An assembly includes an implantable medical device (IMD) including a conductive housing, and a fixation element assembly attached to the IMD. The fixation element assembly includes a set of active fixation tines and an insulator to electrically isolate the set of active fixation tines from the conductive housing of the implantable medical device. A delivery tool interface is located at a proximal end of the implantable medical device and configured to connect to a delivery device. The active fixation tines in the set are deployable from a spring-loaded position in which distal ends of the active fixation tines point away from the implantable medical device to a hooked position in which the active fixation tines bend back towards the implantable medical device. The active fixation tines are configured to secure the implantable medical device to a patient tissue when deployed while the distal ends of the active fixation tines are positioned adjacent to the patient tissue. The set of active fixation tines consists of four active fixation tines. The active fixation tines are positioned substantially equidistant from each other in a circular arrangement.
