Initial experience with an electrically active needle electrode have demonstrated that radiofrequency ablative energy can effectively create lesions of homogeneous necrosis. Needle electrodes have been used experimentally from the epicardial surface, from the endocardium ex vivo and in vivo in an internally irrigated form. It has been shown that the use of a narrow-gauge non-irrigated endocardial needle ablation catheter creates very narrow but deep lesions due to the small electrode size. Catheters featuring a retractable needle tipped electrode with intramyocardial saline infusion have also shown promise as a means of accessing deep myocardial circuits in ventricular tachycardia ablation.18