SVC = superior vena cavaAo = aortaPA = pulmonary arteryPV = pulmonary veinRA = right atriumLA = left atriumLV = left ventricleRV = right ventricle Enlarge ImageKey to the heart? Scientists have identified what they say are the heart's "master" stem cells.Credit: Lei Bu et al., Nature 460, 113 (2009) Scientists have identified a cardiac stem cell that gives rise to all of the major cell types in the human heart. The find opens the way to using patients' own cells to heal their damaged hearts. The cells in question express a protein, called Islet 1, which is present in...