Supernormal conduction and linking in an accessory AV pathway

Wide complex tachycardia in a patient with non‐ischemic cardiomyopathy: What is the diagnosis?

“…The astute reader may also notice that the last wide QRS complex (8th beat in Figure2A) has a slightly different morphology (in lead V1) when compared to the preceding seven wide QRS complexes. This may represent subtle fusion between decremental pre-excited AV conduction from the previous sinus beat (7th) and normal AV conduction from the concurrent sinus beat (8th sinus beat denoted by the first red triangle) as illustrated in the ladder diagram (Figure2B).The phenomenon of sustained conduction over A-V accessory pathway alternating with sustained conduction over normal conduction system is explained by the "linking" phenomenon [1][2]. During 1:1 preexcited A-V conduction, retrograde concealed 1:1 conduction into the normal His-Purkinje system perpetuates functional antegrade block in the latter.…”