CD34 and angina pectoris: One clinical trial has shown that low-dose concentration MSCs (20 millions) resulted in greater reduction in LV volumes and increase in LVEF compared to high-dose groups (100 million and 200 million) [29], which was consistent with another comparison results that low-dose intramyocardial injection of CD34+ cells (1∗105 cells/kg) had greater improvement in exercise tolerance and lower weekly angina frequency at both 6 months and 12 months than that of high-dose group (5∗105 cells/kg) [45].