Here is the design of a clinical trial:

Official Title: Betablockers Withdrawal in Patients With Heart Failure With Preserved Ejection Fraction and Chronotropic Incompetence: Effect on Functional Capacity Rationale and Study Design of a Prospective, Randomized, Controlled Trial

Included conditions:
- Heart Failure With Normal Ejection Fraction
- Chronotropic Incompetence

Study Armgroups:
- {'label': 'Arm A', 'type': 'ACTIVE_COMPARATOR', 'description': 'Controlled Withdrawal of Beta-blockers and Cardiopulmonary Exercise Testing (CPET) Patient will be assessed for chronotr0pic incompetence by CPET. If the patient exhibits chronotropic incompetence, we will reduce half dose of previous beta-blocker.\n\nA cardiologist will evaluate clinically the the patient and the heart rate in 3 days. If clinical and heart rate stability (below 90 bpm), the patients will withdraw the beta-blocker and will be assessed by CPET at 15-day.\n\nAfter second CPET, the patient will introduce the half-dose of beta-blocker and will be evaluated in 3 days. If clinical stability, the patient will introduce the previous dose of beta-blocker A third CPET will be performed at 15-day', 'interventionNames': ['Drug: Controlled withdrawal of beta-blockers', 'Diagnostic Test: Cardiopulmonary Exercise Testing']}
- {'label': 'Arm B', 'type': 'ACTIVE_COMPARATOR', 'description': 'Cardiopulmonary Exercise Testing (CPET) and Controlled Withdrawal of Beta-blockers Patient will be assessed for chronotropic incompetence by CPET.If the patient exhibits chronotropic incompetence, a cardiologist will evaluate clinically the patient and the heart rate in 3 days and will be assessed by CPET at 15-day.\n\nAfter second CPET, the patient will reduce half dose of previous beta-blocker. A cardiologist will evaluate clinically the the patient and the heart rate in 3 days. If clinical and heart rate stability (below 90 bpm), the patients will withdraw the beta-blocker and will be assessed by CPET at 15-day.', 'interventionNames': ['Drug: Controlled withdrawal of beta-blockers', 'Diagnostic Test: Cardiopulmonary Exercise Testing']}

Interventions:
- {'type': 'DRUG', 'name': 'Controlled withdrawal of beta-blockers', 'description': 'Controlled withdrawal of previos doses of beta-blockers after diagnosis of chronotropic incompetence', 'armGroupLabels': ['Arm A', 'Arm B']}
- {'type': 'DIAGNOSTIC_TEST', 'name': 'Cardiopulmonary Exercise Testing', 'description': 'Cardiopulmonary Exercise Testing to evaluate the chronotropic incompetence and the primary endpoint (functional capacity)', 'armGroupLabels': ['Arm A', 'Arm B']}

Primary Outcomes:
- {'measure': 'Maximal functional capacity', 'description': 'Maximal functional capacity measured by peak oxygen consumption in the cardiopulmonary exercise testing (CPET). The peak oxygen consumption is expressed in mL/kg/min.The investigators will measure the change of peak oxygen consumption .', 'timeFrame': 'The change in peak oxygen consumption will be measured at baseline, at 15-day and at 30-day'}

Please estimate the sample size based on the assumption: 
The study uses a two-sided test at a 0.05 significance alpha level, with 90% power and an assumption of 20% withdrawals or losses to follow-up.
2.5
        Sample size calculation
        The null hypothesis of the study is that the mean peakVO2 absolute differences from baseline to 15âdays after the withdrawal of betaâblockers will be similar. The sample size determination for this study assumes twoâsided testing at the 0.05 significance alpha level. Because this is a randomized clinical trial, we assume no differences in peakVO2 at baseline among the two arms. Based on a prior study of our group in HFpEF, we assume eligible patients will have a mean (SD) peakVO2 of 10âÂ±â2.8 mL/kg/min.8 Along the same line, and based on prior studies about the deleterious effects of heart rate slowing in HFpEF patients, we speculate a blocker withdrawal will increase peak VO2 about 10%. With this data in mind, we assume a mean change of 1.2 mL/kg/min and a common SD of 2.0,8, 25, 26 a clinical meaningful change according a recent HFA position paper that consider significant clinical changes of peakVO2 those greater than 6% when baseline peakVO2 is lower than 14âmL/min/1.73âm2.27

        Assuming an allocation ratio of 1:1, a total of 42 patients (21 patients per group) would provide 90% of power at a significance alpha levelâ<â0.05. Assuming 20% of withdrawals or losses to followâup, a total of 26 patients per arm (52 patients) will be enrolled. The software used for sample size calculation was âxsampsiâ from Stata 14.1.