Methods, systems and devices for providing cardiac resynchronization therapy (CRT) to a patient using a leadless cardiac pacemaker (LCP) implanted in or proximate the left ventricle of a patient. A setup phase is used to establish parameters in the therapy delivery. In operation, the method and/or device will sense at least one non-paced cardiac cycle to determine a native R-R interval, and then delivers a synchronization pace at an interval less than the native R-R interval followed by a plurality of pace therapies delivered at the R-R interval or a modification thereof