Abstract: A system for synchronizing a target device to a cardiac cycle, including: (a) a target device that collects data or performs an operation that is to be timed to the cardiac cycle; (b) a signaling device that emits a signal indicating the occurrence of a cardiac contraction and/or ECG feature; and (c) a calibration device that determines the relationship of the signal from the signaling device to the actual cardiac cycle. In operation, the calibration device calculates a time offset between the timing of the cardiac contraction as determined by the signaling device and the timing of the cardiac contraction and/or ECG feature as determined by the calibration device, and then provides the time offset to the target device.