Figure legends
Figure 1. Both A and B are presenting 12-lead electrocardiography (ECG).
Figure 2. A premature p wave traverses down both fast pathway and slow pathway simultaneously causing 1 to 2 initiation of a narrow complex tachycardia. The green arrows indicate the fast pathway conduction, and the red arrows indicate the slow pathway conduction.
Figure 3. Intracardiac tracings of the double-fire phenomenon. The green arrows indicate the fast pathway conduction, and the red arrows indicate the slow pathway conduction. A A1H1=82 ms, A1H2=339 ms, A2H3=150 ms, A3H4=88 ms, A3H5=400 ms, H0H1=504 ms, H1H2=255 ms, H2H3=328 ms, AA intervals=500 ms. B A1H1=73 ms, A1H2=356 ms, A2H3=181 ms, A2H4=438 ms, AA intervals = 502 ms.