MRI monitoring of focal cerebral ischemia in peroxisome proliferator-activated receptor (PPAR)-deficient mice.

Peroxisome proliferator-activated receptors (PPARs) are a potential target for neuroprotection in focal ischemic stroke. These nuclear receptors have major effects in lipid metabolism, but they are also involved in inflammatory processes. Three PPAR isotypes have been identified: alpha, beta (or delta) and gamma. The development of PPAR transgenic mice offers a promising tool for prospective therapeutic studies. This study used MRI to assess the role of PPARalpha and PPARbeta in the development of stroke. Permanent middle cerebral artery occlusion induced focal ischemia in wild-type, PPARalpha-null mice and PPARbeta-null mice. T(2)-weighted MRI was performed with a 7 T MRI scan on day 0, 1, 3, 7 and 14 to monitor lesion growth in the various genotypes. General Linear Model statistical analysis found a significant difference in lesion volume between wild-type and PPAR-null mice for both alpha and beta isotypes. These data validate high-resolution MRI for monitoring cerebral ischemic lesions, and confirm the neuroprotective role of PPARalpha and PPARbeta in the brain.

Endocytosis, autophagy and JNK inhibition in neuroprotection against excitotoxicity and neonatal cerebral ischemia

Abstract : Neonatal stroke occurs in 1 out of 4000 live births and usually leads to serious motor and cognitive disabilities. Ischemic brain injury results from a complex of pathophysiological events that evolve over space and time making it difficult to devise successful therapy. To date, there are no effective treatments for perinatal brain damage. Most clinical trials of neuroprotectaot drugs have failed because of their side-effects. For this reason it is important to find ways to target drugs specifically into the stressed cells. In this study we plan to contribute to the development of an efficient neuroprotective strategy against excitotoxic cell death in the neonate. In order to achieve this goal, several strategies were followed. A recently described phenomenon of induced endocytosis associated with excitotoxicity was more deeply investigated. As a simplified model we used dissociated cortical neurons exposed to an excitotoxic dose of NMDA, and we showed that this phenomenon depends on clathrin and dynamin. Using a model of neonatal focal cerebral ischemia, we demonstrated that the excitotoxicity-related endocytosis targets molecules such as TAT peptides into stressed neurons. These appear to be viable, raising the possibility of using this phenomenon as a doorway for neuroprotection. One part of the project was devoted to the study of the TAT-conjugated JNK inhibitory peptide, D-JNKI1. Adose-response study showed strong neuroprotection over a wide dose-range in the case of delayed administration (either intravenous or intraperitoneal). Since D-JNKI1 is aTAT-linked peptide, we investigated the role of its own NMDA-induced endocytosis in its neuroprotective efficacy. Furthermore, we showed that this endocytosis is JNK dependent, and that D-JNKI1 regulates its own uptake. We additionally studied the different types of cell death involved in a model of neonatal focal cerebral ischemia. Necrosis occurred rapidly in the center of the lesion whereas apoptosis and autophagic cell death occurred late at the lesion border. Inhibiting apoptosis was not protective, but use of autophagy inhibitor 3methyladenine provided a strong neuroprotection. Finally, combining two neuroprotectants that target different intracellular pathways was neuroprotective in a severe model of cerebral ischemia where neither of the drugs was efficient when administered individually. Résumé : L'ischémie néonatale connaît une incidence de 1 naissance sur 4000, entraînant généralement de sérieux dysfonctionnements moteurs et cognitifs. L'ischémie cérébrale résulte d'évènements physiopathologiques complexes qui évoluent dans l'espace et le temps rendant difficile la conception de thérapies efficaces. A l'heure actuelle, aucun traitement n'existe pour lutter contre les accidents vasculaires cérébraux qui se produisent autour de la naissance. La plupart des essais cliniques concernant des molécules neuroprotectrices ont échoué du fait de leurs effets secondaires néfastes. Pour cette raison, il est important de trouver des moyens de cibler les drogues dans les cellules stressées spécifiquement. Dans cette étude nous visons à participer au développement d'une stratégie neuroprotectrice efficace contre l'ischémie cérébrale chez le nouveau-né. Dans ce but, plusieurs stratégies ont été poursuivies. Un nouveau phénomène d'endocytose induite par un stimulus excitotoxique a été récemment décrit. Une partie de cette étude va consister à mieux comprendre ce phénomène. Pour céla, nous avons utilisé comme modèle d'étude simplifié des cultures dissociées de neurones corticaux exposées à une dose excitotoxique de NMDA. Nous avons ainsi montré que cette endocytose associée à l'excitotoxicité dépend de la clathrine et de la dynamine. A l'aide d'un modèle d'ischémie cérébrale focale chez le raton de 12 jours, nous avons démontré que cette endocytose induite par l'excitotoxicité permet de cibler des molécules diverses et en particulier les peptides TAT dans les neurones stressés. Ces neurones fortement endocytiques apparaissent comme étant encore viables, ouvrant la possibilité d'utiliser cette endocytose comme moyen d'entrée pour des molécules thérapeutiques. Une partie du projet a été consacrée à l'étude d'un inhibiteur de la voie JNK, couplé au TAT, appelé D-JNKI1. Des études de dose réponse du D-JNKI1 ont été réalisées chez l'animal, testant les effets d'une administration retardée en injection intraveineuse ou intra péritonéale. Ces études démontrent qu'une large gamme de dose permet d'obCenir une réduction de la taille de la lésion. Comme D-JNK11 est couplé au peptide TAT, nous avons étudié la contribution que sa propre endocytose lors de l'excitotoxicité apporte à ses effets protecteurs. Par ailleurs, nous avons montré que cette endocytose induite par l'excitotoxicité dépend de la voie de signalisation JNK et que D-JNK11 est donc capable de réguler sa propre entrée. Nous avons en parallèle étudié les différents types de mort cellulaires impliqués dans le développement de la lésion dans un modèle sévère d'ischémie cérébrale chez le raton nouveau-né. La mort cellulaire par nécrose se développe rapidement dans le centre de la lésion alors que les morts cellulaires par apoptose et autophagique vont apparaître plus tard et au bord de la lésion. Inhiber l'apoptose n'a pas permis de réduire la taille de la lésion alors que l'utilisation d'un inhibiteur d'autophagie, la 3-méthyladénine, procure une forte neuroprotection. Finalement, la combinaison de deux peptides qui ciblent différentes voies de signalisation intracellulaire permet d'obtenir une bonne protection dans le modèle d'ischémie sévère dans lequel aucun des deux peptides administré séparément n'a donné d'effets bénéfiques.

Recommendations on percutaneous coronary intervention for the reperfusion of acute ST elevation myocardial infarction

Little information is currently available from the various societies of cardiology on primary percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI). Since primary PCI is the main method of reperfusion in AMI in many centres, and since of all cardiac emergencies AMI represents the most urgent situation for PCI, recommendations based on scientific evidence and expert experience would be useful for centres practising primary PCI, or those looking to establish a primary PCI programme. To this aim, a task force for primary PCI in AMI was formed to develop a set of recommendations to complement and assist clinical judgment. This paper represents the product of their recommendations.

The impact of fasting on the interpretation of triglyceride levels for predicting myocardial infarction risk in HIV-positive individuals: the D:A:D study.

We assessed whether fasting modifies the prognostic value of these measurements for the risk of myocardial infarction (MI). Analyses used mixed effect models and Poisson regression. After confounders were controlled for, fasting triglyceride levels were, on average, 0.122 mmol/L lower than nonfasting levels. Each 2-fold increase in the latest triglyceride level was associated with a 38% increase in MI risk (relative rate, 1.38; 95% confidence interval, 1.26-1.51); fasting status did not modify this association. Our results suggest that it may not be necessary to restrict analyses to fasting measurements when considering MI risk.

Toward high-resolution myocardial tagging.

Magnetic resonance imaging with preceding tissue tagging is a robust method for assessing cardiac motion of the entire heartbeat cycle with a high degree of accuracy. One limitation of this technique, however, is the low resolution of the obtained displacement map of the labeled points within the myocardium. By a new tagging technique, which is based on the combination of two or more measurements of the same slice but with different grid positions, a highly improved resolution of cardiac motion data can be achieved. In combination with a multi-heart-phase echo-planar imaging sequence, such images with doubled grid frequency can be acquired in two short breath-hold periods.

Alterations in the local myocardial motion pattern in patients suffering from pressure overload due to aortic stenosis.

BACKGROUND: MR tissue tagging allows the noninvasive assessment of the locally and temporally resolved motion pattern of the left ventricle. Alterations in cardiac torsion and diastolic relaxation of the left ventricle were studied in patients with aortic stenosis and were compared with those of healthy control subjects and championship rowers with physiological volume-overload hypertrophy. METHODS AND RESULTS: Twelve aortic stenosis patients, 11 healthy control subjects with normal left ventricular function, and 11 world-championship rowers were investigated for systolic and diastolic heart wall motion on a basal and an apical level of the myocardium. Systolic torsion and untwisting during diastole were examined by use of a novel tagging technique (CSPAMM) that provides access to systolic and diastolic motion data. In the healthy heart, the left ventricle performs a systolic wringing motion, with a counterclockwise rotation at the apex and a clockwise rotation at the base. Apical untwisting precedes diastolic filling. In the athlete's heart, torsion and untwisting remain unchanged compared with those of the control subjects. In aortic stenosis patients, torsion is significantly increased and diastolic apical untwisting is prolonged compared with those of control subjects or athletes. CONCLUSIONS: Torsional behavior as observed in pressure- and volume-overloaded hearts is consistent with current theoretical findings. A delayed diastolic untwisting in the pressure-overloaded hearts of the patients may contribute to a tendency toward diastolic dysfunction.

Circadian Variations of Ischemic Burden Among Patients with Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

Introduction Le rythmes circadiens influencent différents paramètres de la physiologie et de la physiopathologie cardiovasculaire. Récemment, une relation entre la taille d'un infarctus et l'heure du jour à laquelle il se produit a été suggérée dans des modèles expérimentaux d'infarctus du myocarde. Le but de cette étude a été de déterminer si les rythmes circadiens pouvaient influencer la gravité d'un infarctus en terme de taille et de mortalité chez les patients hospitalisés pour un infarctus du myocarde avec sus-décalage du segment ST (STEMI) ayant bénéficié d'une intervention coronarienne percutanée primaire (ICPP). Méthode Chez 353 patients consécutifs admis avec un STEMI et traités par ICPP, l'heure à la survenue des symptômes, le pic de créatine kinase (reflet de la taille d'un infarctus) et le suivi à 30 jours ont été collectés. Les patients ont été répartis en 4 groupes en fonction de l'heure de survenue de leurs symptômes (00 :00 - 05h59, 06:00 - 11 59 12 00-17h59 et 18h00-23h59). Résultats Aucune différence statistiquement significative n'a été retrouvée entre les différents groupes en ce qui concerne les caractéristiques des patients ou de leur prise en charge. Après analyse multivariée, nous avons mis en évidence une différence statistiquement significative entre les pics de créatine kinase chez les patients avec survenue des symptômes entre 00 :00 et 05:59, qui étaient plus élevés que les pics de créatine kinase chez les patients avec survenue des symptômes à tout autre moment de la journée (augmentation moyenne de 38,4%, ρ <0.05). A 30 jours, la mortalité des patients avec survenue des symptômes entre 00 :00 et 05:59 était également significativement plus élevé que celle des patients avec survenue à tout autre moment de la journée (p <0.05). Conclusion Notre étude démontre une corrélation indépendante entre la taille d'un infarctus STEMI traité par ICPP et le moment de la journée où les symptômes apparaissent. Ces résultats suggèrent que ce moment devrait être un paramètre important à prendre en compte pour évaluer le pronostic des patients.

Influence of socioeconomic factors on delays, management and outcome amongst patients with acute myocardial infarction undergoing primary percutaneous coronary intervention.

The outcome after primary percutaneous coronary intervention (pPCI) for ST-elevation myocardial infarction (STEMI) is strongly affected by time delays. In this study, we sought to identify the impact of specific socioeconomic factors on time delays, subsequent STEMI management and outcomes in STEMI patients undergoing pPCI, who came from a well-defined region of the French part of Switzerland. A total of 402 consecutive patients undergoing pPCI for STEMI in a large tertiary hospital were retrospectively studied. Symptom-to-first-medical-contact time was analysed for the following socioeconomic factors: level of education, origin and marital status. Main exclusion criteria were: time delay beyond 12 hours, previous treatment with fibrinolytic agents or patients immediately referred for coronary artery bypass graft surgery. Therefore, 222 patients were finally included. At 1 year, there was no difference in mortality between the different socioeconomic groups. Furthermore, there was no difference in management characteristics between them. Symptom-to-first-medical-contact time was significantly longer for patients with a low level of education, Swiss citizens and unmarried patients, with median differences of 23 minutes, 18 minutes and 13 minutes, respectively (p <0.05). Nevertheless, no difference was found regarding in-hospital management and clinical outcome. This study demonstrates that symptom-to-first-medical-contact time is longer amongst people with a lower educational level, Swiss citizens and unmarried people. Because of the low mortality rate in general, these differences in delays did not affect clinical outcomes. Still, tertiary prevention measures should particularly focus on these vulnerable populations.

Improved myocardial tagging contrast in cine balanced SSFP images.

PURPOSE: To improve the tag persistence throughout the whole cardiac cycle by providing a constant tag-contrast throughout all the cardiac phases when using balanced steady-state free precession (bSSFP) imaging. MATERIALS AND METHODS: The flip angles of the imaging radiofrequency pulses were optimized to compensate for the tagging contrast-to-noise ratio (Tag-CNR) fading at later cardiac phases in bSSFP imaging. Complementary spatial modulation of magnetization (CSPAMM) tagging was implemented to improve the Tag-CNR. Numerical simulations were performed to examine the behavior of the Tag-CNR with the proposed method, and to compare the resulting Tag-CNR with that obtained from the more commonly used spoiled gradient echo (SPGR) imaging. A gel phantom, as well as five healthy human volunteers, were scanned on a 1.5T scanner using bSSFP imaging with and without the proposed technique. The phantom was also scanned with SPGR imaging. RESULTS: With the proposed technique, the Tag-CNR remained almost constant during the whole cardiac cycle. Using bSSFP imaging, the Tag-CNR was about double that of SPGR. CONCLUSION: The tag persistence was significantly improved when the proposed method was applied, with better Tag-CNR during the diastolic cardiac phase. The improved Tag-CNR will support automated tagging analysis and quantification methods.

Vasopressine lors d'infarctus myocardique aigu: implications cliniques [Vasopressin in acute myocardial infarct: clinical implications]

Since current data on vasopressin (AVP) secretion during the early phase of myocardial infarction is not extensive, plasma AVP was measured in 26 patients with acute myocardial infarction. Twelve had an increased AVP concentration (23.2 +/- 7.0 pg/ml; mean +/- SEM) whereas 14 had an AVP level less than 3 pg/ml (1.96 +/- 0.14 pg/ml). The patients with AVP greater than 3 pg/ml had higher heart rate and plasma osmolality than those with AVP less than 3 pg/ml. Blood pressure values were the same in both groups of patients. There was no difference in peak CPK and iso CPK activities between the two groups. Seven patients with AVP greater than 3 pg/ml died within the next few days, while only 1 patient with AVP less than pg/ml died. It thus appears that increased AVP concentration during acute myocardial infarction is associated with a poor prognosis. Whether it is a cause or a consequence of an unfavourable course of myocardial infarction remains to be determined.

Acute multivessel revascularization improves 1-year outcome in ST-elevation myocardial infarction: a nationwide study cohort from the AMIS Plus registry.

BACKGROUND: The optimal strategy for percutaneous coronary intervention (PCI) of ST-segment elevation myocardial infarction (STEMI) in multi-vessel disease (MVD), i.e., multi-vessel PCI (MV-PCI) vs. PCI of the infarct-related artery only (IRA-PCI), still remains unknown. METHODS: Patients of the AMIS Plus registry admitted with an acute coronary syndrome were contacted after a median of 378 days (interquartile range 371-409). The primary end-point was all-cause death. The secondary end-point included all major adverse cardiovascular and cerebrovascular events (MACCE) including death, re-infarction, re-hospitalization for cardiac causes, any cardiac re-intervention, and stroke. RESULTS: Between 2005 and 2012, 8330 STEMI patients were identified, of whom 1909 (24%) had MVD. Of these, 442 (23%) received MV-PCI and 1467 (77%) IRA-PCI. While all-cause mortality was similar in both groups (2.7% both, p>0.99), MACCE was significantly lower after MV-PCI vs. IRA-PCI (15.6% vs. 20.0%, p=0.038), mainly driven by lower rates of cardiac re-hospitalization and cardiac re-intervention. Patients undergoing MV-PCI with drug-eluting stents had lower rates of all-cause mortality (2.1% vs. 7.4%, p=0.026) and MACCE (14.1% vs. 25.9%, p=0.042) compared with those receiving bare metal stents (BMS). In multivariate analysis, MV-PCI (odds ratio, OR 0.69, 95% CI 0.51-0.93, p=0.017) and comorbidities (Charlson index ≥ 2; OR 1.42, 95% CI 1.05-1.92, p=0.025) were independent predictors for 1-year MACCE. CONCLUSION: In an unselected nationwide real-world cohort, an approach using immediate complete revascularization may be beneficial in STEMI patients with MVD regarding MACCE, specifically when drug-eluting stents are used, but not regarding mortality. This has to be tested in a randomized controlled trial.

Foot skin blood flow following infrainguinal revascularization for critical lower limb ischemia.

INTRODUCTION: The aim of this study was to assess the blood flow in the feet before and after lower limb revascularization using laser Doppler imaging (LDI). METHODS: Ten patients with critical lower limb ischemia were prospectively enrolled from June to October 2004. All patients underwent successful unilateral surgical interventions including above-knee bypass, distal bypass and endarterectomy. Skin blood flow (SBF) over the plantar surface of both forefeet and heels was measured by LDI 24h before and 10 days after revascularization, expressed in perfusion units (PU), and reported as mean+/-SD. RESULTS: Measurements in the forefoot and heel were similar. Before revascularization mean SBF was significantly lower in the ischemic foot (130+/-71 PU) compared to the contralateral foot (212+/-68 PU), p<0.05. After revascularization a significant increase of the SBF in the forefoot (from 135+/-67 to 202+/-86 PU, p=0.001) and hindfoot (from 148+/-58 to 203+/-83, p=0.001) was observed on the treatment side. However, a large decrease of the SBF was seen in forefoot and hindfoot on the untreated side (from 250+/-123 PU to 176+/-83 and from 208+/-116 to 133+/-40, p=0.001, respectively). CONCLUSION: This study confirms the benefits of revascularization in patients with nonhealing foot lesions due to critical limb ischemia. A significant increase of the SBF was observed on the treatment side. However, an unexpected decrease was observed on the untreated side.