Anisotropic conduction block and reentry in neonatal rat ventricular myocyte monolayers
Por:
de Diego, C, Chen, F, Xie, Y, Pai, R, Slavin, L, Parker, J, Lamp, S, Qu, Z, Weiss, J and Valderrabano, M
Publicada:
1 ene 2011
Resumen:
de Diego C, Chen F, Xie Y, Pai RK, Slavin L, Parker J, Lamp ST, Qu Z, Weiss JN, Valderrabano M. Anisotropic conduction block and reentry in neonatal rat ventricular myocyte monolayers. Am J Physiol Heart Circ Physiol 300: H271-H278, 2011. First published October 29, 2010; doi: 10.1152/ajpheart.00758.2009.-Anisotropy can lead to unidirectional conduction block that initiates reentry. We analyzed the mechanisms in patterned anisotropic neonatal rat ventricular myocyte monolayers. Voltage and intracellular Ca (Ca-i) were optically mapped under the following conditions: extrastimulus (S1S2) testing and/or tetrodotoxin (TTX) to suppress Na current availability; heptanol to reduce gap junction conductance; and incremental rapid pacing. In anisotropic monolayers paced at 2 Hz, conduction velocity (CV) was faster longitudinally than transversely, with an anisotropy ratio [AR = CVL/CVT, where CVL and CVT are CV in the longitudinal and transverse directions, respectively], averaging 2.1 +/- 0.8. Interventions decreasing Na current availability, such as S1S2 pacing and TTX, slowed CVL and CVT proportionately, without changing the AR. Conduction block preferentially occurred longitudinal to fiber direction, commonly initiating reentry. Interventions that decreased gap junction conductance, such as heptanol, decreased CVT more than CVL, increasing the AR and causing preferential transverse conduction block and reentry. Rapid pacing resembled the latter, increasing the AR and promoting transverse conduction block and reentry, which was prevented by the Cai chelator 1,2-bis oaminophenoxy ethane-N,N,N',N'-tetraacetic acid (BAPTA). In contrast to isotropic and uniformly anisotropic monolayers, in which reentrant rotors drifted and self-terminated, bidirectional anisotropy (i.e., an abrupt change in fiber direction exceeding 45 degrees) caused reentry to anchor near the zone of fiber direction change in 77% of monolayers. In anisotropic monolayers, unidirectional conduction block initiating reentry can occur longitudinal or transverse to fiber direction, depending on whether the experimental intervention reduces Na current availability or decreases gap junction conductance, agreeing with theoretical predictions.
Filiaciones:
Weiss, J:
Univ Calif Los Angeles, David Geffen Sch Med, Div Cardiol, Cardiovasc Res Lab,Dept Med Cardiol & Physiol, Los Angeles, CA 90095 USA
Green Published
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