Caracterizacion de las ramas del arco aórtico en una muestra de poblacion colombiana: un estudio con material de autopsia / Characterization of aortic arch branches in a colombian population sample. A study with autopsy material

La variabilidad del arco aórtico y sus ramas emergentes presentan implicaciones en los abordajes quirúrgicos de tórax y cuello, y posiblemente en el desarrollo de procesos ateromatosos ubicados a ese nivel y accidentes cerebrovasculares. Se evaluaron 122 arcos aórticos de individuos adultos de ambos sexos obtenidos como material de autopsia. Se identificó la configuración general de la emergencia de las ramas colaterales de los arcos y se determinó la morfometría de sus componentes con medición electrónica. Se observó la presencia de la configuración usual (tipo A) en 87 arcos (71,3 por ciento); un tronco braqui-bicarotideo (tipo B) en 21 piezas anatómicas (17,2 por ciento) y en 10 casos (8,2 por ciento) la arteria vertebral izquierda se originó directamente del arco aórtico (tipo C); en 4 especímenes (3,3 por ciento) se presentó emergencia atípica de las ramas. El calibre de la aorta en el punto previo a la emergencia de sus ramas y justo después de emitir su última colateral fue de 20,1mm (DE 3,19) y 17,2mm (DE 2,57) respectivamente, con una disminución del 14,5 por ciento. El calibre de las arterias sublavias (7,7mm, DE 1,10) fue significativamente mayor (P=0,0001) que el de las arterias carótidas (6,4mm, DE 0,78). El diámetro de las arterias carótidas derecha e izquierda fue de 6,5mm (DE 0,81) y 6,3mm (DE 0,75) respectivamente. La arteria subclavia derecha presentó mayor calibre que la izquierda (7,9mm, DE 1,09; 7,6mm, DE 1,12) sin diferencia estadisticamente significativa (P=0,0801). La distancia entre el origen del tronco braquiocefálico y el de la subclavia izquierda fue de 32,8mm (DE 6,16) y la longitud del tronco braquiocefálico fue 30,2mm+/-5,27. Se destaca la alta frecuencia de arcos con emergencia de dos y cuatro ramas. Los calibres de las ramas son menores a lo reportado en la literatura.

The variability of the aortic arch and its emergent branches have implications in the surgical approaches of the thorax and neck, and possibly in the development of the atheromatous processes located at that level and the cerebrovascular accidents. We evaluated 122 aortic arches from adult individuals of both sexes obtained as autopsy material. We identified the general configuration of the emergence of the collateral branches of the arcs and determined the morphometry of its components with electronic measurement. We observed the usual configuration (type A) in 87 arches (71.3 percent); a brachio-bicarotid trunk (type B) in 21 anatomical specimens (17.2 percent) and in 10 cases (8.2 percent) the left vertebral artery originated directly from the aortic arch (type C); 4 specimens (3.3 percent) presented atypical emergency in the branches. The caliber of the aorta at the point prior to the emergence of its branches and just after casting his last side was 20.1mm (DS 3.19) and 17.2mm (DS 2.57) respectively, with a decrease of 14.5 percent. The caliber of the subclavian arteries (7.7mm, SD 1.1) was significantly higher (P=0.0001) than of the carotid arteries (64mm, SD 0.78). The diameter of the carotid arteries both right and left were 6.5mm (DS 0.81) and 6.3mm (DS 0.75) respectively. The right subclavian artery presented higher caliber than the left (7.9mm, DS 1.09; 7.6mm, DS 1.12) without significant statistical difference (P=0.0801). The difference between the origin of the brachiocephalic trunk and the left subclavian artery was 32.8 (DS 6.16); the brachiocephalic trunk length was 30.2mm +/- 5.27. It highlights the high frequency of arches with emergency of two and four branches. The calibers of the branches are smaller than those reported in the literature.

Effect of carotid and aortic baroreceptors on cardiopulmonary reflex: the role of autonomic function

We determined the sympathetic and parasympathetic control of heart rate (HR) and the sensitivity of the cardiopulmonary receptors after selective carotid and aortic denervation. We also investigated the participation of the autonomic nervous system in the Bezold-Jarish reflex after selective removal of aortic and carotid baroreceptors. Male Wistar rats (220-270 g) were divided into three groups: control (CG, N = 8), aortic denervation (AG, N = 5) and carotid denervation (CAG, N = 9). AG animals presented increased arterial pressure (12 percent) and HR (11 percent) compared with CG, while CAG animals presented a reduction in arterial pressure (16 percent) and unchanged HR compared with CG. The sequential blockade of autonomic effects by atropine and propranolol indicated a reduction in vagal function in CAG (a 50 and 62 percent reduction in vagal effect and tonus, respectively) while AG showed an increase of more than 100 percent in sympathetic control of HR. The Bezold-Jarish reflex was evaluated using serotonin, which induced increased bradycardia and hypotension in AG and CAG, suggesting that the sensitivity of the cardiopulmonary reflex is augmented after selective denervation. Atropine administration abolished the bradycardic responses induced by serotonin in all groups; however, the hypotensive response was still increased in AG. Although the responses after atropine were lower than the responses before the drug, indicating a reduction in vagal outflow after selective denervation, our data suggest that both denervation procedures are associated with an increase in sympathetic modulation of the vessels, indicating that the sensitivity of the cardiopulmonary receptors was modulated by baroreceptor fibers.

Acute and chronic electrical activation of baroreceptor afferents in awake and anesthetized subjects

Electrical stimulation of baroreceptor afferents was used in the 1960's in several species, including human beings, for the treatment of refractory hypertension. This approach bypasses the site of baroreceptor mechanosensory transduction. Chronic electrical stimulation of arterial baroreceptors, particularly of the carotid sinus nerve (Hering's nerve), was proposed as an ultimate effort to treat refractory hypertension and angina pectoris due to the limited nature of pharmacological therapy available at that time. Nevertheless, this approach was abandoned in the early 1970's due to technical limitations of implantable devices and to the development of better-tolerated antihypertensive medications. More recently, our laboratory developed the technique of electrical stimulation of the aortic depressor nerve in conscious rats, enabling access to hemodynamic responses without the undesirable effect of anesthesia. In addition, electrical stimulation of the aortic depressor nerve allows assessment of the hemodynamic responses and the sympathovagal balance of the heart in hypertensive rats, which exhibit a well-known decrease in baroreflex sensitivity, usually attributed to baroreceptor ending dysfunction. Recently, there has been renewed interest in using electrical stimulation of the carotid sinus, but not the carotid sinus nerve, to lower blood pressure in conscious hypertensive dogs as well as in hypertensive patients. Notably, previous undesirable technical outcomes associated with electrical stimulation of the carotid sinus nerve observed in the 1960's and 1970's have been overcome. Furthermore, promising data have been recently reported from clinical trials that evaluated the efficacy of carotid sinus stimulation in hypertensive patients with drug resistant hypertension.