"Supraventricular tachycardia (SVT)” is a rapid heart rate caused by electrical impulses that originate from a site other than the SA node, such as the muscle of the atria (known as “atrial myocardium”) or the AV node.
The heart is made up of four chambers. Upper two chambers are called left and right atria and bottom two chambers are called left and right ventricles. Heart valves are present between right atrium and ventricle, left atrium and ventricle, from right ventricle to the main pulmonary (lung) artery and from left ventricle to aorta (main artery of body).
Normal control or pacemaker of the heart is sinoatrial (SA) node. It starts electrical impulse to cause contraction of atria so that blood is pumped into ventricles. Through atrioventricular (AV) node, the pulse moves into vetnricles causing contraction and pumping of blood into lungs (right ventricle) and the body (left ventricle).
"Supraventricular" means "above the ventricles" and "tachycardia" is "fast heart rate". Hence, Supraventricular tachycardia (SVT) refers to an abnormally rapid heart rate originating above the heart's ventricles.
The condition occurs during time of low activity or rest. It can go unnoticed when it is periodic but becomes a serious problem if occurs repetitively.
Prolong SVT can lead to myocardial (heart muscle) failure as well as congestive heart failure.
Common symptoms associated with different states of SVT are
Slow SVT or infrequent attacks of SVT
No clinical signs
Fast SVT (heart rate above 300 beats per minute)
Congestive heart failure (CHF)