Fig. 3. Effects of pacing cycle length (PCL) on longitudinal (θL) and transverse (θT) conduction velocities during treatment of isolated hearts with 1 μm racemic bupivacaine (A  and B ), levobupivacaine (C  and D ), or ropivacaine (E  and F ). The central closed circle represents the pacing site. Numbers indicate local activation times expressed in milliseconds. Isochrones are drawn at 10-ms intervals. The underlined activation times indicate the sites between which longitudinal and transverse conduction velocities were measured in panels. Conduction velocities were slowed by shortening the PCL from 1,000 to 300 ms. Heavy lines indicate coalescence of at least two isochrones because of unidirectional conduction block. LAD = left anterior descending coronary artery; LV = left ventricle.