ABSTRACT
Objective:To investigate the hemodynamic characteristics and dynamic cerebral autoregulation(dCA) of patients with severe carotid stenosis before carotid endarterectomy(CEA), and to analyze their correlations with hyperperfusion after CEA.Methods:A total of 63 patients with unilateral severe carotid artery atherosclerotic stenosis who underwent CEA were consecutively recruited prospectively in Xuanwu Hospital, Capital Medical University from January 2021 to August 2021. According to postoperative hyperperfusion, patients were divided into hyperperfusion group (13 cases) and non-hyperperfusion group (50 cases). The general clinical data and hemodynamic parameters were compared between the two groups. The dCA was evaluated by the transfer function analysis that measured the fluctuation amplitude of mean cerebral blood flow velocity(CBFV) with blood pressure change, the time difference of phase with blood pressure change, and the correlation between mean CBFV and blood pressure change. The value of dCA for predicting postoperative hyperperfusion was analyzed through the ROC curve and the area under the curve(AUC).Results:①The proportion of hypertension in hyperperfusion group was higher than that in non-hyperperfusion group ( P<0.05). ②The peak systolic velocity (PSV) at the stenosis lesion of the internal carotid artery, the end-diastolic velocity (EDV) at the stenosis lesion of the internal carotid artery and the ratio of PSV at the stenosis lesion of the internal carotid artery to the distal internal carotid artery in the hyperperfusion group were higher than the non-hyperperfusion group.And the PSV of the ipsilateral middle cerebral artery in the hyperperfusion group was lower than the non-hyperperfusion group (all P<0.05). ③In the very low-frequency and low-frequency region, the phase in the hyperperfusion group was lower than that in the non-hyperperfusion group (all P<0.05), while there was no significant difference in the high-frequency regions( P>0.05). In the three regions of very low-frequency, low-frequency and high-frequency, there were no significant differences in the gain and coherence between the two groups(all P>0.05). ④The best cutoff value of phase in the very low-frequency was 33.28 for predicting hyperperfusion after CEA (AUC=0.766, 95% CI=0.629-0.904, P=0.03), with the specificity of 0.700, and sensitivity of 0.846. Conclusions:There are differences in hemodynamics and dCA between the hyperperfusion group and the non-hyperperfusion group after CEA. The impaired preoperative dynamic cerebral autoregulation is an independent predictor of postoperative hyperperfusion.
ABSTRACT
ABSTRACT Background: Cerebral autoregulation (CA) is the ability of intracranial vessels to maintain a constant cerebral blood flow (CBF) during changes of cerebral perfusion pressure (CPP) related to fluctuations in blood pressure, postural changes or increased metabolic demands. It has been suggested that individuals with silent cerebral small vessel disease (SVD) may have impaired CA, but information is inconclusive. We describe the protocol of a study aimed to assess the association between white matter hyperintensities (WMH) of presumed vascular origin and poor dynamic CA, and to determine the effects of head-up and body positioning in patients with this condition. Methods: Using a case-control study design, we will assess the relationship between severity of WMH and dynamic CA, measured by continuous transcranial Doppler assessment of CBF velocities in the middle cerebral arteries (MCAs) combined with beat-to-beat blood pressure monitoring. Dynamic CA will be analyzed by calculating the mean flow index as the ratio of median arterial pressure and mean flow velocities of the MCAs. Participants will be categorized as case-patients if the MRI shows moderate-to-severe WMH. For every case-patient, an age- and sex-matched healthy individual with no neuroimaging evidence of SVD will be selected as a control. Comment: This study will assess whether head-up and body positioning impairs dynamic CA in the setting of diffuse subcortical damage related to SVD, providing further evidence on the importance of CPP in maintaining the CBF. If positive, the study will provide evidence favoring the stop of aggressive hypertensive therapy or interventions promoting orthostatic hypotension to reduce the risk of further ischemic brain damage in these cases.
RESUMEN Antecedentes: La autorregulación cerebral (CA) es la capacidad de los vasos cerebrales de mantener un flujo sanguíneo constante durante cambios en la presión de perfusión cerebral (PPC) relacionados con fluctuaciones de la presión arterial, cambios posturales o aumento de las demandas metabólicas. Se ha sugerido que las personas con enfermedad de pequeño vaso cerebral pueden tener CA deteriorada, pero la información no es concluyente. Describimos el protocolo de un estudio cuyo objetivo es evaluar la asociación entre hiperintensidades de substancia blanca y CA dinámica deficiente, para determinar los efectos del posicionamiento de cabeza y cuerpo en estos pacientes. Métodos: Utilizando un diseño de caso-control, evaluaremos la relación entre la severidad de las hiperintensidades de substancia blanca y la CA dinámica, mediante Doppler transcraneal continuo de las velocidades de flujo en las arterias cerebrales medias (ACM) combinadas con monitoreo de la presión arterial. La CA dinámica se analizará calculando el índice de flujo medio y la relación entre la presión arterial media y las velocidades medias de flujo de las ACM. Los participantes se clasificarán como casos si la IRM muestra hiperintensidades de substancia blanca. Para cada caso, se seleccionará a un individuo sin evidencia de enfermedad de pequeño vaso como control. Comentario: Este estudio evaluará si el posicionamiento de la cabeza hacia arriba afecta la CA dinámica en el contexto del daño subcortical difuso relacionado con enfermedad de pequeño vaso, proporcionando evidencia adicional sobre la importancia de la PPC en el mantenimiento del flujo en estos sujetos. El estudio proporcionará evidencia sobre el uso de terapia hipertensiva agresiva o intervenciones que promueven la hipotensión ortostática para reducir el riesgo de daño cerebral isquémico.