ANATOMIC STUDIES The story properly begins with the elucidation of the specialized conduction system of the heart. It was long appreciated that electrical connections bridged the atrial and ventricular chambers.4,5 Stanley Kent in 1893 described lateral atrioventricular (AV) connections and thought these constituted the normal specialized AV conduction system.6 This work proved controversial and was, in fact, rejected by such notables as Sir Thomas Lewis and Keith Flack. In a later study Dr. Kent described lateral connections with node-like Inhibitors,research,lifescience,medical structures which he felt constituted the normal AV conduction system.7 The work of His8 and Tawara9 clearly established the anatomy of the AV node and

His–Purkinje system. Moreover, they proved that section of the His bundle Inhibitors,research,lifescience,medical resulted in complete AV block and described the His–Purkinje system. It was clearly Wood et al.10 who first described the presence of a right-sided accessory pathway (AP) in a patient with an ECG pattern of pre-excitation and Öhnell who described left-sided APs in patients with pre-excitation.11 Other pioneer observations

include Inhibitors,research,lifescience,medical those of Mahaim and Benatt who described connections between the AV node or His bundle to fascicles on ventricular myocardium.12 In an important study, Lev and Lerner13 presented a detailed investigation of 33 fetal and neonatal hearts and found no evidence for any lateral AV communications. They interpreted Inhibitors,research,lifescience,medical Kent’s finding of nodal tissue as being really atrial tissue: in neonates there is sparse collagen in the AV groove, and, depending on the angle of the sections, these may be misinterpreted as AV connections. It is, therefore, surprising that the eponym “Kent” bundle is still used to describe abnormal AV connections. CLINICAL AND INVASIVE ENDOCARDIAL STUDIES Inhibitors,research,lifescience,medical Drs Wolff, Parkinson, and White are correctly credited with describing the entity that bears their names. Their article was published in the American Heart Journal in August 1930.1 They described 11 patients with short P-R and bundle branch block, who also suffered

with paroxysmal supraventricular tachycardia (SVT) and/or atrial selleck fibrillation (AF). None of these patients had any evidence of structural cardiac disease, and the investigators confirmed (actually had reported previously) that administration of atropine would serve to normalize AV conduction with disappearance of the “bundle check branch block” pattern (Figure 1). The authors felt that the entity was “neurogenic” in origin and was of little clinical consequence. Figure 1 Simultaneous recording of three-lead ECG obtained from the original article by Drs Wolff, Parkinson, and White.1 (Reproduced with permission from Elsevier.) It was only later that Mines14 demonstrated that the concept of circus movement tachycardia was as a mechanism of tachycardia. According to T.N.