[Computer simulations of microreentry in the SAN]

We have studied the dynamics of reentry inside the SAN. We have found that reentry is unstable at high intercellular conductance. Rotating reentry induces a slow migrating crescent-shaped functional block near the boundary of the SAN. An abnormal conduction from atrial tissue into the SAN occurs after decay of the reentry. ACh increases lifespan of the reentry in the SAN.