Here is the design of a clinical trial:

Official Title: Multicenter Phase IIb Clinical Trial, Double-blind, Randomized, Controlled Placebo for to Assess the Efficacy of Intracoronary Infusion of Autologous Adult Stem Cells Mononuclear Marrow Unexpanded on Functional Recovery in Patients With Idiopathic Dilated Cardiomyopathy and Heart Failure.

Included conditions:
- Idiopathic Dilated Cardiomyopathy

Study Armgroups:
- {'label': 'Infusion of autologous mononuclear bone marrow cells', 'type': 'EXPERIMENTAL', 'description': 'Infusion of autologous mononuclear bone marrow cells plus conventional medical treatment (as indicated by clinician)', 'interventionNames': ['Drug: Infusion of autologous mononuclear bone marrow cells']}
- {'label': 'Placebo infusion', 'type': 'PLACEBO_COMPARATOR', 'description': 'Placebo infusion plus conventional medical treatment (as indicated by clinician)', 'interventionNames': ['Drug: Placebo infusion']}

Interventions:
- {'type': 'DRUG', 'name': 'Infusion of autologous mononuclear bone marrow cells', 'description': 'Infusion of autologous mononuclear bone marrow cells plus conventional medical treatment (as indicated by clinician)', 'armGroupLabels': ['Infusion of autologous mononuclear bone marrow cells']}
- {'type': 'DRUG', 'name': 'Placebo infusion', 'description': 'Placebo infusion plus conventional medical treatment (as indicated by clinician)', 'armGroupLabels': ['Placebo infusion']}

Primary Outcomes:
- {'measure': 'Changes in ventricular function measured angiographically.', 'timeFrame': '24 months'}

Please estimate the sample size based on the assumption: 
Alpha risk of 0.05, beta risk of 0.2 (power of 80%), common standard deviation of 10, correlation coefficient of 0.5, and a loss to follow-up rate of 10%.
Sample size calculation
        A sample size calculation was performed based on the clinical trial study already completed by our group [32]. In this study, a mean increase in ejection fraction of 9.4âÂ±â9.9% was observed. At the end of the follow-up, mean values of LVEF were 38% among responders, and 27% among non-responders. The sample size calculation was done using GRANMO (v7.12) for paired or repeated measures in two groups. Accepting an alpha risk of 0.05 and a beta risk of 0.2 in a two-sided contrast, 17 subjects are required in the first group and 34 in the second one to detect a difference equal to or greater than 9âunits. It is assumed a common standard deviation of 10 and a correlation coefficient between the initial and final measurement of 0.5. A loss to follow-up rate of 10% has been estimated. However, an interim analysis has been planned in order to re-calculate trial sample size based on the mean increase in ejection fraction observed in the first 20 patients that complete a 6âmonthsâ follow-up period.