The incredible contributions of Pick, Langendorf, and Katz deserve

mention.17–19 They undertook detailed and painstaking analyses of literally thousands of strips from patients with the WPW syndrome and concluded that the arrhythmias were due to differences in conduction properties between the AV node and the AP, which allowed for initiation of SVT by premature beats. Remarkably they described concealed conduction into the pathway and the relationship between SVT and AF for these patients. Much of their pioneering observations were substantiated by intracardiac studies. Drs Durrer and Wellens20,21 were the first to systematically use programmed electrical studies in Inhibitors,research,lifescience,medical numbers to clearly define the tachycardia mechanisms in patients with WPW. They showed that premature cardiac stimulation could induce orthodromic (SVT) (antegrade conduction over the AV node, retrograde conduction over the AP) as

well as antidromic tachycardias (antegrade conduction over the AP, retrograde conduction over the node). These Inhibitors,research,lifescience,medical observations and others22,23 provided Inhibitors,research,lifescience,medical the framework for the use of intracardiac studies to define AP location and physiology. SURGICAL CONTRIBUTIONS Prior to the current era of catheter ablation, patients with SVT intractable to drug therapy were treated with surgical dissection of the AV junction.24,25 This approach was largely used for management of the patient with atrial fibrillation refractory Inhibitors,research,lifescience,medical to drug therapy but would not be appropriate for those with

APs since extirpation of the AV junction would not mitigate against rapid conduction over an AP. Durrer and Roos26 performed intraoperative mapping and cooling (in an important proof of concept Autophagy Compound Library experiment) to locate and transiently prevent conduction in a patient with a right-sided AP. Subsequently Burchell et al.27 used intraoperative mapping and abolished pre-excitation with a local injection of procainamide. Inhibitors,research,lifescience,medical A limited surgical incision over this area resulted in only transient loss of pre-excitation. Sealy et al.28 were the first to successfully ablate an AP in a human. The Duke team initially used an epicardial approach but subsequently showed that APs in all locations (both free wall and septal) could Pharmacological Reviews be successfully ablated using an endocardial technique.29 Only later was a cryo-epicardial technique used by Guiraudon et al.30 CATHETER ABLATION The technique of catheter ablation of the AV junction was introduced by Scheinman et al. in 1981.31 The technique involved use of high-energy direct-current shocks delivered to the region of the AV junction. This was followed by attempts to use catheter techniques for ablation of APs in various locations. In 1984 Fisher et al.32 used this technique for attempted ablation of left-sided APs via the coronary sinus. This technique was abandoned due to limited efficacy and risk of cardiac tamponade.