Paroxysmal Supraventricular Tachycardias and the Preexcitation Syndromes

Paroxysmal supraventricular tachycardia (PSVT) has been a well-recognized clinical syndrome and an electrocardiographically defined arrhythmia since the early days of electrocardiography. The clinical syndrome was defined in European literature in the 19th century. In 1867, Cotton reported on an “unusually rapid action of the heart,” and this was followed by further observations by French and German scientists.1,2 Variously referred to as Bouveret’s syndrome and later as paroxysmal atrial tachycardia, it was described classically as “a fully unprovoked tachycardia attack, lasting a few seconds or several days, in patients who as a rule have otherwise healthy hearts.”1 It has been electrocardiographically defined in the 10th Bethesda Conference on Optimal Electrocardiography as “a tachycardia usually characterized by an atrial rate of 140 to 240 beats per minute (bpm) and by an abrupt onset and termination. It may or may not be associated with intact A-V conduction. Specific electrophysiological studies may elicit specific mechanisms such as retrograde and anterograde pathways and sites of reentry.”3 In the past 25 years, this has been an intensively studied arrhythmia, with extensive definition of its genesis, presentation, subtypes, and electrophysiology. Pharmacologic therapy and, later, nonpharmacologic therapy have been investigated and refined. This is now a classic story in the evolution of clinical cardiac electrophysiology and forms a fundamental cornerstone in the modern treatment of cardiac arrhythmias. Epidemiology