Fetal Cardiac Anatomy and Normal Echocardiographic Appearance
Begin with orientation: confirm situs by stomach, spine, and cardiac apex; normal levocardia means the apex points left and anterior, with a cardiac axis near 45 degrees (roughly 15–75 degrees). Systematically inspect the four-chamber view: two atria, two ventricles, offset atrioventricular valves (tricuspid insertion slightly more apical), intact crux, and the flap of the foramen ovale opening into the left atrium. The right ventricle is normally a little more trabeculated and may be slightly larger; the moderator band and Eustachian valve are normal structures, not masses or septal defects. Then sweep through the outflow tracts: the aorta arises centrally from the left ventricle and the pulmonary artery crosses anteriorly from the right ventricle. Great-vessel and arch views should show the ductal arch as a 'hockey stick' and the aortic arch as a 'candy cane', with the trachea to the right of the aortic arch in normal left arch. The three-vessel trachea view helps confirm pulmonary artery, aorta, and superior vena cava arrangement. Normal pulmonary artery is slightly larger than the aorta, and the ductus arteriosus continues the pulmonary artery to the descending aorta. A common trap is calling normal right-heart dominance or a foramen ovale flap an abnormality; another is failing to assess situs because the heart looks structurally normal. Worked example: if the stomach is left, apex left, aortic arch left of trachea, and systemic veins connect to the right atrium, conclude normal situs solitus with a left aortic arch. Rule of thumb: in a normal heart, 'left is left'-stomach, apex, aortic arch, and pulmonary venous return to the left atrium-and the outflow tracts cross rather than run parallel.