Figure 1. Four original atrial and ventricular electrograms obtained during control and treatment with 1, 5, and 10 micro Meter (+) bupivacaine. Coated silver wire recording electrodes were placed on the right atrium and on the right ventricular pulmonary conus. The electrograms were displayed on a fast-writing, high-resolution chart recorder. The dashed lines show the electric threshold limit (80% of the amplitude of the electrogram [ECG] upstroke wave) for onset to offset of the timing trigger between atrial and ventricular pulses. The time interval (solid horizontal bar) between the atrial and ventricular pulses describes AV conduction time. At 10 micro Meter (+) bupivacaine there is no ventricular pulse following the atrial pulse, which indicates second-degree atrioventricular dissociation. With increasing bupivacaine concentration, the period between atrial pulses increases, which indicates a decrease in atrial heart rate.