hélio de almeidaFor part of the victims of high blood pressure, the arsenal of available medicines and therapies is not capable of controlling the disease adequately. The disease resists treatments and shows itself in a severe form, causing lesions in organs like the heart, the kidneys and the circulatory system. A study by a team of researcher from the School of Medicine of the University of São Paulo (FMUSP) is helping to people to understand and to diagnose one of the causes of the refractory manifestation of the disease. Led by Professor Eduardo Moacyr Krieger, a group of researchers from FMUSP’s Heart Institute and Radiology Department has created a tool for diagnosis and demonstrated how a problem in the anatomy of the nervous system – the existence of an artery compressing an region of the cerebral trunk – may be one of the factors causing severe resistant hypertension.
This region, known as the rostral ventrolateral region of the bulb, is responsible for the so-called sympathetic activity, which maintains the workings of the cardiovascular system. In the majority of people, the artery in question, usually a branch of the vertebral artery, passes far away from the cerebral trunk. But there are individuals who show the artery touching on the region. And in others the artery is not just stuck to the rostral ventrolateral region of the bulb, but causes a pressure so strong that it goes as far as to deform it. “Since the end of the 1970’s, evidence has arisen that the pulsing of this artery may excite the region and increase sympathetic activity, which leads to the contraction of the vessels and to an increase in blood pressure”, says Fernanda Marciano Consolim-Colombo, the coordinator of the clinical research laboratory of InCor’s Hypertension Unit and one of those responsible for the research.
The team from FMUSP developed a method for detecting the anatomical problem, and, by means of this, associated the degree of compression to the increase of the sympathetic activity connected with hypertension. The research was carried out on two fronts. One of them, under the responsibility of Claudia Costa Leite, the head of the Resonance Department of FMUSP’s Radiology Department, created a standard for getting images by means of magnetic resonance capable of mapping the existence or not of the anatomical problem. This stage yielded a scientific article published in the Neuroradiology magazine.
Hand on ice
The following stage, carried out at InCor’s Hypertension Unit, consisted of mapping the sympathetic activity of three groups of patients: one that showed a strong compression of the artery, another that showed the artery touching on the region, but without pressing it, and a third one with the artery passing far away. By means of an examination called micro-neuromyography, in which an electrode is put into a nerve of the leg, the degree of electrical stimulation of the vascular system was evaluated in two situations: at rest and with stimulation (putting the patient’s hand in a bucket of ice, which makes the pressure rise). It was discovered that the group with strong compression caused by the artery showed a sympathetic activity above normal, even during the rest.
In another finding, it was found that there is no difference in the sympathetic activity in individuals in which the artery passes far from the rostral ventrolateral region of the bulb and those in which the artery just touches it. In other words, the problem is concentrated on the patients with a deformation of the cerebral trunk. This stage was described in the doctoral thesis of Mauricio Sendeski, supervised by Eduardo Krieger and by physician Fernanda Marciano Consolim-Colombo, earning them a scientific article published in February on the Hypertension magazine.
The discovery of the association of the compression caused by the artery in the sympathetic system and hypertension was made by chance by an American neurosurgeon, Peter Jannetta, then a professor at the Medical Center of the University of Pittsburgh, in the state of Pennsylvania, which had specialized in a kind of microsurgery to separate from the cerebral trunk a vessel that compresses the facial nerve and causes pain or involuntary reflexes in the face.
Teflon
When doing these operations, he observed that some people also showed compression of the rostral ventrolateral region of the medulla, and that, amongst them, the cases of severe hypertension were common. Jannetta proposed a surgical treatment for the problem, which consists of separating the artery from the region and installing between them an insulation made of Teflon. The surgical treatment showed good results in 50% of the cases, evidencing that in a significant part of the sick it is not an isolated cause of the hypertension. Since then, this variable is taken into consideration by doctors that treat the disease, but the degree of compression caused by the vessel capable of causing the problem was not known.
One of the merits of the work from FMUSP was to show, for the first time, that only the cases of serious compression cause severe hypertension. “The discoveries are important for identifying, amongst hypertensive patients with signs of neurovascular compression, the individuals that have an altered sympathetic activity”, says physician Eduardo Krieger. The next step will be to map the lesions caused in organs in patients that show this compression. This may open the way to finding more adequate treatments. Surgical decompression is one of the possibilities, provided that it is proved that there is a clear indication of the problem. Another possibility is treatment with medicines that act specifically on this area, and the use of larger quantities and doses of antihypertensive drugs, since it is known that the organism is refractory to them for physiological reasons.
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