Scientists from Stevens Institute of Technology and Baylor College of Medicine used 4D optical coherence tomography (OCT) to study the pumping mechanism underlying the developing mammalian heart. 4D OCT allowed them to investigate the functional relation between blood flow and heart wall dynamics within different regions of the embryonic heart at a level of detail not currently accessible by other methods. 4D OCT could potentially enable scientists to assess cardiac pumping over embryonic development as the heart tube remodels, which could reveal functional changes during early cardiogenesis that lead to congenital heart defects. The researchers used 4D OCT to obtain structural and Doppler hemodynamic imaging of the beating heart in live mouse embryos at embryonic day 9.25. The pumping assessment was performed based on the volumetric blood flow rate, flow resistance within the heart tube, and pressure gradient induced by heart wall movements. The relation between the blood flow, the pressure gradient, and the resistance to flow was evaluated through temporal analyses and Granger causality testing. Mouse embryo and heart with blood flow. Wang and Larina, doi 10.1117/1.JBO.25.8.086001. Courtesy of Wang and Larina. The scientists’ observations suggest that localized heart tube pumping in the ventricles functions through a combination of suction and pushing mechanisms. The imaging scales and dynamic contrasts available with OCT enabled mm-level imaging depth with a microscale resolution that captured the entire mouse heart at mid-gestation stages. OCT provided a clear view of fine cardiac structures as well as blood flow. The high imaging speed of OCT together with post-acquisition synchronization allowed the scientists to reconstruct the fast dynamics of the beating heart. Scientists Shang Wang at Stevens Institute and Irina Larina at Baylor hope their approach will inspire new ideas and designs in imaging and measurement techniques to assess embryonic cardiac biomechanics. In particular, the 4D OCT method could lead to a better understanding of the mechanisms contributing to congenital heart defects. The research was published in the Journal of Biomedical Optics (www.doi.org/10.1117/1.JBO.25.8.086001).