 Afterwards the clinically indicated, elective CRT implantation is performed by experienced physicians of the Medical Clinic I. Routinely, an arterial pressure catheter for invasive blood pressure monitoring usually arteria radialis is inserted. In addition, 2 peripheral venous accesses are established. The system of the CRT system is carried out via a small pectoral section. The cardiac probes are inserted into the heart via the subclavian vein. First, the probe is implanted in the right ventricle and, if necessary, a probe is placed in the right atrium. 