On making causal claims: A review and recommendations

Social scientists often estimate models from correlational data, where the independent variable has not been exogenously manipulated; they also make implicit or explicit causal claims based on these models. When can these claims be made? We answer this question by first discussing design and estimation conditions under which model estimates can be interpreted, using the randomized experiment as the gold standard. We show how endogeneity--which includes omitted variables, omitted selection, simultaneity, common methods bias, and measurement error--renders estimates causally uninterpretable. Second, we present methods that allow researchers to test causal claims in situations where randomization is not possible or when causal interpretation is confounded, including fixed-effects panel, sample selection, instrumental variable, regression discontinuity, and difference-in-differences models. Third, we take stock of the methodological rigor with which causal claims are being made in a social sciences discipline by reviewing a representative sample of 110 articles on leadership published in the previous 10 years in top-tier journals. Our key finding is that researchers fail to address at least 66 % and up to 90 % of design and estimation conditions that make causal claims invalid. We conclude by offering 10 suggestions on how to improve non-experimental research.

Acute alcohol consumption and injury: risk associations and attributable fractions for different injury mechanisms.

OBJECTIVE: Most studies on alcohol as a risk factor for injuries have been mechanism specific, and few have considered several mechanisms simultaneously or reported alcohol-attributable fractions (AAFs)-which was the aim of the current study. METHOD: Data from 3,592 injured and 3,489 noninjured patients collected between January 2003 and June 2004 in the surgical ward of the emergency department of the Lausanne University Hospital (Switzerland) were analyzed. Four injury mechanisms derived from the International Classification of Diseases, 10th Revision, were considered: transportation-related injuries, falls, exposure to forces and other events, and interpersonal violence. Multinomial logistic regression models were calculated to estimate the risk relationships of different levels of alcohol consumption, using noninjured patients as quasi-controls. The AAFs were then calculated. RESULTS: Risk relationships between injury and acute consumption were found across all mechanisms, commonly resulting in dose-response relationships. Marked differences between mechanisms were observed for relative risks and AAFs, which varied between 15.2% and 33.1% and between 10.1% and 35.9%, depending on the time window of consumption (either 6 hours or 24 hours before injury, respectively). Low and medium levels of alcohol consumption generally were associated with the most AAFs. CONCLUSIONS: This study underscores the implications of even low levels of alcohol consumption on the risk of sustaining injuries through any of the mechanisms considered. Substantial AAFs are reported for each mechanism, particularly for injuries resulting from interpersonal violence. Observation of a so-called preventive paradox phenomenon is discussed, and prevention or intervention measures are described.

Interventions for smoking cessation in hospitalised patients.

BACKGROUND: Smoking contributes to reasons for hospitalisation, and the period of hospitalisation may be a good time to provide help with quitting. OBJECTIVES: To determine the effectiveness of interventions for smoking cessation that are initiated for hospitalised patients. SEARCH METHODS: We searched the Cochrane Tobacco Addiction Group register which includes papers identified from CENTRAL, MEDLINE, EMBASE and PsycINFO in December 2011 for studies of interventions for smoking cessation in hospitalised patients, using terms including (hospital and patient*) or hospitali* or inpatient* or admission* or admitted. SELECTION CRITERIA: Randomized and quasi-randomized trials of behavioural, pharmacological or multicomponent interventions to help patients stop smoking, conducted with hospitalised patients who were current smokers or recent quitters (defined as having quit more than one month before hospital admission). The intervention had to start in the hospital but could continue after hospital discharge. We excluded studies of patients admitted to facilities that primarily treat psychiatric disorders or substance abuse, studies that did not report abstinence rates and studies with follow-up of less than six months. Both acute care hospitals and rehabilitation hospitals were included in this update, with separate analyses done for each type of hospital. DATA COLLECTION AND ANALYSIS: Two authors extracted data independently for each paper, with disagreements resolved by consensus. MAIN RESULTS: Fifty trials met the inclusion criteria. Intensive counselling interventions that began during the hospital stay and continued with supportive contacts for at least one month after discharge increased smoking cessation rates after discharge (risk ratio (RR) 1.37, 95% confidence interval (CI) 1.27 to 1.48; 25 trials). A specific benefit for post-discharge contact compared with usual care was found in a subset of trials in which all participants received a counselling intervention in the hospital and were randomly assigned to post-discharge contact or usual care. No statistically significant benefit was found for less intensive counselling interventions. Adding nicotine replacement therapy (NRT) to an intensive counselling intervention increased smoking cessation rates compared with intensive counselling alone (RR 1.54, 95% CI 1.34 to 1.79, six trials). Adding varenicline to intensive counselling had a non-significant effect in two trials (RR 1.28, 95% CI 0.95 to 1.74). Adding bupropion did not produce a statistically significant increase in cessation over intensive counselling alone (RR 1.04, 95% CI 0.75 to 1.45, three trials). A similar pattern of results was observed in a subgroup of smokers admitted to hospital because of cardiovascular disease (CVD). In this subgroup, intensive intervention with follow-up support increased the rate of smoking cessation (RR 1.42, 95% CI 1.29 to 1.56), but less intensive interventions did not. One trial of intensive intervention including counselling and pharmacotherapy for smokers admitted with CVD assessed clinical and health care utilization endpoints, and found significant reductions in all-cause mortality and hospital readmission rates over a two-year follow-up period. These trials were all conducted in acute care hospitals. A comparable increase in smoking cessation rates was observed in a separate pooled analysis of intensive counselling interventions in rehabilitation hospitals (RR 1.71, 95% CI 1.37 to 2.14, three trials). AUTHORS' CONCLUSIONS: High intensity behavioural interventions that begin during a hospital stay and include at least one month of supportive contact after discharge promote smoking cessation among hospitalised patients. The effect of these interventions was independent of the patient's admitting diagnosis and was found in rehabilitation settings as well as acute care hospitals. There was no evidence of effect for interventions of lower intensity or shorter duration. This update found that adding NRT to intensive counselling significantly increases cessation rates over counselling alone. There is insufficient direct evidence to conclude that adding bupropion or varenicline to intensive counselling increases cessation rates over what is achieved by counselling alone.

Repeated sprinting on natural grass impairs vertical stiffness but does not alter plantar loading in soccer players.

This study aimed to determine changes in spring-mass model (SMM) characteristics, plantar pressures, and muscle activity induced by the repetition of sprints in soccer-specific conditions; i.e., on natural grass with soccer shoes. Thirteen soccer players performed 6 × 20 m sprints interspersed with 20 s of passive recovery. Plantar pressure distribution was recorded via an insole pressure recorder device divided into nine areas for analysis. Stride temporal parameters allowed to estimate SMM characteristics. Surface electromyographic activity was monitored for vastus lateralis, rectus femoris, and biceps femoris muscles. Sprint time, contact time, and total stride duration lengthened from the first to the last repetition (+6.7, +12.9, and +9.3%; all P < 0.05), while flight time, swing time, and stride length remained constant. Stride frequency decrease across repetitions approached significance (-6.8%; P = 0.07). No main effect of the sprint number or any significant interaction between sprint number and foot region was found for maximal force, mean force, peak pressure and mean pressure (all P > 0.05). Center of mass vertical displacement increased (P < 0.01) with time, together with unchanged (both P > 0.05) peak vertical force and leg compression. Vertical stiffness decreased (-15.9%; P < 0.05) across trials, whereas leg stiffness changes were not significant (-5.9%; P > 0.05). Changes in root mean square activity of the three tested muscles over sprint repetitions were not significant. Although repeated sprinting on natural grass with players wearing soccer boots impairs their leg-spring behavior (vertical stiffness), there is no substantial concomitant alterations in muscle activation levels or plantar pressure patterns.

Deuxième contribution é l'étude de Formica bruni Kutter (Hymenoptera, Formicidae)

Formica bruni décrite en 1966 par Kutter appartient au sous-genre Coptoformica Müll. connue de Forel sous le nom de Formica pressilabris "un peu exsecta ". La biologie de cette espèce est demeurée inconnue jusqu'à nous jours. La découverte d'une nouvelle station au Bois de Chênes, près de Nyon (Vaud, Suisse), nous a poussé à entreprendre une série de travaux afin de savoir dans quelle mesure cette espèce diffère des autres espèces de Coptoformica. La zone étudiée comportait 61 nids en 1978, 18 nids habités par 7 sociétés en 1983 et 2 nids occupés par deux sociétés en juillet 1984. F. bruni est une espèce vraisemblablement polygyne et facultativement polycalique; aucune agressivité n'a été observée entre les sociétés qui, d'autre part, exploitent en commun un même territoire trophique. Les sociétés sont de petites tailles et leur territoire exploité ainsi que leur taux d'activité dépendent principalement de la quantité de nourriture à disposition. Différents facteurs susceptibles de la quasi extinction de cette espèce dans cette station sont discutés (fauchage, pâturage, etc...).

Fluoride supplements (tablets, drops, lozenges or chewing gums) for preventing dental caries in children.

BACKGROUND: Dietary fluoride supplements were first introduced to provide systemic fluoride in areas where water fluoridation is not available. Since 1990, the use of fluoride supplements in caries prevention has been re-evaluated in several countries. OBJECTIVES: To evaluate the efficacy of fluoride supplements for preventing dental caries in children. SEARCH METHODS: We searched the Cochrane Oral Health Group's Trials Register (to 12 October 2011), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 3), MEDLINE via OVID (1950 to 12 October 2011), EMBASE via OVID (1980 to 12 October 2011), WHOLIS/PAHO/MEDCARIB/LILACS/BBO via BIREME (1982 to 12 October 2011), and Current Controlled Trials (to 12 October 2011). We handsearched reference lists of articles and contacted selected authors. SELECTION CRITERIA: We included randomised or quasi-randomised controlled trials comparing, with minimum follow-up of 2 years, fluoride supplements (tablets, drops, lozenges) with no fluoride supplement or with other preventive measures such as topical fluorides in children less than 16 years of age at the start. The main outcome was caries increment measured by the change in decayed, missing and filled tooth surfaces (DMFS). DATA COLLECTION AND ANALYSIS: Two review authors, independently and in duplicate, assessed the eligibility of studies for inclusion, and carried out risk of bias assessment and data extraction. In the event of disagreement, we sought consensus and consulted a third review author. We contacted trial authors for missing information. We used the prevented fraction (PF) as a metric for evaluating the efficacy of the intervention. The PF is defined as the mean caries increment in controls minus mean caries increment in the treated group divided by mean caries increment in controls. We conducted random-effects meta-analyses when data could be pooled. We assessed heterogeneity in the results of the studies by examining forest plots and by using formal tests for homogeneity. We recorded adverse effects (fluorosis) when the studies provided relevant data. MAIN RESULTS: We included 11 studies in the review involving 7196 children.In permanent teeth, when fluoride supplements were compared with no fluoride supplement (three studies), the use of fluoride supplements was associated with a 24% (95% confidence interval (CI) 16 to 33%) reduction in decayed, missing and filled surfaces (D(M)FS). The effect of fluoride supplements was unclear on deciduous or primary teeth. In one study, no caries-inhibiting effect was observed on deciduous teeth while in another study, the use of fluoride supplements was associated with a substantial reduction in caries increment.When fluoride supplements were compared with topical fluorides or with other preventive measures, there was no differential effect on permanent or deciduous teeth.The review found limited information on the adverse effects associated with the use of fluoride supplements. AUTHORS' CONCLUSIONS: This review suggests that the use of fluoride supplements is associated with a reduction in caries increment when compared with no fluoride supplement in permanent teeth. The effect of fluoride supplements was unclear on deciduous teeth. When compared with the administration of topical fluorides, no differential effect was observed. We rated 10 trials as being at unclear risk of bias and one at high risk of bias, and therefore the trials provide weak evidence about the efficacy of fluoride supplements.

Discours économique et évolution institutionnelle, les apports de J. R. Commons

John Roger Commons est, de manière quasi systématique, considéré comme l'un des pères fondateurs de l'ancien institutionnalisme américain. On souligne tout aussi couramment l'influence que la philosophie pragmatiste a pu avoir sur ses travaux, du moins en ce qui concerne son ouvrage de 1934. Plus rares sont les commentateurs soulignant le rôle qu'a le langage, a fortiori le langage de l'économiste, dans l'analyse qu'il fait de l'évolution institutionnelle. Notre but sera de souligner ce fait : pour Commons, dire c'est faire, dans la lignée de la linguistique performativiste, dire c'est agir sur l'évolution institutionnelle. Abstract : John Roger Commons is well known as one of the founders of old institutionnalism. It is current to emphazise his philosophical roots : the american pragmatism, at least in his masterpiece of 1934. On the other hand, it is less frequent to point out the important role that the langage, and a fortiori economics' langage, has in his understanding of institutional evolution. Our aim will be to spotlight this point : for Commons, we can do things with words, on the way of performativist linguistic, when we use words, we influence institutional evolution.

Mineral inventory of continuously erupting basaltic andesites at Arenal volcano, Costa Rica: implications for interpreting monotonous, crystal-rich, mafic arc stratigraphies

Except for the first 2 years since July 29, 1968, Arenal volcano has continuously erupted compositionally monotonous and phenocryst-rich (similar to35%) basaltic andesites composed of plagioclase (plag), orthopyroxene (opx), clinopyroxene (cpx), spinel olivine. Detailed textural and compositional analyses of phenocrysts, mineral inclusions, and microlites reveal comparable complexities in any given sample and identify mineral components that require a minimum of four crystallization environments. We suggest three distinct crystallization environments crystallized low Mg# (<78) silicate phases from andesitic magma but at different physical conditions, such as variable pressure of crystallization and water conditions. The dominant environment, i.e., the one which accounts for the majority of minerals and overprinted all other assemblages near rims of phenocrysts, cocrystallized clinopyroxene (Mg# similar to71-78), orthopyroxene (Mg# similar to71-78), titanomagnetite and plagioclase (An(60) to An(85)). The second environment cocrystallized clinopyroxene (Mg# 71-78), olivine (<Fo(78)), titanomagnetite, and very high An (similar to90) plagioclase, while the third cocrystallized clinopyroxene (Mg# 71-78) with high (>7) Al/Ti and high (>4 wt.%) Al2O3, titanomagnetite with considerable Al2O3 (10-18 wt.%) and possibly olivine but appears to lack plagioclase. A fourth crystallization environment is characterized by clinopyroxene (e.g., Mg#=similar to78-85; Cr2O3=0.15-0.7 wt.%), Al-, Cr-rich spinel olivine (similar toFo(80)), and in some circumstances high-An (>80) plagioclase. This assemblage seems to record mafic inputs into the Arenal system and crystallization at high to low pressures. Single crystals cannot be completely classified as xenocrysts, antecrysts (cognate crystals), or phenocrysts, because they often contain different parts each representing a different crystallization environment and thus belong to different categories. Bulk compositions are mostly too mafic to have crystallized the bulk of ferromagnesian minerals and thus likely do not represent liquid compositions. On the other hand, they are the cumulative products of multiple mixing events assembling melts and minerals from a variety of sources. The driving force for this multistage mixing evolution to generate erupting basaltic andesites is thought to be the ascent of mafic magma from lower crustal levels to subvolcanic depths which at the same time may also go through compositional modification by fractionation and assimilation of country rocks. Thus, mafic magmas become basaltic andesite through mixing, fractionation and assimilation by the time they arrive at subvolcanic depths. We infer new increments of basaltic andesite are supplied nearly continuously to the subvolcanic reservoir concurrently to the current eruption and that these new increments are blended into the residing, subvolcanic magma. Thus, the compositional monotony is mostly the product of repetitious production of very similar basaltic andesite. Furthermore, we propose that this quasi-constant supply of small increments of magma is the fundamental cause for small-scale, decade-long continuous volcanic activity; that is, the current eruption of Arenal is flux-controlled by inputs of mantle magmas. (C) 2004 Elsevier B.V. All rights reserved.

Simulation of interface dynamics across pore discontinuities

We study the dynamics of a water-oil meniscus moving from a smaller to a larger pore. The process is characterised by an abrupt change in the configuration, yielding a sudden energy release. A theoretic study for static conditions provides analytical solutions of the surface energy content of the system. Although the configuration after the sudden energy release is energetically more convenient, an energy barrier must be overcome before the process can happen spontaneously. The energy barrier depends on the system geometry and on the flow parameters. The analytical results are compared to numerical simulations that solve the full Navier-Stokes equation in the pore space and employ the Volume Of Fluid (VOF) method to track the evolution of the interface. First, the numerical simulations of a quasi-static process are validated by comparison with the analytical solutions for a static meniscus, then numerical simulations with varying injection velocity are used to investigate dynamic effects on the configuration change. During the sudden energy jump the system exhibits an oscillatory behaviour. Extension to more complex geometries might elucidate the mechanisms leading to a dynamic capillary pressure and to bifurcations in final distributions of fluid phases in porous

In vivo measurements of atrial repolarization alternans based on standard pacemaker technology

It has been shown that repolarization alternans, a beat-to-beat alternation in action potential duration, enhances dispersion of repolarization above a critical heart rate and promotes susceptibility to ventricular arrhythmias. It is unknown whether repolarization alternans is measurable in the atria using standard pacemakers and whether it plays a role in promoting atrial fibrillation. In this work, atrial repolarization alternans amplitude and periodicity are studied in a sheep model of pacing-induced atrial fibrillation. Two pacemakers, each with one right atrial and ventricular lead, were implanted in 4 male sheep after ablation of the atrioventricular junction. The first one was used to deliver rapid pacing for measurements of right atrial repolarization alternans and the second one to record a unipolar electrogram. Atrial repolarization alternans appeared rate-dependent and its amplitude increased as a function of pacing rate. Repolarization alternans was intermittent but no periodicity was detected. An increase of repolarization alternans preceding episodes of non-sustained atrial fibrillation suggests that repolarization alternans is a promising parameter for assessment of atrial fibrillation susceptibility.

Molecular clock is involved in predictive circadian adjustment of renal function.

Renal excretion of water and major electrolytes exhibits a significant circadian rhythm. This functional periodicity is believed to result, at least in part, from circadian changes in secretion/reabsorption capacities of the distal nephron and collecting ducts. Here, we studied the molecular mechanisms underlying circadian rhythms in the distal nephron segments, i.e., distal convoluted tubule (DCT) and connecting tubule (CNT) and the cortical collecting duct (CCD). Temporal expression analysis performed on microdissected mouse DCT/CNT or CCD revealed a marked circadian rhythmicity in the expression of a large number of genes crucially involved in various homeostatic functions of the kidney. This analysis also revealed that both DCT/CNT and CCD possess an intrinsic circadian timing system characterized by robust oscillations in the expression of circadian core clock genes (clock, bma11, npas2, per, cry, nr1d1) and clock-controlled Par bZip transcriptional factors dbp, hlf, and tef. The clock knockout mice or mice devoid of dbp/hlf/tef (triple knockout) exhibit significant changes in renal expression of several key regulators of water or sodium balance (vasopressin V2 receptor, aquaporin-2, aquaporin-4, alphaENaC). Functionally, the loss of clock leads to a complex phenotype characterized by partial diabetes insipidus, dysregulation of sodium excretion rhythms, and a significant decrease in blood pressure. Collectively, this study uncovers a major role of molecular clock in renal function.

Low-dose radiotherapy (2x2 Gy) in indolent lymphoma

Dans la prise en charge des maladies oncologiques, la priorité est évidemment d'assurer le contrôle de la maladie (soit le taux de récidive local et la survie globale), surtout lorsque celle-ci est diagnostiquée tôt, à un stade précoce. Cependant, lorsque la maladie est plus avancée et que ce contrôle ne peut être assuré de façon raisonnable, l'accent de la prise en charge est surtout axé sur le confort du patient. Le principe est de fournir à celui-ci, dans la mesure du possible, une qualité de vie acceptable, avec notamment des douleurs bien contrôlées.Dans le cadre de ce travail de thèse, nous nous sommes intéressés à la prise en charge palliative des lymphomes non hodgkiniens (LNH) de bas grade. La survie de ces patients peut être relativement longue (de 5 à 10 ans selon les séries), cependant, le traitement est rarement à visée curative, contrairement aux lymphomes de haut grade, dont la survie est bien moindre, mais avec une chance de guérison après un traitement intensif.Plusieurs études cliniques, à la fois prospectives et rétrospectives, ont démontré l'intérêt d'une irradiation à faible dose {2x2 Gy) lors d'atteintes tymphomateuses à l'origine de symptômes gênants (douleurs, compression par une masse, dyspnée, entre autres). Etant donné la facilité d'administration de ce traitement (seulement 2 séances de radiothérapie sont nécessaires), et sa quasi absence de survenue d'effets secondaires avec cette faible dose totale (4 Gy), nous avons voulu y apporter une contribution suisse.Notre étude rétrospective a permis d'inclure 43 patients entre le CHUV et les HUG. Les résultats que nous avons obtenus sont également dans la ligne des autres études parues, avec un excellent contrôle local, soit un soulagement rapide et durable des symptômes dans la majorité des cas.Nous espérons que ce travail de thèse, publié sous forme d'un article dans « International Journal of Radiation Oncology, Biology, Physics », permettra une prise en charge plus optimale des ces patients en leur apportant un traitement facile à administrer, efficace, sans effets secondaires dans la majorité des cas, et pouvant être répété un grand nombre de fois si nécessaire.

Tout savoir sur les salaires

La question des différences salariales apparaît quasi quotidiennement dans l'actualité. Qu'elle soit abordée sous l'angle de la discrimination entre hommes et femmes, de l'écart entre le salaire le plus bas et celui le plus élevé dans les entreprises ou des différences qui existent entre les branches économiques, elle préoccupe et interpelle. Et tout particulièrement les apprenants qui, au moment de se lancer dans le monde du travail, s'interrogent sur la voie professionnelle à choisir.

Acetylcholinesterase inhibitor treatment for myasthenia gravis.

BACKGROUND: In myasthenia gravis, antibody-mediated blockade of acetylcholine receptors at the neuromuscular junction abolishes the naturally occurring 'safety factor' of synaptic transmission. Acetylcholinesterase inhibitors provide temporary symptomatic treatment of muscle weakness, but there is controversy about their long-term efficacy, dosage and side effects. OBJECTIVES: To evaluate the efficacy of acetylcholinesterase inhibitors in all forms of myasthenia gravis. SEARCH STRATEGY: We searched The Cochrane Neuromuscular Disease Group Specialized Register (5 October 2009), The Cochrane Central Register of Controlled Trials CENTRAL) (The Cochrane Library Issue 3, 2009), MEDLINE (January 1966 to September 2009), EMBASE (January 1980 to September 2009) for randomised controlled trials and quasi-randomised controlled trials regarding usage of acetylcholinesterase inhibitors in myasthenia gravis. Two authors scanned the articles for any study eligible for inclusion. We also contacted the authors and known experts in the field to identify additional published or unpublished data. SELECTION CRITERIA: Types of studies: all randomised or quasi-randomised trials.Types of participants: all myasthenia gravis patients diagnosed by an internationally accepted definition.Types of interventions: treatment with any form of acetylcholinesterase inhibitor.Types of outcome measuresPrimary outcome measureImprovement in the presenting symptoms within 1 to 14 days of the start of treatment.Secondary outcome measures(1) Improvement in the presenting symptoms more than 14 days after the start of treatment.(2) Change in impairment measured by a recognised and preferably validated scale, such as the quantitative myasthenia gravis score within 1 to 14 days and more than 14 days after the start of treatment.(3) Myasthenia Gravis Association of America post-intervention status more than 14 days after start of treatment.(4) Adverse events: muscarinic side effects. DATA COLLECTION AND ANALYSIS: One author (MMM) extracted the data, which were checked by a second author. We contacted study authors for extra information and collected data on adverse effects from the trials. MAIN RESULTS: We did not find any large randomised or quasi-randomised trials of acetylcholinesterase inhibitors in generalised myasthenia gravis. One cross-over randomised trial using intranasal neostigmine in a total of 10 subjects was only available as an abstract. AUTHORS' CONCLUSIONS: Except for one small and inconclusive trial of intranasal neostigmine, no randomised controlled trial has been conducted on the use of acetylcholinesterase inhibitors in myasthenia gravis. Response to acetylcholinesterase inhibitors in observational studies is so clear that a randomised controlled trial depriving participants in the placebo arm of treatment would be difficult to justify.

The L-Type Ca2+ and KATP channels may contribute to pacing-induced protection against anoxia-reoxygenation in the embryonic heart model

Rapport de synthèse : Implication des canaux Ca2+ de type L et des canaux KATP dans la protection induite par pacing dans un modèle de coeur embryonnaire soumis à l'anoxieréoxygénation. Contexte et but : le canal Ca2+ de type L, les canaux K+ du sarcolemme (sarcKatp) et de la mitochondrie (mitoKatp) interviennent dans le préconditionnement ischémique ou pharmacologique du myocarde. La présente étude cherche à déterminer dans quelle mesure ces canaux peuvent aussi jouer un rôle dans la cardioprotection induite par pacing. Méthodes :des coeurs d'embryons de poulet âgés de 4 jours ont été soumis in ovo à un pacing durant 12 heures, en pratiquant une stimulation électrique ventriculaire asynchrone intermittente à 110% de la fréquence cardiaque intrinsèque. Les coeurs contrôles (sham) et les coeurs stimulés ont ensuite été soumis in vitro à une période d'anoxie de 30 minutes, suivie d'une réoxygénation de 60 minutes. Les coeurs ont été exposés à l'agoniste du canal Ca2+ de type L (Bay-K-8644, BAY-K) ou à son bloqueur (vérapamil, VERAP), à l'antagoniste non sélectif des canaux KATP (glibenclamide, GLIB), ainsi qu'à l'agoniste du canal mitoKATP (diazoxide, DIAZO), ou à son antagoniste (5-hydroxydécanoate, 5-HD). L'électrocardiogramme, le délai électro-mécanique (DEM) reflétant le couplage excitation-contraction, ainsi que la contractilité myocardique ont été systématiquement déterminés pendant l'anoxieréoxygénation. Résultats : en normoxie, la fréquence cardiaque, l'intervalle QT, la conduction atrioventriculaire, le DEM et le raccourcissement ventriculaires étaient identiques dans les coeurs sham et les coeurs stimulés. Par contre, au cours de la réoxygénation post-anoxique, les arythmies cessaient plus précocément et le DEM ventriculaire retrouvait plus rapidement son niveau initial dans les coeurs stimulés, comparés aux sham. Dans les coeurs sham, BAY-K (mais pas le VERAP), DIAZO (mais pas le 5HD) ou GLIB accéléraient la récupération du DEM ventriculaire, reproduisant ainsi la protection induite par le pacing. En revanche, aucun de ces agents n'affectait la récupération des cceurs stimulés. Conclusion : un pacing ventriculaire chronique et intermittent délivré à une fréquence quasi physiologique améliore la tolérance myocardique à une anoxie-réoxygénation ultérieure. L'approche pharmacologique amontré qu'une activation discrète du canal Ca2+ de type L, une inhibition du canal sarcKATP et/ou une ouverture du canal mitoKATP peuvent contribuer à la cardioprotection induite par le pacing.