Myocardial wall thickness is one of the crucial parameters affecting the lesion formation produced by radiofrequency current (RF) delivering. Knowing the tissue characterization is critical for improving the durability of the RF lesion. A novel dielectric based method (KODEX-EPD) has been developed for measuring the tissue thickness at the catheter-tissue interface. The authors of this study report for the first time the tissue characterization (i.e. atrial wall thickness) of the cavo-tricuspid isthmus in a series of patients undergoing common atrial flutter ablation, showing a higher thickness close to the tricuspid valve as compared to the inferior vena cava. This can affect the outcome of ablation