One emerging concept is that some form of injury or inflammation is a prerequisite for the success of circulating-cell participation in differentiated tissue structure and function. Once reperfusion is achieved in acute myocardial infarction, an intense inflammatory cascade is unleashed. The architecture of the left ventricle rearranges, leading to ventricular remodeling. The "homing process"involves stem cell migration to the sites of injury or ischemia, which provides an environment that is favorable to growth and function. This microenvironment is a stimulus for homing and differentiation of stem cells of the appropriate lineage. It increases vascular permeability and expression of adhesion proteins like integrin, along with homing receptors that facilitate the attachment, which is mediated by cell-to-cell contact and chemoattractant release from local tissue injury.The migratory capacity of stem cells might be dependent on natural growth factors such as vascular endothelial growth factor (VEGF) , stromal cell-derived factor-1 (SDF-1)and stem cell factor (SCF).The expression of VEGF ,SDF-1 and SCF is highly up-regulated in hypoxic tissue, supporting the hypothesis that these factors may represent homing signals crucial to the recruitment of circulating progenitor cells to assist the endogenous repair mechanisms in the infarcted tissue. This study will examine whether cardiac rehabilitation increases the concentration of stem cell factors released into the bloodstream and if these factors are correlated with the improvement of heart function.
Exercise training has beneficial hemodynamic effects in patients with congestive heart failure.A similar benefit may be seen after MI, with an improvement in functional capacity averaging 20 percent. More important, however, is the possible effect on survival. In a meta-analysis of 24 trials examining the effect of cardiac rehabilitation after MI, there was a significant reduction in mortality with rehabilitation (odds ratio 0.81). Previous studies focused on the effect of rehabilitation comes from the improvement of oxygen utilization in skeletal muscle. The effects on cardiac morphology and perfusion status were rather little to be addressed. In this study, we will collect the questionaires, blood sampling for assay of stem cell factors, maximal O2 consumption, and cardiac MRI before and after cardiac rehabilitation.SDF-1 (stromal cell derived factor-1), SCF(stem cell factor), and VEGF (vasculoendothelial growth factor) will be measured by ELISA. Cardiac MRI will provide the information about (1) LV function, (2) scar size, and (3) perfusion status (dipyridamole stress MRI).
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
NONE
Enrollment
58
Those in the training group participated in a 3-month rehabilitation training program at an exercise intensity of 55% to 70% of peak oxygen uptake (VO2); those in the nontraining group continued their usual lifestyle.
National Taiwan University Hospital
Taipei, Taiwan
Myocardial Blood Flow at Baseline and 3-month Follow-up
First-pass, contrast-enhanced myocardial perfusion images acquired for 80 heart beats in the left ventricle. Short-axis views were obtained after intravenous administration of gadodiamide. Perfusion studies were performed at rest and during the stress induced by a 4 min infusion of dipyridamole at a concentration of 0.14 mg/kg of body weight per minute.To determine absolute MBF values at rest and stress status, we adopted a model-independent deconvolution method proposed by Jerosch-Herold et al, a method that was previously validated in experimental animal studies by comparison with blood-flow measurements with radiolabelled microspheres.
Time frame: 3 months
Angiogenic Cytokines at Baseline and 3-month Follow-up
Angiogenic cytokines such as vascular endothelial growth factor (VEGF), stromal-derived factor-1 (SDF-1) and stem cell factor (SCF) are known to increase the formation of new vessels at ischaemic sites and thus enhance myocardial perfusion. To rule out any effect of short-term exercise on cytokines levels, blood samples were always taken after at least 72 h of physical inactivity and overnight fasting when the subject had rested in the sitting position for at least 10 min. The plasma samples were immediately frozen and stored at -70°C. High-sensitivity ELISA (Bender MedSystems, R\&D) were used to measure plasma levels of SCF, SDF-1 and VEGF according to the manufacturer's protocols.
Time frame: 3 months
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