“…The PV was mapped with a steerable circular catheter measuring 15-30 mm in diameter (according to the PV diameter as determined by venography) equipped with twenty 1 mm electrodes in a loop made of shape-retaining material (Lasso; Biosense Webster, Diamond Bar, California, USA) orthogonal to the shaft. The PV muscle potentials were defined as described previously 15 and were recorded in a bipolar mode from 10 bipoles through the band pass filters of 30-500 Hz and an amplification of 1 to 2 cm/mV on polygraphy (EP Med System; Century Medical, Tokyo, Japan).…”