Linking by collision initiated in the absence of preexisting reentrant tachycardia.
Dynamic functional block in 1 limb of a reentrant circuit ("linking") can be maintained by either repetitive interference or collision of successive impulses entering the circuit. Occurrence of linking by collision during attempted overdrive pacing of reentrant tachycardias accounts for the entrainment phenomenon. To investigate whether linking by collision can be initiated in the absence of preexisting tachycardia, a human reentrant circuit model was studied. The model consisted of the atrioventricular node and His-Purkinje system as anterograde limb and an electronic stimulator that served as "retrograde limb" by initiating a paced atrial impulse at a predetermined ventriculoatrial interval following each sensed ventricular depolarization. In 3 patients with intact ventriculoatrial conduction, "reentrant tachycardia" was initiated by a ventricular extra-stimulus (V2), which retrogradely blocked bilaterally below the His bundle. When this same V2 was followed, instead, by a paced V2V2 train at a cycle length equal to the programmed ventriculoatrial interval of the "tachycardia," it could be shown that each beat of the train not only "traversed" the simulated "retrograde limb" but also retrogradely collided with a prior circulating impulse in the anterograde limb of the circuit, thereby constituting linking by collision at a supra-Hisian level with inability of even a single "reentrant cycle" to be completed; "tachycardia" became manifest only after termination of the V2V2 train. The findings suggest the existence of a unique mechanism for initiation of certain clinical reentrant tachycardias during incremental pacing.
Lehmann
M H
MH
Electrophysiology Laboratory, Wayne State University, Detroit, Michigan.
Steinman
R T
RT
D000368:Aged; D001283:Atrioventricular Node / Q000503:physiopathology; D002036:Bundle of His / Q000503:physiopathology; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D004594:Electrophysiology; D006325:Heart Atria / Q000503:physiopathology; D006327:Heart Block / Q000503:physiopathology; D006329:Heart Conduction System / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011690:Purkinje Fibers / Q000503:physiopathology; D013610:Tachycardia / Q000503:physiopathology*