LAUSR

To the Editor: The study described in this article investigated the relationship between chronic hypertension and leptomeningeal collateral flow in patients with acute large vessel occlusion. This is a very interesting clinical trial with clear, logical evidence. Chronic hypertension was defined as having blood pressure ≥140/90 mm Hg documented on ≥2 occasions by the medical institution or at a health checkup before the index stroke or as the use of antihypertensive medications before onset. The leptomeningeal collateral flow was assessed by digital subtraction angiography following the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology Collateral Flow Grading System. This study demonstrated that chronic hypertension had a detrimental effect on the acute leptomeningeal collateral flow in patients with acute large vessel occlusion, independent of admission blood pressure. Moreover, premorbid use of antihypertensive agents seemed to improve collateral status. A temporal growth of the ischemic core into the penumbral area (ischemic brain tissue that has not yet undergone infarction) is modulated by collateral blood flow after arterial occlusion. Good collaterals are associated with smaller ischemic infarcts and greater clinical outcomes after recanalization therapy, whereas those with poor collaterals have increased rates of hemorrhagic transformation and symptomatic intracerebral hemorrhage. Thus, it is important and necessary to investigate the risk factors that may damage or improve collateral circulation. Although the present study is novel, the results should be interpreted with more caution. First, serious selective bias might exist under the circumstance of assessment of collateral circulation using digital subtraction angiography. In this cohort, ≈95% of angiography patients had undergone endovascular therapy, implying that digital subtraction angiography was used as part of endovascular therapeutic methods instead of initially assessing the collateral circulation only. As a result, patients with large infarction in early time window evaluated by computed tomography or patients with poor collateral circulation assessed by magnetic resonance angiography or computed tomography angiography were excluded from angiography, whereas those with good collateral circulation might undergo angiography even in the late time window. This was reflected by the fact that the Guest Editor for this article was Natalia S. Rost, MD, MPH. at patients with excellent collaterals had a significant different puncture time compared with those with poor collaterals. Consequently, more patients with good collateral circulation, as well as early time window, were enrolled in the final analysis of the present study, which introduced bias and limited the generalizability of the results. Considering the data set was collected from 2011 to 2017, it would be helpful to provide the criteria for angiography or endovascular therapy in different period of the registry. Second, patients in the present study were divided into 3 groups: no chronic hypertension, chronic hypertensive with antihypertensive medications, and chronic hypertensive without antihypertensive medications. However, the control of hypertension was unsatisfactory in some cohorts. A study had shown that about 40.7% of Chinese adults with hypertension were taking prescribed antihypertensive medications, and only 15.3% achieved satisfied blood pressure control.5 Thus, analysis of premorbidity hypertension control rate of patients would be helpful to determine the role of high blood pressure and hypertension in collateral circulation. Finally, we appreciate the meaningful work done by the authors and their contributions to the literature. We hope the items mentioned above would increase the value of this well-written article.