Fig. 1

Sinoatrial node is a long structure with slower more caudal portion of the node producing a flat or inverted p-wave in the inferior leads and faster more cranial portion of the node producing more upright p-waves. a Baseline electroanatomic map of sinus node map pre-isoproterenol at a baseline rate around 110 beats per minute. b Map following ablation: note that ablation was delivered at a more cranial portion of the sinus node