RESUMO
The endothelium is a thin monocellular layer that covers all the inner surface of the blood vessels, separating the circulating blood from the tissues. It is not an inactive organ, quite the opposite. It works as a receptor-efector organ and responds to each physical or chemical stimulus with the release of the correct substance with which it may maintain vasomotor balance and vascular-tissue homeostasis. It has the property of producing, independently, both agonistic and antagonistic substances that help to keep homeostasis and its function is not only autocrine, but also paracrine and endocrine. In this way it modulates the vascular smooth muscle cells producing relaxation or contraction, and therefore vasodilatation or vasoconstriction. The endothelium regulating homeostasis by controlling the production of prothrombotic and antithrombotic components, and fibrynolitics and antifibrynolitics. Also intervenes in cell proliferation and migration, in leukocyte adhesion and activation and in immunological and inflammatory processes. Cardiovascular risk factors cause oxidative stress that alters the endothelial cells capacity and leads to the so called endothelial "dysfunction" reducing its capacity to maintain homeostasis and leads to the development of pathological inflammatory processes and vascular disease. There are different techniques to evaluate the endothelium functional capacity, that depend on the amount of NO produced and the vasodilatation effect. The percentage of vasodilatation with respect to the basal value represents the endothelial functional capacity. Taking into account that shear stress is one of the most important stimulants for the synthesis and release of NO, the non-invasive technique most often used is the transient flow-modulate "endothelium-dependent" post-ischemic vasodilatation, performed on conductance arteries such as the brachial, radial or femoral arteries. This vasodilatation is compared with the vasodilatation produced by drugs that are NO donors, such as nitroglycerine, called "endothelium independent". The vasodilatation is quantified by measuring the arterial diameter with high resolution ultrasonography. Laser-Doppler techniques are now starting to be used that also consider tissue perfusion. There is so much proof about endothelial dysfunction that it is reasonable to believe that there is diagnostic and prognostic value in its evaluation for the late outcome. There is no doubt that endothelial dysfunction contributes to the initiation and progression of atherosclerotic disease and could be considered an independent vascular risk factor. Although prolonged randomized clinical trials are needed for unequivocal evidence, the data already obtained allows the methods of evaluation of endothelial dysfunction to be considered useful in clinical practice and have overcome the experimental step, being non-invasive increases its value making it use full for follow-up of the progression of the disease and the effects of different treatments.
Assuntos
Doenças Cardiovasculares/epidemiologia , Endotélio Vascular/fisiopatologia , Aterosclerose/epidemiologia , Humanos , Óxido Nítrico/fisiologia , Sistema Renina-Angiotensina , VasodilataçãoRESUMO
La vasodilatación y el aumento de flujo posisquemia de la arteria humeral, evaluados por eco-Doppler, son provocados por la liberación de sustancias vasodilatadoras del endotelio arterial, principalmente óxido nítrico, y expresan su estado funcional. La arteria humeral es considerada "subrogante" de las arterias coronarias y su respuesta es similar a la del resto de la circulación, permitiendo conocer el estado funcional del endotelio de la circulación coronaria y general. En el presente estudio se observó una marcada disminución de la vasodilatación posisquémica en sujetos asintomáticos, sin evidencia clínica de enfermedad cardiovascular y portadores de factores de riesgo, especialmente en los fumadores, hipercolesterolémicos e hipertensos. Por otra parte, se comprobó un deterioro de la función endotelial inversamente proporcional a la edad de los sujetos, independiente del sexo o los factores de riesgo. La prueba de vasodilatación posisquémica es incruenta, reproducible, al alcance de cualquier centro médico, y permite estratificar riesgos y evaluar terapéuticas en todas las edades
Assuntos
Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Ecocardiografia Doppler , Endotélio Vascular , Vasodilatação , Aterosclerose , Hipercolesterolemia , Hipertensão , Fatores de Risco , FumarRESUMO
La vasodilatación y el aumento de flujo posisquemia de la arteria humeral, evaluados por eco-Doppler, son provocados por la liberación de sustancias vasodilatadoras del endotelio arterial, principalmente óxido nítrico, y expresan su estado funcional. La arteria humeral es considerada "subrogante" de las arterias coronarias y su respuesta es similar a la del resto de la circulación, permitiendo conocer el estado funcional del endotelio de la circulación coronaria y general. En el presente estudio se observó una marcada disminución de la vasodilatación posisquémica en sujetos asintomáticos, sin evidencia clínica de enfermedad cardiovascular y portadores de factores de riesgo, especialmente en los fumadores, hipercolesterolémicos e hipertensos. Por otra parte, se comprobó un deterioro de la función endotelial inversamente proporcional a la edad de los sujetos, independiente del sexo o los factores de riesgo. La prueba de vasodilatación posisquémica es incruenta, reproducible, al alcance de cualquier centro médico, y permite estratificar riesgos y evaluar terapéuticas en todas las edades (AU)