Contrary to the initial belief that the heart is a terminally differentiated organ that cannot replace its own cell damage, there is now proof that the circulating blood provides the injured tissue with adult stem and progenitor cells, which have the potential to differentiate into cardiomyocytes and ultimately improve cardiac function. Thus, transplantation of stem cells into the myocardium in patients with severe myocardial dysfunction post-myocardial infarction is being currently investigated for experimental as well as for clinical purposes. Many issues regarding the mode of action remain to be elucidated. The BOOST trial was the first completed, randomized study that showed safety, feasibility and efficacy of the method. However, a more recent doubleblind, placebo-controlled study failed to reveal an increase in global left ventricular nejection fraction and cast doubt on the efficacy of the method. Thus, further randomized studies are needed to evaluate this novel approach in the treatment of ischemic heart failure and determine its role, safety and efficacy
