Here is the design of a clinical trial:

Official Title: Randomised Controlled Trial Into the Role of Ramipril in Fibrosis Reduction in Rheumatic Heart Disease: The RamiRHeD Trial Protocol

Included conditions:
- Rheumatic Heart Disease
- Mitral Stenosis
- Rheumatic Mitral Stenosis
- Fibrosis; Heart
- ACE Inhibitor

Study Armgroups:
- {'label': 'control', 'type': 'PLACEBO_COMPARATOR', 'description': 'control patients will be given a placebo', 'interventionNames': ['Drug: Placebos']}
- {'label': 'treatment', 'type': 'EXPERIMENTAL', 'description': 'Ramipril 5 mg treatment group', 'interventionNames': ['Drug: Ramipril 5Mg Oral Capsule']}

Interventions:
- {'type': 'DRUG', 'name': 'Placebos', 'description': "the control group will be given placebo inside a capsule, so study participant won't be able to know the drug and doses inside the capsule (for masking). Placebo will be given until 5 days prior to Mitral valve replacement surgery.", 'armGroupLabels': ['control'], 'otherNames': ['control group']}
- {'type': 'DRUG', 'name': 'Ramipril 5Mg Oral Capsule', 'description': "the treatment group will be given each Ramipril 2,5 mg inside a capsule as an initial dose, for 2 weeks. If there is no serious adverse effect in the observation period of 2 weeks, Ramipril 5 mg inside a capsule will be given for the next weeks until 5 days before the mitral valve surgery date. Study participant won't be able to know the drug and doses inside the capsule (for masking)", 'armGroupLabels': ['treatment'], 'otherNames': ['treatment group']}

Primary Outcomes:
- {'measure': 'ST2 expression in mitral valve tissue and papillary muscle', 'description': 'expression of ST2 in mitral valve tissue, using immunohistochemistry method', 'timeFrame': 'a year'}

Please estimate the sample size based on the assumption: 
The statistical assumptions include a significance level (Z0.95) of 1.96, a standard normal distribution (δ N(0,1)=1), and a margin of error (E) of 0.05 for a 95% confidence interval. Additionally, a 10% dropout rate is considered.
Sample size and randomisation
        This is a pioneering study analysing the effects of 5âmg ramipril on ST2 expression in mitral valve tissue in humans. A previous study that used ST2 human tissue was conducted by Marzullo et al in 2016.12 The used carotid tissue from carotid endarterectomy, with a sample size of 41 consecutive patients. Because our study will use human tissue samples, we approached the sample size calculation using the multistage non-finite population method, using this specified precision estimation formula13: N=(ZÎ´)/E, with N=sampleâsize; Z0.95= 1.96; Î´ N(0,1)=1; and E=0.05 for a 0.95 CI. Therefore, we calculated a required sample of 1.65(1)/0.05=33 samples.
        According to the sample size of the previous study that analysed ST in human tissue and a sample size formula that is commonly used in in vivo studies, we decided to use a sample size of 30 for each arm, and with the addition of a drop out rate of 10%, this became total of 66 for the two arms.
        The number includes a 10% dropout and withdrawal from each group. Randomisation will be done with an equal ratio of ramipril to placebo. A computerised sequence generator is used for randomisation. It will be linked with codes for placebo and treatment tablets provided by the manufacturer that was contracted to produce the trial medication. Researchers and participants will be blinded. After randomisation, the treatment pack and capsule will be identical between the two groups and will contain either active tablets or placebo. The principal investigator will have no access to the randomisation list.