Ventricular preexcitation

Pre-excitation syndrome is an abnormal heart rhythm in which the ventricles of the heart become depolarized too early, which leads to their partial premature contraction.Normally, the atria and the ventricles are electrically isolated, and electrical contact between them exists only at the 'atrioventricular node'. In all pre-excitation syndromes, at least one more conductive pathway is present. Physiologically, the normal electrical depolarization wave is delayed at the atrioventricular node to allow the atria to contract before the ventricles. However, there is no such delay in the abnormal pathway, so the electrical stimulus passes to the ventricle by this tract faster than via normal atrioventricular/bundle of His system, and the ventricles are depolarized (excited) before (pre-) normal conduction system.Several types of pre-excitation syndrome have been described.