Cardiac vagal index varies according to field position in male elite football players / índice vagal cardíaco varia com a posição em campo de jogadores da elite do futebol

BACKGROUND: Cardiac vagal index (CVI) is supposedly higher in athletes and may differ between sports and/or between field positions. OBJECTIVE: To compare CVI: a) between elite football players vs. non-athletes and b) according to five football positions. METHOD: 242 football players of the first Brazilian/Angolan division were divided in five positions (N): goalkeepers (17), defenders (44), wingers (34), midfielders (87) and forwarders (60) and compared with 303 age-matched healthy non-athletes. CVI was estimated from a 4-second exercise test by quantifying the ratio of two cardiac cycle durations, before and at the end of a fast unloaded cycling exercise. RESULTS: Football players had resting and maximal heart rates of, respectively, 59 and 190 bpm and measured VO2max of 62.2 mL/(kg.min). Players and non-athletes showed similar CVI results (median-[P25-P75]) - 1.63-[1.46-1.84] vs 1.61-[1.41-1.81] (p = 0.22). Wingers tended to have a higher CVI (1.84-[1.60-1.99]), especially when compared to defenders (1.53-[1.41-1.72] (p = 0.01). There was a modest non-physiologically relevant association between VO2max and CVI (r = 0.15). CONCLUSIONS: Football players did not differ from non-athletes in CVI; however, among players, wingers were more often vagotonic, which may represent a hemodynamic advantage for match situations, where rapid heart rate transitions and faster oxygen delivery to muscles are required.

FUNDAMENTOS: O índice vagal cardíaco (IVC) é supostamente maior em atletas e pode diferir entre esportes e dentro do mesmo esporte. OBJETIVO: Comparar o IVC: a) entre futebolistas e não atletas e b) de acordo com cinco posições do futebol. MÉTODO: 242 jogadores da primeira divisão brasileira/angolana foram divididos em cinco posições (N): goleiros (17), zagueiros (44), laterais (34), meio-campistas (87) e atacantes (60) e comparados com 303 não-atletas saudáveis da mesma idade. IVC foi estimado a partir do teste de exercício de 4 segundos, quantificando a relação entre as durações de dois ciclos cardíacos - antes e ao final de uma pedalada rápida e sem carga RESULTADOS: As frequências cardíacas de repouso e máxima dos futebolistas foram, respectivamente, 59 e 190 bpm e o VO2max de 62,2 mL/(kg.min). Futebolistas e não-atletas mostraram resultados semelhantes de IVC (mediana- [P25-P75]) - 1,63- [1,46-1,84] vs 1,61- [1,41-1,81] (p = 0,22). Os laterais tenderam a ter maior IVC (1,84- [1,60-1,99]), especialmente quando comparados aos defensores (1,53- [1,41-1,72] (p = 0,01). Houve uma modesta associação fisiologicamente irrelevante entre VO2max e IVC (r = 0,15). CONCLUSÕES: jogadores da elite do futebol não diferem de não-atletas em IVC; entretanto, entre eles, os alas se mostraram mais frequentemente vagotônicos, o que pode representar uma vantagem hemodinâmica para situações de jogo, onde são necessárias transições rápidas da frequência cardíaca e um aporte mais rápido de oxigênio para os músculos ativos.

Características definidoras da Resposta Disfuncional ao Desmame Ventilatório como indicadores de acurácia do desmame ventilatório / Defining characteristics of the Dysfunctional Ventilatory Weaning Response as indicators of accuracy of ventilatory weaning / Características definitorias de la Respuesta Disfuncional al Destete Ventilatorio como indicadores de precisión del destete ventilatorio

Objetivou-se avaliar as características definidoras do diagnóstico Resposta Disfuncional do Desmame Ventilatório, como indicadores de acurácia das tentativas de desmame. Estudo observacional de 38 eventos de tentativa de desmame ventilatório em pacientes adultos internados em terapia intensiva. Para as características definidoras foram calculadas: sensibilidade, especificidade, valores preditivos positivos e negativos, acurácia ou sensibilidade, razão de verossimilhança e razão de chances diagnóstica. Também foram consideradas as medianas do número de características definidoras nos eventos de sucesso e insucesso. Foram consideradas acuradas: agitação, deterioração nos gases sanguíneos arteriais em relação aos parâmetros basais, uso moderado da musculatura acessória da respiração, aumento da frequência respiratória em relação aos parâmetros basais e frequência respiratória aumentada de forma significativa em relação aos parâmetros basais. Houve diferença estatística nas medianas do número de características definidoras observadas. Conclui-se que a característica definidora e o número delas influenciariam o sucesso da decisão sobre o desmame.

The study aimed to analyze the defining characteristics of the Dysfunctional Ventilatory Weaning Response as an indicator of the accuracy of ventilatory weaning. Observational study of 38 events of ventilatory weaning in adult patients admitted to intensive care. For the defining characteristics, it was calculated: sensitivity, specificity, positive and negative predictive values, accuracy or efficiency, likelihood ratio positive and negative, and diagnostic odds ratio. It was also considered the median number of defining characteristics in the event of success and failure. It was considered accurate: agitation, deterioration in arterial blood gases from baseline parameters, moderate use of accessory muscles of respiration, increased respiratory rate from baseline parameters and respiratory rate increases significantly with respect to baseline parameters. There was statistical difference in the median number of defining characteristics observed. It was concluded that the defining characteristic and the number of them would influence the success of the weaning decision.

El estudio tuvo como objetivo evaluar las características que definen el diagnóstico de Respuesta Disfuncional al Destete Ventilatorio como indicador de la exactitud del destete ventilatorio. Estudio observacional de 38 eventos de destete ventilatorio en pacientes adultos ingresados en cuidados intensivos. Para las características definitorias se calcularon: sensibilidad, especificidad, valores predictivos positivos y negativos, precisión o sensibilidad, cocientes de probabilidad y odds ratio diagnóstica. Fueran consideradas las medianas del número de características definitorias en casos de éxito o de fracaso. Se consideraron precisas: agitación, deterioro de los parámetros de gases en sangre arterial desde la línea de base, uso moderado de los músculos accesorios de la respiración, aumento de la frecuencia respiratoria a partir de parámetros de línea de base y frecuencia respiratoria aumentada significativamente en comparación con los parámetros de línea de base. Hubo diferencia estadísticamente significativa en la mediana del número de características definitorias observadas. Se concluye que la característica definitoria y el número de ellas influyen en el éxito de la decisión sobre el destete ventilatorio.

Comparação entre métodos de avaliação da modulação vagal cardíaca / Comparison of assessment methods of cardiac vagal modulation

FUNDAMENTO: Diversos métodos têm sido utilizados para avaliar a modulação vagal cardíaca; entretanto, há lacunas quanto a associação e acurácia desses métodos. OBJETIVO: Investigar a associação entre três métodos válidos, reprodutíveis e comumente utilizados para avaliação da modulação vagal cardíaca, e comparar as suas acurácias. MÉTODOS: Trinta homens saudáveis (23 ± 4 anos) e 15 homens com coronariopatia (61 ± 10 anos) foram avaliados em ordem contrabalanceada pela Variabilidade da Frequência Cardíaca (VFC; variáveis: domínio do tempo = pNN50, DPNN e RMSSD, domínio da frequência = AF ms² e AF u.n.), Arritmia Sinusal Respiratória (ASR) e Teste de Exercício de 4 segundos (T4s). RESULTADOS: Indivíduos saudáveis apresentaram maior modulação vagal nos três métodos (p < 0,05). No grupo saudável houve correlação (p < 0,05) entre os resultados da VFC (pNN50 e DPNN) e da ASR, mas não houve correlação entre o T4s e os outros dois métodos estudados. No grupo com coronariopatia houve correlação entre os resultados da VFC (pNN50, DPNN, RMSSD, AF ms² e AF u.n.) e da ASR. Em adição, houve correlação entre o T4s e a ASR. Por fim, os métodos ASR e T4s apresentaram tamanho do efeito mais preciso e melhor acurácia (p < 0,05) comparados à VFC. CONCLUSÃO: A VFC e a ASR geraram resultados parcialmente redundantes em indivíduos saudáveis e em pacientes com coronariopatia, enquanto o T4s gerou resultados complementares a VFC e ASR em indivíduos saudáveis. Além disso, os métodos ASR e T4s foram mais precisos para discriminar a modulação vagal cardíaca entre indivíduos saudáveis e pacientes com coronariopatia comparados à VFC.

BACKGROUND: Several methods have been used to assess cardiac vagal modulation, but there are gaps regarding the association and accuracy of these methods. OBJECTIVE: To investigate the association between three valid, reproducible and commonly methods used to assess cardiac vagal modulation and compare their accuracies. METHODS: Thirty healthy men (23 ± 4 years) and 15 men with coronary artery disease (61 ± 10 years) were evaluated in counterbalanced design by Heart Rate Variability (HRV; variables: the time domain = pNN50, SDNN and RMSSD, the frequency domain HF = ms² and HF n.u.), Respiratory Sinus Arrhythmia (RSA) and 4-second Exercise Test (T4s). Thirty healthy men (23 ± 4 years) and 15 men with coronary artery disease (61 ± 10 years) were evaluated in counterbalanced order by Heart Rate Variability (HRV; variables: the time domain = pNN50, SDNN and RMSSD, the frequency domain HF = ms² and HF n.u.), Respiratory Sinus Arrhythmia (RSA) and 4-second Exercise Test (T4s). RESULTS: Healthy subjects had higher vagal modulation by the three methods (p <0.05). There was a correlation in the healthy group (p <0.05) between the results of HRV (SDNN and pNN50 and RSA, but there was no correlation between the T4s and the other two methods. In the group with coronary artery disease, there was a correlation between the results of HRV (pNN50, SDNN, RMSSD, HF ms² and HF n.u.) and RSA. In addition, there was a correlation between the RSA and T4s. Finally, the T4s and RSA methods presented more accurate effect size and better accuracy (p <0.05), when compared to the HRV. CONCLUSION: HRV and RSA generated partially redundant results in healthy subjects and in patients with coronary artery disease, while the T4s generated results that were complementary to HRV and RSA in healthy subjects. In addition, RSA and T4s methods were more accurate when discriminating cardiac vagal modulation between healthy subjects and patients with coronary artery disease, when compared to HRV.

Efeito agudo da intensidade do exercício de força na modulação autonômica cardíaca pós-exercício / Acute effect of resistance exercise intensity in cardiac autonomic modulation after exercise / Efecto agudo de intensidad del ejercicio de fuerza en la modulación autónoma del corazón post-ejercicio

FUNDAMENTO: O balanço simpatovagal cardíaco se altera após o exercício de força. Contudo, o impacto das características do treinamento de força nessa resposta ainda não está claro. OBJETIVO: Analisar o efeito agudo da intensidade do exercício de força para tronco e membros superiores na modulação autonômica cardíaca pós-exercício. MÉTODOS: Quinze homens jovens realizaram três sessões experimentais em ordem aleatória: controle (C), exercício de força com 50 por cento de 1-RM (E50 por cento) e exercício de força com 70 por cento de 1-RM (E70 por cento). As sessões incluíram 05 exercícios para tronco e membro superior, realizados em três séries de 12, 9 e 6 repetições, respectivamente. Antes e aos 20 e 50 minutos após as intervenções, a frequência cardíaca foi medida para posterior análise espectral da sua variabilidade. RESULTADOS: Em comparação aos valores anteriores à intervenção, o intervalo RR e a banda de alta frequência (AF) aumentaram (maiores alterações: + 112 ± 83 ms; +10 ± 11 un, respectivamente, p < 0,01), enquanto que a banda de baixa frequência (BF) e a razão BF/AF diminuíram (maiores alterações: -10 ± 11 un; -2 ± 2, respectivamente, p < 0,01) após a sessão C. Nenhuma dessas variáveis se alterou significantemente após a sessão E50 por cento (p > 0,05). Em comparação aos valores pré-exercício, o intervalo RR e a banda AF diminuíram (maiores alterações: -69 ± 105 ms; -13 ± 14 un, respectivamente, p < 0,01), enquanto que a banda BF e a razão BF/AF aumentaram (maiores alterações: -13 ± 14 un, +13 ± 14 un e +3 ± 3 un, respectivamente, p < 0,01) após a E70 por cento. CONCLUSÃO: A maior intensidade de exercício de força para tronco e membros superiores promoveu, agudamente, maior aumento do balanço simpatovagal cardíaco pós-exercício.

BACKGROUND: Cardiac sympathovagal balance is altered after resistance exercise. However, the impact of the characteristics of resistance training in this response remains unclear. OBJECTIVE: Analyze the acute effect of resistance exercise intensity for trunk and upper limbs in cardiac autonomic modulation after exercise. METHODS: Fifteen young men performed three experimental sessions in random order: control (C), resistance exercise with 50 percent of 1-RM (E50 percent) and resistance exercise with 70 percent of 1-RM (E70 percent). The sessions included 05 exercises for the trunk and upper limbs performed in three sets of 12, 9 and 6 repetitions, respectively. Before and at 20 and 50 minutes after the interventions, the heart rate was measured for spectral analysis of variability. RESULTS: In comparison to the values before the intervention, the RR interval and the band of high frequency (HF) increased (major changes: + 112 ± 83 ms; +10 ± 11 un, respectively, p < 0.01), while the low frequency band (LF) and LF/HF ratio decreased (major changes: -10 ± 11 pc; -2 ± 2, respectively, p < 0.01) after the session C. None of these variables changed significantly after the E50 percent session (p > 0.05). Compared to pre-exercise values, the RR interval and the HF band decreased (major changes: -69 ± 105 ms; -13 ± 14 un, respectively, p <0.01), while the LF band and the LF/HF ratio increased (major changes: -13 ± 14 un, 13 ± 3 14 ± 3 and un, respectively, p <0.01) after E70 percent. CONCLUSION: The higher intensity of resistance exercise for trunk and upper limbs promoted, in an acute manner, greater increase in cardiac sympathovagal balance after exercise.

FUNDAMENTO: El balance simpatovogal cardíaco se altera después del ejercicio de fuerza. Sin embargo, el impacto de las características del entrenamiento de fuerza en esta respuesta no está claro. OBJETIVO: Analizar el efecto agudo de intensidad del ejercicio de fuerza para el tronco y miembros en la modulación autonómica del corazón post-ejercicio. MÉTODOS: Quince hombres jóvenes realizaron tres sesiones experimentales en orden aleatorio: control (C), ejercicio de fuerza con el 50 por ciento de 1-RM (E50 por ciento) y ejercicio de fuerza con el 70 por ciento de 1-RM (E70 por ciento). Las sesiones incluyeron 05 ejercicios para tronco y miembro superior, realizados en tres series de 12, 9 y 6 repeticiones, respectivamente. Antes y a los 20 y 50 minutos después de las intervenciones, la frecuencia cardiaca se midió para un análisis espectral posterior de su variabilidad. RESULTADOS: En comparación con los valores anteriores de la intervención, el intervalo RR y la banda de alta frecuencia (AF) se incrementó (cambios importantes: + 112 ± 83 ms; +10 ± 11 un, respectivamente, p < 0,01), mientras que la banda de baja frecuencia (BF) y la razón BF/AF disminuyeron (cambios importantes: -10 ± 11 un; -2 ± 2, respectivamente, p < 0,01) tras la sesión C. Ninguna de estas variables se alteró significantemente tras la sesión E50 por ciento (p > 0,05). En comparación a los valores pre ejercicio, el intervalo RR y la banda AF disminuyeron (cambios importantes: -69 ± 105 ms; -13 ± 14 un, respectivamente, p < 0,01), mientras que la banda BF y la razón BF/AF aumentaron (cambios importantes: -13 ± 14 un, +13 ± 14 un y +3 ± 3 un, respectivamente, p < 0,01) tras la E70 por ciento. CONCLUSIÓN: La mayor intensidad de ejercicio de fuerza para el tronco y miembros superiores produjo de modo agudo, un mayor incremento simpatovagal cardíaco post-ejercicio.

Ovariectomy does not affect the cardiac sympathovagal balance of female SHR but estradiol does

The low incidence of cardiovascular diseases, including hypertension, in premenopausal women has led to the conclusion that ovarian hormones may have a protective effect on the cardiovascular system. We evaluated the effects of ovariectomy and/or estradiol on sympathovagal balance and heart rate variability (HRV) in female spontaneously hypertensive rats (SHR) with tachycardia and compared them to Wistar rats (12 weeks old; N = 8-12). Ovariectomy (OVX) and/or estradiol (10 µg/kg) did not affect basal arterial pressure in either rat strain, but estradiol increased basal heart rate (HR) in OVX SHR (454 ± 18 vs 377 ± 9 bpm). HR changes elicited by methylatropine and propranolol were used to evaluate the sympathovagal balance. Ovariectomy did not affect the cardiac sympathovagal balance of any group, while estradiol increased sympathetic tone in OVX SHR (120 ± 8 vs 56 ± 10 bpm) and sham-operated Wistar rats (57 ± 7 vs 28 ± 4 bpm), and decreased the parasympathetic tone only in OVX SHR (26 ± 7 vs 37 ± 5 bpm). HRV was studied in the frequency domain (Fast Fourier Transformation). Spectra of HR series were examined at low frequency (LF: 0.2-0.75 Hz) and high frequency (HF: 0.75-3 Hz) bands. The power of LF, as well as the LF/HF ratio, was not affected by ovariectomy, but estradiol increased both LF (29 ± 4 vs 18 ± 3 nu in Wistar sham-operated, 26 ± 5 vs 15 ± 3 nu in Wistar OVX, 50 ± 3 vs 38 ± 4 nu in SHR sham-operated, and 51 ± 3 vs 42 ± 3 nu in SHR OVX) and LF/HF (0.48 ± 0.08 vs 0.23 ± 0.03 nu in Wistar sham-operated, 0.41 ± 0.14 vs 0.19 ± 0.05 nu in Wistar OVX, 0.98 ± 0.11 vs 0.63 ± 0.11 nu in SHR sham-operated, and 1.10 ± 0.11 vs 0.78 ± 0.1 nu in SHR OVX). Thus, we suggest that ovariectomy did not affect the cardiac sympathovagal balance of SHR or Wistar rats, while estradiol increased the sympathetic modulation of HR.

Normotensos com resposta pressórica exagerada ao exercício possuem tônus vagal cardíaco aumentado / Normotensive individuals with exaggerated exercise blood pressure response have increased cardiac vagal tone

FUNDAMENTO: Valores exagerados da pressão arterial sistólica (PAS) durante um teste cardiopulmonar de exercício máximo (TCPE) são classicamente considerados como inapropriados e associados a um maior risco para desenvolvimento de doenças cardiovasculares. Sabe-se que o sistema nervoso autônomo modula a PA no exercício. Contudo, não está claramente estabelecido o comportamento do tônus vagal cardíaco (TVC) em indivíduos saudáveis com uma resposta pressórica exagerada no TCPE. OBJETIVO: Analisar o comportamento do TVC em homens adultos saudáveis que apresentam uma resposta pressórica exagerada no TCPE. MÉTODOS: De 2.505 casos avaliados entre 2002-2009, foram identificados criteriosamente 154 casos de homens, entre 20-50 anos de idade, saudáveis e normotensos. A avaliação incluía exame clínico, medidas antropométricas, testes de exercício de 4 segundos (tônus vagal cardíaco) e TCPE realizado em cicloergômetro, com medidas de pressão arterial a cada minuto pelo método auscultatório. Baseado no valor máximo de PAS obtido no TCPE, a amostra foi dividida em tercis, comparando-se o TVC, a carga máxima e o VO2 máximo. RESULTADOS: Os valores de TVC diferiram entre os indivíduos que se apresentavam nos tercis inferior e superior para a resposta da PAS ao TCPE, respectivamente, 1,57 ± 0,03 e 1,65 ± 0,04 (média ± erro padrão da média) (p = 0,014). Os dois tercis também diferiam quanto ao VO2 máximo (40,7 ± 1,3 vs 46,4 ± 1,3 ml/kg-1.min-1; p = 0,013) e a carga máxima (206 ± 6,3 vs 275 ± 8,7 watts; p < 0,001). CONCLUSÃO: Uma resposta pressórica exagerada durante o TCPE em homens adultos saudáveis é acompanhada de indicadores de bom prognóstico clínico, incluindo níveis mais altos de condição aeróbica e de tônus vagal cardíaco.

BACKGROUND: Exaggerated systolic blood pressure (SBP) levels during a maximal cardiopulmonary exercise test (CPET) are classically considered as inappropriate and associated with a higher risk for the development of cardiovascular diseases. It is known that the autonomic nervous system modulates the BP during exercise. However, the behavior of the cardiac vagal tone (CVT) has not been fully established in healthy individuals with an exaggerated BP response to CPET. OBJECTIVE: To analyze the behavior of the CVT in healthy adult males presenting an exaggerated BP response to CPET. METHODS: Of the 2,505 cases evaluated between 2002-2009, 154 cases were thoroughly identified, consisting of healthy male normotensive subjects aged 20-50 years. The evaluation included clinical assessment, anthropometric measurements, 4-second exercise test (cardiac vagal tone) and cardiopulmonary exercise test (CPET) performed in a cycle-ergometer, with BP measurements being taken every minute through auscultation. Based on the maximum SBP value obtained at the CPET, the sample was divided in tertiles, comparing CVT, maximum workload and VO2 max. RESULTS: The CVT results differed between individuals in the lower tertile and upper tertile for the SBP response to the CPET, respectively: 1.57 ± 0.03 and 1.65 ± 0.04 (mean ± standard error of mean) (p = 0.014). The two tertiles also differed regarding the VO2 max (40.7 ± 1.3 vs 46.4 ± 1.3 ml/kg-1.min-1; p = 0.013) and the maximum workload (206 ± 6.3 vs 275 ± 8.7 watts; p < 0.001). CONCLUSIOn: An increased BP response during the CPET in healthy adult males is accompanied by indicators of good clinical prognosis, including higher levels of aerobic fitness and cardiac vagal tone.

Polar S810 como recurso alternativo ao eletrocardiograma no teste de exercício de 4 segundos / Polar S810 as an alternative resource to the use of the electrocardiogram in the 4-second exercise test

FUNDAMENTO: O teste de exercício de 4 segundos (T4s) avalia o tônus vagal cardíaco durante o transiente inicial da frequência cardíaca (FC), em exercício dinâmico súbito, por meio da identificação do índice vagal cardíaco (IVC) obtido a partir do eletrocardiograma (ECG). OBJETIVO: Testar a utilização do monitor de frequência cardíaca (MFC) Polar S810 como recurso alternativo ao ECG na aplicação do T4s. MÉTODOS: Neste trabalho, 49 indivíduos do sexo masculino (25 ± 20 anos, 176 ± 12 cm, 74 ± 6 kg) realizaram o T4s. Os intervalos RR foram registrados simultaneamente por ECG e MFC. Calcularam-se média e desvio padrão do último intervalo RR do período pré-exercício ou o primeiro do período de exercício, aquele que for mais longo (RRB), do mais curto intervalo RR do período de exercício (RRC) e do IVC obtidos por ECG e MFC. Utilizou-se o teste t de Student para amostras dependentes (p < 0,05) para testar a significância das diferenças entre as médias. Para identificar a concordância entre o ECG e o MFC, utilizou-se a regressão linear, com cálculo do coeficiente de correlação de Pearson e a estratégia proposta por Bland e Altman. RESULTADOS: A regressão linear apresentou r² de 0,9999 para o RRB, 0,9997 para o RRC e 0,9996 para o IVC. A estratégia de Bland e Altman apresentou desvio padrão de 0,92 ms para o RRB, 0,86 ms para o RRC e 0,002 para o IVC. CONCLUSÃO: O MFC Polar S810 se mostrou eficiente na aplicação do T4s quando comparado ao ECG.

BACKGROUND: The 4-second exercise test (T4s) evaluates the cardiac vagal tone during the initial heart rate (HR) transient at sudden dynamic exercise, through the identification of the cardiac vagal index (CVI) obtained from the electrocardiogram (ECG). OBJECTIVE: To evaluate the use of the Polar S810 heart rate monitor (HRM) as an alternative resource to the use of the electrocardiogram in the 4-second exercise test. METHODS: In this study, 49 male individuals (25 ± 20 years, 176 ±12 cm, 74 ± 6 kg) underwent the 4-second exercise test. The RR intervals were recorded simultaneously by ECG and HRM. We calculated the mean and the standard deviation of the last RR interval of the pre-exercise period, or of the first RR interval of the exercise period, whichever was longer (RRB), of the shortest RR interval of the exercise period (RRC), and of the CVI obtained by ECG and HRM. We used the Student t-test for dependent samples (p < 0.05) to test the significance of the differences between means. To identify the correlation between the ECG and the HRM, we used the linear regression to calculate the Pearson's correlation coefficient and the strategy proposed by Bland and Altman. RESULTS: Linear regression showed r² of 0.9999 for RRB, 0.9997 for RRC, and 0.9996 for CVI. Bland e Altman strategy presented standard deviation of 0.92 ms for RRB, 0.86 ms for RRC, and 0.002 for CVI. CONCLUSION: Polar S810 HRM was more efficient in the application of T4s compared to the ECG.

Schwannoma in Head and Neck: Preoperative Imaging Study and Intracapsular Enucleation for Functional Nerve Preservation

PURPOSE: In treating schwannoma patients, it is critical to determine the origin of the tumor to preserve nerve function. We evaluated the validity of preoperative imaging studies in distinguishing the neurological origin of the schwannomas of the head and neck, and the efficacy of intracapsular enucleation in preserving nerve function. MATERIALS AND METHODS: In 7 cases of schwannomas in the head and neck region, we predicted whether the tumor originated from the vagus nerve or the cervical sympathetic chain through imaging studies including computed tomography (CT) and magnetic resonance imaging (MRI). All patients were performed intracapsular enucleation, and the function of the vagus nerve and the sympathetic nerve was evaluated preoperatively and postoperatively. RESULTS: Preoperative imaging studies showed 6 cases where the tumor was located between the carotid artery and the internal jugular vein, and 1 case where the tumor was located posteriorly, displacing the carotid artery and the internal jugular vein anteriorly. At the time of operation, we confirmed schwannoma originating from the vagus nerve on the first 6 cases, and schwannoma originating from the sympathetic nervous system on the last case. All patients went through successful intracapsular enucleation, and of the seven schwannoma cases, 6 patients maintained normal postoperative neurological function (85.7%). CONCLUSION: Preoperative imaging studies offer valuable information regarding the location and origination of the tumor, and intracapsular enucleation helped us to preserve the nerve function.

Training-related changes in the R-R interval at the onset of passive movements in humans

The aim of the present study was to determine whether training-related alterations in muscle mechanoreflex activation affect cardiac vagal withdrawal at the onset of exercise. Eighteen male volunteers divided into 9 controls (26 ± 1.9 years) and 9 racket players (25 ± 1.9 years) performed 10 s of voluntary and passive movement characterized by the wrist flexion of their dominant and non-dominant limbs. The respiratory cycle was divided into four phases and the phase 4 R-R interval was measured before and immediately following the initiation of either voluntary or passive movement. At the onset of voluntary exercise, the decrease in R-R interval was similar between dominant and non-dominant forearms in both controls (166 ± 20 vs 180 ± 34 ms, respectively; P > 0.05) and racket players (202 ± 29 vs 201 ± 31 ms, respectively; P > 0.05). Following passive movement, the non-dominant forearm of racket players elicited greater changes than the dominant forearm (129 ± 30 vs 77 ± 17 ms; P < 0.05), as well as both the dominant (54 ± 20 ms; P < 0.05) and non-dominant (59 ± 14 ms; P < 0.05) forearms of control subjects. In contrast, changes in R-R interval elicited by the racket players' dominant forearm were similar to that observed in the control group, indicating that changes in R-R interval at the onset of passive exercise were not attenuated in the dominant forearm of racket players. In summary, cardiac vagal withdrawal induced by muscle mechanoreflex stimulation is well-maintained, despite long-term exposure to training.

Avaliando a atividade vagal cardíaca na eletrocardiografia convencional / Evaluating cardiac vagal activity on a conventional electrocardiogram

OBJETIVO: Determinar a viabilidade da utilização de traçado convencional de eletrocardiografia (ECG) para avaliação da atividade vagal cardíaca (AVC). MÉTODOS: Foram analisados, retrospectivamente, 1.395 indivíduos (995 homens), na faixa de idade de 46 + 17,2 anos (média ± desvio padrão), com traçados de ECG convencional para medida do Delta RR, que representa a diferença, em ms, entre o maior e o menor intervalo RR, e com resultados da avaliação autonômica parassimpática, o teste de exercício de quatro segundos (T4s), que quantifica a AVC por meio do índice vagal cardíaco (IVC). Foram obtidas curvas ROC para determinar os valores de Delta RR com melhor relação entre sensibilidade e especificidade para os pontos de corte de baixa e alta AVC, respectivamente, de 1,20 e 1,95. RESULTADOS: Os valores de delta RR correlacionaram-se significativamente com os de IVC (r = 0,40; p < 0,001). Foram identificados < 60 ms e > 120 ms como os melhores pontos de corte para baixa e alta AVC, com sensibilidade de 75 por cento e 57 por cento, especificidade de 62 por cento e 79 por cento e áreas das curvas ROC de 0,76 e 0,74, respectivamente. CONCLUSÃO: A medida visual do delta RR em um traçado de ECG parece ser válida para a avaliação clínica preliminar e rápida da AVC, podendo ser útil em consultórios, emergências ou situações nas quais o uso de métodos mais sofisticados de avaliação autonômica não seja viável, oportuno ou conveniente.

OBJECTIVE: To determine the viability of using a conventional electrocardiogram (ECG) tracing for assessment of CVA. METHODS: We retrospectively analyzed 1395 individuals (995 males), aged 46 ± 17.2 years (mean ± standard deviation) with conventional ECG tracings to measure the delta RR (which represents the difference in milliseconds (ms) between the greatest and smallest RR interval) and results of a second autonomic parasympathetic evaluation, the 4-second exercise test (T4s), that quantifies CVA by the cardiac vagal index (CVI). ROC curves were obtained to determine the values of Delta RR for a closer correlation with sensitivity and specificity for 1.20 and 1.95 ms, the low and high CVA cutoff points, respectively. RESULTS: The delta RR levels correlated significantly with those of the CVI (r=0.40; p<0.001). We identified < 60 and > 120 ms as the best cutoff points for low and high CVA. Sensitivity was 75 percent and 57 percent, specificity was 62 percent and 79 percent, and the areas of the ROC curves were 0.76 and 0.74, respectively. CONCLUSION: The visual measurement of delta RR on an ECG tracing seems to be a valid quick preliminary clinical evaluation of CVA and can be useful in medical offices, emergency units, or situations in which the use of more sophisticated methods may not be feasible, appropriate, or convenient.

Swimming training increases cardiac vagal activity and induces cardiac hypertrophy in rats

The effect of swimming training (ST) on vagal and sympathetic cardiac effects was investigated in sedentary (S, N = 12) and trained (T, N = 12) male Wistar rats (200-220 g). ST consisted of 60-min swimming sessions 5 days/week for 8 weeks, with a 5 percent body weight load attached to the tail. The effect of the autonomic nervous system in generating training-induced resting bradycardia (RB) was examined indirectly after cardiac muscarinic and adrenergic receptor blockade. Cardiac hypertrophy was evaluated by cardiac weight and myocyte morphometry. Plasma catecholamine concentrations and citrate synthase activity in soleus muscle were also determined in both groups. Resting heart rate was significantly reduced in T rats (355 ± 16 vs 330 ± 20 bpm). RB was associated with a significantly increased cardiac vagal effect in T rats (103 ± 25 vs 158 ± 40 bpm), since the sympathetic cardiac effect and intrinsic heart rate were similar for the two groups. Likewise, no significant difference was observed for plasma catecholamine concentrations between S and T rats. In T rats, left ventricle weight (13 percent) and myocyte dimension (21 percent) were significantly increased, suggesting cardiac hypertrophy. Skeletal muscle citrate synthase activity was significantly increased by 52 percent in T rats, indicating endurance conditioning. These data suggest that RB induced by ST is mainly mediated parasympathetically and differs from other training modes, like running, that seems to mainly decrease intrinsic heart rate in rats. The increased cardiac vagal activity associated with ST is of clinical relevance, since both are related to increased life expectancy and prevention of cardiac events.

Brainstem origin of duodenal vagal preganglionic parasympathetic neurons. A WGA-HRP study in the ferret (Mustela Putorius Furo), a human model

The projections of vagal brainstem neurons to the duodenal segment of the gastrointestinal tract were studied in the ferret using the WGA-HRP neurohistochemical technique. Fourteen adult ferrets with weights ranging from 800 gm to 1500 gm were used for the study. The muscular wall of the duodenum of six ferrets was injected with 0.1 ml of 5 WGA-HRP in 0.5 M sodium chloride. The eight remaining ferrets were used as controls. Two of these had injections of 0.1 ml normal saline into the muscular wall of the duodenum. The second set of two ferrets was injected with 0.1 ml of 5 WGA-HRP in buffer after bilateral truncal vagotomy. The third set of two ferrets received intraperitoneal injection of 0.1 ml of 5 WGA-HRP while, in the last set, the tracer was injected into the hepatic portal vein. Following the injections, the ferrets were allowed to survive for 48-72 hours after which each ferret was perfused transcardially first with normal saline followed by a fixative containing 1 paraformaldehyde and 1.25 glutaraldehyde in 0.1 M phosphate buffer, pH 7.4 at room temperature and finally with 10 buffered sucrose at 4 degrees C. Transverse serial frozen sections of the brainstem were then taken and processed for WGA-HRP neurohistochemistry and were analyzed under light and dark-field illuminations. The analyses of the sections taken from the six ferrets injected with WGA-HRP revealed neurons labelled with the tracer in the dorsal motor nucleus of the vagus nerve (DMNV). Sections taken from the control ferrets did not reveal any WGA-HRP labelled neurons in the brainstem

Effect of experimental diabetes and vagotomy on gastric emptying in rats.

The present study was performed to evaluate the rate of whole stomach emptying (WSE) in streptozotocin (STZ) induced rat model of diabetes mellitus by assessing the effect of bilateral gastric vagotomy in control as well as in experimental animals. Our results revealed that delayed emptying of solid foods by the stomach is demonstrated within 5 days of induction of diabetes in rats. After bilateral vagotomy, the later stages of WSE slowed down because of the diabetic state, most probably due to the direct effect of diabetes on the gastric antrum.

Airway rapidly adapting receptors--sensors of pulmonary extra-vascular fluid volume.

The factors regulating transfer of fluid into the pulmonary extra-vascular space and the role of sensory receptors of the airways in detecting such fluid fluxes are reviewed and discussed. It is concluded that the rapidly adapting receptors (RARs) located in apposition to bronchial venules are highly sensitive to changes in the pulmonary extra-vascular space produced by mild elevations of left atrial pressure, plasmapheresis and pulmonary lymphatic obstruction and their activation causes respiratory stimulation, an increase in tracheal tone and cough. There is a reflex diuresis also following the stimulation of these receptors by pulmonary lymphatic obstruction. It is proposed that the RARs function as a sensory component of the pulmonary defence mechanisms which preserve the 'milieu interior'.

Refractory epilepsy: diagnosis and management.

Persistence of seizures despite appropriate medical treatment is called refractory epilepsy. Persistent seizures have enormous psychosocial, behavioural and cognitive effects in addition to effects on mortality. Almost 2,40,000 to 3,20,000 patients of refractory epilepsy in India are potential candidates for epilepsy surgery. Causes of refractory or intractable epilepsy are inadequate anti-epileptic treatment, difficulty in treating some epileptic syndromes and difficulty in controlling seizures due to structural brain diseases. Careful evaluation of historical details, especially based on an eyewitness account is the most important aspect in establishing the diagnosis of epilepsy. Raised serum prolactin level helps in differentiating convulsive seizures from non-epileptic convulsions. Video electroencephalographic monitoring is proved effective and efficient mean to establish the rightful diagnosis. Recent developments in neuro-imaging have revolutionised the diagnosis of underlying pathology in patients with refractory epilepsies. Patients with refractory epilepsy should be referred to a specialised epilepsy centre where facilities for epilepsy surgery are available. When medical therapy fails, other options are helpful like use of newer anti-epileptic drugs, vagus nerve stimulation or consideration of epilepsy surgery.

Fever induction pathways: evidence from responses to systemic or local cytokine formation

The immune and central nervous systems are functionally connected and interacting. The concept that the immune signaling to the brain which induces fever during infection and inflammation is mediated by circulating cytokines has been traditionally accepted. Administration of bacterial lipopolysaccharide (LPS) induces the appearance of a so-termed "cytokine cascade" in the circulation more or less concomitantly to the developing febrile response. Also, LPS-like fever can be induced by systemic administration of key cytokines (IL-1ß, TNF-alpha, and others). However, anti-cytokine strategies against IL-1ß or TNF-alpha along with systemic injections of LPS frequently lead to attenuation of the later stages of the febrile response but not of the initial phase of fever, indicating that cytokines are rather involved in the maintenance than in the early induction of fever. Within the last years experimental evidence has accumulated indicating the existence of neural transport pathways of immune signals to the brain. Because subdiaphragmatic vagotomy prevents or attenuates fever in response to intraperitoneal or intravenous injections of LPS, a role for vagal afferent nerve fibers in fever induction has been proposed. Also other sensory nerves may participate in the manifestation of febrile responses under certain experimental conditions. Thus, injection of a small dose of LPS into an artificial subcutaneous chamber results in fever and formation of cytokines within the inflamed tissue around the site of injection. This febrile response can be blocked in part by injection of a local anesthetic into the subcutaneous chamber, indicating a participation of cutaneous afferent nerve signals in the manifestation of fever in this model. In conclusion, humoral signals and an inflammatory stimulation of afferent sensory nerves can participate in the generation and maintenance of a febrile response

Subdiaphragmatic vagotomy induces NADPH diaphorase in the rat dorsal motor nucleus of the vagus

Axotomy of the vagal motor neurons by cervical vagotomy induces NADPH diaphorase staining due to increased nitric oxide synthase expression in both the rat dorsal motor nucleus and nucleus ambiguous; furthermore, cerical vagotomy leads to cell death of the dorsal motor nucleus cells. Subdiaphragmatic vagotomy axotomizes the vagal motor cells further from the brainstem than cervical vagotomy, and cuts the fibers running only to the abdominal viscera. Here we report that subdiaphragmatic vagotomy is sufficient to induce NADPH diaphorase staining in the dorsal motor nucleus but does not induce staining in the nucleus ambiguus. Because the neurons of the dorsal motor nucleus do not undergo cell death after subdiaphragmatic vagotomy and are able to re-enervate the gut, the increased nitric oxide synthase expression after distal axotomy may be related more to regeneration than degeneration.

Recurrent Asystoles Associated with Vasovagal Reaction during Venipuncture

A 17-year-old high school student presented with a history of habitual faintings. On 24-hour Holter monitoring, cardiac asystoles were recorded, the longest lasting approximately 7 or 8 seconds during venipuncture procedures. The asystole associated with venipuncture demonstrated the cardioinhibitory effects of vasovagal reaction with blood-injury phobia. He also had a positive response during head-up tilt test showing hypotension and relative bradycardia after intravenous isoproterenol injection. After administration of oral beta blocker, he did not show further or recurrent cardiac asystole during blood injury procedure on electrocardiographic examination. Venipuncture is the most common invasive medical procedure performed in hospital settings. While venipuncture is considered to be reasonably safe, serious complication may occur even when only a small volume of blood is withdrawn. Therefore, medical personnel should be prepared to provide appropriate care.

Posible función del núcleo motor dorsal del vago sobre el trabajo de parto en la rata / Possible function of the dorsal motor nucleus of the vagus nerve on parturition labor in the rat

La lesión electrolítica unilateral o bilateral del núcleo motor dorsal del vago (NMDV) en la rata grávida produjo distocia, la que consistió en la supresión del trabajo de parto o bien, en el retraso del mismo (5-34 horas). Por lo que respecta a la salud de los productos, en el primer caso, todos murieron en el útero, mientras que en el segundo, la mortalidad varió del 37 al 100 por ciento. En contraste, el parto en las ratas embarazadas con falsa lesión de NMDV ocurrió en la fecha esperada o bien, con un ligero retraso de 2 a 4 horas pero, en todos los casos, los productos nacieron en buenas condiciones de salud. Finalmente, los resultados se discuten en un modelo del control neuroendocrino del parto en la rata y sugieren que la lesión del NMDV en la rata grávida produce distocia, ésta puede explicarse de manera tentativa por la falla de la función integradora del núcleo paraventricular y/o del núcleo supraquiasmático, con la consiguiente disfunción de los sistemas eferentes ocitocinérgicos y/o el aumento de la susceptibilidad farmacológica principalmente del cérvix a la ocitocina y a la acetilcolina