Imaging will be performed at the 3 imaging centers (BWH, OHI, and UAB). To minimize participant and site burden, only a baseline and single follow-up imaging time point will be pursued. Imaging tests (PET and echo) will be scheduled on the same day for patient convenience if possible, and no more than one week apart. "Baseline" study visit imaging will follow the open label run-in period of the parent trial to enhance long-term compliance and eliminate risk of radiation exposure for any individuals with immediate intolerance to the LDM study protocol. The imaging tests proposed are non-invasive, routinely performed, and historically well tolerated by patients.