Precise identification of the atrial fibrosis is essential for successful catheter ablation of atrial arrhythmias in patients with atrial fibrillation. Voltage mapping of endocardial electrograms is currently used to delineate the anatomical substrate, but this is influenced by the direction of the activation wave front and is limited by the patient-specific thresholds. Mapping of local myocardial electrical impedance may overcome these limitations.

Clinical series: Patients with atrial arrythmias undergoing catheter ablation of these will be submitted to mapping of both voltage and tissue impedance. Likewise, the accuracy of the two maps identifying the extent of the substrate will be assesssed by gadolinium imaging. The impedance system is already constructed and certified for clinical research use.

Inclusion Criteria:

• Age between 18 and 85 years.
• That they understand and sign the informed consent.
• That they do not present any contraindication.- Pass the exploration and tests prior to bioimpedance measurements.

Exclusion Criteria:

• Age outside the range described in the inclusion criteria.
• Subjects who present any type of complication during the procedure.
• Pregnancy.

Patients with atrial arrhythmias undergoing catheter ablation