Classification of supraventricular tachycardias (SVT)
Some tachycardias occur in the atria or the AV connection and, therefore, are supraventricular in origin. In this case, the ventricles are activated through the His-Purkinje fast-conducting system, as a result of which narrow ventricular complexes are usually formed. There are two main types of supraventricular tachycardias (SVT).
The first type is reciprocal tachycardias involving the AV connection. They involve an additional electrical connection between the atria and the ventricles.
In this case, the impulse can circulate repeatedly and at high speed between the atria and the ventricles in a circle consisting of a normal AV connection and an additional AV connection. As a rule, such tachycardia is not associated with any other pathology of the heart.
The second type is atrial tachyarrhythmias, due to frequent pathological electrical activity within the atria (ie, AF, TP, and atrial tachycardia). At the same time, the AV-node is not an integral part of the tachycardia mechanism, but only transmits (partially or completely) impulses from the atria to the ventricles. Tachycardias of this type are often associated with various heart diseases.
Some tachycardias occur in the atria or the AV connection and, therefore, are supraventricular in origin. All of them have one common feature: since they arise above the level of the bundle of the His branch, the ventricles are activated by impulses propagating through a specialized intraventricular rapidly conducting system, and therefore ventricular complexes are usually normal and narrow.
However, it is very important to realize and take into account that there are significant differences in the mechanisms of development, ECG signs and approaches to the treatment of various forms of supraventricular tachycardias (SVT). It is necessary to determine the type of tachycardia, and not just treat all tachycardias with narrow QRS complexes as supraventricular tachycardias (SVT).