Computer simulations of reentrant activity in the rabbit sinoatrial node

With the aid of detailed computer simulations, we have estimated distributions of membrane potential and ionic currents in the core region of a sinoatrial node reentry. We observe reduced amplitudes of the measured quantities in the core; the core sizes for potential and currents did not always coincide. Simulations revealed that acetylcholine, when applied in the vicinity of unstable reentry, attracted the reentry to become the core and to stabilize its rotation. Anatomically detailed simulations of sinoatrial node and surrounding atrial tissue revealed that reentry always rotated around small strips of connective tissue. Acetylcholine superfusion over superior part of the sinoatrial node resulted in a drift of reentry in the cranial direction. Under the latter conditions, reentry may coexist with the pacemaker in the caudal part of the sinoatrial node.