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.