Supraventricular arrhythmias (SVTs) are the most common arrhythmias encountered in clinical practice with an estimated incidence of 35/100,000 person-years in the general population. SVT subtypes have well-characterized age- and sex-specific distributions. Early in the experience of electrophysiology as a field, epicardial surgical mapping played a major role in the advancement of our understanding of the pathophysiology of cardiac arrhythmias and was also the treatment-of-choice for patients with SVTs refractory to medical therapy. Advancements in catheter-based techniques have long since supplanted surgical mapping/ablation as first-line invasive treatment. Today, SVTs are among the most common arrhythmias treated in the cardiac electrophysiology laboratory. The proportion of patients treated with catheter ablation is highly variable and modulated by arrhythmia risk, patient age, symptoms, and comorbidities. As a representative example, half the study population received ablation in a contemporary series of patients with the Wolff-Parkinson-White syndrome. Endocardial catheter ablation for SVT is an appealing strategy because it is a potentially curative treatment with a procedural success rate in excess of 95 in experienced centers. The risk of major complication during SVT ablation, such as vascular complications (bleeding and thrombosis), heart block, cardiac tamponade and, rarely, injury to the coronary arteries and/or phrenic nerves, is as low as 0.8 in contemporary series. Despite the excellent safety and efficacy profile of endocardial procedures, a minority of patients with SVT will have unsuccessful ablation. The reasons for failure vary according to the arrhythmia location and mechanism as well as individual operator concern regarding damage to adjacent structures, such as the phrenic nerve or coronary arteries. Percutaneous epicardial access with mapping and ablation is a valuable treatment strategy for patients with SVT refractory to endocardial ablation and may allow safe therapy for patients with higher risk arrhythmia locations.
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