Supernormal Conduction in the Left Bundle Branch Unmasked by the Linking Phenomenon |
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Authors: | FRANCESCO LUZZA GIUSEPPE ORETO ANTONINO DONATO GAETANO SATULLO IGNAZIO M SCIMONE |
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Institution: | Istituto Pluridisciplinare di Clinica Medica-Cattedra di Malattie Cardiovascolari, Università di Messina, Italy. |
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Abstract: | This presentation reflects a case of phase-3 left bundle branch block (LBBB). Analysis reveals that relatively early QRS complexes are wide, whereas beats occurring later than a critical time are narrow. There are, however, two unexpected phenomena: (1) an overlap occurs between the range of R-R intervals resulting in normal intraventricular conduction and the range of R-R intervals resulting in LBBB pattern. Complexes that follow a wide beat are often wide although they are associated with relatively long R-R intervals, whereas complexes that follow a normal beat tend to be normal even after relatively short R-R cycles. This is due to concealed retrograde penetration of the bundle branch that is blocked in anterograde direction (the so-called linking phenomenon). (2) Some early supraventricular impulses, paradoxically, resulted in normal intraventricular conduction. The phenomenon is a manifestation of supernormal LBB conduction, and only occurs following a wide QRS complex associated with retrograde activation of the LBB. The linking phenomenon reveals or unmasks the supernormal phase of LBB conduction. Following a retrograde and delayed activation of the LBB, the refractory period of the bundle branch is postponed, in such a way that a supraventricular impulse is allowed to occur during the early phase of supernormal conduction. |
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Keywords: | bundle branch block concealed conduction supernormality |
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