Despite the high success rate of a CRT-D implant, there is a possibility of 10% that the LV lead cannot be implanted in patients undergoing a trans-venous system implantation. In this case, the patients may undergo multiple procedures before a lead is successfully implanted. These implant failures are not due to patient selection but rather to patients heart anatomy leading to lead stability problems, phrenic nerve stimulation (also called diaphragmatic stimulation) and poor electrical measurements.