Termination of spontaneous tachycardia in a patient with WPW syndrome.

1 wo previous reports have demonstrated dual AV nodal pathways as the causative mechanism of spontaneous SVT termination in the WPW syndrome. Westveer et al’ reported a patient with WPW and non-sustained antidromic SVT, where SVT termination was related to retrograde dual AV nodal pathways. Retrograde conduction of the SVT occurred over the slow retrograde AV nodal pathway with concealment into the retrograde fast pathway. Once retrograde concealed penetration of the fast pathway disappeared, the fast pathway becamecapable ofantegrade conduction and a reentrantAV nodal ventricular echo occurred terminating the SVT Adams et al3 reported a patient with WPW and orthodromic Wi’. The SVF utilized the accessory pathway fur retrograde conduction and a slow AV nodal pathway fur antegrade conduction. In this case, spontaneous SVT termination was related to a suddenjump in antegrade conduction from the slow to the fast pathway, advancing the VTso that block occurred in the accessory pathway or atrium. In our case, spontaneous termination of SVT was related to a sudden jump from antegrade fast to slow pathway. The conduction through the slow pathway was slow enough to allow recovery ofexcitability ofthe fast pathway which became available fur retrograde conduction (closing the AV nodal circuit) and preempted the conduction over the left accessory pathway (most probably for anatomic reasons). The SVT finally terminated when Wenckebach block occurred in the slow pathway. Boris Strasberg, M.D.; Ruben F Lewin, M.D.; Samuel Sclarovsky. M.D.; AlexArditti, M.D.; andJacob Agmon, M.D., Israel arid lone Massada Centerfor Heart Diseases, Beilinson Medical Center, Petah-Tikva, Israel