Sensations of dizziness or fainting (pre-syncope or syncope) on standing up from a lying or a seated position are usually associated with impaired blood pressure regulation leading to inadequate perfusion of the brain. The purpose of this project was to develop a simple method to provide scientists and doctors a convenient way to monitor cardiovascular control during orthostatic stress with the non-invasive FinometerTM device. This apparatus provides a continuous estimate of arterial blood pressure (BP) contour from the finger and computes brachial blood pressure contours (systolic (SBP) and diastolic (DBP) blood pressure), heart rate (HR), stroke volume and cardiac output (Q) from the Modelflow equation. In this thesis, a method was implemented to obtain an estimate of central venous pressure (CVP) to provide greater insight into cardiovascular control. The accuracy and potential errors resulting from measurement of finger arterial pressure were also evaluated. The thesis first examined whether key variables essential to monitor cardiovascular control can be reliably measured by the FinometerTM in comparison to independent methods. HR was accurate and precise at rest and during stress (difference between methods: 0.05± 0.18 beats/min). According to standards established by the American Association for the Advancement of Medical Instrumentation (AAMI); at rest, DBP was accurate but not precise (1.6± 8.8 mmHg) and SBP was not accurate but precise (14.2± 8.0 mmHg). These errors could be due to an improper use of our reference method. The post-test correction for individual characteristics proposed by the FinometerTM developers did improve overall Q estimation (0.255± 0.441 L/min (6.9%) instead of 0.797± 0.441 L/min (22.4%)) when compared with Doppler ultrasound but did not account for the increasing error with a greater orthostatic stress induced by lower body negative pressure. Using finger BP instead of aortic BP to calculate Q did not explain this error as revealed by a new approach that compared the simultaneous pulse contours from different methods. Indeed, there was no significant difference between the error of the estimation of Q from the finger arterial pulse compared to the estimation of Q from the independent measurement by tonometry on the brachial artery at rest (-1.13± 14.67%) and at the maximum orthostatic stress used (-0.61± 9.33%) (p>0.05). Using brachial BP to calculate Q did not improve the result found with finger BP. The first hypothesis of this thesis that CVP could be estimated from outputs of the FinometerTM compared to direct venous pressure measurement was supported for the individual (0.2± 1.7 mmHg) and test specific (0.1± 1.2 mmHg) equations. The general equations derived from group data were accurate but not precise enough (0.4± 2.8 mmHg) to be used in clinical and research setting. The success of the individual equations suggests that it might be possible to derive a personal equation that will be useful over a long period for similar tests by using a catheter only once. The second and third hypotheses related to the cause of discrepancy between Q from FinometerTM and Q from Doppler, were not supported by the data. However, a new contour analysis method introduced here in a graphical format might provide an opportunity for systematic analyses of the deviation between methods. It could reveal sources of error allowing future improvements in the accuracy and precision of Q from FinometerTM during orthostatic or physical stress.

Sensations of dizziness or fainting (pre-syncope or syncope) on standing up from a lying or a seated position are usually associated with impaired blood pressure regulation leading to inadequate perfusion of the brain. The purpose of this project was to develop a simple method to provide scientists and doctors a convenient way to monitor cardiovascular control during orthostatic stress with the non-invasive FinometerTM device. This apparatus provides a continuous estimate of arterial blood pressure (BP) contour from the finger and computes brachial blood pressure contours (systolic (SBP) and diastolic (DBP) blood pressure), heart rate (HR), stroke volume and cardiac output (Q) from the Modelflow equation. In this thesis, a method was implemented to obtain an estimate of central venous pressure (CVP) to provide greater insight into cardiovascular control. The accuracy and potential errors resulting from measurement of finger arterial pressure were also evaluated. The thesis first examined whether key variables essential to monitor cardiovascular control can be reliably measured by the FinometerTM in comparison to independent methods. HR was accurate and precise at rest and during stress (difference between methods: 0.05± 0.18 beats/min). According to standards established by the American Association for the Advancement of Medical Instrumentation (AAMI); at rest, DBP was accurate but not precise (1.6± 8.8 mmHg) and SBP was not accurate but precise (14.2± 8.0 mmHg). These errors could be due to an improper use of our reference method. The post-test correction for individual characteristics proposed by the FinometerTM developers did improve overall Q estimation (0.255± 0.441 L/min (6.9%) instead of 0.797± 0.441 L/min (22.4%)) when compared with Doppler ultrasound but did not account for the increasing error with a greater orthostatic stress induced by lower body negative pressure. Using finger BP instead of aortic BP to calculate Q did not explain this error as revealed by a new approach that compared the simultaneous pulse contours from different methods. Indeed, there was no significant difference between the error of the estimation of Q from the finger arterial pulse compared to the estimation of Q from the independent measurement by tonometry on the brachial artery at rest (-1.13± 14.67%) and at the maximum orthostatic stress used (-0.61± 9.33%) (p>0.05). Using brachial BP to calculate Q did not improve the result found with finger BP. The first hypothesis of this thesis that CVP could be estimated from outputs of the FinometerTM compared to direct venous pressure measurement was supported for the individual (0.2± 1.7 mmHg) and test specific (0.1± 1.2 mmHg) equations. The general equations derived from group data were accurate but not precise enough (0.4± 2.8 mmHg) to be used in clinical and research setting. The success of the individual equations suggests that it might be possible to derive a personal equation that will be useful over a long period for similar tests by using a catheter only once. The second and third hypotheses related to the cause of discrepancy between Q from FinometerTM and Q from Doppler, were not supported by the data. However, a new contour analysis method introduced here in a graphical format might provide an opportunity for systematic analyses of the deviation between methods. It could reveal sources of error allowing future improvements in the accuracy and precision of Q from FinometerTM during orthostatic or physical stress.

Les syncopes récurrentes d'origine inexpliquée ou vasovagale affectent le fonctionnement physique et psychologique des patients vivant avec cette condition. Pourtant, peu de recherches se sont intéressées à comprendre la qualité de vie (QV) générale de ces patients, soit leur capacité à atteindre leurs objectifs dans différents domaines de vie, et les facteurs qui l'influence. Conséquemment, l'influence du sexe et du type de syncope sur la QV demeure inconnue. Qui plus est, aucune recherche n'a encore évalué les perceptions entretenues par les individus concernant leurs pertes de conscience. Pourtant, des études suggèrent que ces perceptions, appelées représentations de la maladie, affectent l'adaptation physique et psychologique des patients. L'incertitude entourant les causes et traitements des syncopes récurrentes suggère aussi l'importance d'explorer les perceptions des patients pour mieux comprendre leur influence sur la QV. Objectifs,Article 1 : Examiner les représentations de la maladie chez les hommes et les femmes souffrant de pertes de conscience récurrentes d'origine vasovagale (SVV) ou inexpliquée (SI) et référés pour un test de table basculante (TTB). Article 2 : Examiner la relation entre la QV, les représentations de la maladie, le sexe et le type de syncope chez les patients souffrant de syncope récurrentes référés pour un TTB. Méthode, Cent quinze (115) patients ont été interviewés un mois avant leur TTB à l'aide d'une entrevue semi-structurée et de questionnaires. Statistiques, Article 1 : les différences entre hommes et femmes et entre patients avec SVV et SI ont été examinées à l'aide d'une MANCOVA. Les représentations de la maladie ont également été catégorisées et explorées à l'aide de khi carrés et de comparaisons binomiales. Article 2, Une ANCOVA a permis d'évaluer l'association entre la QV, le sexe, le type de syncopes et les représentations de la maladie (les comparaisons entre les groupes de représentations de la maladie ont été faites selon les contrastes de type Helmert) en contrôlant pour l'âge et le nombre de syncopes. Une série de régressions linéaires ont permis d'explorer le rôle possible de médiateur des représentations de la maladie dans la relation entre le nombre de syncope et la QV. Résultats, Article 1 : les représentations sont similaires chez les hommes et les femmes ayant des SVV et des SI (tous les p > .10). Bien qu'entre 33% et 50% des patients ne savent pas quoi penser par rapport à leur maladie, l'exploration des réponses révèle divers patrons de représentations. Les patients ont des représentations émotionnelles et des représentations concernant la chronicité de leur condition très diversifiées. La majorité est indécise concernant le contrôle qu'ils peuvent exercer sur les syncopes et la durée cyclique (perception que les syncopes surviennent selon des cycles précis) de la condition. Peu de patients croient que les syncopes ont des conséquences sévères sur leur vie et qu'aucun traitement ne sera efficace pour les guérir. Seulement 19% des patients affirment ne pas être inquiet à propos de leur syncope. Finalement, très peu de patients (15%) ont le sentiment de comprendre leur condition. Article 2 : les résultats indiquent une QV réduite chez les patients avec syncopes récurrentes, particulièrement dans les domaines suivants: affectivité, cognitions, loisirs, travail et santé. Tous les patients ne rapportent toutefois pas une QV appauvrie. Les patients avec des représentations sévères ont une QV appauvrie (p = .022) comparativement aux individus ayant des perceptions peu ou moyennement sévères de leur syncope. Les hommes avec SI rapportent, quant à eux, la QV la plus faible comparativement aux hommes avec SVV, qui présentent une QV normale (p = .007). Finalement, les résultats suggèrent l'hypothèse d'un rôle médiateur des représentations de la maladie dans l'association entre le nombre de syncope et la QV. Conclusion, les patients vivant avec des pertes de conscience récurrentes d'origine vasovagale ou inexpliquée affichent un manque de compréhension concernant leur condition et présentent des représentations variées à propos des syncopes. La QV est appauvrie, surtout chez les patients ayant des représentations plus sévères de leur condition et chez les hommes avec SI. Les résultats suggèrent donc un besoin d'éducation, ainsi que de support chez ces patients afin d'améliorer leur compréhension de leur problématique ainsi que leur QV. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR :Syncope récurrentes, Qualité de vie, Représentations de la maladie, Sexe et types de syncopes.

Thesis--Lund. / Extra t.p., with thesis note, inserted. "Corrigenda": slip inserted. Bibliography: p. [299]-305.

Academisch Proefschrift--Universiteit van Amsterdam, 2007. / Description based on print version record. Includes bibliographical references (p. 91-108).

Syncope is a common Emergency Department (ED) presentation. An important proportion of syncope patients are at risk of developing serious adverse events (SAEs), such as deaths or arrhythmias following ED disposition. Currently, no clinically-useful decision tool exists to reliably identify high-risk patients. This study derived a clinical decision tool to identify syncope patients at risk of developing SAEs after ED disposition. This study also examined key methodological considerations involved in deriving decision tools by comparing two different methodological approaches: a traditional and modern approach. The traditional approach led to an eight-variable decision tool that allowed simple clinical interpretation and use. The modern approach, which aims to avoid data-driven methodology and statistical overfitting, was used to derive a ten-variable decision tool. Both decision tools displayed acceptable and comparable performance in internal validation studies (c-statistic 0.87, 95% confidence interval 0.84-0.89). A future external validation study is required to comprehensively compare the methods.

Orientador: Rossano César Bonatto / Resumo: Introdução. A síncope pode ser definida como a perda súbita e transitória autolimitada da consciência e do tônus postural, sendo uma queixa comum nos serviços de urgência e emergência. Ela engloba diversos diagnósticos diferenciais, dentre eles alguns que podem representar ameaça à vida. Objetivo. Este trabalho tem como objetivo discutir a diversidade de etiologias da síncope, e como conduzir uma investigação apropriada a partir da história e achados clínicos do paciente, otimizando os recursos disponíveis no serviço e evitando a realização de exames complementares desnecessários, através da padronização de um protocolo de investigação, diagnóstico e tratamento de síncope na faixa etária pediátrica, de acordo com a nossa realidade institucional, baseado nas melhores evidências disponíveis na literatura científica. Método. Estudo da revisão da literatura, realizado nas principais fontes: Pubmed, Embase, LILACs e Uptodate, com a utilização das palavras-chave: Síncope OR Desmaio OR Syncope, Criança OR Crianças OR Niño OR Child OR Children OR Protocolo OR Protocol OR Diretrizes OR Guidelines. 8 Conclusão. Foi elaborado protocolo de investigação, diagnóstico e tratamento para síncope, considerando as principais patologias que acometem a faixa etária pediátrica. Deve-se realizar anamnese detalhada, com descrição dos pródromos, da crise, dos antecedentes familiares e do exame físico, incluindo aferição da pressão arterial. É recomendada a realização de eletrocardiograma, principalme... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Background. Syncope can be defined as a transient loss of consciousness and postural tone, and it’s considered as a common complaint in urgency and emergency care settings. It encompasses many different diagnosis, among them some that may represent risk to life. Objective. This dissertation aims to discuss the diversity of syncope etiologies, and how to conduct a proper investigation based on history and clinical findings of the patient, optimizing available resources and avoiding unnecessary exams, through a standardized protocol for investigation, diagnosis and treatment of syncope for the pediatric age group, according to our institutional reality and based on the best evidence from scientific literature. Methods. Literature review study, done through the main databases: Pubmed, Embase, LILACs and Uptodate, using the keywords: Síncope OR Desmaio OR Syncope, Criança OR Crianças OR Niño OR Child OR Children OR Protocolo OR Protocol OR Diretrizes OR Guidelines. Conclusion. A protocol for investigation, diagnosis and treatment for syncope was elaborated, considering the main causes that affect the pediatric age group. A detailed anamnesis should be performed, describing prodrome, the episode and family history, and also a physical exam, including blood pressure measurement. It is recommended to perform an electrocardiogram (ECG), specially if the characteristics of syncope are not vasovagal. The other exams are indicated according to the diagnostic hypothesis. The majority of ... (Complete abstract click electronic access below) / Mestre

Left atrial myxomas are the most common type of benign primary cardiac tumor. Patients can present with generalized symptoms, such as fatigue, symptoms from obstruction of the myxoma, or even embolization of the myxoma causing distal thrombosis. We describe a case with several-month duration of syncopal episodes that occurred after coughing and with exertion. Computed tomography of the chest showed a 6.1 cm by 4.5 cm mass in the left atrium, later evaluated with an echocardiogram. Cardiothoracic surgery removed the mass, and it was determined to be an atrial myxoma. It is important for an internist to be able to diagnose an atrial myxoma because of the risks associated with embolization and even sudden death as myxoma can block blood supply from atrium to ventricle.

A síncope neurocardiogênica (SINC) é causada por redução global e aguda do fluxo sanguíneo cerebral, subsequente à hipotensão arterial, com perda transitória da consciência e do tônus postural. Entretanto, existem divergências, quanto às repostas das variáveis cardiovasculares que antecedem o início da SINC, provocada pelo seu principal teste diagnóstico, a manobra postural passiva (MPP) ou Tilt-test. Recentemente, a possibilidade de analisar as variáveis cardiovasculares, com métodos computacionais não-invasivos, lineares (ML) e não lineares (MNL) tem permitido o estudo das entropias, da variabilidade da frequência cardíaca (VFC), da pressão arterial sistólica (VPAS) e da sensibilidade barorreflexa (SBR); estudos preliminares sugerem que a SINC poderia estar relacionada ao desequilíbrio da modulação autonômica dessas variáveis. Objetivo: usar métodos computacionais, ML e MNL, na análise da VFC, e ML na análise da VPAS e da SBR, em pacientes com história clínica de SINC, com resposta positiva ou negativa à MPP, e em indivíduos saudáveis. Métodos: Foram estudados 51 indivíduos, divididos em 3 grupos, sendo 16 positivos, 18 negativos e 17 saudáveis. Os ML usam algoritmos nos domínios do tempo (DT) e da frequência (DF) (Transformada rápida de Fourier), e os MNL usam alogarítmos da entropia amostral (SampEn) m=2 e r= 20%. Foram analisados 2 momentos: Pré-Tilt (posição supina; trechos com 1000-1500 pontos) e Tilt pré-síncope (70º de inclinação; trechos com 1000-1500 pontos; anteriores à síncope), sendo estudados os mesmos momentos para o grupo controle. Resultados: Não foram encontradas diferenças estatísticas entre os grupos TTP, TTN e Controle para os parâmetros: Idade (anos), Peso (kg), Altura (m) e IMC (kg/m2), pressão arterial sistólica (PAS), pressão arterial diastólica (PAD), frequência cardíaca (FC) e frequência respiratória. Na análise VFC por meio de ML no DT e DF, no momento Pré-Tilt e Tilt pré-síncope, não foi encontrada diferenças estatísticas 8 entre os grupos TTP, TTN e Controle para os parâmetros Mean-iRR(ms), SDiRR(ms), RMSSD(ms), LF(un) (ms2), HF(un) (ms2) e LF/HF. Comparando-se os momentos Pré-Tilt vs Tilt nos grupos TTP, TTN e Controle (análise intra-grupo) observamos diferenças significantes para as variáveis: Mean-iRR(ms), SD-iRR(ms), RMSSD(ms), LF(un), HF(un) (ms2) e LF/HF. Houve na análise da VFC por MNL (SampEn) no grupo Controle, redução significativa dos valores entre as fases Pré-Tilt vs Tilt (2,19 ± 0,40 vs 1,68 ± 0,50, p = 0,001). Houve em ambos os grupos (TTP, TTN e Controle) aumento significativo do LF-PAS, quando comparamos as fases Pré-Tilt vs Tilt (TTP: 6,72 ± 5,67 vs 13,03 ± 10,759 mmHg2, p = 0,001; TTN: 7,25 ± 4,22 vs 13,42 ± 8,62 mmHg2, p = 0,013; Controle: 5,99 ± 2,20 vs 23,07 ± 6,26 mmHg2, p < 0,0001). Além disso, evidenciaram-se maiores valores, estatisticamente significantes, quando comparamos os grupos Controle vs TTP no momento Tilt (23,07 ± 6,26 vs 13,03 ± 10,59 mmHg2, p < 0,001) e Controle vs TTN no momento Tilt (23,07 ± 6,26 vs 13,42 ± 8,62 mmHg2, p < 0,001). Houve em todos os grupos redução significativa da SBR, quando comparamos as fases Pré-Tilt vs Tilt (TTP: 30,22 ± 15,67 vs 13,16 ± 6,08 ms/mmHg, p < 0,0001; TTN: 22,98 ± 11,23 vs 11,55 ± 3,34 ms/mmHg, p < 0,0001; e Controle: 26,75 ± 6,94 vs 12,25 ± 3,88 ms/mmHg, p < 0,0001). Além disso, no grupo TTP e Controle, houve redução significativa dos valores do índice de efetividade barorreflexa (BEI) entre as fases Pré-Tilt vs Tilt (0,50 ± 0,15 vs 0,40 ± 0,13, p = 0,033) e (0,54 ± 0,07 vs 0,46 ± 0,16, p =0, 030) respectivamente. Conclusões: os achados do presente estudo permitiram as seguintes conclusões: 1- a VFC, com métodos lineares (domínios do tempo e frequência) e não lineares (Entropia Amostral), bem como a VPAS (domínios do tempo e da frequência) e a SBR não documentaram nas fases Pré-Tilt e Tilt pré- síncope (fase de estabilidade das variáveis, após a mudança postural até momento anterior ao aparecimento dos pródromos ou da síncope), diferenças estatísticas entre os 2 grupos de pacientes adultos e com história altamente sugestiva de SINC, como doença isolada, com Tilt-test positivo e negativo; 2- o grupo Controle saudável somente foi diferente dos grupos TTP e TTN no parâmetro LF da VPAS; a importância fisiológica desse achado é de difícil explicação, porque não existem na 9 literatura, para esse parâmetro, valores normais da média e dos intervalos de confiança. / Neurocardiogenic syncope (SYN) is caused by a global and acute reduction of cerebral blood flow, subsequent to hypotension, with transient loss of consciousness and postural tone. However, there are differences in the responses of the cardiovascular variables that precede the beginning of the SYN, caused by its main diagnostic test, the passive postural maneuver (PPM) or Tilt-test. Recently, the possibility of analyzing cardiovascular variables using non-invasive, linear (ML) and non-linear (MNL) computational methods has allowed the study of entropies, heart rate variability (HRV), systolic blood pressure variability (VPAS) and baroreflex sensitivity (SBR). Preliminary studies suggest that the SYN could be related to the imbalance of the autonomic modulation of these variables. Objective: To use computer methods, ML and MNL, in the analysis of HRV, and ML in the analysis of VPAS and SBR, in patients with a clinical history of SYN, with positive or negative response to PPM, and in healthy individuals. Methods: Fifty-one individuals were studied, divided into three groups: 16 positive, 18 negative and 17 healthy. MLs use algorithms in the time (DT) and frequency (DF) (Fast Fourier Transform) algorithms, and MNLs use sample entropy m (2) and r = 20%. Two moments were analyzed: Pre-Tilt (supine position, recording 1000-1500 points) and pre-syncope Tilt (70º inclination, recording 1000-1500 points, prior to syncope), being studied the same moments for the control group. Results: There were no statistical differences between the TTP, TTN and Control groups for the parameters: Age (years), Weight (kg), Height (m) and BMI (kg / m2), systolic blood pressure Diastolic (DBP), heart rate (HR) and respiratory rate. No statistical differences were found between the TTP, TTN and Control groups (in the Pre-Tilt and Tilt) for the Mean-iRR (ms), SD-iRR (ms), RMSSD (ms), LF (un) (ms2), HF (un) (ms2) and LF / HF. Comparing the Pre-Tilt vs Tilt moments in the TTP, TTN and Control groups (intra-group analysis) we observed significant differences for the variables: Mean-iRR (ms), SD-iRR (ms), RMSSD (ms), 11 LF (Un), HF (un) (ms2) and LF / HF. There was a significant reduction in the values between the Pre-Tilt vs Tilt phases (2.19 ± 0.40 vs 1.68 ± 0.50, p = 0.001) in the analysis of HRV by MNL (SampEn) in the Control group. There was a significant increase in LF-PAS in both groups (TTP, TTN and Control) when we compared the Pre-Tilt vs Tilt phases (TTP: 6.72 ± 5.67 vs 13.03 ± 10.759 mmHg2, p = 0.001; TTN: 7.25 ± 4.22 vs 13.42 ± 8.62 mmHg2, p = 0.013; Control: 5.99 ± 2.20 vs. 23.07 ± 6.26 mmHg2, p <0.0001). In addition, statistically significant higher values were found when we compared the Control vs TTP groups at the time of Tilt (23.07 ± 6.26 vs 13.03 ± 10.59 mmHg2, p <0.001) and Control vs. TTN at the time of Tilt (23.07 ± 6.26 vs 13.42 ± 8.62 mmHg2, p <0.001). There was a significant reduction of SBR in all groups when comparing the Pre-Tilt vs Tilt phases (TTP: 30.22 ± 15.67 vs. 13.16 ± 6.08 ms / mmHg, p <0.0001; P <0.0001, and control: 26.75 ± 6.94 vs 12.25 ± 3.88 ms / mmHg, p <0, 0001). In addition, in the TTP and Control group, there was a significant reduction in baroreflex effectiveness index (EIB) between the Pre-Tilt vs. Tilt phases (0.50 ± 0.15 vs. 0.40 ± 0.13, p = 0.033) and (0.54 ± 0.07 vs 0.46 ± 0.16, p = 0.030) respectively. Conclusions: The findings of the present study allowed the following conclusions: 1 - HRV, with linear methods (time and frequency domains) and nonlinear (Entropy Amostral), as well as VPAS (time domain and frequency domain) and SBR did not document Pre-Tilt and Tilt phases pre-syncope (Stability of variables, after postural change until the time before prodrome or syncope appeared), statistical differences between the 2 groups of adult patients and with a highly suggestive history of SYN, As isolated disease, with positive and negative Tilt-test; 2- the Healthy control group was only different from the TTP and TTN groups in the LF parameter of the VPAS; The physiological importance of this finding is difficult to explain because there are no normal values of the mean and confidence intervals in the literature for this parameter.

A síncope neurocardiogênica (SINC) é causada por redução global e aguda do fluxo sanguíneo cerebral, subsequente à hipotensão arterial, com perda transitória da consciência e do tônus postural. Entretanto, existem divergências, quanto às repostas das variáveis cardiovasculares que antecedem o início da SINC, provocada pelo seu principal teste diagnóstico, a manobra postural passiva (MPP) ou Tilt-test. Recentemente, a possibilidade de analisar as variáveis cardiovasculares, com métodos computacionais não-invasivos, lineares (ML) e não lineares (MNL) tem permitido o estudo das entropias, da variabilidade da frequência cardíaca (VFC), da pressão arterial sistólica (VPAS) e da sensibilidade barorreflexa (SBR); estudos preliminares sugerem que a SINC poderia estar relacionada ao desequilíbrio da modulação autonômica dessas variáveis. Objetivo: usar métodos computacionais, ML e MNL, na análise da VFC, e ML na análise da VPAS e da SBR, em pacientes com história clínica de SINC, com resposta positiva ou negativa à MPP, e em indivíduos saudáveis. Métodos: Foram estudados 51 indivíduos, divididos em 3 grupos, sendo 16 positivos, 18 negativos e 17 saudáveis. Os ML usam algoritmos nos domínios do tempo (DT) e da frequência (DF) (Transformada rápida de Fourier), e os MNL usam alogarítmos da entropia amostral (SampEn) m=2 e r= 20%. Foram analisados 2 momentos: Pré-Tilt (posição supina; trechos com 1000-1500 pontos) e Tilt pré-síncope (70º de inclinação; trechos com 1000-1500 pontos; anteriores à síncope), sendo estudados os mesmos momentos para o grupo controle. Resultados: Não foram encontradas diferenças estatísticas entre os grupos TTP, TTN e Controle para os parâmetros: Idade (anos), Peso (kg), Altura (m) e IMC (kg/m2), pressão arterial sistólica (PAS), pressão arterial diastólica (PAD), frequência cardíaca (FC) e frequência respiratória. Na análise VFC por meio de ML no DT e DF, no momento Pré-Tilt e Tilt pré-síncope, não foi encontrada diferenças estatísticas 8 entre os grupos TTP, TTN e Controle para os parâmetros Mean-iRR(ms), SDiRR(ms), RMSSD(ms), LF(un) (ms2), HF(un) (ms2) e LF/HF. Comparando-se os momentos Pré-Tilt vs Tilt nos grupos TTP, TTN e Controle (análise intra-grupo) observamos diferenças significantes para as variáveis: Mean-iRR(ms), SD-iRR(ms), RMSSD(ms), LF(un), HF(un) (ms2) e LF/HF. Houve na análise da VFC por MNL (SampEn) no grupo Controle, redução significativa dos valores entre as fases Pré-Tilt vs Tilt (2,19 ± 0,40 vs 1,68 ± 0,50, p = 0,001). Houve em ambos os grupos (TTP, TTN e Controle) aumento significativo do LF-PAS, quando comparamos as fases Pré-Tilt vs Tilt (TTP: 6,72 ± 5,67 vs 13,03 ± 10,759 mmHg2, p = 0,001; TTN: 7,25 ± 4,22 vs 13,42 ± 8,62 mmHg2, p = 0,013; Controle: 5,99 ± 2,20 vs 23,07 ± 6,26 mmHg2, p < 0,0001). Além disso, evidenciaram-se maiores valores, estatisticamente significantes, quando comparamos os grupos Controle vs TTP no momento Tilt (23,07 ± 6,26 vs 13,03 ± 10,59 mmHg2, p < 0,001) e Controle vs TTN no momento Tilt (23,07 ± 6,26 vs 13,42 ± 8,62 mmHg2, p < 0,001). Houve em todos os grupos redução significativa da SBR, quando comparamos as fases Pré-Tilt vs Tilt (TTP: 30,22 ± 15,67 vs 13,16 ± 6,08 ms/mmHg, p < 0,0001; TTN: 22,98 ± 11,23 vs 11,55 ± 3,34 ms/mmHg, p < 0,0001; e Controle: 26,75 ± 6,94 vs 12,25 ± 3,88 ms/mmHg, p < 0,0001). Além disso, no grupo TTP e Controle, houve redução significativa dos valores do índice de efetividade barorreflexa (BEI) entre as fases Pré-Tilt vs Tilt (0,50 ± 0,15 vs 0,40 ± 0,13, p = 0,033) e (0,54 ± 0,07 vs 0,46 ± 0,16, p =0, 030) respectivamente. Conclusões: os achados do presente estudo permitiram as seguintes conclusões: 1- a VFC, com métodos lineares (domínios do tempo e frequência) e não lineares (Entropia Amostral), bem como a VPAS (domínios do tempo e da frequência) e a SBR não documentaram nas fases Pré-Tilt e Tilt pré- síncope (fase de estabilidade das variáveis, após a mudança postural até momento anterior ao aparecimento dos pródromos ou da síncope), diferenças estatísticas entre os 2 grupos de pacientes adultos e com história altamente sugestiva de SINC, como doença isolada, com Tilt-test positivo e negativo; 2- o grupo Controle saudável somente foi diferente dos grupos TTP e TTN no parâmetro LF da VPAS; a importância fisiológica desse achado é de difícil explicação, porque não existem na 9 literatura, para esse parâmetro, valores normais da média e dos intervalos de confiança. / Neurocardiogenic syncope (SYN) is caused by a global and acute reduction of cerebral blood flow, subsequent to hypotension, with transient loss of consciousness and postural tone. However, there are differences in the responses of the cardiovascular variables that precede the beginning of the SYN, caused by its main diagnostic test, the passive postural maneuver (PPM) or Tilt-test. Recently, the possibility of analyzing cardiovascular variables using non-invasive, linear (ML) and non-linear (MNL) computational methods has allowed the study of entropies, heart rate variability (HRV), systolic blood pressure variability (VPAS) and baroreflex sensitivity (SBR). Preliminary studies suggest that the SYN could be related to the imbalance of the autonomic modulation of these variables. Objective: To use computer methods, ML and MNL, in the analysis of HRV, and ML in the analysis of VPAS and SBR, in patients with a clinical history of SYN, with positive or negative response to PPM, and in healthy individuals. Methods: Fifty-one individuals were studied, divided into three groups: 16 positive, 18 negative and 17 healthy. MLs use algorithms in the time (DT) and frequency (DF) (Fast Fourier Transform) algorithms, and MNLs use sample entropy m (2) and r = 20%. Two moments were analyzed: Pre-Tilt (supine position, recording 1000-1500 points) and pre-syncope Tilt (70º inclination, recording 1000-1500 points, prior to syncope), being studied the same moments for the control group. Results: There were no statistical differences between the TTP, TTN and Control groups for the parameters: Age (years), Weight (kg), Height (m) and BMI (kg / m2), systolic blood pressure Diastolic (DBP), heart rate (HR) and respiratory rate. No statistical differences were found between the TTP, TTN and Control groups (in the Pre-Tilt and Tilt) for the Mean-iRR (ms), SD-iRR (ms), RMSSD (ms), LF (un) (ms2), HF (un) (ms2) and LF / HF. Comparing the Pre-Tilt vs Tilt moments in the TTP, TTN and Control groups (intra-group analysis) we observed significant differences for the variables: Mean-iRR (ms), SD-iRR (ms), RMSSD (ms), 11 LF (Un), HF (un) (ms2) and LF / HF. There was a significant reduction in the values between the Pre-Tilt vs Tilt phases (2.19 ± 0.40 vs 1.68 ± 0.50, p = 0.001) in the analysis of HRV by MNL (SampEn) in the Control group. There was a significant increase in LF-PAS in both groups (TTP, TTN and Control) when we compared the Pre-Tilt vs Tilt phases (TTP: 6.72 ± 5.67 vs 13.03 ± 10.759 mmHg2, p = 0.001; TTN: 7.25 ± 4.22 vs 13.42 ± 8.62 mmHg2, p = 0.013; Control: 5.99 ± 2.20 vs. 23.07 ± 6.26 mmHg2, p <0.0001). In addition, statistically significant higher values were found when we compared the Control vs TTP groups at the time of Tilt (23.07 ± 6.26 vs 13.03 ± 10.59 mmHg2, p <0.001) and Control vs. TTN at the time of Tilt (23.07 ± 6.26 vs 13.42 ± 8.62 mmHg2, p <0.001). There was a significant reduction of SBR in all groups when comparing the Pre-Tilt vs Tilt phases (TTP: 30.22 ± 15.67 vs. 13.16 ± 6.08 ms / mmHg, p <0.0001; P <0.0001, and control: 26.75 ± 6.94 vs 12.25 ± 3.88 ms / mmHg, p <0, 0001). In addition, in the TTP and Control group, there was a significant reduction in baroreflex effectiveness index (EIB) between the Pre-Tilt vs. Tilt phases (0.50 ± 0.15 vs. 0.40 ± 0.13, p = 0.033) and (0.54 ± 0.07 vs 0.46 ± 0.16, p = 0.030) respectively. Conclusions: The findings of the present study allowed the following conclusions: 1 - HRV, with linear methods (time and frequency domains) and nonlinear (Entropy Amostral), as well as VPAS (time domain and frequency domain) and SBR did not document Pre-Tilt and Tilt phases pre-syncope (Stability of variables, after postural change until the time before prodrome or syncope appeared), statistical differences between the 2 groups of adult patients and with a highly suggestive history of SYN, As isolated disease, with positive and negative Tilt-test; 2- the Healthy control group was only different from the TTP and TTN groups in the LF parameter of the VPAS; The physiological importance of this finding is difficult to explain because there are no normal values of the mean and confidence intervals in the literature for this parameter.