Endothelial dysfunction assessment by flow-mediated dilation in a high-altitude population

Abstract

IntroductionEndothelial function at high altitude has been measured only in populations that are genetically adapted to chronic hypoxia. The objective of this study was to evaluate endothelial dysfunction (ED) in a nongenetically adapted high-altitude population of the Andes mountains, in Huancayo, Peru (3,250 meters above sea level).MethodsParticipants included 61 patients: 28 cases and 33 controls. The cases were subjects with hypertension, diabetes mellitus, obesity, or a history of stroke or coronary artery disease. Flow-mediated vasodilation (FMD) of the brachial artery was measured in the supine position, at noon, after 5 minutes of resting. The brachial artery was identified above the elbow. Its basal diameter was measured during diastole, and FMD was tested after 5 minutes of forearm ischemia. Intima–media complex in the right carotid artery was also determined. An increase in the artery’s baseline diameter <10% indicated a positive test. Endothelium-independent vasodilation was evaluated with sublingual nitrate administration. The intima–media complex in the right carotid artery was also measured.Results100% of diabetics had ED; ED was also found in 68.8% of obese individuals, 55% of hypertensive patients, and 46.5% of controls. Age, height, body mass index, and waist diameter were higher in the cases as compared with the controls. A total of 57.9% (n=11) of the cases and 45.2% (n=19) of the controls presented ED. Patients without ED had a mean increase in brachial artery diameter of 23.16%, while in those with ED it was only 3.84%. Individuals with diabetes or hypertension had a greater thickness of the carotid artery intima media layer (1.092 versus 0.664 cm) (p=0.037). A positive test for ED was associated with a greater basal diameter of the brachial artery (4.66±0.62 versus 4.23±0.59 cm) (p=0.02). A total of 7 patients presented paradoxical response, developing posthyperemia vasoconstriction.DiscussionThe proportion of ED was high among controls and among patients with risk factors. Controls showed better FMD profiles than subjects studied in Tibet and the Himalayas.

Characteristics of Cerebral Stroke in the Tibet Autonomous Region of China

“…Due to the prevalence of hypertension and overweight (body mass index >25) being greater in the stroke belt than Tibet. Hypoxia is a unique risk factor in Tibet to cause stroke [56][57][58][59][60][61][62][63][64][65].…”

“…This is the primary response to hypoxia and causes dysfunction of endothelial cells [57]. Subsequently, hypoxia induces oxidative stress and releases more reactive oxygen species (ROS) from mitochondria [57][58][59]. Free radicals activate the expression of cytokines, chemokines, and adhesion molecules [59].…”

Edad vascular y disfunción endotelial en personas que viven a gran altura

“…Por otro lado, a la DE se ha relacionado con los factores de riesgo coronario, de forma que la vasodilatación mediada por flujo sanguíneo está disminuida en estadios tempranos de la enfermedad cardiovascular en pacientes con hipertensión arterial, hipercolesterolemia, fumadores y diabéticos (35) . Calderon-Gerstein et al, en su investigación realizada a 3250 m s. n. m. reporta DE en 100 % de diabéticos, 68,8 % de obesos, y en 55 % de hipertensos (36) . Otro estudio al mismo nivel de altitud encontró DE en 82,4 %, 71,5 % y 50 % de individuos hipertensos, diabéticos y obesos respectivamente (36) .…”

“…Calderon-Gerstein et al, en su investigación realizada a 3250 m s. n. m. reporta DE en 100 % de diabéticos, 68,8 % de obesos, y en 55 % de hipertensos (36) . Otro estudio al mismo nivel de altitud encontró DE en 82,4 %, 71,5 % y 50 % de individuos hipertensos, diabéticos y obesos respectivamente (36) .…”

“…Yao et al (2014) reportaron en un estudio de 1083 pacientes entre 30 a 80 años, que la vasodilatación mediada por flujo disminuye con el incremento del SCORE de Framingham en ambos sexos, (en varones R = -0,308; p< 0,001; y para mujeres: R = -0.577; p< 0,001) (38) . Campuzano et al, en un estudio de 52 personas con una media de 55,77 +-14,96 años, sin distribución por sexos encontró que la función endotelial es peor en pacientes con factores de riesgo, pero sin enfermedad ateroesclerótica clínica, que en pacientes sin ellos (35) , al analizar los resultados obtuvo que la vasodilatación mediada por flujo fue casi 4 veces mayor en el grupo de pacientes sin factores de riesgo en comparación a los que presentaron al menos un factor de riesgo (36) . En nuestra serie encontramos hallazgos similares, se objetiva que a mayor número de factores de riesgo cardiovascular es mayor la disfunción endotelial, también se encontró que la hipertensión arterial fue casi siete veces más frecuente en personas con DE en comparación a los portadores de función endotelial normal (OR=6,72; IC95 % = 1,37-32,99; p= 0,009).…”