Write An Essay On Supraventricular Tachycardia

Supraventricular Tachycardia

Narrow complex tachycardias are defined by the presence in the electrocardiogram of a QRS complex with less than 120 msec duration and a heart rate more than 100 beats per minute. They are usually of supraventricular origin, though narrow complex ventricular tachycardias were rarely reported in the literature (Hayes et al, 1991).

Supraventricular origin of the tachycardia means the obligatory involvement of one or more of the cardiac structures above bifurcation of His bundle. Those include the atrial myocardium, the AV node, the proximal His bundle, the coronary sinus, the pulmonary veins, the venae cavae, or abnormal atrio-ventricular connections, namely bypass tracts (Lau, 2008).

Although pharmacologic treatment is still in use for suppression and treatment of SVTs, particularly for atrial arrhythmias, reported efficacy and side effects limited their application. Radiofrequency catheter ablation has recently

It requires two separate pathways with different electrophysiologic characteristics, linked both proximally and distally, forming a functional or an anatomic circuit (Figure 2). Reentry occurs when the impulse that initially excites and conducts via the first pathway fails to conduct via the second part of the circuit as it is refractory and thus not excitable. Through the distal part of the circuit, the impulse then enters the formerly refractory tissue of the second pathway causing its excitation in a retrograde direction. The impulse must be transmitted within one limb of the circuit sufficiently slowly to allow the previously refractory tissue to recover excitability. If the impulse conducted in the second pathway in a retrograde manner arrives at the proximal part of the circuit when the first pathway is again excitable, then the impulse can reenter the first pathway leading to reentrant arrhythmia or a “circus movement” (Ferguson and Di Marco,