Ventricular Pre-excitation

Pre-excitation is a condition in which an accessory pathway exists between the atria and the ventricles, often referred to as the bundle of Kent. When the accessory pathway conducts in an anterograde direction, the ventricles are “pre-excited,” yielding the characteristic delta wave on the ECG. Because of the accessory pathway, patients are at risk for developing antidromic (wide complex, anterograde conduction through the accessory pathway and retrograde conduction through the atrioventricular node) or orthodromic (narrow complex, anterograde conduction through the atrioventricular node and retrograde conduction through the accessory pathway) reentrant rhythms. When dysrhythmias occur involving the accessory pathway, it is referred to as the Wolf-Parkinson-White syndrome.


Depiction of orthodromic and antidromic atrioventricular reentrant tachycardias possible with the Wolf-Parkinson-White syndrome. The red bars in panel A represent possible locations of the accessory pathway (type A, between LA and LV; type B, between RA and RV). The blue line in panel B represents orthodromic conduction (narrow complex) and the blue line in panel C represents antidromic conduction (wide complex). RA, right atrium; RV, right ventricle; LA, left atrium; LV, left ventricle.



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