Right parasternal four-chamber (R-4C) view of the foramen ovale in a 2-day-old healthy foal. The arrowheads indicate the fluttering septum primum at the base of the ostium of pulmonary vein III (ostium III). The yellow bar indicates a 1 cm distance between the septum primum and septum secundum. LA: left atrium; LV: left ventricle; RA: right atrium; RV: right ventricle.