Yokokawa M, et al. - Given complete conduction block along the cavo-tricuspid isthmus (CTI) is the endpoint for radiofrequency catheter ablation (RFA) of CTI-dependent atrial flutter (AFL), researchers assessed the utility of the temporal link between the P wave and the local atrial electrograms in determining complete CTI block. RFA of CTI was performed in 125 patients (age 63 ± 11 years). Study participants were divided into a training set including the first 100 patients, and a validation set with the next 25 patients. Findings demonstrated that during pacing from the coronary sinus, the temporal link between the P wave in lead V₁ and A₂ served as a simple and reliable indicator of complete block during RFA of CTI-AFL.