A Comparison of Beat-to-Beat Blood Pressure Variability in Acute and Subacute Stroke Patients with Cerebral Infarction

Abstract

Cerebrovascular dysautoregulation is well recognised following acute stroke, and thus blood pressure (BP) changes may have important effects on cerebral blood flow. Whilst absolute BP levels have been shown to influence outcome in some studies, the importance of short-term BP variability has not been addressed. We assessed beat-to-beat BP and pulse interval variability non-invasively using the Finapres device in 32 patients with CT-diagnosed acute cerebral infarction compared to a control group matched with respect to age and sex. Systolic BP variability was assessed as the standard deviation (SD) of all measurements and as the root mean squared of successive differences (RMS; which removes the portion of variability related to the underlying BP level). Systolic BP variability (taken as either the SD or the RMS) was significantly greater in acute stroke patients than controls. This difference is unlikely to reflect impaired cardiac baroreceptor sensitivity in acute stroke patients as no differences were observed in pulse interval variability compared to controls, but may be related to alterations in peripheral vascular resistance mediated by centrally induced changes in sympathetic nervous system activity. The prognostic significance of increased BP variability and the implications for BP management in acute stroke require further evaluation.

Which Parameters of Beat-to-Beat Blood Pressure and Variability Best Predict Early Outcome After Acute Ischemic Stroke?

“…38 Finapres mean BP values are consistently lower for SBP and DBP compared with casual BP measurements and therefore cannot be directly compared. 37 The beat-to-beat BPV results presented here are comparable to those previously reported after stroke when longer recording periods were taken; Robinson et al 33 reported SBP variability of 13.0 (4.6) mm Hg in acute cerebral infarct patients, with no significant change in BPV at follow-up 10 to 14 days later. No control group was used in this study because the main objectives of the investigation were to examine the effect of mean BP levels and BPV on outcome in stroke patients.…”

“…To examine the effect of BPV at different BP levels, as had been similarly described in previous studies, [31][32][33] subjects were divided into 4 groups according to each BP measure to give groups of approximately equal size. Each group was then divided according to the appropriate group median BPV into low-variability (Յmedian) and high-variability (Ͼmedian) subjects.…”

“…We did not detect any difference in BPV between stroke subtypes, though the study was too small to establish whether the increased BPV was related to any particular stroke site such as the insular cortex. The exact mechanisms underlying the beat-to-beat BPV after stroke are unknown, but a reduction in cardiac BRS after acute cerebral infarction is well established, 19,33 and decreased BRS is well known to result in a rise in BPV. 34,39 In keeping with these findings, Tokgozoelu et al 40 have shown that heart rate variability is reduced after acute stroke, particularly where the lesion lies in the region of the insular cortex.…”

“…Increased BPV is associated with increased evidence of target organ damage in the elderly and hypertensive populations 30,31 and in cardiovascular events. 32 A previous study has shown that BPV is increased after acute stroke compared with age-and sex-matched control subjects, 33 although the prognostic relevance of this finding is currently unknown.…”

Prognostic Significance of Short-Term Blood Pressure Variability in Acute Stroke

“…40 Increased BPV following acute stroke may also be a predictor of short-term outcome post stroke though data are limited. In studies involving only ischaemic stroke patients, beat-to-beat SBPV was greater in acute stroke compared to controls, 41 and high mean arterial and diastolic beat-to-beat BPV was associated with a worse prognosis. 11 In addition, high SBPV using casual BP readings was associated with an increase in death or early neurological deterioration.…”