Symbol detection with list sphere decoder (LSD) is an emerging technology targeted on multiple-input multiple-output (MIMO) telecommunication systems. The LSD algorithm requires maintaining a list of candidate symbols with shortest Euclidean distances to the received symbol. For energy efficiency, memory-based list is preferred over registers with long list lengths. In this paper, two hardware units for alleviating processing of such lists are presented. The list is stored as a heap in the memory and the proposed list updating units are incorporated with application specific processors. With presented principles, the number of clock cycles per list insertion gets very close to the theoretical lower bound with heap data structure.