To explore spontaneous termination of atrial flutter (Afl) by a pure sodium channel blocker, pilsicainide (PLS), dynamic low voltage zones (LVZ), conduction velocity (CV) and block lines (BL) were analyzed by N3D-map in a canine model. A 9F noncontact multielectrode array catheter was deployed, and raw data were recorded superimposing onto the virtual 3D-RA endocardium. The threshold of LVZ was set at 30% of the major peak negative amplitude (MPN). Spontaneous termination was obtained after intravenous PLS (5-3Omg) during stable Afl. Results: 1) Twenty-one Afl episodes were induced in all canines. After PLS, 2) the Afl cycle length was significantly prolonged (p<0.05), 3) CV in LVZ was significantly prolonged, 4) the extent of LVZ was dynamically enlarged (p<0.05), and 5) LVZ was enlarged with BL functionally prolonged. 6) Spontaneous termination occurred in LVZ with significantly prolonged CV. 7) Afl was terminated after dynamic MPN forwarded into LVZ and conducted decrementally. Conclusion: 1) PLS made LVZ dynamically extended, with functional block lines prolonged. 2) Decremental conduction in LVZ can be a crucial factor for termination of Afl. 3) The extent of LVZ after PLS can have relationship with CV and the length of functional BL,
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