TRANSMEMBRANE POTENTIAL PROPERTIES OF ATRIAL CELLS AT DIFFERENT SITESOF A SPIRAL WAVE REENTRY - CELLULAR EVIDENCE FOR AN EXCITABLE BUT NONEXCITED CORE

Transmembrane action potentials (TAPs) were recorded during simultaneo us mapping of a reentrant wavefront induced in canine isolated atria. The activation pattern was visualized dynamically using a high resolut ion electrode catheter mapping system. During functional reentry (spir al wave), cells in the core of the spiral wave remained quiescent near their resting membrane potential. Cells away from the core progressiv ely gained TAP amplitude and duration, and at the periphery of the spi ral wave the cells generated TAPs with full height and duration. Durin g anatomical reentry, when the tip of the wavefront remained attached to the obstacle (a condition of high source-to-sink ratio); the TAP ne ar the obstacle had normal amplitude and duration. However, when the t ip of the wavefront detached from the obstacle (condition of lowered s ource-to-sink ratio) the TAP lost amplitude and duration. These result s are consistent with the theory that the source-to-sink ratio determi nes the safety factor for wave propagation and wave block near the cor e. With decreasing source-to-sink ratio, TAP progressively decreases i n amplitude and duration. In the center of the core, the cells, while excitable, remain quiescent near their resting potential. This decreas e reflects a progressive decrease in the source-to-sink ratio. TAP van ishes in the core where cells remain quiescent near their resting pote ntial, Functional and meandering reentrant wavefronts are compatible w ith the spiral mechanism of reentry where block at the rotating point is provided by the steep curvature of the wave tip.