Characterizing Hemodynamic Compensation and Stroke Risk in Stenosis Patients

描述（由申请人提供）：这项工作的总体目的是评估卒中风险与血流动力学代偿策略之间的关系，使用新的3.0特斯拉MRI协议测量，在有症状的颅内（IC）狭窄闭塞性疾病患者中。最近的研究表明，有症状的IC动脉狭窄患者两年缺血性卒中发生率高。IC狭窄患者的治疗包括血管成形术、IC支架置入术或搭桥的血运重建术，然而，识别最有可能从这些更积极的干预中获益的患者，而不是单独的医疗管理，一直存在问题。血流动力学损伤的精确测量可能需要更好地定义中风风险和指导治疗决策。具体来说，在脑灌注压受损（CPP）的IC狭窄患者中，血流动力学受损的程度反映了血管增加动脉脑血容量（aCBV）和/或发展侧支以补充脑血流量（CBF）的自身调节能力。CBF担保和aCBV自动调节的流行被假设与卒中风险有独特的相关性；然而，这种相关性的程度一直存在争议。对卒中风险进行分层的关键障碍在于缺乏1)高特异性测量多种血流动力学因素的方法和(2)能够监测损伤纵向进展的无创方法。我们已经证明了相对较新的、无创的MRI方法在评估脑血管反应性（CVR）、aCBV和侧支CBF方面的临床应用。我们假设从这些参数的集体测量中可以更完整地证明中风的风险。因此，我们建议实施一种新的、经过验证的血流动力学MRI方案来评估IC狭窄患者的组织水平损伤和代偿策略。采用联合测量多个脑区侧支脑血流、aCBV和CVR的方法，结合将上述变量作为可能的预后因素的统计模型，我们将量化两年卒中风险与血流动力学代偿机制的关联程度。这项无创和多方面的研究旨在扩大卒中诊断基础设施，并阐明这一高危人群卒中的新的血流动力学预后指标。

DESCRIPTION (provided by applicant): The overall aim of this work is to assess the relationship between stroke risk and hemodynamic compensation strategies, as measured using a novel 3.0 Tesla MRI protocol, in patients with symptomatic intracranial (IC) steno-occlusive disease. Recent studies have shown high two-year ischemic stroke rates in symptomatic patients with IC arterial stenosis. Therapy for IC stenosis patients includes revascularization with angioplasty, IC stenting, or bypass, however identification of patients most likely to benefit from these more aggressive interventions, rather than medical management alone, has been problematic. Accurate measurements of hemodynamic compromise are likely required to better define stroke risk and guide treatment decisions. Specifically, in IC stenosis patients with compromised cerebral perfusion pressure (CPP), the extent of hemodynamic compromise reflects the autoregulatory capacity of vasculature to increase arterial cerebral blood volume (aCBV) and/or develop collaterals to supplement cerebral blood flow (CBF). The prevalence of CBF collateralization and aCBV autoregulation has been hypothesized to correlate uniquely with stroke risk; however the extent of this correlation has been debated. The critical barrier to stratifying stroke risk rests with a lack of i) methodology for measuring multiple hemodynamic factors with high specificity and (ii) noninvasive approaches capable of monitoring longitudinal progression of impairment. We have demonstrated the clinical utility of relatively new, noninvasive MRI approaches for assessing cerebrovascular reactivity (CVR), aCBV, and collateral CBF. We hypothesize that stroke risk can be more completely evinced from collective measurements of these parameters. Therefore, we propose to implement a novel, validated hemodynamic MRI protocol to assess tissue-level impairment and compensation strategies in patients with IC stenosis. Using a collective approach combining measurements of collateral CBF, aCBV and CVR in multiple brain regions, in conjunction with a statistical model incorporating the above variables as possible prognostic factors, we will quantify the extent to which two-year stroke risk is associated with hemodynamic compensation mechanisms. The noninvasive and multi-faceted scope of this investigation is intended to expand the diagnostic stroke infrastructure and elucidate new hemodynamic prognostic indicators of stroke in this high-risk population.