Deterioration of Left Ventricular Chamber Performance After Bed Rest

Perhonen, Merja; Zuckerman, Julie H.; Levine, Benjamin D.

doi:10.1161/01.cir.103.14.1851

Cited by 129 publications

(127 citation statements)

References 34 publications

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“…First, tissue Doppler imaging may be more sensitive than conventional echocardiography for detection of abnormalities in LV diastolic function in individuals with SCI. Second, our data showing lower Em and higher E/Em in subjects with SCI corroborate previous reports demonstrating impaired LV compliance in individuals subjected to prolonged bed rest and space flight, 7,8 thus indicating that physical inactivity may be associated with diastolic dysfunction. Nevertheless, this latter assumption is challenged by the lack of influence of injury level on LV diastolic function, as shown herein.…”

Section: Discussionsupporting

confidence: 90%

“…6 Similarly, the development of LV diastolic dysfunction has been reported in individuals subjected to prolonged physical inactivity, 7,8 thereby suggesting that patients with SCI might be at a higher risk of developing abnormalities in LV function. The aim of this study was to investigate cardiac functional and structural parameters in SCI and able-bodied subjects and evaluate the impact of clinical, hemodynamic, metabolic and inflammatory variables in this regard.…”

Section: Introductionmentioning

confidence: 93%

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Altered left ventricular diastolic function in subjects with spinal cord injury

et al. 2010

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Study design: This is cross-sectional study. Objectives: The aim of this study is to investigate the cardiac structure and function of subjects with spinal cord injury (SCI) and the impact of metabolic, hemodynamic and inflammatory factors on these parameters. Setting: São Paulo, Brazil. Methods: Sixty-five nondiabetic, nonhypertensive, sedentary, nonsmoker men (34 with SCI and 31 healthy subjects) were evaluated by medical history, anthropometry, laboratory tests, analysis of hemodynamic and inflammatory parameters and echocardiography. Results: Subjects with SCI had lower systolic blood pressure and higher levels of C-reactive protein and tumor necrosis factor receptors than the healthy ones. Echocardiography data showed that the SCI group presented similar left ventricular (LV) structural and systolic parameters, but lower initial diastolic velocity (Em) (9.2 ± 0.5 vs 12.3 ± 0.5 cm s À1 ; Po0.001) and higher peak early inflow velocity (E)/Em ratio (7.7±0.5 vs 6.1±0.3; P ¼ 0.009) compared with the able-bodied group, even after adjustment for systolic blood pressure and C-reactive protein levels. Furthermore, injured subjects with E/Em 48 had lower peak spectral longitudinal contraction (Sm) (9.0±0.7 vs 11.6±0.4 cm s À1 ; Po0.001) and cardiac output (4.2 ± 0.2 vs 5.0 ± 0.2 l min À1 ; P ¼ 0.029), as well as higher relative wall thickness (0.38±0.01 vs 0.35±0.01; P ¼ 0.005), than individuals with SCI with E/Emo8, but similar age, body mass index, blood pressure, injury level, metabolic parameters and inflammatory marker levels. Conclusion: Subjects with SCI presented impaired LV diastolic function in comparison with ablebodied ones. Moreover, worse LV diastolic function was associated with a pattern of LV concentric remodeling and subclinical decreases in systolic function among injured subjects. Overall, these findings might contribute to explain the increased cardiovascular risk reported for individuals with SCI.

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Section: Discussionsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 93%

Altered left ventricular diastolic function in subjects with spinal cord injury

et al. 2010

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“…This method has been validated against standard invasive techniques, including thermodilution and direct Fick at rest, during exercise and changes in orthostatic stress, with a typical error (expressed as coefficient of variation) of 4% to 5%. 16 This method has been used extensively in our laboratory and others, 1,2,5,12,15,17 and it has been reviewed recently in detail. 18 Stroke volume (SV) was calculated from cardiac output and the HR measured during rebreathing.…”

Section: Cardiac Outputmentioning

confidence: 99%

“…This dosage was chosen because it induced a reduction in plasma volume of 7% to 14% after administration for Ϸ2 hours, equivalent to the loss of plasma volume observed after 2 weeks of head-down bed rest. 17,22 An oral potassium supplement of 20 mEq was given before the injection of furosemide. After injection, urine was collected and cuff BP was measured every 15 minutes.…”

Section: Acute Hypovolemiamentioning

confidence: 99%

Vasoconstrictor Reserve and Sympathetic Neural Control of Orthostasis

2004

Self Cite

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Background-We tested the hypothesis that individual variability in orthostatic tolerance is dependent on the degree of neural and vasomotor reserve available for vasoconstriction. Methods and Results-Muscle sympathetic nerve activity (MSNA) and hemodynamics were measured in 12 healthy young volunteers during 60°head-up tilt (HUT), followed by a cold pressor test (CPT) in HUT. Orthostatic tolerance was determined by progressive lower-body negative pressure (LBNP) to presyncope. The same protocols were performed randomly in normovolemic and hypovolemic conditions. We found that mean arterial pressure increased and stroke volume decreased, whereas heart rate (HR), MSNA, and total peripheral resistance (TPR) increased during HUT (all PϽ0.01). Application of the CPT in HUT did not increase HR or decrease stroke volume further but elevated mean arterial pressure (PϽ0.01) and increased MSNA and TPR in some subjects. There was a positive correlation between the time to presyncope from Ϫ50 mm Hg LBNP (equivalent to 60°HUT alone) and the changes in MSNA produced by the CPT under both conditions (rϭ0.442, Pϭ0.039). Those who had greater increases in MSNA had greater increases in TPR during the CPT and longer time to presyncope (both PϽ0.05). One subject had dramatic increases in MSNA but small increases in TPR during the CPT, which indicates a disassociation between sympathetic activity and the increase in peripheral vascular resistance. Conclusions-These results support our hypothesis and suggest that vasoconstrictor capability is a contributor to orthostatic tolerance in humans. Vasoconstrictor reserve therefore may be one mechanism underlying individual variability in orthostatic intolerance.

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“…A redução do volume plasmático tem sido apontada como um dos principais determinantes desta síndrome 5,6 . Entretanto, sabe-se que perdas agudas de 10-15% da volemia (semelhante ao volume perdido após uma semana no espaço) 29,[31][32][33] , não levam geralmente a quadros clínicos de intolerância ortostática da mesma intensidade 29,70 . Além disso, no modelo HDT, demonstrou-se que a restauração do estado volêmico não impede completamente o desenvolvimento da intolerância ortostática 22 .…”

Section: Controle Geral Da Circulação Em 0gunclassified

Efeitos cardiovasculares agudos da exposição ao ambiente microgravitacional

Santos¹,

Bonamino²

2003

Arq. Bras. Cardiol.

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AtualizaçãoCom a perspectiva do aumento crescente de missões espaciais tripuladas de curta e longa duração, torna-se cada vez mais importante o conhecimento dos efeitos do ambiente espacial modificado -notadamente o interior das naves espaciais -sobre o organismo humano. Não subestimando a importância dos outros fatores ambientais como as radiações cósmicas, a atmosfera artificial das espaçonaves (e das vestimentas para as atividades extraveiculares), a ausência de ciclo claro/escuro natural e o confinamento, a virtual ausência de gravidade é certamente a maior causa de alterações fisiológicas e doenças reconhecidas até hoje nos astronautas e animais de experimentação lançados ao espaço. Neste contexto, não é demais lembrar que as formas de vida na Terra evoluíram durante milhões de anos em presença de gravidade 1 (1G), de modo que sua morfologia e fisiologia se desenvolveram no sentido de melhor adequação possível a este valor.No que diz respeito ao aparelho cardiovascular, a abolição da gravidade manifesta-se principalmente pelo fim do peso da coluna líquida dentro dos vasos sangüíneos, ou seja, ausência da pressão hidrostática (P hid ), com importantes repercussões sobre a dinâmica dos sistemas venoso, capilar e arterial. Além disso, a função circulatória torna-se ainda mais alterada pela anulação da compressão extrínseca sobre os vasos normalmente exercida pelo peso dos tecidos e órgãos adjacentes. A longo prazo somam-se a estes fatores o descondicionamento físico e a atrofia muscular 1 , aumentando assim o número de variáveis que influenciam o comportamento do sistema cardiovascular. Finalmente, é importante lembrar que a mudança do ambiente terrestre para o microgravitacional tem repercussões sobre o comportamento intrínseco do sistema nervoso, onde fenôme-nos de sensibilização e habituação (processo de aprendizado) estão constantemente em curso, modificando as respostas autonômicas no sentido de melhor adaptação ao novo ambiente.O presente artigo tem por objetivo discutir os efeitos imediatos e a curto prazo da abolição da gravidade sobre o sistema cardiovascular humano, assim como as respostas adaptativas agudas do organismo, visando à homeostase circulatória. Este processo é denominado pelos fisiologistas de "aclimatação aguda" à microgravidade *. Na inexistência de uma periodização formal, por respostas agudas devem ser entendidos aqui os processos fisiológicos que tomam lugar no período compreendido entre a imediata instalação da gravidade zero (0G) até os primeiros dias de sua vigência. Estudo da função cardiovascular em microgravidadeOs efeitos da microgravidade sobre o sistema cardiovascular têm sido estudados em vôos espaciais de curta e longa duração, assim como em experimentos de simulação fora do ambiente espacial. No que se refere aos vôos, os experimentos têm sido realizados na presença de uma série de fatores limitantes, como as restrições de espaço físico, tempo e equipamentos, a ausência de condições controles ótimas em função, por exemplo, do estresse psicológico, da postura corporal na f...

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Deterioration of Left Ventricular Chamber Performance After Bed Rest

Abstract: Chronic HDTBR leads to ventricular remodeling, which is not seen with equivalent degrees of acute hypovolemia. This remodeling leads to a greater decrease in SV during orthostatic stress after bed rest than hypovolemia alone, potentially contributing to orthostatic intolerance.

Cited by 129 publications

References 34 publications

Altered left ventricular diastolic function in subjects with spinal cord injury

Altered left ventricular diastolic function in subjects with spinal cord injury

Vasoconstrictor Reserve and Sympathetic Neural Control of Orthostasis

Efeitos cardiovasculares agudos da exposição ao ambiente microgravitacional

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