Children's National Health System 2 articles published in JoVE Medicine Optocardiography and Electrophysiology Studies of Ex Vivo Langendorff-perfused Hearts Luther M. Swift1,2, Rafael Jaimes III1,2, Damon McCullough1,2, Morgan Burke1,2, Marissa Reilly1,2, Takuya Maeda1,2,3, Hanyu Zhang4, Nobuyuki Ishibashi1,2,3, Jack M. Rogers4, Nikki Gillum Posnack1,2,5 1Center for Neuroscience Research, Children's National Hospital, 4Department of Biomedical Engineering, School of Engineering, University of Alabama at Birmingham, 5Department of Pediatrics, Department of Pharmacology & Physiology, School of Medicine and Health Sciences, George Washington University The objective of this study was to establish a method for investigating cardiac dynamics using a translational animal model. The described experimental approach incorporates dual-emission optocardiography in conjunction with an electrophysiological study to assess electrical activity in an isolated, intact porcine heart model. Cancer Research Detection and Monitoring of Tumor Associated Circulating DNA in Patient Biofluids Erin R. Bonner1,2, Karim Saoud1, Sulgi Lee1,2, Eshini Panditharatna3, Madhuri Kambhampati1, Sabine Mueller4,5, Javad Nazarian1,2,5 1 Here, we present a protocol to detect tumor somatic mutations in circulating DNA present in patient biological fluids (biofluids). Our droplet digital polymerase chain reaction (dPCR)-based method enables quantification of the tumor mutation allelic frequency (MAF), facilitating a minimally invasive complement to diagnosis and temporal monitoring of tumor response.