Mitsunori Maruyama et al. JACEP 2017;3:1252-1261 Atrial Capture Within the “Transition Zone” in Typical AVNRT With Type 1 Termination The atrium was reset with the seventh ventricular stimulus when the QRS morphology first became stable (asterisk). Thus, the atrial resetting occurred beyond the “fusion period” but within the “transition zone” by its definition. The TPP was 158 ms (TCLsum 2,534 ms – PCLsum 2,376 ms), which was compatible with AVNRT. Abbreviations as in Figure 1. Mitsunori Maruyama et al. JACEP 2017;3:1252-1261 2017 American College of Cardiology Foundation