Despite a rapidly increasing number of renal denervation (RDN) procedures, only little is known regarding the patient or procedural characteristics influencing the outcome. None of the detectable variables like number of ablation points, temperature rise, impedance drop, have been shown to correlate with the blood pressure (BP) reduction. In this study, the investigators assess different patient and procedural characteristics, like exact patient medication, stress hormones, heart rate variability, and focus on the change of the catecholamine spill-over, and the impact on BP and heart rate after RDN and after EP ablation. The investigators hypothesize the correlation between reduction of catecholamine spill-over due to denervation and the BP reduction. In this study, the investigators will assess 40 patients undergoing RDN and 40 patients undergoing EP ablation.