A supraventricular tachycaria (SVT) is a tachycardia or rapid rhythm of the heart in which the origin of the electrical signal is either the atria or the AV node. These rhythms, by definition, are either initiated or maintained by the atria or the AV node. This is in contrast to the deadlier ventricular tachycardias, which are rapid rhythms that originate from the ventricles of the heart, that is, below the atria or AV node.