More frequent stimulation leads to slower conduction, known as decremental conduction. If conduction to the ventricles occurs solely through the pathway (maximal pre-excitation), as occurs during arrhythmias like antidromic atrioventricular re-entrant tachycardia, the ECG appearance is of QRS complexes with a left bundle branch block morphology which can be mistaken for ventricular tachycardia. However, due to their slow decremental conduction, during sinus rhythm the 12-lead ECG will often show little pre-excitation.
More frequent stimulation results in slower conduction, known as decremental conduction. If conduction to the ventricles occurs solely through a pathway (maximal pre-excitation), as happens during arrhythmias such as antidromic atrioventricular re-entrant tachycardia, the ECG appearance is of QRS complexes with a left bundle branch block morphology that might be mistaken for ventricular tachycardia. However, due to their slow decremental conduction, during sinus rhythm the 12-lead ECG will typically show little pre-excitation.