Heart failure is a leading cause of death worldwide. Current therapies only 
delay progression of the cardiac disease or replace the diseased heart with 
cardiac transplantation. Stem cells represent a recently discovered novel 
approach to the treatment of cardiac failure that may facilitate the replacement 
of diseased cardiac tissue and subsequently lead to improved cardiac function 
and cardiac regeneration. A stem cell is defined as a cell with the properties 
of being clonogenic, self-renewing, and multipotent. In response to 
intercellular signalling or environmental stimuli, stem cells differentiate into 
cells derived from any of the three primary germ layers: ectoderm, endoderm, and 
mesoderm, a powerful advantage for regenerative therapies. Meanwhile, a cardiac 
progenitor cell is a multipotent cell that can differentiate into cells of any 
of the cardiac lineages, including endothelial cells and cardiomyocytes. Stem 
cells can be classified into three categories: (1) adult stem cells, (2) 
embryonic stem cells, and (3) induced pluripotential cells. Adult stem cells 
have been identified in numerous organs and tissues in adults, including 
bone-marrow, skeletal muscle, adipose tissue, and, as was recently discovered, 
the heart. Embryonic stem cells are derived from the inner cell mass of the 
blastocyst stage of the developing embryo. Finally through transcriptional 
reprogramming, somatic cells, such as fibroblasts, can be converted into induced 
pluripotential cells that resemble embryonic stem cells. Four classes of stem 
cells that may lead to cardiac regeneration are: (1) Embryonic stem cells, (2) 
Bone Marrow derived stem cells, (3) Skeletal myoblasts, and (4) Cardiac stem 
cells and cardiac progenitor cells. Embryonic stem cells are problematic because 
of several reasons: (1) the formation of teratomas, (2) potential immunologic 
cellular rejection, (3) low efficiency of their differentiation into 
cardiomyocytes, typically 1% in culture, and (4) ethical and political issues. 
As of now, bone marrow derived stem cells have not been proven to differentiate 
reproducibly and reliably into cardiomyocytes. Skeletal myoblasts have created 
in vivo myotubes but have not electrically integrated with the myocardium. 
Cardiac stem cells and cardiac progenitor cells represent one of the most 
promising types of cellular therapy for children with cardiac failure.