Concealed Wenckebach Phenomenon in a 3:1 Atrioventricular Block

Atypical Wenckebach Block and Concealed Conduction

“…Since then, several clinical and experimental studies have indicated that block may occur at more than one level in the A-V conduction system [ 1,2,6,[8][9][10], Experimental preparations utilizing iso lated myocardial tissue with microclectrode techniques [9,10] have demonstrated differ ing levels of block in the A-V nodal region responsible for a variety of A-V conduction ratios (including rare 4:2 conduction), due to different levels of concealment. A variety of other arrhythmias displaying conduction dis turbances, e.g., atrial flutter with variable block, have similarly been explained on the basis of two or even three levels of block within ihe A-V conduction system [6] Such block may occur in the atrionodal, actual A-V nodal, or nodal-Hisian regions [2,9], Dual A-V nodal pathways have been well recognized [11]. They are often designated 'fast' and 'slow' on the basis of their relative atrio-His conduction times and account for the majority of episodes of paroxysmal SVT [11] Daniato and Lau [3] and Damato et al [4] demonstreated retrograde concealed con duction in the A-V nodal region accounting for a variety of conduction disturbances.…”