Abstract 207: Evidence for ATP-Sensitive Potassium Current-Mediated Polymorphism in the Dynamics of Long-Duration Ventricular Fibrillation and Asystole in Isolated Canine Heart
Long-duration ventricular fibrillation (LDVF) commonly occurs during cardiac arrest. During LDVF gradients in VF rate (VFR) and excitability develop between left ventricular (LV) endocardium (ENDO) and epicardium (EPI) culminating in complete asystole. The role of ATP-sensitive potassium current (IKATP) in the electrical gradients and asystole during LDVF is poorly understood. We performed transmural electrode mapping (4 needles x 10 leads) of activation in LV during LDVF (10 or 20 min) in isolated canine hearts in the absence (control, n=8) and presence (n=6) of IKATP blocker glibenclamide (30–60 μM). The time course of VFR throughout LDVF was compared between ENDO and EPI. In 4 of 8 control hearts, asystole occurred at 6.2 ± 0.3 min of LDVF (early asystole, Control A). However, the rest (4/8) of control hearts (late asystole, Control B) and all 6 glibenclamide treated hearts (GLIB) maintained LDVF for at least 10 min (Figure, A). Control A and Control B were not different with respect to relevant background information (e.g., weight, sex, etc.). In both ENDO and EPI, VFR was significantly slower throughout LDVF in Control A than in both Control B and GLIB, but not different between Control B and GLIB. An ENDO-to-EPI VFR gradient developed in all three groups reaching maximum between 3 and 4 min of LDVF (Figure, B). Thereafter, the VFR gradient declined in Control A (due to progressive VFR slowing in all layers and eventual asystole) but was maintained in Control B and GLIB. The maximal VFR gradient (in Hz) was not different between the three groups (Control A, 2.83 ± 0.56; Control B, 3.66 ± 0.34; GLIB, 3.48 ± 0.48; NS). We conclude that this model of LDVF exhibits polymorphism with respect to the speed of VFR decline and the onset of asystole. The observed outcomes of IKATP blockade suggest that this polymorphism is mediated through a bimodal (either high or low) activation of IKATP. However, IKATP activation does not determine ENDO-to-EPI gradient in VFR in this model of LDVF.
- © 2010 by American Heart Association, Inc.