Figure legends
Figure 1. (A) P-wave morphology of atrial premature contraction (APC) in a 12-lead electrogardiogram. (B) The activation map of the APCs demonstrated a focal pattern originating from the posteromedial inferior vena cava (IVC) ostium. The earliest activation site was located 6.2 mm below the IVC ostium, and (C) a local signal with a fragmented and low amplitude (0.05 mV) was recorded. CS, coronary sinus; IVC, inferior vena cava; SVC, superior vena cava.