electrical conduction system, like Wolff-Parkinson-White syndrome,
while others are due to the structural basic structural problems within the
heart, like Marfan syndrome.
Pulmonary embolus, a blood clot to the lung, can also cause sudden death.
Clots form in the leg or arm and may break off and flow to the lung where they
decrease the lung's ability to get oxygen from the air to the body. Risk factors
for blood clots include surgery, prolonged immobilization (for example, hospitalization,
long car rides or plane trips), trauma, or certain diseases like cancer.
Blunt chest trauma, such is in a motor vehicle accident, may result in
ventricular fibrillation. (please see commotio cordis below)
Next: What about sudden cardiac arrest in the young? »
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