I. The role of research ethics committees in observational studies: epidemiological registries, case reports, interviews, and retrospective studies

Abstract It is often unclear to the clinical investigator whether observational studies should be submitted to a research ethics committee (REC), mostly because, in general, no active or additional interventions are performed. Moreover, obtaining an informed consent under these circumstances may be challenging, either because these are very large epidemiological registries, or the subject may no longer be alive, is too ill to consent, or is impossible to contact after being discharged. Although observational studies do not involve interventions, they entail ethical concerns, including threats such as breaches in confidentiality and autonomy, and respect for basic rights of the research subjects according to the good clinical practices. In this context, in addition to their main function as evaluators from an ethical, methodological, and regulatory point of view, the RECs serve as mediators between the research subjects, looking after their basic rights, and the investigator or institution, safeguarding them from both legal and unethical perils that the investigation could engage, by ensuring that all procedures are performed following the international standards of care for research. The aim of this manuscript is to provide information on each type of study and its risks, along with actions to prevent such risks, and the function of RECs in each type of study.

Fasting insulin and alanine amino transferase, but not FGF21, were independent parameters related with irisin increment after intensive aerobic exercising

Abstract Background Irisin is a protein cleaved from fibronectin type III domain-containing protein 5 and has been implicated in the beneficial effects of exercise. However, it is unknown which factors contribute to irisin increment after intensive exercising in humans. This study aimed to assess independent factors related with serum irisin after 2 weeks of supervised physical activity in young sedentary healthy women. Design and Methods We developed a comparative, interventional, longitudinal, and prospective study at a third-level specialty health center. Between March 2010 and August 2011, 82 sedentary young adult women, without chronic diseases or regular medical treatments, were recruited. A total of 38 women fulfilled selection criteria, and irisin concentrations were quantified before and after the intervention. Independent factors related with irisin increment were evaluated according to mild to moderate and vigorous intensity of physical activity. A supervised treadmill exercise test following the Bruce’s protocol was conducted from Monday to Friday during 2 weeks. In addition, anthropometric measurements were taken, and fibroblast growth factor 21 (FGF21), glucose, insulin, and liver transaminases were measured. Results Intensity of exercising was directly related to irisin (p = 0.02) and FGF21 (p = 0.01) serum levels. However, an independent and significant relationship between FGF21 and irisin was not confirmed. A novel association was found between alanine aminotransferase (ALT) and irisin, showing a positive and significant correlation (r = 0.37, p = 0.02). The association was particularly strong with higher intensity of aerobic exercising (r = 0.64, p = 0.01). Linear regression model adjusted for glucose and body mass index confirmed an independent association between ALT and irisin and also between insulin and irisin (adjusted R² = 0.12, p = 0.04). Such association increased after grouping in moderate to vigorous physical activity intensity (adjusted R² = 0.46, F = 4.7, p = 0.03). Conclusions Serum irisin and FGF21 levels significantly increased after 2 weeks of supervised physical activity. However, only fasting insulin and ALT, but not FGF21, were independent parameters explaining irisin increment, mainly after moderate to vigorous exercising.

Comportamiento diferencial de la tensión arterial de pacientes con síncope neuro-cardiogénico en la fase inicial de la prueba de inclinación / Differential behaviour of blood pressure in patients with neurocardiogenic syncope during the initial stage of the tilt table test

Neurocardiogenic syncope (NCS) is diagnosed by means of a head-up tilt table tests (HUTT). This is a prolonged test although early outcome predictors are known. METHODS: We conducted a study among patients engaged in a syncope study protocol. We performed HUTT in all of them and compared the basal arterial pressure with the arterial pressure at the end of a the 70 degrees tilting. RESULTS: We performed 185 HUTT studies. Systolic blood pressure (BP) raised 0.9% among patients with a negative test, whereas patients with a positive HUTT showed a 2.3% decrease (p = 0.2) in the same measurement. Diastolic BP increased 34% among negative HUTT patients and 14.9% among patients with positive test (p = 0.02). We calculated a relative risk of 1.45 for positive test when the combination of systolic BD decrease and dyastolic increase was present, according to the percentage of change (IC95%: 1.1 to 7.8). CONCLUSIONS: The combination of systolic BP reduction and diastolic BP elevation at the end of the 70 degrees tilting is associated with an increased risk of having a positive HUTT. These changes might be related to differential sympathetic stimulation.

Fibrilación auricular: nuevos aspectos sobre una vieja enfermedad / Atrial Fibrillation: new aspects of an old disease

La fibrilación auricular es la arritmia encontrada más frecuentemente en la clínica. Los principales problemas derivados de ella son los eventos trombóticos recurrentes y el deterioro de la clase funcional. La fibrilación auricular induce alteraciones de los canales iónicos, que la perpetoan. El tratamiento de la FA se encamina a corregir estas alteraciones y regresar al ritmo sinusal, al tiempo que se debe controlar la frecuencia cardiaca y prevenir eventos embólicos por medio de anticoagulación o tratamiento con antiagregantes plaquetarios. Actualmente existen recursos con antiarrítmicos de clase IC o clase III para intentar recuperar el ritmo sinusal. Las tasas de éxito son variables y las mejores se obtienen con flecainida o propafenona en los casos sin cardiopatía estructural y amiodarona cuando ésta existe. Las combinaciones de pacientes y fármacos son múltiples, cada caso debe ser individualizado. Los nuevos antiarrítmicos de clase III han mostrado eficacia pero con tasas relativamente altas de reacciones adversas como taquicardia helicoidal. La anticoagulación sería el tratamiento preferido para la mayoría de los enfermos, pero se debe ajustar en cada caso. Las terapias como la ablación con catéter focal o lineal, así como la estimulación auricular o biauricular y los desfibriladores implantables requieren de un seguimiento a mayor plazo y también necesitan de tratamiento antiarrítmico agregado. La cirugía tiene una morbi-mortalidad alta, por lo que el riesgo supera al beneficio.

Cardiac conduction distrurbances in mixed connective tissue disease

Objetivo: Determinar la prevalencia de trastornos de conducción cardiaca en pacientes con enfermedad mixta de tejido conectivo, atendidos en un instituto de la Ciudad de México y su relación con otras manifestaciones de la enfermedad. Método: Ciento trece pacientes admitidos en el Instituto con diagnóstico de enfermedad mixta de tejido conectivo fueron divididos en aquellos con alteraciones de conducción (n=23) y sin estos (n=90). Durante un período de seguimiento de 10.2 ñ 7.8 años, se examinaron, el curso clínico, duración de la enfermedad, tratamiento, tipos de trastornos de conducción y alteraciones sistémicas. Resultados: Observamos un marcado predominio de mujeres en ambos grupos. Las alteraciones de conducción ocurrieron en cerca de 20 por ciento de los pacientes con enfermedad mixta de tejido conectivo y no encontramos diferencias significativas entre los grupos durante el seguimiento. Como era de esperarse, una diferencia significativa entre ambos fue la desviación del aQRS, relacionado a la presencia del bloqueo de fascículo anterior de la rama izquierda del HH, la más frecuente de las alteraciones de conducción observadas. Durante el seguimiento un paciente del grupo A murió, pero ninguno en el grupo B. Conclusión: Las alteraciones de conducción estuvieron presentes en 20 por ciento, en concordancia con lo referido por otros autores en la literatura. Sin embargo, no participaron en la evolución de la enfermedad.