Altered short-term fractal scaling properties of HR indicate an increased risk for cardiac mortality, particularly sudden cardiac death, in the random population of elderly subjects.

Background and Purpose-Measurement of natriuretic peptides provides prognostic information in various patient populations. The prognostic value of natriuretic peptides among patients with acute stroke is not known, although elevated peptide levels have been observed. Methods-A series of 51 patients (mean age, 68Ϯ11years) with first-ever ischemic stroke underwent a comprehensive clinical examination and measurements of plasma atrial natriuretic peptides (N-ANP) and brain natriuretic peptides (N-BNP) in the acute phase of stroke. The patients were followed-up for 44Ϯ21 months. Risk factors for all-cause mortality were assessed. Control populations, matched for gender and age, consisted of 51 patients with acute myocardial infarction (AMI) and 25 healthy subjects. Results-Plasma concentrations of N-ANP (meanϮSD, 988Ϯ993 pmol/L) and N-BNP (751Ϯ1608 pmol/L) in the stroke patients were at the same level as those in the AMI patients (NS for both), but significantly higher than those of the healthy subjects (358Ϯ103 pmol/L, PϽ0.001 and 54Ϯ26 pmol/L, PϽ0.01, respectively). Elevated levels of N-ANP and N-BNP predicted mortality after stroke (risk ratio [RR] 4.3, PϽ0.01 and RR 3.9, PϽ0.01, respectively) and after AMI (PϽ0.05), and remained independent predictors of death after stroke even after adjustment for age, diabetes, coronary artery disease, and medication (RR 3.9, PϽ0.05 and RR 3.7, PϽ0.05, respectively). Conclusion-Plasma levels of natriuretic peptides are elevated in the acute phase of stroke and predict poststroke mortality.

Abnormal long-term HR dynamics predict poststroke mortality. This measure may have value in the risk stratification of stroke patients.

Background and Purpose-Traditional spectral and nonspectral methods have shown that heart rate (HR) variability is reduced after stroke. Some patients with poor outcome, however, show randomlike, complex patterns of HR behavior that traditional analysis techniques are unable to quantify. Therefore, we designed the present study to evaluate the complexity and correlation properties of HR dynamics after stroke by using new analysis methods based on nonlinear dynamics and fractals ("chaos theory"). Methods-In addition to the traditional spectral components of HR variability, we measured instantaneous beat-to-beat variability and long-term continuous variability analyzed from Poincaré plots, fractal correlation properties, and approximate entropy of R-R interval dynamics from 24-hour ambulatory ECG recordings in 30 healthy control subjects, 31 hemispheric stroke patients, and 15 brain stem stroke patients (8 medullary, 7 pontine) in the acute phase of stroke and 6 months after stroke. Results-In the acute phase, the traditional spectral components of HR variability and the long-term continuous variability from Poincaré plots were impaired (PϽ0.01) in patients with hemispheric and medullary brain stem stroke, but not in patients with pontine brain stem stroke, in comparison with control subjects. At 6 months after stroke, measures of HR variability in hemispheric stroke patients were still lower (PϽ0.05) than those of the control subjects. Various complexity and fractal measures of HR variability were similar in patients and control subjects. The conventional frequency domain measures of HR variability as well as the Poincaré measures showed strong correlations (Pearson correlation coefficient, rϭ0.68 to rϭ0.90) with each other but only weak correlations (rϭ0.09 to rϭ0.56) with the complexity and fractal measures of HR variability. Conclusions-Hemispheric and medullary brain stem infarctions seem to damage the cardiovascular autonomic regulatory system and appear as abnormalities in the magnitude of HR variability. These abnormalities can be more easily detected with the use of analysis methods of HR variability, which are based on moment statistics, than by methods based on nonlinear dynamics. Abnormal HR variability may be involved in prognostically unfavorable cardiac complications and other known manifestations of autonomic failure associated with stroke.

A stress response consisting of elevated levels of cortisol and catecholamines is common after acute stroke. The plasma levels of natriuretic peptides are known to be elevated after ischemic stroke, but the relations of these neurohormonal systems in the acute phase of stroke and their impact on long-term prognosis have not been studied previously. A series of 51 consecutive patients (mean age 68+/-11 years) with an ischemic first-ever stroke underwent a comprehensive clinical investigation, scoring of their neurologic deficit by Scandinavian Stroke Scale (SSS), Barthel Index (BI) and Modified Ranking Scale (MRS) as well as measurements of plasma cortisol, norepinephrine, epinephrine, ACTH and atrial (N-ANP) and brain (N-BNP) natriuretic peptides on the 2nd and 7th days after ischemic stroke. The patients were followed up for 44+/-21 months. Higher levels of cortisol, ACTH and natriuretic peptides were observed in the stroke patients who died (n=22) during the follow-up than in the stroke survivors. Cortisol levels associated significantly with the 2nd and 7th day N-ANP and N-BNP levels, catecholamine levels (r= 0.55 - 0.94, p<0.01 for all) and measures of neurologic deficit (r= 0.36 - -0.44, p<0.05). High acute phase cortisol levels assessed either in the morning (RR=5.4, p<0.05) or in the evening (RR=5.8, p<0.05) predicted long-term mortality after stroke in multivariate analysis. Activation of the hypothalamus-pituitary-adrenal axis in ischemic stroke is associated with elevated levels of natriuretic peptides. High cortisol and natriuretic peptide values predict long-term mortality after ischemic stroke, suggesting that this profound neurohumoral disturbance is prognostically unfavourable.