Ultra-high density mapping with multielectrode catheter may improve slow conduction channels identification in ventricular tachycardia substrate ablation procedures compared to conventional point by point mapping.

This study compares the ability of both mapping catheters to detect slow conduction channels in areas of myocardial scar and their utility to assess substrate modification after ablation.

This is a prospective, randomized controlled study. Twenty patients with sustained ventricular tachycardia and structurally abnormal ventricle(s) will be prospectively enrolled. In all patients a detailed pre and post-ablation electroanatomical mapping will be performed, and these maps will be merged with CT and/or MRI images. Patients will be randomly assigned to two groups. In Group A patients both pre and post-ablation mapping will be performed firstly by conventional point by point mapping using a Navistar Thermocool catheter, and secondly by multielectrode contact mapping using a Pentaray catheter. In this group, target ablation sites will be guided by point by point map. In Group B patients, both pre and post-ablation mapping will be performed firstly by multielectrode contact mapping using a Pentaray catheter, and secondly by conventional point by point mapping using a Navistar Thermocool catheter. In this group target ablation sites will be guided by multielectrode contact mapping.

Slow conduction channels will be identified by color-coded voltage map adjustment of the lower and upper thresholds and also the presence of fractioned electrograms with the delayed component showing sequential orthodromic activation. The entrances of these channels will be the target of the ablation sites (scar dechanneling technique).

Inclusion Criteria:

• Patients with indication for ventricular tachycardia substrate ablation.

Exclusion Criteria:

• Pregnant woman.
• Reduced expectancy of life (less than 12 months)
• Patient participating in another clinical study that investigates a drug or device
• Psychologically unstable patient or denies to give informed consent
• Any cause that contraindicate ablation procedure or antiarrhythmic drug