What can cause the heart to go into VF?  How does a defibrillator work
to restore the heart to its proper condition?  How significant is each
minute between the onset of VF and the application of a defibrillator?

Hi joestrom:

Thanks for the interesting questions. I'll tackle your questions one at a time.

1. What can cause the heart to go into VF?

Having a heart attack is the most common cause of ventricular
fibrillation - but there are other causes as well. The following list
shows them:

* acute or previous heart attack
* heart-related conditions such as high blood pressure, poor blood
supply to the heart muscle because of coronary artery disease,
atherosclerosis, heart valve disease, heart muscle disease called
cardiomyopathy, tumors, and infections
* ischemia (lack of oxygen to the heart muscle because of narrowed
coronary arteries or shock)
* congenital heart disease 
* heart surgery
* diseases of the heart muscle, such as cardiomyopathies
* electrocution accidents or accidents involving direct trauma to the heart
* hypothermia
* proarrhythmias from drug toxicity
* chemical imbalances in the body
* other medical conditions such as thyroid disease, certain lung
diseases, electrolyte imbalance, and alcohol and drug abuse

Ventricular Fibrillation
URL: http://health.allrefer.com/health/ventricular-fibrillation-info.html

Ventricular Fibrillation or Pulseless Ventricular Tachycardia
URL: http://www.nda.ox.ac.uk/wfsa/html/u10/u1006_03.htm

Cardiac Arrythmias
http://www.uhhs.com/download/heart/arrythmias.pdf

What is Ventricular Fibrillation?
http://www.medtronic.com/tachy/patient/whatis_vf.html


2. How does a defibrillator work to restore the heart to its proper condition?  

A very short explanation can be found here:

The Defibrillator File 
URL: http://www.nitcentral.com/oddsends/defibril.htm
Quote: "According to Darla, a defibrilator "de-fibrillates." When the
heart is fibrillating, it is fluttering. The heart monitor looks like
a series of "V"s. The defibrillator jolts the heart back into a normal
rhythm so it can actually pump blood to the body. If a person is
flatline, Darla says that the defibrillator won't do any good!"

Another good explanation is found here:

CPR's Role in Rescue
URL: http://science.howstuffworks.com/cpr5.htm
Quote: "In order to restore a normal heartbeat, an electrical shock
must be delivered to the heart. This is called defibrillation. The
shock itself doesn't switch the heart back on - it's not like flipping
a tripped circuit breaker. Instead, defibrillation actually stops the
heart briefly! This gives the pacemaking cells a chance to
re-establish a normal heartbeat."


3. How significant is each minute between the onset of VF and the
application of a defibrillator?

An excellent answer can be found here:

Sudden Cardiac Arrest
URL: http://www.heartsine.com/support/
Quote: "As the length of time between the onset of sudden cardiac
arrest and the application of defibrillation therapy increases the
less likely it will become that the restoration of a normal heartbeat
and full recovery will occur. In general, for every minute that passes
between the onset of cardiac arrest and defibrillation the probability
of survival decreases by 7 to 10 percent. After 10 minutes the
probability of survival is extremely low."

Search Strategy (on Google):
* VF OR "Ventricular fibrillation" causes 
* "causes of VF OR "cause of Ventricular fibrillation" 
* how does a defibrillator work?
* "defibrillator works"
* "defibrillator works" normal rhythm
* VF "time between" defibrillation

I hope this helps!

websearcher