Impact of cell number and microvascular obstruction in patients with bone-marrow derived cell therapy: final results from the randomized, double-blind, placebo controlled intracoronary Stem Cell therapy in patients with Acute Myocardial Infarction (SCAMI) trial.

Background: In patients with acute myocardial infarction (AMI), the number of transplanted autologous bone-marrow cells (BMC) has been linked to improvement in left ventricular ejection fraction (LVEF). Complete obstruction of myocardial microvasculature is indicated by microvascular obstruction (MO) in cardiac magnetic resonance imaging (CMR). We analyzed whether the number of transplanted cells and presence of MO were associated with improved LVEF in the double-blind, placebo-controlled, randomized intracoronary Stem Cell therapy in patients with Acute Myocardial Infarction (SCAMI) trial.
Methods and Results: Patients (N = 42) received study therapy mean 7 days after AMI. Median number of transplanted BMC was 324 × 10(6). CMR was performed prior to study therapy and annually up to 3 years and revealed no difference between BMC and placebo population. Patients treated with a cell number above the median experienced a significant improvement in LVEF compared with patients with cell number below the median 3.6 ± 3.4 versus -0.5 ± 6.4 % (difference 4.1, 95 % CI 0.2 to 8.1 %, p = 0.04) at 6 months. The difference in LVEF change between the groups remained with 3.8 % (p = 0.12) at 12 months, 4.5 % (p = 0.07) at 24 months and 5.6 % (p = 0.03) at 36 months. BMC treated patients without MO experienced a better improvement in LVEF compared with patients with MO at 6, 12, 24 and 36 months with 3.5, 5.3, 6.4 and 3.2 %.
Conclusions: In the randomized, placebo-controlled double-blind SCAMI trial improvement in LVEF up to 3 years was higher in BMC patients treated with a high cell number or without MO.