Effects of @entity955 shocks on the ventricles in isolated XXXX hearts.

@entity742 @entity1457 @entity2224 @entity955 @entity67
BACKGROUND: The effects of cardioversion of @entity955 on the activation sequence of the ventricles have not been previously studied. In this study we examined the events in the ventricle that follow the application of @entity1457 . METHODS AND RESULTS: We used video imaging technology to study the sequence of activation on the surface of the ventricles in the Langendorff-perfused @entity742 heart. We recorded transmembrane potentials simultaneously from over 20000 sites on the epicardium before and after biphasic shocks applied by a programmable @entity955 . The first epicardial activation after the shock depended on both the voltage and timing of the shock. During @entity67 as low as 10 V produced ventricular excitation, although the time between the shock and the first epicardial activation (latency) was approximately 30 ms. As the shock voltage was increased to 120 V, latency decreased to zero and the entire epicardium was depolarized within 30 ms. For 120-V shocks delivered late in systole, the depolarization sequence produced by the shock was similar to the previous repolarization sequence. Shocks of 120 V applied 150 to 300 ms after the previous ventricular excitation induced @entity2224 . @entity2224 was induced by multiple focal beats after the shock, which produced waves that propagated but broke down into reentry within regions of high repolarization gradients. CONCLUSIONS: These results demonstrate that @entity955 shocks excite the ventricles even at low shock voltages. In addition, @entity2224 can be induced by shocks given in the vulnerable period by producing focal patterns that break down into reentrant waves.
