Further supporting the concept of image-based guidance for timing initiation of CXCR4 blockade, Jujo et al. demonstrated that a single-dose injection of the small molecule CXCR4 antagonist AMD3100 administered after the onset of MI in mice improved cardiac function, whereas continuous therapy with AMD3100 was associated with worse outcome 23. Here, CXCR4 is linked to myocardial infarction.