Most supraventricular tachycardia results from abnormal electrical connections in the heart that short-circuit the normal electrical system. What causes these abnormal pathways is not clear. In the case of Wolff-Parkinson-White syndrome, the condition may be inherited. Overly high levels of the heart medicine digoxin (such as Lanoxicaps or Lanoxin) can cause supraventricular tachycardia.

Supraventricular tachycardia (SVT) is an abnormal fast heart rhythm that starts in the upper chambers, or the atria, of the heart. ("Supraventricular" means above the ventricles, "tachy" means fast, and "cardia" means heart.) Normally, the heart's electrical system precisely controls the rhythm and rate at which the heart beats. In supraventricular tachycardia, abnormal electrical connections (or abnormal firing of the connections) cause the heart to beat too fast.

Sometimes it is normal to have an increased heart rate—for example, during exercise, with a high fever, or when under stress. This fast heart rate, called sinus tachycardia, is a normal response to these stressors and is not considered a medical problem. This topic addresses the types of supraventricular tachycardias that are considered abnormal. These include: Atrioventricular nodal reentrant tachycardia (AVNRT), the most common type (after atrial fibrillation).

A description of your symptoms is one of the most important clues in diagnosing supraventricular tachycardia. Your doctor will ask what, if anything, triggers the episodes, how long they last, if they start and stop suddenly, whether anything stops them, and whether the beats are regular or irregular. Because supraventricular tachycardia is a problem with your heart's electrical system, the most important test is an electrocardiogram (EKG, ECG).

Patients may experience sensations of flip flops, heart pounding or a fluttering sensation after an ablation and this is considered perfectly normal. If a person finds that their heart is racing and they feel that it is the same problem as before the ablation, we ask that people go to their nearest walk-in clinic, Emergency Department or family doctor’s office to get an electrocardiogram recording of their palpitations.

You can reduce your risk of having episodes of supraventricular tachycardia by avoiding certain stimulants or stressors, such as caffeine, nicotine, some medicines (for example, decongestants), illegal drugs (such as methamphetamines and cocaine), excess alcohol, lack of sleep, and overeating. If fast heart rates continue, long-term medicines such as beta-blockers may be used to help prevent a recurrence of the fast heart rate.

Sustained sinus bradycardia or tachycardia is defined by more than 30 seconds of a stable rhythm to distinguish it from transient responses associated sleep disordered breathing events or arousals.