Reduced ejection fraction heart failure (HFrEF) is a complex and multifactorial condition. It is characterized by a decrease in the ability of the left ventricle to eject blood effectively during systole, resulting in an ejection fraction of less than 40%. This insufficiency in blood pumping leads to inadequate tissue perfusion and a series of adverse physiological adaptations that further compromise cardiac function, representing an important challenge in conducting treatment. The pathophysiology of HFrEF involves multiple mechanisms starting from the remodeling of the left ventricle in the face of some initial aggression, such as a heart attack, which culminates in a progressive deterioration of the contractile function. Additionally, neurohormonal systems are activated in response to the decrease in cardiac output, resulting in hyperactivation of the sympathetic nervous system and the renin-angiotensin-aldosterone axis, which leads to the activation of inflammatory cascades, mainly involving Interleukin 6 (IL-6) and Tumor Necrosis Factor Alpha (TNF-alfa), and disease progression. HFrEF is more prevalent in elderly populations and leads to increased hospital admissions. Furthermore, B12 depletion is more common in the elderly population and these two associated factors, functional impairment of the heart, disruption in the inflammatory cascade and depletion of nutrients, such as vitamin B12, can impact patients; quality of life in the long term. The reduction in B12 levels leads to changes in the cardiac and brain systems, due to the increase in homocysteine and the triggering of the inflammatory cascade. B12 supplementation through Chlorella Pyrenoidosa (microalgae - functional food) reduces cardiac damage and modulate the inflammatory cascade. And also High-Density Transcranial Direct Current Stimulation (HD-tDCS), a non-invasive technique capable of modulating neuronal excitability and inducing anti-inflammatory effects. In this sense, the objective is to evaluate the effects of HD-tDCS and the consumption of Chlorella Pyrenidosa to improve B12 levels and inflammatory response in patients with HFrEF.

This study is a controlled, double-blind, randomized, crossover model clinical trial involving 28 participants with HFrEF admitted to a hospital for surgery and post-surgical outpatient care. Assessments will be carried out at baseline and after treatments through nutritional, clinical and laboratory assessment. The protocol is divided into two phases: the hospital phase with the implementation of the HD-tDCS protocol and the outpatient phase with the implementation of the Chlorella Pyrenoidosa protocol. The randomization of participants divides them into two groups: the active group that receives the intervention and the sham/control group that does not receive the intervention. In the hospital phase of the research, the protocol with HD-tDCS must be started before the surgical procedure, consisting of 5 sessions, applied once a day, for a period of up to 5 days before surgery, with stimulation in the Dorsolateral Prefrontal Cortex, with an intensity of 4mA and duration of 20 minutes each, with anodal stimulus. After post-surgery, at hospital discharge, the washout period of the groups is considered, in this phase another assessment of the group is considered and these are inverted, where the sham group in the previous phase becomes the active group at this stage and vice versa. The active group will receive the intervention through Chlorella pyreinodosa, the protocol in this phase is guided by the consumption of Chlorella p. in a home environment for 30 days until returning for evaluation from surgery, with the active group consuming 10 tablets, 5g/day, containing 4mcg of B12 from organic Chlorella pyrenoidosa in tablets (Registration with Health Surveillance (Anvisa)/Ministry of Health (MS)/Brazil No. 6.7273.000 - classification of functional food) during a period of thirty days and de control group will not receive. After this period, the active group and the control group must return for nutritional assessment and collection of final exams.

Inclusion Criteria:

• Patients with stable HFrEF diagnosis and surgical indication;
• Adults and elderly people (20 to 80 years old);
• Able to respond to commands and give consent to participate in the research;
• Able to respond to simple commands and provide informed consent.

Exclusion Criteria:

• Patients with a clinical history of neuromuscular or cognitive instability,
• Pregnancy and contraindications for receiving neurostimulation (such as cardiac pacemakers and metallic brain implants);
• Patients with contraindications to the use of Chlorella (gastritis, esophagitis, peptic ulcers),;
• Patients with stroke and tumors.

The research includes the responsible researcher, assistant and collaborator. The Collaborating Researcher is responsible for applying the technique to the patient not knowing which stimulus will be true or sham. He must apply the research tools and fill out de forms. The Collaborating Researcher should alert the Main Researcher and Assistant Research if regards signs or symptoms in patient resulting adverse effects.

In this way, the patient and the Collaborating Researcher are blinding.