Determination of the myocardial area at risk after reperfused acute myocardial infarction with different imaging techniques: cardiac magnetic resonance imaging, multidetector computed tomography and histopathological validation

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Protection du greffon cardiaque durant l'ischémie froide de la reperfusion

Le manque crucial d'organes est un problème majeur rencontré en transplantation cardiaque. L'objectif de ce travail est de tenter d'améliorer la protection du greffon cardiaque durant la conservation froide et lors de la reperfusion. Les résultats majeurs que nous avons obtenus sont les suivants : Parmi les solutions de conservation cardiaque les plus utilisées, cliniquement et/ou expérimentalement, les solutés LYPS (issu de notre laboratoire) et Celsior assurent la meilleure préservation. De plus, la présence des ions calcium dans les solutés, de type intracellulaire ou extracellulaire, est déterminante pour la qualité de la conservation. La microperfusion est une technique de préservation de longue durée du cœur supérieure à la technique de simple immersion. L'application d'une basse pression de reperfusion protège les cœurs en situation d'ischémie chaude irréversible. Cette protection semble impliquer le pore de transition membranaire de la mitochondrie. Paradoxalement, nous n'avons pas obtenu de cardioprotection après une ischémie froide avec le soluté Saint-Thomas. La plupart de ces résultats nous ont permis de faire le point sur des controverses existantes dans le domaine de la conservation froide du greffon cardiaque. Par ailleurs, nous avons abordé deux nouvelles voies, originales, de protection visant à modifier la structure même du cardiomyocyte : Modifications des structures membranaires, par incorporation d'acides gras insaturés dans les cardiomyocytes. Cet enrichissement nous a permis d'abaisser l'activité contractile des cellules cardiaques à basse température (7ʿC). Modifications génétiques, par transduction de gènes thérapeutiques dans le myocarde. Dans cette approche, les vecteurs viraux herpétiques de type amplicons semblent être de très bons candidats pour la thérapie génique myocardique.LYON1-BU Santé (693882101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

[Improving donor heart preservation ex vivo].: Improving donor heart preservation ex vivo

Communication suite à la séance du 31 mai 2011 "Optimiser la reprise fonctionnelle d'un greffon en attente de transplantation" - 21 pagesNational audienceThere is a shortage of heart donors. Some available organs are lost through deterioration prior to transplantation. Indeed, from the moment of brain death until reperfusion in the recipient, cardiac grafts (and also kidney, lung and liver grafts) can undergo irreversible damage due to cardioplegia, the harvesting procedure, and hypothermic transport. The noxious phenomena occurring during cold ischaemia and myocardial reperfusion have been studied for more than 40 years. It was long believed that only the ischaemic phase was harmful, through depletion of energy stores, ionic imbalance, and metabolic disruption. We now know that the heart graft can also be damaged during the reperfusion phase, through calcium overload, free radical production, and mitochondrial changes. Preconditioning and post-conditioning procedures are being developed to protect the ischemic organ

Brain Death Does Not Change Epicardial Action Potentials and Their Response to Ischemia–Reperfusion in Open-chest Pigs

International audienceBackground: It is debated whether brain death (BD) causes transient functional ischemia. Here we used monophasic action potential (AP) recording, as a sensitive means to assess, during BD, (i) whether ischemia was present, (ii) the effect of BD on a subsequent ischemia-reperfusion challenge. Methods: Period 1: BD was induced (BD group, six pigs) or not (sham maneuver, C group, six pigs) and effects were followed up for 3 hours. Period 2: LAD ligation ischemia was applied for 20 min to all hearts, and was followed by 60-min reperfusion. Results: Period 1: plasma norepinephrine was 3.1, 6.3 and 5 fold larger in BD versus C at respectively 1, 120 and 180 minutes and systolic blood pressure was larger by 26% at 1 min and 35% at 120 minutes. The arterio-venous difference in lactate was similar or lower in BD versus C. In both groups, at all times, AP had rectangular plateau shape and the action potential duration (APD 50) followed a linear relationship to the RR interval (R 2 = 0.89 and 0.73, slope = 0.42±0.02 and 0.46±0.06 in BD and C respectively). Period 2: ischemia caused a similar (50%) APD shortening in BD and C. Restoration of APD upon reperfusion was complete in both groups. Conclusions: These data suggest that BD does not cause direct cardiac ischemia and does not change the response of the heart to subsequent ischemia-reperfusion challenge

Postconditioning by Delayed Administration of Ciclosporin A: Implication for Donation after Circulatory Death (DCD)

International audienceHeart transplantation is facing a shortage of grafts. Donation after Circulatory Death (DCD) would constitute a new potential of available organs. In the present work, we aimed to evaluate whether Postconditioning (ischemic or with ciclosporin-A (CsA)) could reduce ischemia-reperfusion injury in a cardiac arrest model when applied at the start of reperfusion or after a delay. An isolated rat heart model was used as a model of DCD. Hearts were submitted to a cardiac arrest of 40 min of global warm ischemia (37 °C) followed by 3 h of 4 °C-cold preservation, then 60 min reperfusion. Hearts were randomly allocated into the following groups: control, ischemic postconditioning (POST, consisting of two episodes each of 30 s ischemia and 30 s reperfusion at the onset of reperfusion), and CsA group (CsA was perfused at 250 nM for 10 min at reperfusion). In respective subgroups, POST and CsA were applied after a delay of 3, 10, and 20 min. Necrosis was lower in CsA and POST versus controls (p < 0.01) whereas heart functions were improved (p < 0.01). However, while the POST lost its efficacy if delayed beyond 3 min of reperfusion, CsA treatment surprisingly showed a reduction of necrosis even if applied after a delay of 3 and 10 min of reperfusion (p < 0.01). This cardioprotection by delayed CsA application correlated with better functional recovery and higher mitochondrial respiratory index. Furthermore, calcium overload necessary to induce mitochondrial permeability transition pore (MPTP) opening was similar in all cardioprotection groups, suggesting a crucial role of MPTP in this delayed protection of DCD hearts

Non-beating HL-1 cells for confocal microscopy: application to mitochondrial functions during cardiac preconditioning.

International audienceHL-1, the first cell line with a cardiac phenotype for biological experiments, displays spontaneous electrophysiological and mechanical regular activity, and cyclic calcium movements. We isolated a derived line, devoid of transient movements, for confocal microscopy experiments. These cells do express cardiac proteins: connexin 43, the cardiac isoform of dihydropyridine receptors, desmin, and developmental myosin but have no sarcomeric arrangement. They still possess the electrophysiological characteristics and ionic currents of cardiac cells, among them the cardiac potassium current IKr. We also found diazoxide and glibenclamide sensitive potassium channels with properties similar to IK(ATP) in adult cardiac myocytes. The pacemaker current I(f) was not observed, in agreement with the cells showing excitability but lacking in pacemaker activity. The absence of movement is an advantage for studies which include changes of media in order to follow morphological changes under continuous perfusion. We observed however a basal spontaneous movement of mitochondria and we developed a method to quantify its amplitude using confocal microscopy. No mitochondrial depolarization could be detected when the membrane potential was measured by using very low light photomultiplier and confocal fluorescence imaging under the K(ATP) channel opener diazoxide. Thus cardiac pharmacological preconditioning by K(ATP) channel openers might involve other routes than mitochondrial K channels targeting

Quantitative stiffness assessment of cardiac grafts using ultrasound in a porcine model: A tissue biomarker for heart transplantation

International audienceBackground Heart transplantation is the definitive treatment for many cardiovascular diseases. However, no ideal approach is established to evaluate heart grafts and it mostly relies on qualitative interpretation of surgeon based on the organ aspect including anatomy, color and manual palpation. In this study we propose to assess quantitatively the Shear Wave Velocity (SWV) using ultrasound as a biomarker of cardiac viability on a porcine model. Methods The SWV was assessed quantitatively using a clinical ultrasound elastography device (Aixplorer, Supersonics Imagine, France) linked to a robotic motorized arm (UR3, Universal Robots, Denmark) and the elastic anisotropy was obtained using a custom ultrasound research system. SWV was evaluated as function of time in two porcine heart model during 20h at controlled temperature (4°C). One control group (N = 8) with the heart removed and arrested by cold cardioplegia and immerged in a preservation solution. One ischemic group (N = 6) with the organ harvested after 30 min of in situ warm ischemia, to mimic a donation after cardiac death. Hearts graft were revived at two preservation times, at 4 h (N = 11) and 20 h (N = 10) and the parameters of the cardiac function evaluated. Findings On control hearts, SWV remained unchanged during the 4h of preservation. SWV increased significantly between 4 and 20h. For the ischemic group, SWV was found higher after 4h (3.04 +/-0.69 vs 1.69+/-0.19 m/s, p = 0.007) and 20h (4.77+/-1.22 m/s vs 3.40+/-0.75 m/s, p = 0.034) of preservation with significant differences. A good correlation between SWV and cardiac function index was found (r 2 =0.88) and manual palpation score (r 2 =0.81). Interpretation Myocardial stiffness increase was quantified as a function of preservation time and harvesting conditions. The correlation between SWV and cardiac function index suggests that SWV could be used as a marker of graft viability. This technique may be transposed to clinical transplantation for assessing the graft viability during transplantation process

Comparison between Multi Line Transmission and Diverging Wave Imaging: assessment of image quality and motion estimation accuracy

International audienceHigh frame rate imaging is particularly important in echocardiography for a better assessment of the cardiac function. Several studies showed that Diverging Wave Imaging (DWI) and Multi Line Transmit (MLT) are promising methods for achieving a high temporal resolution. The aim of this study was to compare MLT and compounded motion compensated (MoCo) DWI for the same transmitted power, the same frame rates (image quality and Speckle Tracking Echocardiography-STE assessment) and the same packet size (Tissue Doppler Imaging-TDI assessment). Our results on static images showed that MLT outperforms DW in terms of resolution (by 30% in average). However, in terms of contrast, MLT outperforms DW only for the depth of 11 cm (by 40% in average), the result being reversed at a depth of 4 cm (by 27 % in average). In vitro results on a spinning phantom at 9 different velocities showed that similar STE axial errors (up to 2.3% difference in median errors and up to 2.1% difference in the interquartile ranges) are obtained with both ultrafast methods. On the other hand, the median lateral STE estimates were up to 13% more accurate with DW than with MLT. On the opposite, the accuracy of TDI was only up to ~3% better with MLT, but the achievable DW Doppler frame rate was up to 20 times higher. However, our overall results showed that the choice of one method relative to the other is therefore dependent on the application. More precisely, in terms of image quality, DW is more suitable for imaging structures at low depths, while MLT can provide an improved image quality at the focal point that can be placed at higher depths. In terms of motion estimation, DW is more suitable for color Doppler related applications, while MLT could be used to estimate velocities along selected lines of the image