Transcranial stimulation lowers blood pressure in resistant hypertensives, study finds

Finding non-pharmacological alternatives to help manage resistant hypertension has been the goal of many research groups. And a study recently published in the journal Frontiers in Cardiovascular Medicine indicates that transcranial direct current stimulation (tDCS) may be an option.

As the name suggests, the disease is refractory to available pharmacological treatments. Patients take three or more classes of antihypertensive drugs a day – usually at the maximum dose – but still live with high blood pressure and are at increased risk of heart, vascular and brain complications.

At the Faculty of Physical Education of Universidade Estadual de Campinas (FEF-Unicamp), researchers evaluated the effects of a single session (acute stimulation) and ten consecutive sessions (prolonged stimulation) of tDCS on peripheral and central blood pressure in 13 volunteers with resistant hypertension. Six months before the start of the study, patients were evaluated for their adherence to drug treatment – ​​which was maintained during the study – and other clinical conditions that could influence blood pressure were ruled out.

“In acute stimulation, there were patients with a reduction of 15 mmHg [milímetros de mercúrio] on 24-hour systolic blood pressure, assessed by ambulatory monitoring. A reduction of this magnitude can greatly reduce cardiovascular risks”, says Bruno Rodrigues, coordinator of the research supported by Fapesp, to Agência Fapesp.

With a degree in physical education, a doctorate in pathophysiology and a postdoctoral degree from the Instituto do Coração (InCor) of the Faculty of Medicine of the University of São Paulo (FM-USP), Rodrigues is currently a professor at FEF-Unicamp.

“This was a small study and more robust research is needed. With a larger body of evidence that corroborates our findings, it will be possible to think of tDCS as a form of intervention in the emergency room for patients with hypertensive crisis”, he evaluates.

Tolerance

The results of the clinical trial also show that prolonged stimulation did not decrease brachial blood pressure (measured in the brachial artery, in the arm, in the office and followed for 24 hours). “One of the assumptions is that continuous stimulation for ten days may have increased tolerance and, therefore, would only have worked in the initial period, returning later to normal”, says Rodrigues.

Previous research by the group, also supported by Fapesp, had revealed the potential of transcranial stimulation in relation to cardiac autonomic control and the reduction of blood pressure in patients with mild to moderate hypertension, raising the possibility that tDCS could be used to treat resistant hypertensives.

The current work, a double-blind, randomized, crossover clinical trial (a model in which volunteers are randomly divided into groups without either the participants or the researchers knowing what type of intervention each received) compared the effects of real stimulation (tDCS). ) and in a fictitious way (sham) in 20-minute sessions, which followed two research protocols. Patients randomly selected for sham stimulation received pulses only during the first three minutes of the session and spent a further 17 minutes with electrodes on the skin simulating the therapy, while the others received full stimulation for 20 minutes. After a one-week break, all underwent ten consecutive sessions. After a new interval, those who received placebo were treated with true stimulation and vice versa.

We also tested the effects of stimulation on the autonomic nervous system (the one that controls functions such as breathing, blood circulation, temperature, digestion and divides into the sympathetic and parasympathetic branches) and related blood markers (cortisol, noradrenaline, acetylcholinesterase and cytokines). to mechanisms and substances that have been associated with blood pressure control.

The hyperactivity of the sympathetic nervous system (responsible for the body’s responses to situations of imminent danger, for example, to accelerate heart rate and respiratory rate) is considered one of the main causes of arterial hypertension and stands out even more in resistant hypertensive patients. It is associated with increased heart rate, chances of arrhythmias, vasoconstriction and remodeling of blood vessels and the heart. On the other hand, the activation of the parasympathetic nervous system (which has the opposite effect, slowing down the body) has been related to an improvement in cardiac function, reduction of blood pressure levels and even of inflammatory parameters.

All studies were carried out in partnership with Heitor Moreno Junior, coordinator of the Resistant Hypertension Outpatient Clinic at Unicamp’s Faculty of Medical Sciences.

Stimulation showed some effects that need to be further studied. “Acutely or prolonged, tDCS caused reduced modulation of the sympathetic nervous system and increased vagal modulation [parassimpática]. Such findings may still be related to the increase of an anti-inflammatory cytokine [um tipo de proteína produzido por células do sistema imune] in blood plasma, such as interleukin-10.” The next step will be to prove the direct association of tDCS with the modulation of the autonomic system.