Abstract 18448: Partial Blockade of Inwardly Rectifying K+ Current Enhances Electrotonic Interactions and Destabilizes Spiral Wave Reentry
Introduction: Spiral wave (SW) reentry is a principal mechanism for the maintenance of tachyarrhythmias, such as ventricular tachycardia/fibrillation (VT/VF). We have recently reported that partial blockade of the inward rectifier K+ current (IK1) destabilizes the rotation center of SWs without enhancement of wavefront-tail interaction in the arm, in favor of their termination (ESC 2012), but underling mechanisms remain to be clarified. We hypothesized that alteration in electrotonic influence due to decreased membrane conductance plays a role in destabilization of the SW rotation center.
Methods: A 2-dimensional ventricular muscle layer was prepared in Langendorff-perfused rabbit hearts, and optical action potential signals were recorded from the epicardial surface of the left ventricle. The dynamics of SW reentry were analyzed during VT induced by modified cross-field stimulation. The space constant (λ) was estimated by a decay of electrotonic depolarization induced by injection of subthreshold cathodal current.
Results: Partial blockade of IK1 by 50 µM Ba2+ significantly increased theλ: e.g., the value in a direction across the fiber orientation (λT) increased from 0.82±0.19 mm in control to 1.27±0.33 mm after 50 µM Ba2+ (n=5, P<0.05, Figure A). SW reentry under control condition rotated around a short line of block (FBL, 4.2±1.4 mm, n=12). In contrast, SW reentry induced after 50 µM Ba2+ was destabilized: the FBL was significantly prolonged (11.7±3.2 mm, n=12, P<0.05) and, in 6/12 hearts, showed a prominent change in its shape with a cycle of a few rotations, resulting from intermittent conduction block near the rotation center (Figure B).
Conclusions: These results suggest that partial IK1 blockade enhances electrotonic interactions, which could contribute to destabilization of SW reentry.
- © 2012 by American Heart Association, Inc.