Two major challenges in imaging the living, beating heart are the contrasting problems of high-frequency heart beating and low-frequency morphological changes. Overcoming these problems is essential to quantifying physiological changes throughout heart development, repair and, in certain species, regeneration. We have previously demonstrated how using prospective optical gating, in combination with light-sheet microscopy, can allow the synchronised capture of 3D images of the in vivo beating zebrafish heart. However, prospective optical gating alone is limited to snapshots of the heart at chosen target heartbeat phases and only over the scale of tens of minutes. We have now developed an adaptive prospective optical gating system that we are using in combination with light-sheet microscopy to enable a range of 3D-timelapse imaging experiments. Here we will demonstrate this technology, highlight the benefits of reduced phototoxicity and demonstrate key areas where we have begun to exploit these technologies to further describe and understand cardiac function and dynamics. Our adaptive prospective optical gating technology allows us to carry out 48+ hour, in vivo, 3D-timelapse imaging of the computationally frozen heart across developmental stages, e.g. heart looping and trabeculation, and throughout injury response and repair. Imaging across these timescales is not possible with retrospective optical gating techniques, which lead to significant phototoxic responses: only with our adaptive prospective optical gating system are such longitudinal studies possible. Our adaptive prospective optical gating system allows researchers to study and understand cardiac development and repair with minimal photoresponse and without the use of chemicals or optogenetics to stop or modify the natural heart beating.