Glossary

Ventricular Fibrillation (VF) is a very rapid, uncoordinated, ineffective series of contractions throughout the lower chambers of the heart.  It is an often fatal form of arrhythmia.

Unless VF is stopped and normal sinus rhythm achieved, these chaotic impulses cause a fatal loss of blood flow.  When the ventricles begin to quiver, and do not employ coordinated contractions, the heart is said to be fibrillating.  In this condition the ventricles cannot pump blood from the heart.  Ventricular fibrillation (VF or V-Fib) is the most serious kind of abnormal heart rhythm, and is a form of cardiac arrest.  It involves the pumping of the lower chambers of the heart.

Ventricular Tachycardia (VT or V-Tach) is a rapid heart beat that originates in one of the lower chambers (the ventricles) of the heart.  To be classified as tachycardia, the heart rate is usually at least 100 beats per minute.

This type of rapid heart rate can originate in either the left or right ventricle.  Ventricular tachycardia which lasts more than 30 seconds is referred to as sustained ventricular tachycardia (but not the abbreviated ‘SVT’).  A period of three to five rapid beats is called a salvo, and six beats or more, but lasting less than 30 seconds is called non-sustained ventricular tachycardia (NSVT).  Rapid ventricular rhythms are more serious than rapid atrial rhythms because they make the heart extremely inefficient.  They also tend to cause more severe symptoms, and have a much greater tendency to result in death.

Although generally considered to be among the life-threatening abnormal rhythms, benign forms of VT do exist.  These occur in people without any structural heart disease.