Characterisation of neonatal cardiac dynamics using ordinal partition network.

The maturation of the autonomic nervous system (ANS) starts in the gestation period and it is completed after birth in a variable time, reaching its peak in adulthood. However, the development of ANS maturation is not entirely understood in newborns. Clinically, the ANS condition is evaluated with monitoring of gestational age, Apgar score, heart rate, and by quantification of heart rate variability using linear methods. Few researchers have addressed this problem from the perspective nonlinear data analysis. This paper proposes a new data-driven methodology using nonlinear time series analysis, based on complex networks, to classify ANS conditions in newborns. We map 74 time series given by RR intervals from premature and full-term newborns to ordinal partition networks and use complexity quantifiers to discriminate the dynamical process present in both conditions. We obtain three complexity quantifiers (permutation, conditional, and global node entropies) using network mappings from forward and reverse directions, and considering different time lags and embedding dimensions. The results indicate that time asymmetry is present in the data of both groups and the complexity quantifiers can differentiate the groups analysed. We show that the conditional and global node entropies are sensitive for detecting subtle differences between the neonates, particularly for small embedding dimensions (m < 7). This study reinforces the assessment of nonlinear techniques for RR interval time series analysis. Graphical Abstract.

Assessment of heart rate variability by application of central tendency measure.

The heart rate variability (HRV) is an indicator of the subject homeostasis alterations. For a healthy individual, the HRV shows a nonlinear behavior, thus requiring a nonlinear approach to provide additional information about HRV dynamics. In this work, the nonlinear techniques, central tendency measure (CTM) and second-order difference plot, are applied to HRV analysis using the successive difference of RR intervals in a time series. In total are analyzed 170 tachograms collected by Polar monitor and then classified into three groups according to a cardiologist: healthy young adults, adults in preoperative evaluation for coronary artery bypass grafting for severe coronary disease and premature newborns. This approach identified the tachograms with high and low variability, which demonstrates the ability of CTM to classify and quantitatively characterize cardiac RR intervals.

Prospective evaluation comparing the effects of enalapril and losartan in left ventricular remodeling after acute myocardial infarction.

BACKGROUND: Previous studies have compared angiotensin receptor blockers and angiotensin-converting enzyme inhibitors in patients with heart failure, but there are few data about the effect of these drugs regarding left ventricular remodeling after myocardial infarction. METHODS: Fifty-two consecutive patients with first anterior wall myocardial infarction within 24 hours of evolution were randomized to receive enalapril (as much as 20 mg; mean, 14.6 mg), or losartan (as much as 50 mg; mean, 48 mg). Left ventricular ejection fraction and ventricular volumes were analyzed in 2 serial radionuclide ventriculograpies, carried out within 4 days after the infarction (mean, 97.4 +/- 114.2 hours) and after 6 months (mean, 177.7 +/- 16.7 days). Ventriculographies were analyzed by a single blinded observer. Mainly because of the unexpected large SD values obtained, the power of the study to demonstrate equivalence between the groups was only 15.7%. RESULTS: The differences obtained between the first and the second ventriculographies, for the enalapril and losartan groups, were: for left ventricular ejection fraction, -0.4% +/- 6.6% versus -1.1% +/- 5.9% (P =. 67; 95% CI, 2.77-4.23); for final systolic volume, 0.07 +/- 7.7 mL/m(2) versus -0.2 +/- 6.1mL/m(2) (P =. 85; 95% CI, -3.57-4.26); for final diastolic volume -0.7 +/- 12.1 mL/m(2) versus -3.6 - 9.9 mL/m(2) (P =. 34; 95% CI, -3.22-9.17). CONCLUSION: This study, although underpowered, suggests that neither enalapril nor losartan was superior as compared with each other for left ventricular remodeling after myocardial infarction; however, powerful evidence of equivalence was not provided.

Application of an automatic adaptive filter for Heart Rate Variability analysis.

The presence of artifacts and noise effects in temporal series can seriously hinder the analysis of Heart Rate Variability (HRV). The tachograms should be carefully edited to avoid erroneous interpretations. The physician should carefully analyze the tachogram in order to detect points that might be associated with unlikely biophysical behavior and manually eliminate them from the data series. However, this is a time-consuming procedure. To facilitate the pre-analysis of the tachogram, this study uses a method of data filtering based on an adaptive filter which is quickly able to analyze a large amount of data. The method was applied to 229 time series from a database of patients with different clinical conditions: premature newborns, full-term newborns, healthy young adults, adults submitted to a very-low-calorie diet, and adults under preoperative evaluation for coronary artery bypass grafting. This proposed method is compared to the demanding conventional method, wherein the corrections of occasional ectopic beats and artifacts are usually manually executed by a specialist. To confirm the reliability of the results obtained, correlation coefficients were calculated, using both automatic and manual methods of ltering for each HRV index selected. A high correlation between the results was found, with highly significant p values, for all cases, except for some parameters analyzed in the premature newborns group, an issue that is thoroughly discussed. The authors concluded that the proposed adaptive filtering method helps to efficiently handle the task of editing temporal series for HRV analysis.

Impact of genetic variants of apolipoprotein E on lipid profile in patients with Parkinson's disease.

The pathogenesis of Parkinson's disease (PD) seems to involve genetic susceptibility to neurodegeneration. APOE gene has been considered a risk factor for PD. This study aimed to evaluate the association of APOE polymorphism with PD and its influence on lipid profile. We studied 232 PD patients (PD) and 169 individuals without the disease. The studied polymorphism was analyzed by PCR/RFLP. The Fisher's exact test, chi-square, ANOVA, and t-test (P < 0.05) were applied. The APOE3/3 genotype was prevalent in PD patients and Controls (P = 0.713) followed by APOE3/4 (P = 0.772). Both groups showed recommended values for lipid profile, with increase in the values of total cholesterol and LDLc, as well as decreased values of triglycerides in PD patients compared with Controls (P < 0.05 for all of them). Increased levels of HDLc, in PD patients, were associated with the APOE3/3 versus APOE-/4 genotypes (P = 0.012). The APOE polymorphism does not distinguish PD patients from Controls, as opposed to the lipid profile alone or in association with APOE. Furthermore, a relationship between increase of HDLc levels and APOE3 in homozygous was found in PD patients only.