O sistema visual exerce importante papel para o reconhecimento do ambiente externo e para estabelecer relações entre objetos, tempo e espaço. Além disso, ele está relacionado com o controle e o desempenho motor. O objetivo deste estudo foi verificar se a privação de luz ambiente alteraria o desempenho e as respostas fisiológicas e psicológicas durante dois modelos de exercício, um fechado e um aberto. Onze ciclistas formaram o grupo de exercício fechado (GEF) e completaram um teste de 20 km, enquanto doze indivíduos ativos formaram o grupo de exercício aberto (GEA) e executaram um teste de potência constante até a exaustão (TWC). Após teste incremental máximo, GEF e GEA realizaram exercício na presença (controle) ou privação (experimental) de luz ambiente, em ordem balanceada. Respostas de desempenho, VE, VO2, VCO2 RER, FC, eletromiografia do músculo vato lateral (EMG), percepção subjetiva de esforço (PSE) e pensamento associado ao exercício (PAE) foram obtidas durante, e no ponto final do exercício, em ambas as condições. O tempo total de exercício indicou a resposta de desempenho em GEF e GEA. As respostas das variáveis fisiológicas e psicológicas foram analisadas durante a realização, ou no ponto final do exercício. A média das respostas geradas durante os 20 km no GEF, e as respostas obtidas no mesmo tempo absoluto do TWC no GEA, pareado pelo menor tempo de exaustão atingido no teste, indicaram as respostas durante a execução do exercício. As respostas obtidas nos 5 segundos finais de cada exercício indicaram as respostas do ponto final do GEF e GEA. A taxa de incremento na PSE foi calculada em GEF e GEA, e o erro de predição da distância real percorrida no teste de 20 km foi obtido no GEF. No GEF, não houve efeito da privação de luz sobre o tempo para completar o teste de 20 km, porém a privação de luz gerou menores respostas (P< 0,01) na VE, VO2, VCO2, EMG e PAE, quando comparada ao controle. No ponto final do exercício, nenhuma diferença foi verificada entre as condições. A privação de luz não alterou a taxa de elevação da PSE ou o erro de predição da distância percorrida. No GEA a privação de luz ambiente reduziu o tempo de exaustão (P< 0,05) no TWC e aumentou a resposta do VO2 e EMG (P< 0,05). Entretanto, não foi observado efeito da privação de luz na VE, VCO2 e FC. No ponto final do exercício observou-se menor EMG com a privação de luz (P< 0,03), mas nenhuma diferença nas demais variáveis foi observada. Maior taxa de elevação na PSE foi observada em ambiente privado de luz. Os resultados do presente estudo podem ser interpretados de acordo com a existência de um \"relógio biológico interno\" que calcula a duração tolerável do exercício de acordo com a aproximação ao ponto final do exercício, sugerindo que os efeitos da privação de luz sobre o desempenho possam depender da presença de um ponto final previamente conhecido / The visual system plays an important role for the environment recognition as well as to set objects, time and space relationships. Furthermore, the visual system is related to the motor learning and performance. The aim of this study was to verify if light deprivation environment would alter performance, and physiological and psychological responses to different exercise modes, closed- and open-loop exercises. Eleven cyclists were the closed-loop exercise group (CLE) and performed a 20 km time trial, while twelve active individuals were the open-loop exercise group (OLE) and cycled to exhaustion during a constant workload exercise. After maximal incremental test CLE and OLE groups performed exercise in a control and experimental condition (i.e. under light deprivation), in a counterbalanced fashion. Performance responses and responses of VE, VO2, VCO2 RER, HR, eletromyography of the vastus lateralis muscle (EMG), ratings of perceived exertion (RPE) and associative thoughts to exercise (ATE) were obtained during exercise and at the exercise endpoint in both the conditions. Time of exercise indicated performance responses in CLE and OLE groups. Physiological and psychological responses were analyzed either during or at the exercise endpoint. Mean responses throughout the 20 km cycling time trial and responses obtained at absolute matched time of exercise, corresponding to the shortest time to exhaustion provided responses along the exercise in CLE and OLE groups, respectively. Responses obtained during the last 5 seconds of the exercises provided responses at the exercise endpoint in both CLE and OLE groups. The rate of increase in RPE was calculated in CLE and OLE groups, and the predictive error of the distance was calculated in the CLE group. In CLE group no effect of light deprivation was observed in the time to complete the 20 km, although the lower response (P< 0.01) of VE, VO2, VCO2, EMG e ATE when compared to control condition. Neither difference was observed in variables at the exercise endpoint. Light deprivation had effect in neither rate of increase in RPE or predictive error of distance. Regarding OLE group the light deprivation decreased the time to exhaustion (P< 0.05) and increased VO2 and EMG (P< 0.05) responses. However, there was no light deprivation effect in VE, VCO2 and HR. Lower EMG was observed at the exercise endpoint in light deprivation condition (P< 0.05) than in control, but no difference was observed in the others. Greater rate of increase in RPE was detected (P< 0.05) in the light deprivation condition than in control. Results of the present study were interpreted according to a \"biological internal clock\" that calculates the tolerable exercise duraton based on the exercise endpoint approximation, suggesting that light deprivation effects on performance may depend on the presence of an exercise endpoint previously known

Mikroprozessorgesteuerte Implantate haben sich in zahlreichen Bereichen der Medizin etabliert. Physiologische, korpereigene Parameter werden erfasst, abgespeichert und konnen durch Telemetriesysteme weitergeleitet werden. Zusatzlich stehen Therapieoptionen zur Verfugung. Dazu zahlen Neurostimulatoren, welche im Bereich der Schmerztherapie und des fortgeschrittenen Morbus Parkinson erfolgreich angewendet werden ebenso wie Systeme zur Medikamentenapplikation. Beispielhaft hat sich die Entwicklung aktiver Implantate jedoch im Bereich der Herzschrittmacher- und Defibrillatortherapie vollzogen. Die vorliegende Arbeit beschaftigt sich mit der Erforschung physiologischer kardialer Parameter und ihrer Erfassung mit Hilfe von implantierbaren Sensoren. Dabei werden grundlegende technische Aspekte, die spezielle Sensorik zur Erfassung verschiedener Parameter und die Signalverarbeitung dargestellt. Es werden die bereits heute vielfaltigen Moglichkeiten implantierbarer kardialer Monitoringsysteme diskutiert. Neue Moglichkeiten wie das Monitoring ischamischer Ereignisse werden eroffnet. / Mikroprocessor controlled implantable systems are standard in many medical specialities. Physiological parameters can be recorded, stored and transfered via telemetry systems. In addition different therapeutic options are available: neurostimulation to treat patients with refractory pain and morbus parkinson, drug pumps for infusion of insulin etc.. Cardiac pacemakers and implantable cardioverter defibrillators were the driving force in the development of implantable sensors. We investigated different physiological cardiac parameters via implantable sensors. In this paper we discuss basic technical aspects, sensors, signal conditioning and signal analysis. The spectrum of available implantable sensors is shown. New options like the monitoring of transient myocardial ischemia are presented.

I ntrodução: A incidência de lesões venosas pós-implante transvenoso de dispositivos cardíacos eletrônicos implantáveis (DCEI) é elevada, sendo a disfunção ventricular e o uso prévio de marcapasso temporário (MPT) ipsilateral ao implante definitivo fatores de risco independentes para sua ocorrência. A utilidade de estratégias terapêuticas profiláticas para a prevenção dessa complicação ainda permanece controversa. O objetivo desse estudo clínico, randomizado e controlado foi avaliar o papel da anticoagulação oral na prevenção das lesões venosas pós-implante transvenoso de DCEI em pacientes de alto risco, analisando a influência na incidência das obstruções venosas, a segurança, a eficácia e as complicações do tratamento. Método: No período de Fevereiro/2004 a Setembro/2007 foram estudados 101 pacientes adultos submetidos ao primeiro implante transvenoso de DCEI, apresentando fração de ejeção do ventrículo esquerdo (FEVE) <=0,40 e/ou presença de MPT ipsilateral ao implante definitivo. Após o procedimento, os pacientes foram randomizados para o uso diário de placebo ou varfarina. Avaliações clínicas e laboratoriais foram realizadas periodicamente. A pesquisa de lesões venosas foi feita pela venografia por subtração digital, seis meses após o implante. A análise dos dados foi realizada segundo o princípio de \"intenção-de-tratar\". Na análise da associação das variáveis demográficas, clínicas e operatórias com a presença de lesões venosas empregou-se os testes Qui-quadrado, Exato de Fisher ou \"t\" de Student e o modelo de regressão logística foi utilizado para a identificação de fatores de risco. Resultados: As características basais foram similares nos dois grupos, não sendo encontradas diferenças significativas entre as variáveis demográficas, clínicas e operatórias. Durante o período de seguimento clínico, ocorreram seis óbitos, quatro relacionados com a progressão da insuficiência cardíaca e duas mortes súbitas. Do total de óbitos, quatro pacientes estavam alocados no Grupo Varfarina e dois no Placebo. Somente um paciente, do Grupo Varfarina, apresentou sangramento gastrintestinal, com necessidade de hospitalização e transfusão de hemoderivados. O valor médio do INR dos pacientes do Grupo Varfarina foi 2,3±0,7 enquanto que no Grupo Placebo foi 1,1±0,3, sendo que esta diferença manteve-se ao longo de todo o período de seguimento. O valor médio da hemoglobina e do hematócrito foi similar em ambos os grupos, sendo 13,9±1,6g/dL e 41,2±4,6%, no Grupo Placebo e 14,0±1,4g/dL e 41,9±3,7%, no Grupo Varfarina. Dos pacientes alocados no Grupo Varfarina, 17 (38,6%) apresentaram obstruções venosas, em comparação a 29 (60,4%) casos do Grupo Placebo, com redução absoluta do risco de 22% (RR= 0,63; IC 95%= 0,013 a 0,42). A comparação das características clínicas dos pacientes que apresentaram lesões venosas com as dos pacientes que não apresentaram mostrou que o uso de varfarina (P=0,037) esteve associado a uma menor incidência de lesões venosas e a presença da doença de Chagas (P= 0,051) esteve associada a uma maior incidência. Somente a ausência de anticoagulação oral foi identificada como fator de risco independente para a ocorrência das lesões venosas (OR= 2,424; IC 95% 1,048 - 5,606; P= 0,038). Conclusão: O uso profilático da anticoagulação mostrou-se seguro e reduziu significativamente a incidência de obstruções venosas pós-implante de DCEI nos pacientes de alto risco. / Introduction: The incidence of venous thrombosis after cardiac devices implantation is high. Ventricular dysfunction and previous transvenous temporary leads ipsilaterally to the permanent implantation are independent risk factors. The effect of prophylactic strategies to prevent these complications remains controversial. The aim of this clinical, randomized and controlled study was to evaluate the role of oral anticoagulant therapy in the prevention of these complications in high risk patients, analyzing the effect on the venous obstructions incidence, the safety, effectiveness and complications of this treatment. Method: Between February 2004 and September 2007, 101 adult patients submitted to first transvenous cardiac devices implantation, with left ventricular ejection fraction <=0.40 and/or previous transvenous temporary leads were evaluated. After device implantation, patients were randomly assigned to receive either placebo or warfarin. Periodical clinical and laboratorial evaluations were performed to anticoagulant management. Following the six-month period, every patient was submitted to a digital subtraction venography. Data analysis was performed according to the \"intention-to-treat\" principle. The association of demographic, clinical and procedure variables with the presence of venous lesions was analyzed by the Chi-square, Fisher\'s exact, or \"t\" Student tests, and logistic regression model was used to identify risk factors. Results: Baseline characteristics were similar in both groups and no significant difference was observed in demographic, clinical and procedure variables. During the follow-up period, six patients died, four related to heart failure progression and two of sudden death. Four of the patients dead were allocated in Warfarin group and two in Placebo group. Only one patient of the Warfarin group presented with gastrointestinal bleeding, requiring hospitalization and blood transfusion. The median INR of patients in the Warfarin group was 2.3 ± 0.7, whereas the median INR in the Placebo group was 1.1 ± 0.3. This difference was maintained throughout the study period. The median hemoglobin and hematocrit values were similar in both groups, with 13.9 ± 1.6g / dL and 41.2 ± 4.6% in the Placebo group and 14.0 ± 1.4g / dL and 41.9 ± 3.7% in the Warfarin group. The frequency of venous obstructions in the Warfarin group was 38.6% compared with 60.4% in the Placebo group (P=0.018), corresponding to an absolute risk reduction of 22% (RR= 0.63, 95% CI= 0.013-0.42). The comparison between obstructed and non-obstructed patients showed that warfarin use was associated with a lower incidence of venous lesions (P= 0.037) and that Chagas\' disease presence was associated with a higher incidence (P= 0.051). Logistic regression analysis showed that only absence of anticoagulant therapy (P=0.038; OR=2.424, 95% CI= 1.048 - 5.606) was a predictor of venous obstruction. Conclusion: The prophylactic use of the anticoagulation therapy has been safe and reduced the frequency of venous thrombosis after transvenous cardiac devices implantation in high risk patients.

Avaliamos os efeitos da estimulação atrial temporária na prevenção da fibrilação atrial no pós-operatório de revascularização do miocárdio com circulação extracorpórea e identificamos os fatores de risco para o aparecimento dessa arritmia. Estudamos 240 pacientes que ao término da cirurgia de revascularização miocárdica submeteram-se ao implante de eletrodos epicárdicos na parede lateral do átrio direito e no teto do átrio esquerdo e foram randomizados em grupo não estimulado, grupo com estímulo atrial direito e grupo com estímulo simultâneo nos átrios direito e esquerdo. Concluímos que a estimulação atrial temporária reduziu a incidência de fibrilação atrial pós-operatória e que a idade avançada e a não estimulação atrial foram fatores preditivos independentes para a ocorrência da arritmia / We studied the effects of temporary atrial pacing to prevent the atrial fibrillation after coronary artery bypass graft surgery and the risk factors to occurrence of this arrhytmia. We followed-up 240 patients after coronary artery bypass graft surgery who suffered temporary pacing atrial implantation at the end of operation. The patients were randomized into three groups according pacing stimulation into right atrial pacing, biatrial pacing and no stimulated patients. We concluded that the temporary atrial pacing reduced the incidence of postoperative atrial fibrillation. In addition older age was also a predictive factor of occurrence of atrial fibrillation

Introdução: A terapia de ressincronização cardíaca (TRC) tem se mostrado como um tratamento eficaz no tratamento de pacientes com insuficiência cardíaca (IC) grave e distúrbio da condução ventricular. A ecocardiografia tridimensional (Eco 3D) consiste em uma nova modalidade diagnóstica com resultados promissores para a identificação da dissincronia cardíaca e avaliação dos resultados da TRC. Objetivos: Estudar os efeitos da TRC no remodelamento reverso do ventrículo esquerdo (VE), em pacientes com miocardiopatia não isquêmica, insuficiência cardíaca e distúrbio da condução intraventricular, por meio da ecocardiografia tridimensional em tempo real. Métodos: De janeiro de 2007 a junho de 2009, foram avaliados 24 pacientes com miocardiopatia dilatada não isquêmica, IC classe funcional (CF) III ou IV (NYHA), com tratamento medicamentoso otimizado, QRS > 120 ms ao eletrocardiograma, e fração de ejeção do ventrículo esquerdo (FEVE) < 0,35 submetidos à TRC. Os pacientes foram avaliados antes, três e seis meses após TRC pela CF (NYHA), qualidade de vida pelo escore de Minnesota (MLHFQ), eletrocardiograma (intervalo PR e duração do QRS), ecocardiograma bidimensional (volumes diastólico VDVE, e sistólico VSVE, do ventrículo esquerdo, fração de ejeção ventricular esquerda - FEVE), Doppler tecidual (TDI) (avaliação da dissincronia cardíaca) e análise tridimensional (VDVE, VSVE, FEVE e dissincronia pela análise do SDI systolic dyssynchrony index). Foi considerado remodelamento reverso redução > 15% do VSVE após a TRC. As diferenças das médias das variáveis contínuas foram analisadas com o teste T não pareado, entre os grupos respondedor e não respondedor, depois de satisfeita a condição de normalidade. Antes da TRC, foi realizada uma análise univariada das características clínicas, eletrocardiográficas e ecocardiográficas para a construção de um modelo de regressão logística. Resultados: 9/24(38%) dos pacientes analisados apresentaram remodelamento ventricular reverso após TRC. O grupo respondedor apresentou menores volumes ventriculares (VDVE: 230 + 35 ml vs 316 + 10 ml, p = 0,045; VSVE: 178 + 30 ml vs 238 + 10 ml, p = 0,047), avaliados pelo método de Simpson, além de maior dissincronia cardíaca, avaliada pelo Eco 3D (SDI:13 + 3% vs 9 + 3%, p = 0,005) e pelo TDI (138 + 31 ms vs 102 + 37 ms, p = 0,026). Após a análise de regressão logística, o SDI (SDI > 11%) foi o único fator independente na predição de remodelamento reverso, seis meses após a TRC (sensibilidade:0,78; especificidade:0,79). Conclusões: O Eco 3D foi eficaz na detecção do remodelamento reverso do VE após a TRC, por meio da detecção da redução dos volumes ventriculares esquerdos (VDVE, VSVE) e da melhora da FEVE. O SDI foi o único preditor independente de remodelamento reverso após a TRC. Apresentaram menor taxa de resposta seis meses após a TRC, os pacientes com maiores volumes ventriculares esquerdos e menor fração de ejeção ventricular esquerda. A TRC melhorou a CF (NYHA) de IC e a qualidade de vida pelo escore de Minnesota / Introduction: Cardiac resynchronization therapy (CRT) consists of an effective treatment for patients with severe heart failure and ventricular conduction disturbance. Three dimensional echocardiography (3D Echo) is a new diagnostic modality with promising results in the identification of cardiac dyssynchrony and for the evaluation of CRT results. Objectives: To evaluate the effects of CRT in the left ventricular (LV) reverse remodeling in patients with non ischemic dilated myocardiopathy, heart failure and intraventricular conduction disturbance by using three dimensional echocardiography. Methods: From January, 2007 to June, 2009, twenty-four consecutive patients with heart failure, sinus rhythm, QRS > 120 ms, and Functional Class III or IV (NYHA), despite optimized medical treatment and left ventricular ejection fraction (LVEF) < 0,35, underwent CRT. All patients were assessed regarding Functional Class (NYHA), and the quality of life was evaluated using the Minnesota Living with Heart Failure Questionnaire (MLHFQ). All patients were submitted to an electrocardiogram, two dimensional echocardiography (2D Echo) including the evaluation of cardiac dyssynchrony by Tissue Doppler Imaging (TDI) and 3D Echo (SDI - systolic dyssynchrony index), before, three and six months after CRT. Left ventricular reverse remodeling was defined as a reduction of at least 15% of the left ventricular systolic volume (LVSV) after CRT. The difference between the mean of the continuous variables were compared by students T test, after being tested for normality. Before CRT, it was performed a univariate analysis of clinical, electrocardiographic and echocardiographic baseline characteristics of the patients for the construction of a logistic regression model. Results: 9/24 (38%) of the patients presented with left ventricular reverse remodeling six months after CRT. Patients who presented LV reverse remodeling had smaller left ventricular volumes estimated by Simpsons rule (LV diastolic volume (LVDV): 230 + 35 ml vs 316 + 10 ml, p = 0,045; LVSV: 178 + 30 ml vs 238 + 10 ml, p = 0,047) and greater cardiac dyssynchrony detected by 3D Echo (SDI: 13 + 3% vs 9 + 3%, p = 0,005) and by TDI (138 + 31 ms vs 102 + 37 ms, p = 0,026). After logistic regression analysis, the best predictors of left ventricular reverse remodeling after CRT were the cardiac dyssynchrony indexes evaluated by TDI (twelve segments) and SDI, but SDI (SDI > 11%) was the only independent factor in the prediction of left ventricular reverse remodeling six months after CRT (sensitivity of 0,78 and specificity of 0,79). Conclusions: 3D Echo was effective in the detection of left ventricular reverse remodeling after CRT, by detecting the reduction in left ventricular volumes (LVDV, LVSV) and the increase in LVEF. SDI was the only independent predictor of LV reverse remodeling after CRT. Patients with larger LV volumes, and smaller LVEF were more prone to not respond six months after CRT. CRT improved Functional Class (NYHA) and quality of life evaluated by MLHFQ

O sistema visual exerce importante papel para o reconhecimento do ambiente externo e para estabelecer relações entre objetos, tempo e espaço. Além disso, ele está relacionado com o controle e o desempenho motor. O objetivo deste estudo foi verificar se a privação de luz ambiente alteraria o desempenho e as respostas fisiológicas e psicológicas durante dois modelos de exercício, um fechado e um aberto. Onze ciclistas formaram o grupo de exercício fechado (GEF) e completaram um teste de 20 km, enquanto doze indivíduos ativos formaram o grupo de exercício aberto (GEA) e executaram um teste de potência constante até a exaustão (TWC). Após teste incremental máximo, GEF e GEA realizaram exercício na presença (controle) ou privação (experimental) de luz ambiente, em ordem balanceada. Respostas de desempenho, VE, VO2, VCO2 RER, FC, eletromiografia do músculo vato lateral (EMG), percepção subjetiva de esforço (PSE) e pensamento associado ao exercício (PAE) foram obtidas durante, e no ponto final do exercício, em ambas as condições. O tempo total de exercício indicou a resposta de desempenho em GEF e GEA. As respostas das variáveis fisiológicas e psicológicas foram analisadas durante a realização, ou no ponto final do exercício. A média das respostas geradas durante os 20 km no GEF, e as respostas obtidas no mesmo tempo absoluto do TWC no GEA, pareado pelo menor tempo de exaustão atingido no teste, indicaram as respostas durante a execução do exercício. As respostas obtidas nos 5 segundos finais de cada exercício indicaram as respostas do ponto final do GEF e GEA. A taxa de incremento na PSE foi calculada em GEF e GEA, e o erro de predição da distância real percorrida no teste de 20 km foi obtido no GEF. No GEF, não houve efeito da privação de luz sobre o tempo para completar o teste de 20 km, porém a privação de luz gerou menores respostas (P< 0,01) na VE, VO2, VCO2, EMG e PAE, quando comparada ao controle. No ponto final do exercício, nenhuma diferença foi verificada entre as condições. A privação de luz não alterou a taxa de elevação da PSE ou o erro de predição da distância percorrida. No GEA a privação de luz ambiente reduziu o tempo de exaustão (P< 0,05) no TWC e aumentou a resposta do VO2 e EMG (P< 0,05). Entretanto, não foi observado efeito da privação de luz na VE, VCO2 e FC. No ponto final do exercício observou-se menor EMG com a privação de luz (P< 0,03), mas nenhuma diferença nas demais variáveis foi observada. Maior taxa de elevação na PSE foi observada em ambiente privado de luz. Os resultados do presente estudo podem ser interpretados de acordo com a existência de um \"relógio biológico interno\" que calcula a duração tolerável do exercício de acordo com a aproximação ao ponto final do exercício, sugerindo que os efeitos da privação de luz sobre o desempenho possam depender da presença de um ponto final previamente conhecido / The visual system plays an important role for the environment recognition as well as to set objects, time and space relationships. Furthermore, the visual system is related to the motor learning and performance. The aim of this study was to verify if light deprivation environment would alter performance, and physiological and psychological responses to different exercise modes, closed- and open-loop exercises. Eleven cyclists were the closed-loop exercise group (CLE) and performed a 20 km time trial, while twelve active individuals were the open-loop exercise group (OLE) and cycled to exhaustion during a constant workload exercise. After maximal incremental test CLE and OLE groups performed exercise in a control and experimental condition (i.e. under light deprivation), in a counterbalanced fashion. Performance responses and responses of VE, VO2, VCO2 RER, HR, eletromyography of the vastus lateralis muscle (EMG), ratings of perceived exertion (RPE) and associative thoughts to exercise (ATE) were obtained during exercise and at the exercise endpoint in both the conditions. Time of exercise indicated performance responses in CLE and OLE groups. Physiological and psychological responses were analyzed either during or at the exercise endpoint. Mean responses throughout the 20 km cycling time trial and responses obtained at absolute matched time of exercise, corresponding to the shortest time to exhaustion provided responses along the exercise in CLE and OLE groups, respectively. Responses obtained during the last 5 seconds of the exercises provided responses at the exercise endpoint in both CLE and OLE groups. The rate of increase in RPE was calculated in CLE and OLE groups, and the predictive error of the distance was calculated in the CLE group. In CLE group no effect of light deprivation was observed in the time to complete the 20 km, although the lower response (P< 0.01) of VE, VO2, VCO2, EMG e ATE when compared to control condition. Neither difference was observed in variables at the exercise endpoint. Light deprivation had effect in neither rate of increase in RPE or predictive error of distance. Regarding OLE group the light deprivation decreased the time to exhaustion (P< 0.05) and increased VO2 and EMG (P< 0.05) responses. However, there was no light deprivation effect in VE, VCO2 and HR. Lower EMG was observed at the exercise endpoint in light deprivation condition (P< 0.05) than in control, but no difference was observed in the others. Greater rate of increase in RPE was detected (P< 0.05) in the light deprivation condition than in control. Results of the present study were interpreted according to a \"biological internal clock\" that calculates the tolerable exercise duraton based on the exercise endpoint approximation, suggesting that light deprivation effects on performance may depend on the presence of an exercise endpoint previously known

Objectives: To determine the physiological strain on industrial workers under thermal stress on extended shifts. To continuously measure deep body core temperatures, heart rates, fluid intake, changes in hydration state and physical fatigue in order to establish acceptable levels of physiological strain. To develop a rational heat stress index compatible with these limits. To design working-in-heat protocols for a self-paced workforce. Methods: A series of studies was conducted over 77 shifts on a group of approximately 50 male volunteers working in thermally stressful environments. Continuously- recorded deep body core temperatures, heart rates, fluid consumption, urinary specific gravity and physical fatigue were measured and recorded. A new field protocol was developed to assess physical fatigue over the working shift. An original methodology was developed to allow any heat stress index to be assessed on a comparative basis with any other index. A review of the commonly used occupational heat stress indices was conducted. A new rational heat stress index was developed, based on existing biophysical relationships and recommended physiological strain limits of deep body core temperature and sweat rate. New protocols designed for self-paced work incorporating the significant risk factors for heat illness were developed and implemented in a workforce of approximately 2000 workers exposed to heat stress. The previous protocols used a shortened shift as the primary intervention to protect worker health. The subsequent protocols removed the shortened shift and replaced this with a range of other interventions. Deep body core temperature, heart rate, fluid consumption, hydration state and fatigue were measured before and after the changes in protocols. / Results: Comparisons of heat stress indices confirmed the wide divergence in guidance provided by many of the commonly-used indices in terms of acceptable working environments. It also highlighted a number of serious shortcomings in the most widely-used indices, especially WBGT and ISO7933. A new, rational heat stress index called Thermal Work Limit (TWL) was developed. This included development of a computer model incorporating key thermal physiological parameters (deep body core temperature, mean skin temperature, sweat rate, skin wettedness). There was no increase in heat stress (as indicated by average workplace environmental conditions), deep body core temperature, mean heart rate, or changes in hydration status after the changes in protocols. Average environmental conditions were severe (WBGT 30.9° C, sd 2.0° C, range 25.7-35.2° C). Environmental conditions in the study were much hotter than those considered acceptable under standards such as the ACGIH. The results showed that miners regularly exceeded those limits allowable under most current indices in terms of maximum deep body core temperature (avg 38.3° C, std dev 0.4° C), maximum temperature rise (1.4° C, 0.4° C) and maximum heat storage (431 kJ, 163 kJ), without reporting any symptoms of heat illness. A significant component of the observed elevated core temperatures was due to the normal circadian rhythm, which was measured at 0.9° C (std dev 0.2° C). Evidence was found that workers "self-pace" when under thermal stress. Fluid intake averaged 0.8 l/h during exposure (sd 0.3 l/h, range 0.3-1.5 1/h). Average urinary specific gravity at start-, mid- and end of shift was 1.0251, 1.0248 and 1.0254 respectively; the differences between start and mid-shift, mid and end-shift, and start and end-shift were not significant. / However, a majority of workers were coming to work in a moderately hypohydrated state (urinary specific gravity avg 1.024, std dev 0.0059). Involuntary dehydration was not found to occur in the study group. This is in contrast to several other studies and some of the leading heat stress standards, which are based on the premise that workers are unable to maintain their hydration status when working in the heat, even when their fluid consumption is equal to their sweat rate. Continuous heart rates measured over a shift (avg 103 bpm, 14% of shifts exceeding avg 110 bpm, 5% exceeding avg 120 bpm) were in excess of those allowable under most current indices On average, workers experienced a peak 10- minute heart rate of 140 bpm and a peak 30-minute heart rate of 130 bpm during their shifts. There was a significant increase in fatigue in the first half of the working shift (P=0.001), with workers on average showing a significant recovery in the second half of their shift (p=0.04). Conclusions: Current heat stress indices provide little common agreement as to acceptable levels of thermal strain or stress for workers, at equivalent levels of environmental stress. IS07933 is seriously flawed and the ACGIH WBGT guidelines are too conservative for acclimatised workers and are unlikely to become widely adopted by industries with well-acclimatised workers. Many of the existing indices show internal inconsistencies. / Most of the physiological heat strain limits used in existing rational heat stress indices (in terms of deep body core temperature and heart rate) are conservative for self-paced, acclimatise d, non-dehydrating male workers. Involuntary dehydration is not unavoidable when acclimatised workers are exposed to thermal stress. Heat stress standards should not limit heat exposure durations for self- paced workers who have access to water on the basis of an unavoidable body water loss. Physical fatigue does occur in workers under heat stress on extended shifts; however, most workers show a significant increase in fatigue in the first half of their shift; whereas data indicates self-paced workers undergo significant recovery in terms of fatigue in the second half of the shift. As the heat exposures in this study cover a wide range of temperatures, humidity levels, wind speeds, body morphology and VO2max, these conclusions are applicable to most thermally stressful settings involving well-informed, well-acclimatised and self-paced male workers. The major category of work type not covered by this study is that of workers in fully-encapsulated (vapour-barrier) protective clothing. In addition, this study examined acute effects of heat stress and strain, not effects that might only be manifest with chronic exposure to heat.

Cardiac Resynchronization Therapy (CRT) is a treatment option for heart failure patients with ventricular dyssynchrony. CRT corrects for dyssynchrony by electrically stimulating the septal and lateral walls of the left ventricle (LV), forcing synchronous con- traction and improving cardiac output. Current selection criteria for CRT rely upon the QRS duration, measured from a surface electrocardiogram, as a marker of electrical dyssynchrony. Unfortunately, 30-40% of patients undergoing CRT fail to benefit from the treatment. A multitude of studies have shown that presence of mechanical dyssynchrony in the LV is an important factor in determining if a patient will benefit from CRT. Furthermore, recent evidence suggests that patient response can be improved by placing the LV pacing lead in the most dyssynchronous or latest contracting segment. The overall goal of this project was to develop methods that allow for accurate assessment and display of regional mechanical dyssynchrony throughout the LV and at the site of the LV pacing lead. To accomplish this goal, we developed a method for quantifying regional dyssynchrony from standard short-axis cine magnetic resonance (MR) images. To assess the effects of LV lead placement, we developed a registration method that allows us to project the LV lead location from dual-plane fluoroscopy onto MR measurements of cardiac function. By applying these techniques in patients undergoing CRT, we were able to investigate the relationship between regional dyssynchrony, LV pacing lead location, and CRT response.

Studium of the clinical impact of different forms of cardiac resynchronization therapy by patients with chronic heart failure MUDr. Lucie Burianová ABSTRACT: Introduction: Biventricular (BiV) pacing decreases mortality and improves quality of life of patients with severe heart failure. Haemodynamic and short time clinical studies suggest that isolated leftventricular pacing could have the same effect. Aims: Compare the effect of BiV and leftventricular pacing by subjects with dilated cardiomyopathy and severe heart failure with the attention to signs of dyssynchrony and remodelation of the left chamber. In methodical substudy compare the results of left chamber volumes and ejection fraction (EF LK) measured by CT angiography and 2-dimensional echocardiography with use of contrast agent (K-ECHO). Methods: Patients indicated for cardiac resynchronization therapy were randomized for either BiV or leftventricular pacing. After implantation of the device they were examinated clinically and by echocardiography every 3 months in the period of one year. Four years from the onset of the study the major adverse events in both groups were evaluated. The results of left chamber volumes and EF LK measured by K-ECHO and CT angiography were compared. Results: We enrolled 33 patients. We found clinical improvement in both...

I ntrodução: A incidência de lesões venosas pós-implante transvenoso de dispositivos cardíacos eletrônicos implantáveis (DCEI) é elevada, sendo a disfunção ventricular e o uso prévio de marcapasso temporário (MPT) ipsilateral ao implante definitivo fatores de risco independentes para sua ocorrência. A utilidade de estratégias terapêuticas profiláticas para a prevenção dessa complicação ainda permanece controversa. O objetivo desse estudo clínico, randomizado e controlado foi avaliar o papel da anticoagulação oral na prevenção das lesões venosas pós-implante transvenoso de DCEI em pacientes de alto risco, analisando a influência na incidência das obstruções venosas, a segurança, a eficácia e as complicações do tratamento. Método: No período de Fevereiro/2004 a Setembro/2007 foram estudados 101 pacientes adultos submetidos ao primeiro implante transvenoso de DCEI, apresentando fração de ejeção do ventrículo esquerdo (FEVE) <=0,40 e/ou presença de MPT ipsilateral ao implante definitivo. Após o procedimento, os pacientes foram randomizados para o uso diário de placebo ou varfarina. Avaliações clínicas e laboratoriais foram realizadas periodicamente. A pesquisa de lesões venosas foi feita pela venografia por subtração digital, seis meses após o implante. A análise dos dados foi realizada segundo o princípio de \"intenção-de-tratar\". Na análise da associação das variáveis demográficas, clínicas e operatórias com a presença de lesões venosas empregou-se os testes Qui-quadrado, Exato de Fisher ou \"t\" de Student e o modelo de regressão logística foi utilizado para a identificação de fatores de risco. Resultados: As características basais foram similares nos dois grupos, não sendo encontradas diferenças significativas entre as variáveis demográficas, clínicas e operatórias. Durante o período de seguimento clínico, ocorreram seis óbitos, quatro relacionados com a progressão da insuficiência cardíaca e duas mortes súbitas. Do total de óbitos, quatro pacientes estavam alocados no Grupo Varfarina e dois no Placebo. Somente um paciente, do Grupo Varfarina, apresentou sangramento gastrintestinal, com necessidade de hospitalização e transfusão de hemoderivados. O valor médio do INR dos pacientes do Grupo Varfarina foi 2,3±0,7 enquanto que no Grupo Placebo foi 1,1±0,3, sendo que esta diferença manteve-se ao longo de todo o período de seguimento. O valor médio da hemoglobina e do hematócrito foi similar em ambos os grupos, sendo 13,9±1,6g/dL e 41,2±4,6%, no Grupo Placebo e 14,0±1,4g/dL e 41,9±3,7%, no Grupo Varfarina. Dos pacientes alocados no Grupo Varfarina, 17 (38,6%) apresentaram obstruções venosas, em comparação a 29 (60,4%) casos do Grupo Placebo, com redução absoluta do risco de 22% (RR= 0,63; IC 95%= 0,013 a 0,42). A comparação das características clínicas dos pacientes que apresentaram lesões venosas com as dos pacientes que não apresentaram mostrou que o uso de varfarina (P=0,037) esteve associado a uma menor incidência de lesões venosas e a presença da doença de Chagas (P= 0,051) esteve associada a uma maior incidência. Somente a ausência de anticoagulação oral foi identificada como fator de risco independente para a ocorrência das lesões venosas (OR= 2,424; IC 95% 1,048 - 5,606; P= 0,038). Conclusão: O uso profilático da anticoagulação mostrou-se seguro e reduziu significativamente a incidência de obstruções venosas pós-implante de DCEI nos pacientes de alto risco. / Introduction: The incidence of venous thrombosis after cardiac devices implantation is high. Ventricular dysfunction and previous transvenous temporary leads ipsilaterally to the permanent implantation are independent risk factors. The effect of prophylactic strategies to prevent these complications remains controversial. The aim of this clinical, randomized and controlled study was to evaluate the role of oral anticoagulant therapy in the prevention of these complications in high risk patients, analyzing the effect on the venous obstructions incidence, the safety, effectiveness and complications of this treatment. Method: Between February 2004 and September 2007, 101 adult patients submitted to first transvenous cardiac devices implantation, with left ventricular ejection fraction <=0.40 and/or previous transvenous temporary leads were evaluated. After device implantation, patients were randomly assigned to receive either placebo or warfarin. Periodical clinical and laboratorial evaluations were performed to anticoagulant management. Following the six-month period, every patient was submitted to a digital subtraction venography. Data analysis was performed according to the \"intention-to-treat\" principle. The association of demographic, clinical and procedure variables with the presence of venous lesions was analyzed by the Chi-square, Fisher\'s exact, or \"t\" Student tests, and logistic regression model was used to identify risk factors. Results: Baseline characteristics were similar in both groups and no significant difference was observed in demographic, clinical and procedure variables. During the follow-up period, six patients died, four related to heart failure progression and two of sudden death. Four of the patients dead were allocated in Warfarin group and two in Placebo group. Only one patient of the Warfarin group presented with gastrointestinal bleeding, requiring hospitalization and blood transfusion. The median INR of patients in the Warfarin group was 2.3 ± 0.7, whereas the median INR in the Placebo group was 1.1 ± 0.3. This difference was maintained throughout the study period. The median hemoglobin and hematocrit values were similar in both groups, with 13.9 ± 1.6g / dL and 41.2 ± 4.6% in the Placebo group and 14.0 ± 1.4g / dL and 41.9 ± 3.7% in the Warfarin group. The frequency of venous obstructions in the Warfarin group was 38.6% compared with 60.4% in the Placebo group (P=0.018), corresponding to an absolute risk reduction of 22% (RR= 0.63, 95% CI= 0.013-0.42). The comparison between obstructed and non-obstructed patients showed that warfarin use was associated with a lower incidence of venous lesions (P= 0.037) and that Chagas\' disease presence was associated with a higher incidence (P= 0.051). Logistic regression analysis showed that only absence of anticoagulant therapy (P=0.038; OR=2.424, 95% CI= 1.048 - 5.606) was a predictor of venous obstruction. Conclusion: The prophylactic use of the anticoagulation therapy has been safe and reduced the frequency of venous thrombosis after transvenous cardiac devices implantation in high risk patients.