ECG for reciprocal tachycardias from AV-connection (AVRT, AVURT)
There are two main types of supraventricular tachycardia (SVT): AV re-entry tachycardias with AV involvement and atrial tachyarrhythmias. (In the Russian-language literature for tachycardia, based on the re-entry mechanism, or “re-entry of the excitation wave”, the term “reciprocal tachycardia” is often used.)
When reciprocal tachycardias involving the AV connection between the atria and the ventricles, there is an additional electrical connection. In this case, the impulse can repeatedly and at high speed circulate between the atria and the ventricles in a circle consisting of a normal AV connection and an additional AV connection. As a rule, from the atria to the ventricles the impulse is conducted through the AV node, and then returns from the ventricles to the atria through an additional connection.
There are two types of additional connections between the atria and the ventricles.
Additional conductive path. In atrioventricular reciprocal (re-entree) tachycardia (AVRT), the additional connection is represented by a bundle of myocardial fibers, which, like a bridge, spreads through the atrioventricular sulcus and thus “bypasses” the AV node. If this additional AV route is able to conduct impulses from the atria to the ventricles, then the patient has WPW syndrome.
In atrioventricular nodal reciprocal (re-entree) tachycardia (AVRT), the AV node and the atrial tissue adjacent to it are functionally dissociated into fast and slow paths, so there are two pathways in the AV node itself. With this tachycardia, AV conduction from the atria to the ventricles is carried out along the slow path, and conduction from the ventricles to the atria through the rapid path.
Atrial tachyarrhythmias. The second group of supraventricular tachycardias (SVT) includes arrhythmias caused by frequent abnormal electrical activity within the atria: AF, TP, and atrial tachycardia. The mechanism underlying this type of tachycardia is limited to atrial tissue.
Unlike tachycardia of the first group, with atrial tachyarrhythmias, the AV node is not part of the mechanism of tachycardia, but only conducts (partially or fully) atrial impulses on the ventricles. Atrial tachyarrhythmias are often associated with diseases of the myocardium, valvular apparatus of the heart, or with extracardiac pathology, while reciprocal tachycardias involving AV compounds are due to the existence of abnormal electrical