Reappraisal of heart rate variability in acute ischemic stroke

Cardiac autonomic dysfunction is a common complication after acute ischemic stroke (IS). Prior investigators have emphasized that infarction of brain stem or hemispheres with insular involvement is related to this dysfunction and may predict poor clinical outcome. From the viewpoint of stroke physicians, however, all stroke patients, particularly large-artery atherosclerosis (LAA) should be monitored for possible cardiac complications after acute IS. This study aimed to investigate cardiac autonomic impaction in patients with acute IS and to make the comparison between LAA and small-vessel occlusion (SVO) subtypes. Of the 126 acute IS patients prospectively enrolled in this study, 32 had LAA, 56 had SVO, and 38 had undetermined etiology according to the Trial of Org 10172 in Acute Stroke Treatment criteria. Cardiac autonomic function of all patients was assessed by measuring heart rate variability (HRV). The low- and high-frequency components of HRV in all stroke patients were significantly lower than those of control subjects after comparing multivariable models, including additional adjustments for age, gender, and all risk factors. There were no significant differences on HRV between LAA and SVO although post hoc comparisons showed that stroke patients of SVO had increased sympathetic modulation and reduced vagal activity. In conclusion, in acute IS patients, both LAA and SVO are predisposed to have cardiac autonomic dysfunction, manifesting as abnormalities in HRV, whether in hemispheric or brain stem lesions. Stroke patients of SVO are at higher risks of cardiac abnormalities, which might suggest an early cardiac dysfunction because of long-term hypertension. The HF component of HRV thought to be for vagal control might be a cardinal marker for predicting cardiac autonomic dysfunction after acute IS. Short-term HRV spectral analysis is a convenient approach for stroke clinicians to assess autonomic function in acute stroke. Long-term follow-up for HRV and clinical outcome relative to LAA and SVO stroke subtypes is warranted, particularly when an abnormal HRV is found at admission.

摘要心臟自律神經功能障礙是急性缺血性中風後常見之併發症。過去的研究發現，腦幹梗塞或大腦半球梗塞合併腦島受損可能與此功能受損有相當程度關聯，因而預測這些患者將會有較差之臨床預後表現。然而，從腦中風臨床醫師之角度與觀點而言，所有的中風患者，尤其是大動脈粥狀動脈硬化中風亞型之患者，因為可能伴隨發生相關之心因性併發症，所以更須嚴密監測其心臟自律神經功能。本研究之目的在探討急性缺血性中風患者對心臟自律神經功能所造成之影響，以及進一步比較大動脈粥狀動脈硬化與小血管阻塞之不同中風亞型對心臟自律神經功能的影響是否有所差異。本前瞻性研究共收錄126位急性缺血性中風病人。 依照腦中風TOAST診斷分類區分，其中32位為大動脈粥狀動脈硬化，56位為小血管阻塞，38位為未確定病因。所有病人皆以測量心率變異性來評估其心臟自律神經功能。經過比較多變項分析包括調整年齡、性別、及所有危險因子之變項後，結果顯示所有中風患者之心率變異性分析之低頻與高頻組成顯著低於控制組之受試者。大動脈粥狀動脈硬化及小血管阻塞兩組之心率變異性分析並無顯著差異，儘管進一步進行事後檢定結果發現，小血管阻塞之病人有較增強之交感調控及迷走活性減弱之現象。總結言之，我們發現大多數急性缺血性中風包括大動脈粥狀動脈硬化及小血管阻塞都可能會引起心率變異性異常，而導致心臟自律神經調控系統受到顯著損傷。小血管阻塞之中風病人似乎較易於造成心臟功能調控受損，可以視為早期心臟病變之指標，而我們推測這與長期高血壓有關。代表迷走神經調控的心率變異性之高頻組成或許可以當成預測心臟自律神經功能指標之主要因子。短期心率變異性頻譜分析可以協助腦中風臨床醫師來篩檢中風患者有無自律神經功能受損。對大動脈粥狀動脈硬化及小血管阻塞之中風病人進行心率變異分析和臨床預後的長期追蹤是一項需考慮之課題，特別是當住院時發現有心率變異分析異常時。