Transmembrane potential properties at the core of functional reentrant wave fronts in isolated canine right atria

Background - The characteristics of transmembrane potential (TMP) at the core of functional reentry in the atrium are not well understood. Methods and Results - In protocol 1 (11 dogs), isolated perfused canine right atria were mapped from the endocardial surface while simultaneous TMPs were recorded from the epicardial surface. Episodes of reentry (n = 64) were induced in the presence of 1 to 5 mu mol/L acetylcholine. Successful simultaneous TMP recordings and activation maps were made in 8 episodes. The TMP was "near the core" if it was within 3.2 mm of the core; otherwise, it was considered to be "in the periphery." The mean cycle length of reentry was 110 +/- 35 ms. The TMP amplitude, duration (90% repolarization), and (dV/dt)(max) near the core (n = 106) were 58 +/- 22 mV, 46 +/- 14 ms, and 33 +/- 20 V/s, respectively, significantly less than those in the periphery (n = 241): 70 +/- 8 mV, 94 +/- 32 ms, and 55 +/- 10 V/s (P < 0.001 for all). In 2 episodes of reentry, the cell at the core remained unexcited at its resting membrane potential. In protocol 2 (2 dogs), we performed simultaneous high-density mapping in 4 episodes of reentry and showed synchronous activation patterns on both surfaces with similar locations of the core. Conclusions - During meandering functional reentry in isolated canine right atria, (1) TMPs of cells near the core have a reduced amplitude, duration, and (dV/dt)(max), and (2) cells at the core may remain unexcited at their resting membrane potential. These findings are compatible with the spiral wave concept of functional reentry in the atrium.