Supraventricular tachycardia, abbreviated as SVT, is a condition characterized by rapid heartbeat, which primarily occurs due to improper electrical activity of heart. Such a type of condition arises at or above the atrioventricular node.
Episodes of fast heartbeat can last for few minutes to 1 to 2 days until the condition gets treated. Increased heartbeat of more than 150 – 279 beats/minutes causes poor cardiac output, which in turn gives rise to the following signs and symptoms :
The following methods are involved in the treatment of supraventricular tachycardia:
In majority of cases, prognosis of the condition mainly depends on the underlying heart disease. Individuals with SVT having a structurally normal heart, have an excellent prognosis. In cases, when SVT occurs due to Wolff-Parkinson-White syndrome, there is a certain percentage of sudden death due to development of atrial fibrillation .
Patients with paroxysmal SVT are at an increase risk of developing heart failure, myocardial ischemia and pulmonary edema. Individuals, who do not have any congenital heart defect and are suffering from SVT, are at least risk of sudden death.
SVT has many causes among which the noted cause is Wolff-Parkinson-White syndrome which can be inherited. It can be caused by other underlying diseases like chronic obstructive pulmonary disease (COPD) or heart failure. Prolonged intake of medicines like digoxin or theophylline, and heart surgery can also predispose to the development of the condition.
Anatomically, the heart has a total of 4 chambers, constituting of 2 atria and 2 ventricles. A heartbeat occurs as a result of electrical signal that is produced by the sinoatrial node. These electrical signals spread across the muscles of the heart causing it to contract, thereby producing a “beat”. Any disturbance in this pathway causes abnormal electrical signals to be transmitted to heart, and this gives rise to the condition known as supraventricular tachycardia. Tachycardia means fast heartbeat and supraventricualr means the region above the ventricles. Therefore, fast heartbeat that originates within the ventricles is termed as supraventricualr tachycardia .
Paroxysmal SVT occurs in about 1 – 3 cases per 1000 individuals. In other words, it has a prevalence rate of 0.2%. Of the several types, atrial fibrillation is the most common type affecting approximately 3 million individuals of US. Statistics have revealed that, by the year 2050, atrial fibrillation will affect more than 7.5 million people.
The incidence of Wolff-Parkinson-White syndrome is estimated to occur in about 3 out of every 1000 individuals  .
There are two mechanisms that trigger the onset of SVT; re-entry and automaticity. In the re-entry mode, individuals experience a sudden increase in the heartbeats; which is characterized by about 150 – 200 beats per minute. In the automaticity mode, there is a gradual increase in heartbeat. Such a type of condition occurs majorly due to generation of the heart’s own electrical signal.
Supraventricular tachycardia can also occur as a result of abnormal electrical activity in the heart due to congenital defect; a condition known as Wolff-Parkinson-White syndrome. In this syndrome, there is a “bypass tract” that bypasses the atrioventricular node, which in turn results in transmission of the fast heartbeat directly to the ventricles. This creates several loops of overlapping signals which predisposes an individual to develop SVT .
There is no way to prevent the onset of SVT. However, to prevent the recurrence of SVT in the future, medications such as verapamil and beta-blockers are used. These drugs along with anti-arrhythmics can also be given for preventing recurrence of SVT episodes.
Supraventricular tachycardia (SVT) is a potentially life threatening condition, demanding immediate medical attention. SVT often refers to paroxysmal supraventricular tachycardia which is an episodic disorder with an abrupt onset and termination. Medications and other therapies help in controlling the occurrence of SVT .