Supraventricular tachycardias (SVTs) affect more than 1% of the population, making them a relatively common clinical problem.<sup>48 Ostrander L., Brandt R.L., Kjelsberg M.D. , e al. Electrocardiographic findings among the adult population of a total natural community, Tecumseh, Michigan Circulation 1965 ;  31 : 888-898

Cliccare qui per andare alla sezione Riferimenti</sup> SVTs encompass a large group of arrhythmias that originate above the bifurcation of the bundle of His. An antiquated term, paroxysmal atrial tachycardia, previously was used to describe SVTs that began and ended abruptly. This term has become obsolete because many such arrhythmias arise from not only the atria, but also the atrioventricular (AV) node, bundle of His, and accessory pathway tissue. Most SVTs have normal narrow-complex morphology,<sup>31 Kalbfleisc S.J., el-Atass R., Calkins H. , e al. Differentiation of paroxysmal narrow QRS complex tachycardias using the 12-lead electrocardiogram J Am Coll Cardiol 1993 ;  21 : 85-89

Cliccare qui per andare alla sezione Riferimenti</sup> but they also may have wide QRS complexes resulting from aberrant conduction or, less commonly, preexcitation. This article discusses SVTs with respect to their classification, mechanisms, electrocardiogram (ECG) manifestations, and medical management. Catheter ablation is available for patients who fail medical therapy or who do not wish to take medications. A detailed discussion of catheter ablation is found in the article by Calkins elsewhere in this issue.