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1.
Phys Rev Lett ; 123(3): 035101, 2019 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-31386457

RESUMO

We develop a comprehensive theoretical model of relativistic collisionless pair shocks mediated by the current filamentation instability. We notably characterize the noninertial frame in which this instability is of a mostly magnetic nature, and describe at a microscopic level the deceleration and heating of the incoming background plasma through its collisionless interaction with the electromagnetic turbulence. Our model compares well to large-scale 2D3V particle-in-cell simulations, and provides an important touchstone for the phenomenology of such plasma systems.

2.
Psychooncology ; 26(4): 469-475, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-27228257

RESUMO

BACKGROUND: Research on the implication of experiential avoidance in the aetiology and maintenance of diverse forms of psychopathology has grown considerably over the last 10 years. However, the potential contribution of experiential avoidance to cancer-related distress has received limited attention. Accordingly, the objective of this study was to examine the association between experiential avoidance, symptoms of anxiety and depression, and quality of life (QoL) during the course of a psychological group intervention for women with breast cancer. METHODS: Fifty-four women with breast cancer participated in a psychological group intervention designed to reduce distress and improve QoL. Participants completed measures of experiential avoidance, anxiety and depressive symptoms, and QoL upon the first and last sessions. RESULTS: A path analysis revealed that, after controlling for baseline measures, smaller reductions in experiential avoidance during the course of the intervention predicted smaller reductions in anxiety and depressive symptoms. Also, experiential avoidance had a negative indirect effect on QoL via depressive symptoms. CONCLUSIONS: Experiential avoidance may perpetuate the emotional problems commonly found in women with breast cancer and attenuate improvements associated with participation in psychological interventions. Implications for clinical practice in psycho-oncology are discussed. Copyright © 2016 John Wiley & Sons, Ltd.


Assuntos
Ansiedade/terapia , Neoplasias da Mama/psicologia , Depressão/terapia , Ajustamento Emocional , Psicoterapia de Grupo/métodos , Qualidade de Vida/psicologia , Adaptação Psicológica , Adulto , Ansiedade/etiologia , Ansiedade/psicologia , Depressão/etiologia , Depressão/psicologia , Feminino , Humanos , Pessoa de Meia-Idade , Resolução de Problemas
3.
Can J Surg ; 60(5): 305-310, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28805187

RESUMO

BACKGROUND: Heart transplantation is no longer considered an experimental operation, but rather a standard treatment; nevertheless the context has changed substantially in recent years owing to donor shortage. The aim of this study was to review the heart transplant experience focusing on very long-term survival (≥ 20 years) and to compare the initial results with the current era. METHODS: From April 1983 through April 1995, 156 consecutive patients underwent heart transplantation. Patients who survived 20 years or longer (group 1) were compared with patients who died within 20 years after surgery (group 2). To compare patient characteristics with the current era, we evaluated our recent 5-year experience (group 3; patients who underwent transplantation between 2010 and 2015), focusing on differences in terms of donor and recipient characteristics. RESULTS: Group 1 (n = 46, 30%) included younger patients (38 ± 11 v. 48 ± 8 yr, p = 0.001), a higher proportion of female recipients (28% v. 8%, p = 0.001) and a lower prevalence of ischemic heart disease (42% v. 65%, p = 0.001) than group 2 (n = 110, 70%). Patients in group 3 (n = 54) were older (52 ± 12 v. 38 ± 11 yr, p = 0.001), sicker (rate of hospital admission at transplantation 48% v. 20%, p = 0.001) and transplanted with organs from older donors (42 ± 15 v. 29 ± 11 yr, p = 0.001) than those in group 1. CONCLUSION: Very long-term survival ( ≥ 20 yr) was observed in 30% of patients transplanted during the first decade of our experience. This outcome will be difficult to duplicate in the current era considering our present population of older and sicker patients transplanted with organs from older donors.


CONTEXTE: De nos jours, la transplantation cardiaque n'est plus considérée comme une intervention expérimentale, mais bien comme une opération standard; mais le contexte a substantiellement changé ces dernières années en raison d'une pénurie de donneurs. Cette étude avait pour but de faire le point sur la situation de la greffe cardiaque, et plus particulièrement sur la survie à très long terme (≥ 20 ans), et de la comparer aux résultats initiaux. MÉTHODES: Entre avril 1983 et avril 1995, 156 patients consécutifs ont subi une greffe cardiaque. Les patients qui ont survécu 20 ans ou plus (groupe 1) ont été comparés aux patients décédés moins de 20 ans après l'intervention (groupe 2). Pour comparer les caractéristiques des premiers patients à celles des cas plus récents, nous avons fait un bilan des 5 années allant de 2010 à 2015 (groupe 3), en portant attention aux différences quant aux caractéristiques des donneurs et des receveurs. RÉSULTATS: Le groupe 1 (n = 46, 30 %) incluait des patients plus jeunes (38 ± 11 ans c. 48 ± 8 ans, p = 0,001), une proportion plus élevée de femmes (28 % c. 8 %, p = 0,001) et la prévalence de maladie cardiaque ischémique y était moindre (42 % c. 65 %, p = 0,001) comparativement au groupe 2 (n = 110, 70 %). Les patients du groupe 3 (n = 54) étaient plus âgés (52 ± 12 ans c. 38 ± 11 ans, p = 0,001), plus malades (taux d'hospitalisation au moment de la transplantation 48 % c. 20 %, p = 0,001) et ont reçu le cœur de donneurs plus âgés (42 ± 15 ans c. 29 ± 11 ans, p = 0,001) que ceux du groupe 1. CONCLUSION: Une survie à très long terme (≥ 20 ans) a été observée chez 30 % des patients ayant reçu leur greffe au cours de la première décennie de notre expérience. Ce résultat sera difficile à reproduire de nos jours étant donné que notre population actuelle est constituée de receveurs plus âgés et plus malades, qui reçoivent le cœur de donneurs plus âgés.


Assuntos
Transplante de Coração/estatística & dados numéricos , Isquemia Miocárdica/epidemiologia , Avaliação de Resultados em Cuidados de Saúde/estatística & dados numéricos , Doadores de Tecidos/estatística & dados numéricos , Adulto , Fatores Etários , Idoso , Feminino , Seguimentos , Transplante de Coração/mortalidade , Humanos , Masculino , Pessoa de Meia-Idade , Isquemia Miocárdica/cirurgia , Quebeque/epidemiologia , Estudos Retrospectivos , Fatores de Tempo
4.
Ann Pharmacother ; 48(7): 837-846, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24740466

RESUMO

BACKGROUND: The effects of sirolimus (SIR), as a substitution for calcineurin inhibitor (CNI) immunoprophylaxis, on renal function in very-long-term cardiac transplant recipients have been a matter of controversy. OBJECTIVE: To assess the impacts of SIR as a substitution for CNI on renal function up to 24 months in long-term cardiac recipients as well as the renal histological changes in patients with suspected CNI-induced nephrotoxicity. METHODS: A total of 23 cardiac transplant recipients aged 57.7 ± 11.2 years, 91 months post-cardiac transplantation were recruited; 15 patients were randomized to CNI-free immune suppression with SIR, and 8 patients were allocated to continue their CNI regimens. Serum creatinine and calculated serum creatinine clearance were measured at prespecified time points up to 24 months. Renal structure and function were assessed by renal biopsies, renal ultrasound, and magnetic resonance imaging at baseline. RESULTS: There were no significant changes in creatinine clearance during the course of the study in patients treated with SIR. However, SIR-treated patients exhibited a significant decrease in 24-hours and nighttime systolic and diastolic blood pressures. Typical findings of significant hypertensive renal disease were detected in 9 of the 11 (82%) patients. Features of chronic CNI toxicity were detected in 6 (55%) patients. CONCLUSIONS: There is a very high rate of hypertensive renal disease concomitantly with some degree of CNI toxicity in long-term cardiac transplant recipients with renal dysfunction. This very high rate of hypertension-related disease may limit the impact of SIR on improving renal function long term following cardiac transplantation.

5.
Palliat Support Care ; 12(4): 277-86, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24128421

RESUMO

OBJECTIVE: Experiencing cancer can give rise to existential concerns causing great distress, and consequently drive individuals to make sense of what cancer may mean to their lives. To date, meaning-based research in the context of cancer has largely focused on one possible outcome of this process, the emergence of positive meanings (e.g. post-traumatic growth). However, negative meanings may also be ascribed to cancer, simultaneously with positive meanings. This study focused on the nature of the co-existence of positive and negative meanings in a sample of individuals diagnosed with colorectal cancer to find out whether negative meaning had an impact on quality of life and psychosocial adjustment above and beyond positive meaning. METHODS: Participants were given questionnaires measuring meaning-made, quality of life, and psychological distress. Semi structured interviews were conducted with a subgroup from the original sample. RESULTS: Hierarchical multiple regression analyses revealed that negative meaning-made (i.e. helplessness) was a significant predictor of poor quality of life and increased levels of depression/anxiety above and beyond positive meaning-made (i.e. life meaningfulness, acceptance, and perceived benefits). Correlational analyses and interview data revealed that negative meaning-made was mainly associated with physical and functional disability, while positive meaning-made was mostly related to emotional and psychological well-being. SIGNIFICANCE OF RESULTS: Meanings of varying valence may simultaneously be ascribed to cancer as it impacts different life dimensions, and they may independently influence quality of life and psychosocial adjustment. The presence of positive meaning was not enough to prevent the detrimental effects of negative meaning on psychosocial adjustment and quality of life among individuals taking part in this study. Future attention to negative meaning is warranted, as it may be at least as important as positive meaning in predicting psychosocial adjustment and quality of life following a cancer diagnosis.


Assuntos
Adaptação Psicológica , Neoplasias Colorretais/psicologia , Qualidade de Vida , Estresse Psicológico/psicologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Entrevistas como Assunto , Masculino , Pessoa de Meia-Idade , Inquéritos e Questionários
6.
Support Care Cancer ; 21(12): 3379-86, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23934224

RESUMO

PURPOSE: A new ambulatory consultative clinic with integrated assessments by palliative care, radiation oncology, and allied health professionals was introduced to (1) assess patients with brain metastases at a regional comprehensive cancer center and (2) inform and guide patients on management strategies, including palliative radiotherapy, symptom control, and end-of-life care issues. We conducted a quality assurance study to inform clinical program development. METHODS: Between January 2011 and May 2012, 100 consecutive brain metastases patients referred and assessed through a multidisciplinary clinic were evaluated for baseline characteristics, radiotherapy use, and supportive care decisions. Overall survival was examined by known prognostic groups. Proportion of patients receiving end-of-life radiotherapy (death within 30 and 14 days of brain radiotherapy) was used as a quality metric. RESULTS: The median age was 65 years, with non-small cell lung cancer (n = 38) and breast cancer (n = 23) being the most common primary cancers. At least 57 patients were engaged in advance care planning discussions at first consult visit. In total, 75 patients eventually underwent brain radiotherapy, whereas 25 did not. The most common reasons for nonradiotherapy management were patient preference and rapid clinical deterioration. Overall survival for prognostic subgroups was consistent with literature reports. End-of-life brain radiotherapy was observed in 9 % (death within 30 days) and 1 % (within 14 days) of treated patients. CONCLUSIONS: By integrating palliative care expertise to address the complex needs of patients with newly diagnosed brain metastases, end-of-life radiotherapy use appears acceptable and improved over historical rates at our institution. An appreciable proportion of patients are not suitable for palliative brain radiotherapy or opt against this treatment option, but the team approach involving nurses, palliative care experts, allied health, and clinical oncologists facilitates patient-centered decision making and transition to end-of-life care.


Assuntos
Neoplasias Encefálicas/radioterapia , Neoplasias Encefálicas/secundário , Cuidados Paliativos/métodos , Equipe de Assistência ao Paciente , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias da Mama/patologia , Neoplasias da Mama/radioterapia , Carcinoma Pulmonar de Células não Pequenas/patologia , Carcinoma Pulmonar de Células não Pequenas/radioterapia , Tomada de Decisões , Feminino , Humanos , Neoplasias Pulmonares/patologia , Neoplasias Pulmonares/radioterapia , Masculino , Pessoa de Meia-Idade , Prognóstico , Encaminhamento e Consulta , Assistência Terminal
7.
J Surg Oncol ; 105(4): 337-41, 2012 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-22095440

RESUMO

BACKGROUND: Few studies describe quality of life (QoL) outcomes following gastrectomy for gastric cancer using a validated instrument. The gastric cancer module for the Functional Assessment of Cancer Therapy system of QoL measurement tools (FACT-Ga) was utilized to determine the changes in QoL following gastrectomy, and during the disease course. METHODS: In 43 patients undergoing gastrectomy for gastric cancer, outcome such as complications, recurrence, and survival were annotated. Karnofsky performance status (KPS) and QoL were determined preoperatively and at each follow-up visit. RESULTS: Nineteen (44%) patients and 24 (56%) patients underwent partial gastrectomy (PG) and total gastrectomy (TG), respectively. Complications occurred in 30%, and one mortality (2.3%) occurred. Median survival was 23 months. KPS, FACT-G, and FACT-Ga scores all decreased after surgery, and normalized by 6 months. There was no significant difference in QoL in patients who had a PG or TG, although the type of gastrectomy did affect KPS. QoL dropped on average 4.4 ± 3.6 months prior to death. CONCLUSIONS: Surgery adversely affects QoL for up to 6 months. Thereafter, QoL mirrors changes in disease status. More studies are required to document the QoL cost-benefit ratio in gastric cancer, which often is accompanied by short survival benefits.


Assuntos
Adenocarcinoma/cirurgia , Gastrectomia , Recidiva Local de Neoplasia/diagnóstico , Qualidade de Vida , Neoplasias Gástricas/cirurgia , Adenocarcinoma/mortalidade , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Recidiva Local de Neoplasia/mortalidade , Neoplasias Gástricas/mortalidade , Inquéritos e Questionários , Taxa de Sobrevida , Resultado do Tratamento , Adulto Jovem
8.
Palliat Support Care ; 9(3): 305-13, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21838951

RESUMO

OBJECTIVE: The number of diagnosed cases of stomach cancer in Western countries is relatively small compared to prevalence rates in Eastern populations. This disparity creates a general lack of information and understanding of the experience of patients treated for this disease in North America. Surgical removal of the stomach, also called total gastrectomy (TG), is presently the only curative treatment available to patients with stomach cancer. Considering the impact such a procedure may have, very little is known about what factors influence an individual's postsurgical quality of life (QL). METHOD: This article reviews current literature and examines three unique case studies. Semi-structured interviews were analyzed using content analysis, a qualitative analytic approach for reporting combined subject responses. RESULTS: Participants included one 37-year-old man with multiple polyps in his stomach and a family history of stomach cancer, one 18 year-old man with a confirmed CDH1 mutation and a family history of stomach cancer, and one 33-year-old man with confirmed metastatic gastric adenocarcinoma. Subjective patient experience was categorized into: (1) making the decision, (2) treatment impact, and (3) life after TG. Prior to surgery, all patients carefully evaluated their perceived risk compared to the treatment consequences and indicated that a certain event triggered their decision. The largest treatment impacts were learning to eat again and adjusting to the physical changes. Each patient endorsed that their experience made them appreciate and make the most of life. SIGNIFICANCE OF RESULTS: This currently represents the only study to investigate the lived experience of TG for prophylaxis or palliation in individuals with and without genetic risk for stomach cancer. Understanding this process will allow all members of the cancer care team, and the patients themselves, to better understand the factors involved in decision making and postoperative adjustment. Fruitful avenues for future research are discussed.


Assuntos
Adenocarcinoma/cirurgia , Gastrectomia/psicologia , Cuidados Paliativos/métodos , Neoplasias Gástricas/cirurgia , Adenocarcinoma/genética , Adenocarcinoma/prevenção & controle , Adenocarcinoma/psicologia , Adolescente , Adulto , Alberta , Tomada de Decisões , Comportamento Alimentar/fisiologia , Comportamento Alimentar/psicologia , Gastrectomia/efeitos adversos , Predisposição Genética para Doença/psicologia , Humanos , Entrevistas como Assunto , Masculino , Cuidados Paliativos/psicologia , Pesquisa Qualitativa , Anos de Vida Ajustados por Qualidade de Vida , Medição de Risco , Perfil de Impacto da Doença , Neoplasias Gástricas/genética , Neoplasias Gástricas/prevenção & controle , Neoplasias Gástricas/psicologia , Redução de Peso/fisiologia
9.
J Cancer Surviv ; 14(3): 261-272, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-31848998

RESUMO

PURPOSE: Gastrointestinal (GI) cancer patients often suffer high rates of distress and social isolation, partially due to symptoms that are embarrassing or difficult to discuss with family or friends. Group support therapies mitigate illness-related stigma and standardization; however, men, in particular, are more averse to joining. Through an ongoing men-only GI cancer support group, this study sought to understand who joined the groups, what facilitated group uptake, and explore men's reasons for enrolling in the group. METHODS: A mixed-methods study design and analysis were used. A qualitative design utilizing open-ended, semi-structured interviews and thematic analysis were used; Theory of Planned Behavior (TPB) directed the inquiry towards facets of group uptake. Standardized measures were also used to assess distress, coping, and quality of life (QoL) and compared with normative values for cancer and general population. Data from qualitative and quantitative findings were triangulated. RESULTS: Participants included 35 male GI cancer patients, aged 28-72, at varying stages of illness and treatment. Themes related to group uptake and enrollment were endorsement; composition; and attitudes, and reasons for joining were learning new coping techniques and affiliations with similar others. Men's QoL and psychological distress scores were on par with cancer patient norms. The scores obtained from quantitative scales corroborated with our qualitative findings. CONCLUSIONS: Despite psychosocial, demographic, and clinical variations, participants were keen on joining a male-only Supportive-Expressive Therapy (SET) group to address their emotional, informational, and supportive care needs and express their solidarity for other patients. IMPLICATIONS FOR CANCER SURVIVORS: Findings bear clinical relevance for designing GI male-centered group formats that endorse men's needs and facilitate their accessibility to group support interventions.


Assuntos
Adaptação Psicológica/fisiologia , Neoplasias Gastrointestinais/reabilitação , Qualidade de Vida/psicologia , Grupos de Autoajuda/normas , Adulto , Idoso , Neoplasias Gastrointestinais/psicologia , Humanos , Masculino , Pessoa de Meia-Idade
10.
Clin Transplant ; 23(2): 249-55, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19402219

RESUMO

BACKGROUND: Ezetimibe decreases cholesterol in cardiac transplant recipients intolerant to statins therapy. The effects of ezetimibe in addition to statins therapy and its relationship with the magnitude of dyslipidemia and statins utilization have not been studied in cardiac transplant recipients. METHODS: The design of this investigation was a retrospective case control study. Twenty-two patients receiving the combination of therapy of statins plus ezetimibe were compared with 43 patients treated with statins only. The endpoints were assessed after three months of follow-up. RESULTS: The addition of ezetimibe decreased low density lipoprotein-cholesterol by 25% compared with a 4% increase in patients receiving statins only. The impact of ezetimibe was similar regardless of the magnitude of dyslipidemia or statins dosage. Ezetimibe increase high density lipoprotein (HDL)-cholesterol only in patients with baseline HDL-cholesterol above 1.3 mM/L (p < 0.05). There was an asymptomatic, but significant increase in creatinine kinase level [+31.4 +/- 8.1 (ezetimibe) vs. + 1.5 +/- 5.0 mM/L (placebo); p = 0.005]. CONCLUSION: Ezetimibe therapy provides a significant reduction in most cholesterol subfractions regardless of the magnitude of dyslipidemia and statins dosage.


Assuntos
Anticolesterolemiantes/uso terapêutico , Azetidinas/uso terapêutico , HDL-Colesterol/efeitos dos fármacos , LDL-Colesterol/efeitos dos fármacos , Dislipidemias/tratamento farmacológico , Transplante de Coração , Atorvastatina , Estudos de Casos e Controles , Colesterol/metabolismo , Quimioterapia Combinada , Ezetimiba , Feminino , Ácidos Heptanoicos/uso terapêutico , Humanos , Masculino , Pessoa de Meia-Idade , Pravastatina/uso terapêutico , Pirróis/uso terapêutico , Estudos Retrospectivos , Sinvastatina/uso terapêutico , Resultado do Tratamento
11.
Ann Pharmacother ; 43(5): 831-9, 2009 May.
Artigo em Inglês | MEDLINE | ID: mdl-19417110

RESUMO

BACKGROUND: Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) provide similar biologic effects in model systems and similar clinical impacts in humans. The changes in the cardiac angiotensin system signaling pathways in the human heart in response to ACE inhibitors versus ARBs have been incompletely studied. OBJECTIVE: To investigate the effects of ACE inhibitors versus valsartan on the angiotensin II signal transduction pathways in the transplanted human heart. METHODS: Twenty-seven stable cardiac transplant recipients were randomized to remain on ACE inhibitor therapy (n = 8) or to receive valsartan (n = 19). Two additional endomyocardial biopsy samples were obtained at baseline and after 9 months of therapy. The expression of cardiac angiotensin type I and II receptors and atrial natriuretic factor (ANF) was measured by quantitative polymerase chain reaction. The expression and phosphorylation levels of selected signal transduction pathways were analyzed by immunoblotting. RESULTS: The mean dose of valsartan was 114 +/- 41 mg/day. The use of valsartan resulted in a similar impact on blood pressure and biochemistry profile. There were no significant changes in the expression of angiotensin type I and II receptors and ANF with valsartan. Similarly, no significant changes in the expression and phosphorylation of Jun N-terminal kinase, extracellular signal-regulated kinase 1 and 2, and p38 mitogen-activated protein kinases or AKT, and mammalian target of rapamycin was observed in the valsartan-treated group. CONCLUSIONS: Valsartan use is associated with similar clinical and molecular cardiac effects as ACE inhibitor therapy in stable long-term cardiac transplant recipients.


Assuntos
Inibidores da Enzima Conversora de Angiotensina/farmacologia , Transplante de Coração , Coração/efeitos dos fármacos , Coração/fisiologia , Hipertensão/tratamento farmacológico , Transdução de Sinais/efeitos dos fármacos , Tetrazóis/farmacologia , Valina/análogos & derivados , Inibidores da Enzima Conversora de Angiotensina/uso terapêutico , Pressão Sanguínea/efeitos dos fármacos , Creatinina/sangue , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Miocárdio/metabolismo , Potássio/sangue , Receptor Tipo 1 de Angiotensina/metabolismo , Receptor Tipo 2 de Angiotensina/metabolismo , Tetrazóis/uso terapêutico , Valina/farmacologia , Valina/uso terapêutico , Valsartana
12.
Phys Rev E ; 100(3-1): 033210, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31640071

RESUMO

In this third paper of a series, we discuss the physics of the population of accelerated particles in the precursor of an unmagnetized, relativistic collisionless pair shock. In particular, we provide a theoretical estimate of their scattering length l_{scatt}(p) in the self-generated electromagnetic turbulence, as well as an estimate of their distribution function. We obtain l_{scatt}(p)≈γ_{p}ε_{B}^{-1}(p/γ_{∞}mc)^{2}c/ω_{p}, with p the particle momentum in the rest frame of the shock front, ε_{B} the strength parameter of the microturbulence, γ_{p} the Lorentz factor of the background plasma relative to the shock front, and γ_{∞} its asymptotic value outside the precursor. We compare this scattering length to large-scale PIC simulations and find good agreement for the various dependencies.

13.
Phys Rev E ; 100(1-1): 013205, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31499760

RESUMO

In this first paper of a series dedicated to the microphysics of unmagnetized, relativistic collisionless pair shocks, we discuss the physics of the Weibel-type transverse current filamentation instability that develops in the shock precursor, through the interaction of an ultrarelativistic suprathermal particle beam with the background plasma. We introduce in particular the notion of the "Weibel frame," or scattering center frame, in which the microturbulence is of mostly magnetic nature. We calculate the properties of this frame, using first a kinetic formulation of the linear phase of the instability, relying on Maxwell-Jüttner distribution functions, then using a quasistatic model of the nonlinear stage of the instability. Both methods show that (i) the Weibel frame moves at subrelativistic velocities relative to the background plasma, therefore at relativistic velocities relative to the shock front; (ii) the velocity of the Weibel frame relative to the background plasma scales with ξ_{b}, i.e., the pressure of the suprathermal particle beam in units of the momentum flux density incoming into the shock; and (iii) the Weibel frame moves slightly less fast than the background plasma relative to the shock front. Our theoretical results are found to be in satisfactory agreement with the measurements carried out in dedicated large-scale 2D3V particle-in-cell simulations.

14.
Phys Rev E ; 100(3-1): 033209, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31639946

RESUMO

In this second paper of a series, we discuss the dynamics of a plasma entering the precursor of an unmagnetized, relativistic collisionless pair shock. We discuss how this background plasma is decelerated and heated through its interaction with a microturbulence that results from the growth of a current filamentation instability in the shock precursor. We make use, in particular, of the reference frame R_{w} in which the turbulence is mostly magnetic. This frame moves at relativistic velocities towards the shock front at rest, decelerating gradually from the far to the near precursor. In a first part, we construct a fluid model to derive the deceleration law of the background plasma expected from the scattering of suprathermal particles off the microturbulence. This law leads to the relationship γ_{p}∼ξ_{b}^{-1/2} between the background plasma Lorentz factor γ_{p} and the normalized pressure of the beam ξ_{b}; it is found to match nicely the spatial profiles observed in large-scale 2D3V particle-in-cell simulations. In a second part, we model the dynamics of the background plasma at the kinetic level, incorporating the inertial effects associated with the deceleration of R_{w} into a Vlasov-Fokker-Planck equation for pitch-angle diffusion. We show how the effective gravity in R_{w} drives the background plasma particles through friction on the microturbulence, leading to efficient plasma heating. Finally, we compare a Monte Carlo simulation of our model with dedicated PIC simulations and conclude that it can satisfactorily reproduce both the heating and the deceleration of the background plasma in the shock precursor, thereby providing a successful one-dimensional description of the shock transition at the microscopic level.

15.
JACC Heart Fail ; 5(12): 891-901, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-29191295

RESUMO

OBJECTIVES: This study investigated temporal changes in the demographics and the prognosis of cardiac allograft vasculopathy (CAV) over 30 years following heart transplantation (HTx). BACKGROUND: Effects of the changing HTx demographics on CAV outcomes, based on International Society for Heart and Lung Transplantation (ISHLT) classification of CAV, have been incompletely investigated. METHODS: Patients who underwent HTx at the Montreal Heart Institute were classified according to the severity of CAV (CAV 0 is no presence of CAV; CAV 1 is mild, CAV 2 to 3 is moderate to severe) and era of HTx (early: 1983 to 1998; recent: 1999 to 2011). We compared the risk of progression, survival, and independent predictors of outcomes among the groups. RESULTS: A total of 298 patients were followed for 11.6 ± 6.6 years. Patients who received transplants in the early era exhibited a higher risk for progression from CAV 1 to a higher grade (adjusted odds ratio: 8.0; 95% confidence interval [CI]: 1.01 to 62.6). The presence of CAV was associated with a significantly increased risk for all-cause mortality in the early era (hazard ratio [HR]: 1.6; 95% CI: 1.1 to 2.5) but not in the recent era (HR: 1.1; 95% CI: 0.2 to 4.9). Regardless of the era, CAV classes 2 to 3 and CAV 1 were associated with a significantly increased risk for all-cause mortality compared to CAV 0 (HR: 6.5; 95% CI: 2.7 to 15.7; and HR: 1.750; 95% CI: 1.001 to 3.046, respectively). CONCLUSIONS: The progression and prognosis of CAV have improved over 30 years. The ISHLT CAV classification accurately and independently predicts long-term outcome following HTx.


Assuntos
Previsões , Rejeição de Enxerto/epidemiologia , Insuficiência Cardíaca/cirurgia , Transplante de Coração/efeitos adversos , Medição de Risco , Adulto , Aloenxertos , Progressão da Doença , Feminino , Seguimentos , Insuficiência Cardíaca/mortalidade , Humanos , Masculino , Pessoa de Meia-Idade , Prognóstico , Estudos Retrospectivos , Fatores de Risco , Taxa de Sobrevida/tendências , Fatores de Tempo
16.
Can J Cardiol ; 22(2): 121-4, 2006 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-16485046

RESUMO

BACKGROUND: Epidemiological information on patients with acute coronary syndromes managed in specialized cardiac centres is limited. OBJECTIVE: To report the evolution of demographics, treatment and outcome of patients admitted to a tertiary coronary care unit (CCU) over a 17-year period. METHODS: A prospective database of 18,719 patients admitted from April 1986 to March 2003 in a 21-bed CCU was analyzed. RESULTS: From 1986 to 2003, the number of admissions increased from 937 to 1577 per year, while the length of stay declined from 7.5 to 3.5 days. The mean age increased from 58.4 to 63.4 years, and the proportion of men remained stable at approximately 70%. The use of coronary angiograms increased from 49.8% to 81.1% in all patients, while fibrinolysis dropped to 0.4%. In-hospital mortality decreased from 9% to 1.5%. The percentage of overall instrumentation (arterial line, central venous catheter, temporary pacemaker, Swan-Ganz catheter and intra-aortic balloon pump) decreased from 38% to 8.1%. From 1995 to 2003, the proportion of stenting during percutaneous transluminal coronary angioplasty increased dramatically from 0% to 86%. In the past five years, surgical revascularization has remained stable at approximately 20% of all admissions. The proportion of patients discharged with a noncoronary chest pain diagnosis has remained constant at approximately 4%. INTERPRETATION: There has been a tremendous increase in efficiency, with an approximate doubling of the admissions turnover rate in a tertiary CCU. Patients with acute coronary syndromes are stratified faster and treated more invasively. Therapeutic advances are reflected by an almost linear 0.5% per year decrease in in-hospital mortality.


Assuntos
Unidades de Cuidados Coronarianos/estatística & dados numéricos , Doença das Coronárias/epidemiologia , Doença das Coronárias/terapia , Distribuição por Idade , Angioplastia Coronária com Balão/estatística & dados numéricos , Revascularização Cerebral/estatística & dados numéricos , Demografia , Feminino , Humanos , Balão Intra-Aórtico/estatística & dados numéricos , Masculino , Pessoa de Meia-Idade , Avaliação de Resultados em Cuidados de Saúde , Estudos Prospectivos , Quebeque/epidemiologia , Estudos Retrospectivos , Distribuição por Sexo , Stents/estatística & dados numéricos , Resultado do Tratamento
17.
Ann Otol Rhinol Laryngol ; 125(8): 667-71, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27095796

RESUMO

OBJECTIVE: A long-term tracheostomy can be a life-altering event and can have significant effects on patients' quality of life (QOL). There is currently no instrument available to evaluate tracheostomy-specific QOL. To address this deficiency, the objective of this study was to create and preliminarily validate a pilot tracheostomy-specific QOL questionnaire to assess its feasibility. METHODS: A multidisciplinary team developed the pilot tracheostomy-specific QOL questionnaire (TQOL) in 3 phases: item generation, item review, and scale construction. The survey was administered at 0 and 2 weeks to a pilot group of tracheostomy patients with concurrent administration of a validated general QOL questionnaire at week 0. Convergence validity, test-retest reliability, and internal consistency were the primary outcome measures. RESULTS: A total of 37 patients completed the study (mean tracheostomy duration = 90 weeks). The convergence validity of the TQOL was moderately strong (r = 0.72), and the test-retest reliability was strong (r = 0.75). The TQOL also demonstrated good internal consistency (Cronbach's alpha = 0.82). CONCLUSION: The TQOL has moderately strong internal consistency, convergence validity, and test-retest reliability. While additional refinement and validation may improve the questionnaire, these initial results are promising and support further development of this tool.


Assuntos
Qualidade de Vida , Inquéritos e Questionários , Traqueostomia , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos de Viabilidade , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Projetos Piloto , Reprodutibilidade dos Testes
18.
Vasc Cell ; 7: 4, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25922663

RESUMO

BACKGROUND: Vascular endothelial growth factor (VEGF) may play a role on the allograft remodelling following cardiac transplantation (CTx). We measured the circulating levels of VEGF-A165 concomitantly with the proinflammatory (Interleukin-8; IL-8), anti-inflammatory (IL-1 receptor antagonist; IL-1RA) and their release from neutrophils of CTx recipients. METHODS: Eighteen CTx recipients aged 49.6 ± 3.1 years, being transplanted for 145 ± 20 months were age-matched to 35 healthy control (HC) subjects. Concomitantly to plasma assessment, circulating neutrophils were isolated, purified and stimulated by vehicle (PBS), N-formyl-Met-Leu-Phe (fMLP, 10(-7) M), bacterial lipopolysaccharide (LPS, 1 µg/mL), or tumour necrosis factor alpha (TNF-α, 10 ng/mL). RESULTS: Compared with HC, CTx recipients exhibited a decrease (-80%) in plasmatic levels of VEGF-A165 (225 ± 42 (HC) vs 44 ± 10 pg/mL (CTx); (p < 0.001). There were no differences in the levels of IL-8 and IL-1RA. Under basal or stimulated conditions, neutrophils from CTx patients exhibited a marked decrease ranging from -30 to -88% on their capacity to release VEGF-A165, IL-8 and IL-1RA upon stimulation. CONCLUSIONS: Long-term CTx recipients exhibit a marked reduction in the circulating levels of VEGF-A165, as well as neutrophil-mediated release of VEGF-A165, IL-1RA and IL-8 compared to healthy volunteers. The mechanisms and physiological impacts of these findings deserve additional investigations.

19.
J Heart Lung Transplant ; 23(4): 413-7, 2004 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15063400

RESUMO

BACKGROUND: Hypertrophic cardiomyopathy is a rare indication for cardiac transplantation, with only anecdotal reports in the literature. Transplantation has been proposed to patients with hypertrophic cardiomyopathy who remained symptomatic despite optimal medical treatment or who progressed to congestive heart failure, and when conventional surgical correction was not or was no longer possible. In this report, we analyze the clinical results of cardiac transplantation in these patients. METHODS: We retrospectively reviewed complete clinical data and prospectively gathered complete follow-up data for 14 patients who underwent orthotopic cardiac transplantation for hypertrophic cardiomyopathy at the Montreal Heart Institute and Ste-Justine Hospital between 1984 and 2001. RESULTS: Ten male (71.4%, 5 adults and 5 children) and 4 female (28.6%, 2 adults and 2 children) patients underwent heart transplantation for hypertrophic cardiomyopathy. The median age of the recipients in the pediatric group was 13 years (range, 6-16) and was 40 years (range, 22-46) in the adult group. Median duration of follow-up was 9.5 years (mean, 8.8 +/- 4.8 years; range, 1-18) and was 100% complete. We found no operative mortality and found 2 late deaths related to coronary graft atherosclerosis. Long-term survival at 5, 10, and 15 years was 100%, 85%, and 64%, respectively. Freedom from acute rejection at 1, 5, and 10 years was 73%, 32%, and 9%, respectively. The remaining 11 survivors exhibit few symptoms and are currently in New York Heart Association Class I or II. CONCLUSIONS: Cardiac transplantation is a valid therapeutic option for patients with symptomatic hypertrophic cardiomyopathy who do not respond to optimal medical management and who are not candidates for conventional surgical treatment. The long-term outcome is excellent in these patients.


Assuntos
Cardiomiopatia Hipertrófica/cirurgia , Transplante de Coração , Análise Atuarial , Adolescente , Adulto , Cardiomiopatia Hipertrófica/mortalidade , Criança , Doença da Artéria Coronariana/epidemiologia , Feminino , Seguimentos , Humanos , Terapia de Imunossupressão , Masculino , Pessoa de Meia-Idade , Complicações Pós-Operatórias/epidemiologia , Estudos Retrospectivos , Análise de Sobrevida , Resultado do Tratamento
20.
Can J Cardiol ; 20(5): 501-4, 2004 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15100751

RESUMO

BACKGROUND: The Thoratec left ventricular assist device (LVAD; Thoratec Laboratories Corporation, USA) was used as a bridge to transplantation at the Montreal Heart Institute. LVAD patients were activated on the waiting list as soon as they were in suitable clinical status. OBJECTIVE: To analyze the effect of introducing the Thoratec LVAD in the heart transplantation program at the Montreal Heart Institute. METHODS: The results of 16 LVAD patients and 20 patients who underwent heart transplantation without LVAD support between January 2000 and February 2002 were reviewed. RESULTS: Sixteen patients in cardiogenic shock underwent emergency implantation of a Thoratec LVAD following acute myocardial infarction (five patients), acute viral cardiomyopathy (five patients), idiopathic cardiomyopathy (three patients), postpartum cardiomyopathy (two patients) and failure to wean from cardiopulmonary bypass (one patient). Thirteen of 16 (81%) LVAD patients underwent heart transplantation, and three LVAD patients were not listed and died from multiorgan failure. The wait for transplantation averaged 17+/-19 days in LVAD patients compared with 87+/-66 days for the 20 patients undergoing transplantation without LVAD support (P=0.01). Survival 12 months following transplantation averaged 84+/-10% in LVAD supported patients and 90+/-7% in those without LVAD support (P=0.6). CONCLUSION: The use of Thoratec LVAD as a bridge to transplantation did not prolong the wait for a donor of patients without LVAD support (United Network Organ Sharing status II). Moreover, listing patients as soon as they appear suitable for transplantation resulted in a short period of LVAD support and a good rate of survival one year after transplantation.


Assuntos
Cardiopatias/epidemiologia , Cardiopatias/terapia , Transplante de Coração , Coração Auxiliar/estatística & dados numéricos , Avaliação de Resultados em Cuidados de Saúde/estatística & dados numéricos , Listas de Espera , Adulto , Feminino , Cardiopatias/etiologia , Cardiopatias/mortalidade , Humanos , Masculino , Prontuários Médicos , Quebeque/epidemiologia , Estudos Retrospectivos , Análise de Sobrevida
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