Heart rate variability and functional outcome in ischemic stroke: a multiparameter approach

Short-Term Blood Pressure Variability in Acute Stroke

Background and Purpose—

Short-term blood pressure variability (BPV) may predict outcome in acute stroke. We undertook a post hoc analysis of data from 2 randomized controlled trials to determine the effect of short-term BPV on 2-week outcome.

Methods—

Controlling Hypertension and Hypotension Immediately Post Stroke (CHHIPS) was a trial of BP-lowering, enrolling 179 acute stroke patients (onset <36 hours). Continue or Stop Post-Stroke Antihypertensives Collaborative Study (COSSACS) compared a strategy of continuation versus temporarily stopping prestroke antihypertensive therapy in 763 acute stroke patients (onset <48 hours). BPV at baseline (defined as SD, coefficient of variation, variation independent of the mean, and average real variability) was derived from standardized casual cuff BP measures (6 readings <30 minutes). Adjusted logistic regression models were used to assess the relation between BPV and death and disability (modified Rankin scale>3) at 2 weeks.

Results—

Seven hundred six (92.5%) and 171 (95.5%) participants were included in the analysis for the COSSACS and CHHIPS data sets, respectively. Adjusted logistic regression analyses revealed no statistically significant associations between any of the included BPV parameters with 2-week death or disability in either study data set: COSSACS, odds ratio SD systolic BP 0.98 (0.78–1.23); CHHIPS, odds ratio SD systolic BP 0.97 (0.90–1.11).

Conclusions—

When derived from casual cuff BP measures, short-term BPV is not a useful predictor of early (2 weeks) outcome after acute stroke. Differing methodology may account for the discordance with previous studies indicating long-term (casual BPV) and short-term (beat-to-beat BPV) prognostic value.

Clinical Trial Registration—

COSSACS was registered on the International Standard Randomised Controlled Trial Register; URL: http://www.isrctn.com . Unique identifier: ISRCTN89712435. CHHIPS was registered on the National Research Register; URL: http://public.ukcrn.org.uk . Unique identifier: N0484128008.

Complexity of heart rate variability predicts outcome in intensive care unit admitted patients with acute stroke

BACKGROUND

Heart rate variability (HRV) has been proposed as a predictor of acute stroke outcome. This study aimed to evaluate the predictive value of a novel non-linear method for analysis of HRV, multiscale entropy (MSE) and outcome of patients with acute stroke who had been admitted to the intensive care unit (ICU).

METHODS

The MSE of HRV was analysed from 1 h continuous ECG signals in ICU-admitted patients with acute stroke and controls. The complexity index was defined as the area under the MSE curve (scale 1-20). A favourable outcome was defined as modified Rankin scale 0-2 at 3 months after stroke.

RESULTS

The trends of MSE curves in patients with atrial fibrillation (AF) (n=77) were apparently different from those in patients with non-AF stroke (n=150) and controls (n=60). In addition, the values of complexity index were significantly lower in the patients with non-AF stroke than in the controls (25.8±.3 vs. 32.3±4.3, p<0.001). After adjustment for clinical variables, patients without AF who had a favourable outcome were significantly related to higher complexity index values (OR=1.15, 95% CI 1.07 to 1.25, p<0.001). Importantly, the area under the receiver operating characteristic curve for predicting a favourable outcome of patients with non-AF stroke from clinical parameters was 0.858 (95% CI 0.797 to 0.919) and significantly improved to 0.903 (95% CI 0.853 to 0.954) after adding on the parameter of complexity index values (p=0.020).

CONCLUSIONS

In ICU-admitted patients with acute stroke, early assessment of the complexity of HRV by MSE can help in predicting outcomes in patients without AF.

Autonomic dysfunction in acute ischemic stroke: an underexplored therapeutic area?

Impaired autonomic function, characterized by a predominance of sympathetic activity, is common in patients with acute ischemic stroke. This review describes methods to measure autonomic dysfunction in stroke patients. It summarizes a potential relationship between ischemic stroke-associated autonomic dysfunction and factors that have been associated with worse outcome, including cardiac complications, blood pressure variability changes, hyperglycemia, immune depression, sleep disordered breathing, thrombotic effects, and malignant edema. Involvement of the insular cortex has been suspected to play an important role in causing sympathovagal imbalance, but its exact role and that of other brain regions remain unclear. Although sympathetic overactivity in patients with ischemic stroke appears to be a negative prognostic factor, it remains to be seen whether therapeutic strategies that reduce sympathetic activity or increase parasympathetic activity might improve outcome.

Airflow pattern complexity during resting breathing in patients with COPD: effect of airway obstruction

We investigated the influence of airway obstruction in the complexity of the airflow pattern in COPD and its use as a marker of disease activity. The sample entropy (SampEnV') and the variability (SDV') of the airflow pattern were measured in a group of 88 subjects with various levels of airway obstruction. Airway obstruction resulted in a reduction in the SampEnV' (p<0.0001) that was significantly correlated with spirometric indices of airway obstruction (R=0.50, p<0.001). The early adverse effects in mild airway obstruction were detected by the SampEnV' with an accuracy of 84%. SDV' increased with airway obstruction (p<0.002). We conclude that (1) the airflow patterns in COPD exhibit reduced complexity compared with healthy subjects; (2) this reduction in complexity is proportional to airway obstruction; and (3) the evaluation of SampEnV' may provide novel respiratory biomarkers suitable to facilitate the diagnosis of respiratory abnormalities in COPD.