Methods, lead retention assemblies and systems may provide a secure connection of electrical leads to an implantable medical device, such as a pacemaker or a defibrillator. The method may include: providing a lead retention assembly including a support member, a first side clamp and a second side clamp, a first port and a second port each defining a respective receptacle in conjunction with the support, and a fastener configured to urge both the first and second side clamps toward the support upon actuation of the fastener; providing at least two electrical lead bodies each including a respective proximal end portion; inserting the respective proximal end portions into the respective receptacles to be in electrical communication with a respective electrical contact in the respective receptacles; and actuating the fastener to thereby clamp the proximal end portions of the respective electrical lead bodies within the first and second ports.