Update: Arrhythmias (V). Paroxysmal supraventricular tachycardias and preexcitation syndromes.

Paroxysmal supraventricular tachycardias are fast and usually regular rhythms that require some structure above the bifurcation of the His bundle to be continued. The 3 most common types are atrial tachycardias, atrioventricular nodal reentrant tachycardias, and tachycardias mediated by an accessory pathway. The last two varieties are discussed in the present manuscript. Their prognosis is benign regarding life expectancy but typically they are symptomatic and chronically recurrent, producing a certain disability. They usually occur in people without structural heart disease. Pharmacologic therapy is possible, but given the high efficacy of catheter ablation, these procedures are frequently chosen. Ventricular preexcitation is due to the presence of an accessory pathway, usually atrioventricular. The clinical course can be asymptomatic, generating a characteristic electrocardiographic pattern, produce paroxysmal supraventricular tachycardias, or facilitate other types of arrhythmias. Very rarely, they can cause sudden cardiac death. The treatment of choice for symptomatic patients is catheter ablation of the accessory pathway. The therapeutic attitude towards asymptomatic preexcitation remains controversial.