Assessing Machine Learning for Diagnostic Classification of Hypertension Types Identified by Ambulatory Blood Pressure Monitoring.

Background: Inaccurate blood pressure (BP) classification results in inappropriate treatment. We tested whether machine learning (ML), using routine clinical data, can serve as a reliable alternative to ambulatory BP monitoring (ABPM) in classifying BP status. Methods: This study employed a multicentre approach involving 3 derivation cohorts from Glasgow, Gdansk, and Birmingham, and a fourth independent evaluation cohort. ML models were trained using office BP, ABPM, and clinical, laboratory, and demographic data, collected from patients referred for hypertension assessment. Seven ML algorithms were trained to classify patients into 5 groups, named as follows: Normal/Target; Hypertension-Masked; Normal/Target-White-Coat (WC); Hypertension-WC; and Hypertension. The 10-year cardiovascular outcomes and 27-year all-cause mortality risks were calculated for the ML-derived groups using the Cox proportional hazards model. Results: Overall, extreme gradient boosting (using XGBoost open source software) showed the highest area under the receiver operating characteristic curve of 0.85-0.88 across derivation cohorts, Glasgow (n = 923; 43% female; age 50.7 ± 16.3 years), Gdansk (n = 709; 46% female; age 54.4 ± 13 years), and Birmingham (n = 1222; 56% female; age 55.7 ± 14 years). But accuracy (0.57-0.72) and F1 (harmonic mean of precision and recall) scores (0.57-0.69) were low across the 3 patient cohorts. The evaluation cohort (n = 6213; 51% female; age 51.2 ± 10.8 years) indicated elevated 10-year risks of composite cardiovascular events in the Normal/Target-WC and the Hypertension-WC groups, with heightened 27-year all-cause mortality observed in all groups, except the Hypertension-Masked group, compared to the Normal/Target group. Conclusions: ML has limited potential in accurate BP classification when ABPM is unavailable. Larger studies including diverse patient groups and different resource settings are warranted.

Contexte: Les erreurs dans la classification des valeurs de la pression artérielle (PA) entraînent une inadéquation du traitement. Nous avons tâché de déterminer si l'apprentissage machine, à l'aide de données cliniques routinières, constituait une solution de rechange fiable à la surveillance ambulatoire de la PA pour définir le statut de la PA. Méthodologie: Cette étude a utilisé une approche multicentrique incluant trois cohortes de dérivation de Glasgow, Gdansk et Birmingham, et une quatrième cohorte d'évaluation indépendante. Les modèles d'apprentissage machine ont été développés en analysant les données démographiques, les valeurs de la PA mesurée au cabinet, les données relatives à la surveillance ambulatoire de la PA et aux épreuves de laboratoire recueillies auprès de patients adressés pour une évaluation de l'hypertension. Sept algorithmes d'apprentissage machine ont été appliqués pour classer les patients en cinq groupes : Normale/Cible; Hypertension-Masquée; Normal/Cible-Blouse blanche; Hypertension-Blouse blanche; Hypertension. Les événements cardiovasculaires sur 10 ans et le risque de mortalité toutes causes confondues sur 27 ans ont été calculés dans les groupes dérivés de l'apprentissage machine à l'aide d'un modèle de risques proportionnels de Cox. Résultats: D'une manière générale, l'amplification de gradient extrême (à l'aide du logiciel ouvert XGBoost) a mis en évidence l'aire sous la courbe de la fonction d'efficacité du récepteur (courbe ROC pour Receiver Operating Characteristic) la plus haute, soit 0,85 à 0,88, pour toutes les cohortes de dérivation : Glasgow (n = 923; 43 % de femmes; âge : 50,7 ± 16,3 ans); Gdansk (n = 709; 46 % de femmes; âge : 54,4 ± 13 ans); Birmingham (n = 1 222; 56 % de femmes; âge : 55,7 ± 14 ans). La précision (0,57 ­ 0,72) et le score F1 (moyenne harmonique de la précision et du rappel) (0,57 ­ 0,69) ont été faibles dans les trois cohortes de patients. La cohorte d'évaluation (n = 6 213; 51 % de femmes; âge : 51,2 ± 10,8 ans) a indiqué un risque d'événements cardiovasculaires composites sur 10 ans élevé dans les groupes Normale/Cible-Blouse blanche et Hypertension-Blouse blanche, tandis qu'une hausse de la mortalité toutes causes confondues sur 27 ans a été observée dans tous les groupes, sauf dans le groupe Hypertension-Masquée, comparativement au groupe Normale/Cible. Conclusions: Le potentiel d'exactitude de la classification de la PA à l'aide de l'apprentissage machine lorsque la surveillance ambulatoire de la PA n'est pas possible est limité. Des études de plus grande envergure portant sur des groupes de patients et des niveaux de ressources diversifiés s'imposent.

Differentiating patients with obstructive sleep apnea from healthy controls based on heart rate-blood pressure coupling quantified by entropy-based indices.

We introduce an entropy-based classification method for pairs of sequences (ECPS) for quantifying mutual dependencies in heart rate and beat-to-beat blood pressure recordings. The purpose of the method is to build a classifier for data in which each item consists of two intertwined data series taken for each subject. The method is based on ordinal patterns and uses entropy-like indices. Machine learning is used to select a subset of indices most suitable for our classification problem in order to build an optimal yet simple model for distinguishing between patients suffering from obstructive sleep apnea and a control group.

Algoritmically improved microwave radar monitors breathing more acurrate than sensorized belt.

This paper describes a novel way to measure, process, analyze, and compare respiratory signals acquired by two types of devices: a wearable sensorized belt and a microwave radar-based sensor. Both devices provide breathing rate readouts. First, the background research is presented. Then, the underlying principles and working parameters of the microwave radar-based sensor, a contactless device for monitoring breathing, are described. The breathing rate measurement protocol is then presented, and the proposed algorithm for octave error elimination is introduced. Details are provided about the data processing phase; specifically, the management of signals acquired from two devices with different working principles and how they are resampled with a common processing sample rate. This is followed by an analysis of respiratory signals experimentally acquired by the belt and microwave radar-based sensors. The analysis outcomes were checked using Levene's test, the Kruskal-Wallis test, and Dunn's post hoc test. The findings show that the proposed assessment method is statistically stable. The source of variability lies in the person-triggered breathing patterns rather than the working principles of the devices used. Finally, conclusions are derived, and future work is outlined.

Mining Knowledge of Respiratory Rate Quantification and Abnormal Pattern Prediction.

The described application of granular computing is motivated because cardiovascular disease (CVD) remains a major killer globally. There is increasing evidence that abnormal respiratory patterns might contribute to the development and progression of CVD. Consequently, a method that would support a physician in respiratory pattern evaluation should be developed. Group decision-making, tri-way reasoning, and rough set-based analysis were applied to granular computing. Signal attributes and anthropomorphic parameters were explored to develop prediction models to determine the percentage contribution of periodic-like, intermediate, and normal breathing patterns in the analyzed signals. The proposed methodology was validated employing k-nearest neighbor (k-NN) and UMAP (uniform manifold approximation and projection). The presented approach applied to respiratory pattern evaluation shows that median accuracies in a considerable number of cases exceeded 0.75. Overall, parameters related to signal analysis are indicated as more important than anthropomorphic features. It was also found that obesity characterized by a high WHR (waist-to-hip ratio) and male sex were predisposing factors for the occurrence of periodic-like or intermediate patterns of respiration. It may be among the essential findings derived from this study. Based on classification measures, it may be observed that a physician may use such a methodology as a respiratory pattern evaluation-aided method.

Masked arterial hypertension in a 64-year-old man with primary aldosteronism.

PURPOSE: Primary aldosteronism is one of the most frequent causes of secondary arterial hypertension, and whether primary aldosteronism is associated with masked hypertension is unknown. MATERIALS AND METHODS: We describe a 64-year-old man with a history of hypothyroidism, recurring hypokalaemia, and normal home and office blood pressure values. Ambulatory blood pressure monitoring revealed masked hypertension with strikingly high systolic blood pressure variability and typical hypertension-mediated organ damage. RESULTS: The patient required gradual escalation of antihypertensive medication to four drugs. During the diagnostic process we identified primary aldosteronism, cobalamin deficiency, severe obstructive sleep apnoea, and low baroreflex sensitivity (1.63 ms/mmHg). Following unilateral adrenalectomy, cobalamin supplementation and continuous positive airway pressure, we observed a spectacular improvement in the patient's blood pressure control, baroreflex sensitivity (4.82 ms/mmHg) and quality of life. CONCLUSIONS: We report an unusual case of both masked arterial hypertension and primary aldosteronism. Elevated blood pressure values were masked in home and office measurements by coexisting hypotension which resulted most probably from deteriorated baroreflex sensitivity. Baroreflex sensitivity increased following treatment, including unilateral adrenalectomy. Hypertension can be masked by coexisting baroreceptor dysfunction which may derive from structural but also functional reversible changes.

Common Strategies and Factors Affecting Off-Line Breath Sampling and Volatile Organic Compounds Analysis Using Thermal Desorption-Gas Chromatography-Mass Spectrometry (TD-GC-MS).

An analysis of exhaled breath enables specialists to noninvasively monitor biochemical processes and to determine any pathological state in the human body. Breath analysis holds the greatest potential to remold and personalize diagnostics; however, it requires a multidisciplinary approach and collaboration of many specialists. Despite the fact that breath is considered to be a less complex matrix than blood, it is not commonly used as a diagnostic and prognostic tool for early detection of disordered conditions due to its problematic sampling, analysis, and storage. This review is intended to determine, standardize, and marshal experimental strategies for successful, reliable, and especially, reproducible breath analysis.

Persistent homology as a new method of the assessment of heart rate variability.

Heart rate variability (hrv) is a physiological phenomenon of the variation in the length of the time interval between consecutive heartbeats. In many cases it could be an indicator of the development of pathological states. The classical approach to the analysis of hrv includes time domain methods and frequency domain methods. However, attempts are still being made to define new and more effective hrv assessment tools. Persistent homology is a novel data analysis tool developed in the recent decades that is rooted at algebraic topology. The Topological Data Analysis (TDA) approach focuses on examining the shape of the data in terms of connectedness and holes, and has recently proved to be very effective in various fields of research. In this paper we propose the use of persistent homology to the hrv analysis. We recall selected topological descriptors used in the literature and we introduce some new topological descriptors that reflect the specificity of hrv, and we discuss their relation to the standard hrv measures. In particular, we show that this novel approach provides a collection of indices that might be at least as useful as the classical parameters in differentiating between series of beat-to-beat intervals (RR-intervals) in healthy subjects and patients suffering from a stroke episode.

The effect of persistent U-shaped patterns in RR night-time series on the heart rate variability complexity in healthy humans.

OBJECTIVE: U-shaped patterns, characteristic periods of time observed in tachograms, are a specific subgroup among very low frequency components characterized by relatively short periods of smooth accelerations followed by decelerations of heart rhythm. In this study, we characterize this phenomenon and its effect on heart rate variability (HRV) parameters. APPROACH: We calculated linear (the mean and standard deviation of RR intervals, RMSSD, pNN50 and the power of the frequency components) and nonlinear (V0, V1 and V2 Porta's symbolic analysis, Shannon and Sample entropy, Guzik's and Porta's asymmetry indexes, the exponents α1 and α2 of detrended fluctuation analysis and the Hurst surface h(q,s) of multiscale multifractal analysis (MMA)) HRV parameters for 65 RR interval night-time series (39 females, 37.5(11.3) years old and 26 males, 41.7(16.5) years old; all without organic heart diseases). All parameters were calculated for original data and for the three kinds of test data in which the following parts of the time series were replaced by 1/f noise: (A) the U-shape patterns annotated in a given data set, (B) randomly chosen windows of similar size as the U-shaped patterns, (C) acceleration-deceleration events shorter than U-shaped patterns. MAIN RESULTS: We found that the U-shaped patterns, as the most persistent structures in RR night-time intervals series, affect the long-range correlation properties (measured by α2). We also found that the U-shaped patterns importantly strictly affect the shape of h(q,s) surface at different scales s. Removing the U-shaped patterns results in the shape of the h(q,s) surface losing the properties characteristic for healthy heart rhythm. The largest quantitative effect of U-shaped patterns was obtained for the power of the VLF component. The mean percentage difference of the VLF component between the original data and the A to C type test data were 19.4%, -4.3% and 5.3%, respectively. SIGNIFICANCE: Although percentage contribution of U-shaped patterns is small compared to the whole night-time series (on the average 3.1%(1.7%) with a standard deviation of 1.7%), these patterns have a considerable impact on the HRV parameters describing the VLF, persistency, nonlinear correlations and multifractal properties.

Subclinical macroangiopathic target organ damage in type 1 diabetes mellitus patients.

PURPOSE: We have summarized key studies regarding the assessment of subclinical macroangiopathic target organ damage (TOD) in type 1 diabetes mellitus (T1DM). RESULTS: Although chronic complications resulting from hyperglycemia, in particular macroangiopathies, are still the first cause of death in T1DM, there has been growing recognition of the role of hypoglycemia in cardiovascular morbidity and mortality. Subclinical TOD diagnosis ensures early implementation of the complex management aiming at either partial reversal of these complications or at least its downturn. To better identify patients with early TODs, several non-invasive diagnostic techniques are employed, including the ultrasonographic assessment of the intima-media thickness (IMT), computed tomography (CT) for coronary artery calcium (CAC) scores, and pulse wave velocity (PWV) measurement for arterial stiffness evaluation. Various studies reported that T1DM patients present an increased IMT. An increasing IMT fairly correlates with the cardiovascular (CV) events risk even after the adjustment to age, diabetes duration, quality of glucose control as well as the presence of hypertension, and chronic complications. Another, well established marker of the organ damage - CAC score is recommended by ACC/AHA guidelines to assess the overall CV risk in T1DM. Also, the arterial stiffness evaluation with PWV may further improve CV risk prediction, which has been reported in multiple studies including the Framingham Heart Study. CONCLUSIONS: There is shortage of data from prospective studies which could confirm the benefits of early treatment initiation based on the presence of the subclinical organ damage in T1DM. Most evidence comes from T2DM trials, where effective preventive measures were identified i.e.: smoking cessation, reasonable blood glucose control, efficacious hypertension treatment, and dyslipidemia management, as well as renoprotection. There is still a field for further research to see if routine assessment of asymptomatic vascular damage and early implementation of aggressive treatment would reduce mortality excess from CVD in T1DM.

Aortic stiffness is not only associated with structural but also functional parameters of retinal microcirculation.

OBJECTIVE: The aim of the study was to test the hypothesis that alterations in large arteries are associated with microvascular remodelling and decreased retinal capillary blood flow. METHODS: The study group comprised of 88 patients with essential hypertension and 32 healthy controls. Retinal microcirculation was evaluated by scanning laser Doppler flowmetry. Macrovascular changes were assessed on the basis of arterial stiffness measurement (carotid-femoral pulse wave velocity), its hemodynamic consequences (central pulse pressure, augmentation pressure, augmentation index) and intima media thickness of common carotid artery. RESULTS: Pulse wave velocity was inversely correlated to mean retinal capillary blood flow in hypertensive patients (R = -0.32, p < 0.01). This relationship remained significant in multivariate regression analysis after adjustment for age, sex, central systolic blood pressure (BP) and body mass index (ß = -31.27, p < 0.001). Lumen diameter (LD) of retinal arterioles was significantly smaller in hypertensive then normotensive subjects (79.4 vs. 83.8, p = 0.03). Central and brachial systolic, diastolic and mean BPs were significantly correlated with LD and outer diameter of retinal arterioles. The relationship between LD and central BPs remained significant in multivariate analysis (ß = -0.15, p = 0.03 for cSBP; ß = -0.22, p = 0.04 for cDBP; ß = -0.21, p = 0.03 for cMBP). Moreover, in a subgroup with cardiac damage central and brachial pulse pressure were positively associated with retinal wall thickness, wall cross sectional area, and wall to lumen ratio. CONCLUSION: In conclusion, the study provides a strong evidence that microcirculation is coupled with macrocirculation not only in terms of structural but also functional parameters.

10Kin1day: A Bottom-Up Neuroimaging Initiative.

We organized 10Kin1day, a pop-up scientific event with the goal to bring together neuroimaging groups from around the world to jointly analyze 10,000+ existing MRI connectivity datasets during a 3-day workshop. In this report, we describe the motivation and principles of 10Kin1day, together with a public release of 8,000+ MRI connectome maps of the human brain.

Aging and Hypertension - Independent or Intertwined White Matter Impairing Factors? Insights From the Quantitative Diffusion Tensor Imaging.

Aging disrupts white matter integrity, and so does continuous elevated blood pressure that accompanies hypertension (HTN). Yet, our understanding of the interrelationship between these factors is still limited. The study aimed at evaluating patterns of changes in diffusion parameters (as assessed by quantitative diffusion fiber tracking - qDTI) following both aging, and hypertension, as well as the nature of their linkage. 146 participants took part in the study: the control group (N = 61) and the patients with hypertension (N = 85), and were divided into three age subgroups (25-47, 48-56, 57-71 years). qDTI was used to calculate the values of fractional anisotropy, mean, radial and axial diffusivity in 20 main tracts of the brain. The effects of factors (aging and hypertension) on diffusion parameters of tracts were tested with a two-way ANOVA. In the right hemisphere there was no clear effect of the HTN, nor an interaction between the factors, though some age-related effects were observed. Contrary, in the left hemisphere both aging and hypertension contributed to the white matter decline, following a functional pattern. In the projection pathways and the fornix, HTN and aging played part independent of each other, whereas in association fibers and the corpus callosum if the hypertension effect was significant, an interaction was observed. HTN patients manifested faster decline of diffusion parameters but also reached a plateau earlier, with highest between-group differences noted in the middle-aged subgroup. Healthy and hypertensive participants have different brain aging patterns. The HTN is associated with acceleration of white matter integrity decline, observed mainly in association fibers of the left hemisphere.

Cognitive Dysfunction in Type 1 Diabetes Mellitus.

CONTEXT: We have summarized key studies assessing the epidemiology, mechanisms, and consequences of cognitive dysfunction (CD) in type 1 diabetes. EVIDENCE SYNTHESIS: In a number of studies, the severity of CD in type 1 diabetes was affected by the age of onset and duration, and the presence of proliferative retinopathy and autonomic neuropathy. Diabetes-related CD has been observed, not only in adults, but also in children and adolescents. Most neuroimaging studies of patients with type 1 diabetes did not show any differences in whole brain volumes; however, they did reveal selective deficits in gray matter volume or density within the frontal, posterior, and temporal cortex and subcortical gray matter. Studies of middle-age adults with long-standing type 1 diabetes using diffusion tensor imaging have demonstrated partial lesions in the white matter and decreased fractional anisotropy in posterior brain regions. The mechanisms underlying diabetes-related CD are very complex and include factors related to diabetes per se and to diabetes-related cardiovascular disease and microvascular dysfunction, including chronic hyperglycemia, hypoglycemia, macro- and microvascular disease, and increased inflammatory cytokine expression. These mechanisms might contribute to the development and progression of both vascular dementia and Alzheimer disease. CONCLUSIONS: Higher rates of CD and faster progression in type 1 diabetes can be explained by both the direct effects of altered glucose metabolism on the brain and diabetes-related cardiovascular disease. Because the presence and progression of CD significantly worsens the quality of life of patients with diabetes, further multidisciplinary studies incorporating the recent progress in both neuroimaging and type 1 diabetes management are warranted to investigate this problem.

Lumen narrowing and increased wall to lumen ratio of retinal microcirculation are valuable biomarkers of hypertension-mediated cardiac damage.

Purpose: In the course of hypertension, left ventricular hypertrophy and diastolic dysfunction develop very often and may progress toward heart failure. The aim of the study was to analyze the relationship between abnormalities of retinal microcirculation and cardiac damage defined as left ventricular hypertrophy and/or diastolic dysfunction.Materials and methods: The study comprised 88 patients with essential hypertension. The group was divided into two subgroups: hypertensives without cardiac damage (n = 55) and with cardiac damage (n = 33). Control group comprised 32 normotensive subjects. Scanning laser Doppler flowmetry was used to evaluate retinal microcirculation. Echocardiography was used to assess cardiac damage.Results: Lumen diameter of retinal arterioles was significantly smaller in patients with cardiac damage vs. controls (77 vs. 84 µm, p = 0.02). Additionally, there was an evident trend with respect to lumen diameter (LD) across all three studied subgroups; i.e.: the smallest dimeters were present in cardiac damage patients, moderate size in hypertensives' without cardiac damage, and the largest diameters in healthy controls (pfor trend < 0.01). Lumen diameter was inversely correlated with cardiac intraventricular septum diameter (R = -0.25, p = 0.02), left ventricular mass (R = -0.24, p = 0.02), and left atrial volume (R = -0.22, p = 0.04). Wall to lumen ratio was associated with intraventricular septum diameter (R = 0.21, p = 0.044) and left atrial volume (R = 0.21, p = 0.045). In multivariable regression analysis, lumen diameter was independently associated with intraventricular septum diameter (ß = -0.05, p = 0.03), left ventricular mass (ß = -1.15, p = 0.04), and left atrial volume (ß = -0.42, p = 0.047); wall to lumen ratio was independently associated with intraventricular septum diameter (ß = 3.67, p = 0.02) and left atrial volume (ß = 30.0, p = 0.04).Conclusions: In conclusion, retinal arterioles lumen diameter and wall to lumen ratio were independent biomarkers of cardiac damage. Retinal examination performed by means of scanning laser Doppler flowmetry might be a valuable tool to improve cardiovascular risk stratification of hypertensive patients.

Prevalence and distribution of left ventricular diastolic dysfunction in treated patients with long-lasting hypertension.

BACKGROUND: Although the presence of sub-clinical left ventricular diastolic dysfunction (LVDD) increases cardiovascular risk, the current ESH/ESC guidelines do not include the presence of this condition in the list of target organ damage or cardiovascular risk charts dedicated to the hypertensive population. Several conditions may predict the LVDD occurrence, however, clustering of these factors with hypertension makes the relationship less clear. Therefore, the aim of this study was to evaluate both the occurrence and the severity of diastolic dysfunction in a large cohort of treated hypertensives. METHODS: We retrospectively analyzed records of 610 hypertensive participants of the CARE NORTH Study who consented to echocardiography and were free of overt cardiovascular disease. Mean age was 54.0 ± 13.9 years (mean ± SD), BMI 29.7 ± 4.8 kg/m2. The exclusion criteria were: established heart failure, LVEF <45%, coronary revascularization, valvular defect, atrial fibrillation, or stroke. The staging of LVDD was based on comprehensive transthoracic echocardiographic measurements. RESULTS: 49.7% percent of the patients had normal diastolic function (38.8% vs. 59.0%, females (F) vs. males (M), respectively; p < .001). Grade 1 LVDD was documented in 24.4% (27.8% and 21.6%; F and M; p = .08) and grade 2 LVDD in 19.3% (24.9% and 14.6%; F and M; p = .001) of the patients. None were diagnosed with grade 3 LVDD. In the logistic regression model, female sex, advancing age, obesity status, established diabetes mellitus, higher 24-hour SBP, and increasing LVMI were identified as the independent variables increasing the odds for the presence of LVDD, whereas blood-lowering therapy attenuated the risk. CONCLUSIONS: There is an unexpectedly high prevalence of different forms of diastolic dysfunction in treated hypertensive patients who are free of overt cardiovascular disease.

Dynamical Pattern Representation of Cardiovascular Couplings Evoked by Head-up Tilt Test.

Shannon entropy (ShE) is a recognised tool for the quantization of the temporal organization of time series. Transfer entropy (TE) provides insight into the dependence between coupled systems. Here, signals are analysed that were produced by the cardiovascular system when a healthy human underwent a provocation test using the head-up tilt (HUT) protocol. The information provided by ShE and TE is evaluated from two aspects: that of the algorithmic stability and that of the recognised physiology of the cardiovascular response to the HUT test. To address both of these aspects, two types of symbolization of three-element subsequent values of a signal are considered: one, well established in heart rate research, referring to the variability in a signal, and a novel one, revealing primarily the dynamical trends. The interpretation of ShE shows a strong dependence on the method that was used in signal pre-processing. In particular, results obtained from normalized signals turn out to be less conclusive than results obtained from non-normalized signals. Systematic investigations based on surrogate data tests are employed to discriminate between genuine properties-in particular inter-system coupling-and random, incidental fluctuations. These properties appear to determine the occurrence of a high percentage of zero values of TE, which strongly limits the reliability of the couplings measured. Nevertheless, supported by statistical corroboration, we identify distinct timings when: (i) evoking cardiac impact on the vascular system, and (ii) evoking vascular impact on the cardiac system, within both the principal sub-systems of the baroreflex loop.

Complexity of cardiovascular rhythms during head-up tilt test by entropy of patterns.

OBJECTIVE: The head-up tilt (HUT) test, which provokes transient dynamical alterations in the regulation of cardiovascular system, provides insights into complex organization of this system. Based on signals with heart period intervals (RR-intervals) and/or systolic blood pressure (SBP), differences in the cardiovascular regulation between vasovagal patients (VVS) and the healthy people group (CG) are investigated. APPROACH: Short-term relations among signal data represented symbolically by three-beat patterns allow to qualify and quantify the complexity of the cardiovascular regulation by Shannon entropy. Four types of patterns: permutation, ordinal, deterministic and dynamical, are used, and different resolutions of signal values in the the symbolization are applied in order to verify how entropy of patterns depends on a way in which values of signals are preprocessed. MAIN RESULTS: At rest, in the physiologically important signal resolution ranges, independently of the type of patterns used in estimates, the complexity of SBP signals in VVS is different from the complexity found in CG. Entropy of VVS is higher than CG what could be interpreted as substantial presence of noisy ingredients in SBP of VVS. After tilting this relation switches. Entropy of CG occurs significantly higher than VVS for SBP signals. In the case of RR-intervals and large resolutions, the complexity after the tilt becomes reduced when compared to the complexity of RR-intervals at rest for both groups. However, in the case of VVS patients this reduction is significantly stronger than in CG. SIGNIFICANCE: Our observations about opposite switches in entropy between CG and VVS might support a hypothesis that baroreflex in VVS affects stronger the heart rate because of the inefficient regulation (possibly impaired local vascular tone alternations) of the blood pressure.

Multistructure index characterization of heart rate and systolic blood pressure reveals precursory signs of syncope.

Recurrent syncope - abrupt loss of consciousness - can have a serious impact on patients' quality of life, comparable with chronic illnesses. Vasovagal syncope (VVS) is a specific reflex syncope, in which an inappropriate reaction of the autonomic nervous system (ANS) plays a key role in the pathophysiology. In syncope diagnosis, an ideal diagnostic method should positively identify vasovagal sensitive patients, without the need to perform a specialised head-up tilt table (HUTT) test. We apply a novel methodology of multistructure index (MI) statistics for seamlessly evaluating the size spectrum of the asymmetry properties of magnitudes of neural reflexes responsible for maintaining the homeostatic dynamics of autonomic control. Simultaneous evaluation using the MI of the effects on heart rate and blood pressure involved in achieving homeostasis of contrasting properties of the dynamics of slow and fast neural regulation reveals a clear distinction between vasovagal patients and healthy subjects, who are/are not susceptible to spontaneous fainting. Remarkably, a healthy cardiovascular response to the HUTT test is indeed evident prior to the test, making the MI a robust novel indicator, clearly distinguishing the cardiovascular autonomic regulation of healthy people from that of vasovagal patients without the need to perform an actual HUTT test.

Compensatory functional reorganization may precede hypertension-related brain damage and cognitive decline: a functional magnetic resonance imaging study.

OBJECTIVES: Our study aimed at exploring structural and functional differences in the brain during higher cognitive processing between middle-aged hypertensive patients and controls matched for sex, age and years of education. METHODS: Two groups of 20 patients took part in MRI examinations. This article reports the results of functional MRI during a Stroop color interference task and structural evaluations based on a modified Fazekas scale. RESULTS: No intergroup differences were found in regards to the severity of white matter lesions (Mann-Whitney U test = 150.5, P > 0.1), nor from the task performance in the scanner (t(35) = 0.2, P > 0.1). However, brain activation patterns between patients and controls varied. Hypertensive patients involved significantly more cerebral areas during the processing, regardless of the task difficulty. Differences were found in 26 diverse regions of both primary and associative cortices (with a peak voxel located in the cuneus, Z = 6.94, P < 0.05 family-wise error corrected at voxel level). CONCLUSION: Our findings provide an insight into the brain mechanisms related to essential hypertension and suggest a functional reorganization (neuroplasticity) early in the course of the disease.