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(Stroke. 1999;30:2238-2248.)
© 1999 American Heart Association, Inc.

Letters to the Editor

Heart Rate Variability Following Ischemic Stroke

Thompson Robinson, MD John Potter, DM

Division of Medicine for the Elderly

Ronney Panerai, PhD

Division of Medical Physics, University of Leicester, Leicester, United Kingdom

Key Words: heart rate • blood pressure • cerebral infarction

	Introduction

 
To the Editor:

We have read with interest the article by Korpelainen and colleagues¹ regarding heart rate variability (HRV) in patients with ischemic stroke. The authors report impaired beat-to-beat HRV as measured by traditional spectral components and impaired long-term continuous HRV as measured by SD2 PoinCare plots in patients with hemispheric and medullary brain stem but not pontine brain stem stroke compared with control subjects. These findings raise a number of important questions regarding cardiovascular autonomic control after acute ischemic stroke.

First, previous work from our department has not identified impairment of HRV, whether assessed by time domain² or frequency domain³ techniques, in keeping with the authors' own findings with regard to SD1 Poincare, complexity, and fractal measures of HRV.¹ Furthermore, absolute levels and variability of blood pressure (BP) are an important consequence of abnormalities of cardiovascular autonomic control after acute ischemic stroke⁴ and an important variable in the interpretation of other cardiovascular data. It is therefore unfortunate that the article does not present the data in respect of BP variability and BP matching between study and control populations.

Second, if impaired HRV is a reproducible finding after acute ischemic stroke, it would be important to speculate on the underlying mechanism. One presumes that it reflects sympathetic hyperactivity, though the low-frequency power is reported as significantly lower in those groups with impaired HRV.¹ Of course, this measure has considerable variability, and it would be more important to compare either the normalized low-frequency power or the low-frequency/high-frequency ratio.

Third, it is . . . [Full Text of this Article]

Juha T. Korpelainen, MD, PhD; Kyösti A. Sotaniemi, MD, PhD Vilho V. Myllylä, MD, PhD

Department of Neurology, University of Oulu, Oulu, Finland