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Abstract
upraventricular tachycardias (SVTs) are a general term describing any rapid heart rate originating above the ventricles. Supraventricular tachycardias are defined as tachycardia resulting from an abnormal mechanism that requires structures in the heart proximal to the bifurcation of the bundle of His for its perpetuation (Garson et al., 1990, Hanisch, 2001).
Supraventricular tachycardias (SVTs) are the most common symptomatic arrhythmia in infancy, often presenting before the age of 4 months (Ludmirsky and Garson, 1990). SVT is much more common than originally estimated (1 in 25000 based upon an estimate made in 1967), and probably occurs in between 1-4/1000. The prevalence of Wolff-Parkinson -White syndrome in children is approximately 2: 1000. In addition, SVT has been recognized as one of the late sequel of heart procedures, which increase by time (Love et al., 2001).
There are 16 different underlying mechanisms of clinical SVT in young, corresponding to three major tachycardia mechanisms: re-entry without an accessory pathway, re-entry with an accessory pathway, and Automatic (Perry, 1997).
Accessory atrioventricular (AV) connection that participates in orthodromic reciprocating tachycardia is the most common mechanism of supraventricular tachycardia that uses the AV node in antegrade and retrograde pathways (Etherdige and Judd, 1999).
Re-entrant tachycardia without an accessory pathway is common in childhood, while atrial and junctional ectopic tachycardia are more commonly associated with abnormal hearts (Bauersfeld et al., 1995).
In survivors of congenital heart surgery, intra-atrial reentrant tachycardia (IART) often develops. This tachyarrhythmia, which has also been called atrial flutter, can be difficult to manage and represents a significant cause for morbidity and mortality in postoperative patients with congenital heart disease (Chan et al., 2000).
There has been much interest in using radiofrequency ablation (RFA) to cure IART when it is difficult to control with antiarrhythmic drugs and is poorly tolerated thermodynamically (Case et al., 2000).
Although episodes of SVT are common during infancy, most patients are free of tachycardia episodes during early childhood and some infants do not have a recurrence of SVT after initial presentation (Perry and Garson, 1990).