Free-breathing 3 T magnetic resonance t(2)-mapping of the heart.

OBJECTIVES: This study sought to establish an accurate and reproducible T(2)-mapping cardiac magnetic resonance (CMR) methodology at 3 T and to evaluate it in healthy volunteers and patients with myocardial infarct. BACKGROUND: Myocardial edema affects the T(2) relaxation time on CMR. Therefore, T(2)-mapping has been established to characterize edema at 1.5 T. A 3 T implementation designed for longitudinal studies and aimed at guiding and monitoring therapy remains to be implemented, thoroughly characterized, and evaluated in vivo. METHODS: A free-breathing navigator-gated radial CMR pulse sequence with an adiabatic T(2) preparation module and an empirical fitting equation for T(2) quantification was optimized using numerical simulations and was validated at 3 T in a phantom study. Its reproducibility for myocardial T(2) quantification was then ascertained in healthy volunteers and improved using an external reference phantom with known T(2). In a small cohort of patients with established myocardial infarction, the local T(2) value and extent of the edematous region were determined and compared with conventional T(2)-weighted CMR and x-ray coronary angiography, where available. RESULTS: The numerical simulations and phantom study demonstrated that the empirical fitting equation is significantly more accurate for T(2) quantification than that for the more conventional exponential decay. The volunteer study consistently demonstrated a reproducibility error as low as 2 ± 1% using the external reference phantom and an average myocardial T(2) of 38.5 ± 4.5 ms. Intraobserver and interobserver variability in the volunteers were -0.04 ± 0.89 ms (p = 0.86) and -0.23 ± 0.91 ms (p = 0.87), respectively. In the infarction patients, the T(2) in edema was 62.4 ± 9.2 ms and was consistent with the x-ray angiographic findings. Simultaneously, the extent of the edematous region by T(2)-mapping correlated well with that from the T(2)-weighted images (r = 0.91). CONCLUSIONS: The new, well-characterized 3 T methodology enables robust and accurate cardiac T(2)-mapping at 3 T with high spatial resolution, while the addition of a reference phantom improves reproducibility. This technique may be well suited for longitudinal studies in patients with suspected or established heart disease.

Respiratory self-navigated postcontrast whole-heart coronary MR angiography: initial experience in patients.

PURPOSE: To assess the diagnostic performance of respiratory self-navigation for whole-heart coronary magnetic resonance (MR) angiography in a patient cohort referred for diagnostic cardiac MR imaging. MATERIALS AND METHODS: Written informed consent was obtained from all participants for this institutional review board-approved study. Self-navigated coronary MR angiography was performed after administration of a contrast agent in 78 patients (mean age, 48.5 years ± 20.7 [standard deviation]; 53 male patients) referred for cardiac MR imaging because of coronary artery disease (n = 40), cardiomyopathy (n = 14), congenital anomaly (n = 17), or "other" (n = 7). Examination duration was recorded, and the image quality for each coronary segment was assessed with consensus reading. Vessel sharpness, length, and diameter were measured. Quantitative values in proximal, middle, and distal segments were compared by using analysis of variance and t tests. A double-blinded comparison with the results of x-ray angiography was performed when such results were available. RESULTS: When patients with different indications for cardiac MR imaging were examined with self-navigated postcontrast coronary MR angiography, whole-heart data sets with 1.15-mm isotropic spatial resolution were acquired in an average of 7.38 minutes ± 1.85. The main and proximal coronary segments could be visualized in 92.3% of cases, while the middle and distal segments could be visualized in 84.0% and 55.8% of cases, respectively. Subjective scores and vessel sharpness were significantly higher in the proximal segments than in the middle and distal segments (P < .05). Anomalies of the coronary arteries could be confirmed or excluded in all cases. Per-vessel sensitivity and specificity for stenosis detection were 64.7% and 85.0%, respectively, in the 31 patients for whom reference standard x-ray coronary angiography results were available. CONCLUSION: The self-navigated coronary MR angiography sequence shows promise for coronary imaging. However, technical improvements are needed to improve image quality, especially in the more distal coronary segments.

Inflammatory Markers and Incident Heart Failure Risk in Older Adults: The Health, Aging, and Body Composition Study

Background: Inflammation is associated with heart failure (HF) risk factors and also directly affects myocardial function. However, the association between inflammation and HF risk in older adults has not been adequately evaluated. Methods: The association of baseline serum concentrations of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF- ), and C-reactive protein (CRP) with incident HF was assessed with Cox proportional hazards models among 2610 older persons without prevalent HF enrolled in the Health, Aging, and Body Composition (Health ABC) Study (age, 73.6±2.9 years; 48.3% men; 59.6% white). Results: Median (interquartile range) baseline concentrations of IL-6, TNF- , and CRP were 1.80 (1.23, 2.76) pg/mL, 3.14 (2.41, 4.06) pg/mL, and 1.64 (0.99, 3.04) µg/mL, respectively. On follow-up (median, 9.4 years), 311 participants (11.9%) developed HF. In models controlling for clinical predictors of HF and incident coronary heart disease, doubling of IL-6, TNF- , and CRP concentrations was associated with 34% (95% CI, 18 -52%; P<.001), 33% (95% CI, 9 - 63%; P=.006), and 13% (95% CI, 3-24%; P=.01) increase in HF risk, respectively. In models including all 3 markers, IL-6 and TNF- , but not CRP, remained significant. Findings were similar across sex and race. Post-HF ejection fraction (EF) was available in 239 (76.8%) cases. When only cases with preserved EF were considered (n=105), IL-6 (HR per doubling, 1.57; 95% CI, 1.28 -1.94; P<.001), TNF- (HR per doubling, 1.59; 95% CI, 1.12-2.26; P=.01), and CRP (HR per doubling, 1.23; 95% CI, 1.05-1.44; P=.01) were all associated with HF risk in adjusted models. In contrast, when only cases with reduced EF (n=134) were considered, only IL-6 attained marginal significance in adjusted models (HR per doubling, 1.20; 95% CI, 0.99 -1.46; P=.06). Participants with 2 or 3 markers above median had pronounced HF risk in adjusted models (HR, 1.66; 95% CI, 1.12-2.46; P=.01; and HR, 1.76; 95% CI, 1.16 -2.65; P=.007, respectively). Addition of IL-6 to the clinical Health ABC HF model improved discrimination (C index from 0.717 to 0.734; P=.001) and fit (decreased Bayes information criterion by 17.8; P<.001). Conclusions: Inflammatory markers are associated with HF risk among older adults and may improve HF risk stratification.

Improved prediction of coronary heart disease with markers of atherosclerosis and of inflammation in older adults?

Background: Several markers of atherosclerosis and of inflammation have been shown to predict coronary heart disease (CHD) individually. However, the utility of markers of atherosclerosis and of inflammation on prediction of CHD over traditional risk factors has not been well established, especially in the elderly. Methods: We studied 2202 men and women, aged 70-79, without baseline cardiovascular disease over 6-year follow-up to assess the risk of incident CHD associated with baseline noninvasive measures of atherosclerosis (ankle-arm index [AAI], aortic pulse wave velocity [aPWV]) and inflammatory markers (interleukin-6 [IL-6], C-reactive protein [CRP], tumor necrosis factor-a [TNF-a]). CHD events were studied as either nonfatal myocardial infarction or coronary death ("hard" events), and "hard" events plus hospitalization for angina, or the need for coronary-revascularization procedures (total CHD events). Results: During the 6-year follow-up, 283 participants had CHD events (including 136 "hard" events). IL-6, TNF-a and AAI independently predicted CHD events above Framingham Risk Score (FRS) with hazard ratios [HR] for the highest as compared with the lowest quartile for IL-6 of 1.95 (95%CI: 1.38-2.75, p for trend <0.001), TNF-a of 1.45 (95%CI: 1.04-2.02, p for trend 0.03), of 1.66 (95%CI: 1.19-2.31) for AAI 0.9, as compared to AAI 1.01-1.30. CRP and aPWV were not independently associated with CHD events. Results were similar for "hard" CHD events. Addition of IL-6 and AAI to traditional cardiovascular risk factors yielded the greatest improvement in the prediction of CHD; C-index for "hard"/total CHD events increased from 0.62/0.62 for traditional risk factors to 0.64/0.64 for IL-6 addition, 0.65/0.63 for AAI, and 0.66/0.64 for IL-6 combined with AAI. Being in the highest quartile of IL-6 combined with an AAI 0.90 or >1.40 yielded an HR of 2.51 (1.50-4.19) and 4.55 (1.65-12.50) above FRS, respectively. With use of CHD risk categories, risk prediction at 5 years was more accurate in models that included IL-6, AAI or both, with 8.0, 8.3 and 12.1% correctly reclassified, respectively. Conclusions: Among older adults, markers of atherosclerosis and of inflammation, particularly IL-6 and AAI, are independently associated with CHD. However, these markers only modestly improve cardiovascular risk prediction beyond traditional risk factors.

On-pump beating heart coronary surgery for high risk patients requiring emergency multiple coronary artery bypass grafting.

BACKGROUND: Cardiopulmonary bypass (CPB) with aortic cross-clamping and cardioplegic arrest remains the method of choice for patients requiring standard myocardial revascularization. Therefore, very high-risk patients presenting with acute coronary syndrome, unstable angina, onset of cardiac decompensation and requiring emergency multiple myocardial revascularization, can have a poor outcome. The on-pump beating heart technique can reduce the mortality and the morbidity in such a selected group of patients and this report describes our clinical experience. METHODS: Out of 290 patients operated for CABG from January 2005 to January 2006, 25 (8.6%) selected high-risk patients suffering from life threatening coronary syndrome (mean age 69 +/- 7 years) and requiring emergency multiple myocardial revascularization, underwent on-pump beating heart surgery. The mean pre-operative left ventricle ejection fraction (LVEF) was 27 +/- 8%. The majority of them (88%) suffered of tri-vessel coronary disease and 6 (24%) had a left main stump disease. Nine patients (35%) were on severe cardiac failure and seven among them (28%) received a pre-operative intra-aortic balloon pump. The pre-operative EuroScore rate was equal or above 8 in 18 patients (73%). RESULTS: All patients underwent on-pump-beating heart coronary revascularization. The mean number of graft/patient was 2.9 +/- 0.6 and the internal mammary artery was used in 23 patients (92%). The mean CPB time was 84 +/- 19 minutes. Two patients died during the recovery stay in the intensive care unit, and there were no postoperative myocardial infarctions between the survivors. Eight patients suffered of transitorily renal failure and 1 patient developed a sternal wound infection. The mean hospital stay was 12 +/- 7 days. The follow-up was complete for all 23 patients survived at surgery and the mean follow-up time was 14 +/- 5 months. One patient died during the follow-up for cardiac arrest and 2 patients required an implantable cardiac defibrillator. One year after surgery they all had a standard trans-thoracic echocardiogram showing a mean LVEF rate of 36 +/- 11.8%. CONCLUSION: Standard on-pump arrested heart coronary surgery has higher mortality and morbidity in emergencies. The on-pump beating heart myocardial revascularization seems to be a valid alternative for the restricted and selected cohort of patients suffering from life threatening coronary syndrome and requiring multiple emergency CABG.

Integrating postoperative value of cardiac Troponin I for a better correlation with in-hospital outcomes after congenital heart surgery.

Objective: Cardiac Troponin-I (cTnI) is a well-recognized early postoperative marker for myocardial damage in adults and children after heart surgery. The present study was undertaken to evaluate whether the integrated value (area under the curve(AUC)) of postoperative cTnI is a better mode to predict long-term outcome than post operative cTnI maximum value, after surgery for congenital heart defects (CHD). Methods: retrospective cohort study. 279 patients (mean age 4.6 years; range 0-17 years-old, 185 males) with congenital heart defect repair on cardiopulmonary by-pass were retrieved from our database including postoperative cTnI values. Maximal post operative cTnI value, post operative cTnI AUC value at 48h and total post operative cTnI AUC value were calculated and then correlated with duration of intubation, duration of ICU stay and mortality. Results: the mean duration of mechanical ventilation was 5.1+/-7.2 days and mean duration of ICU stay was 11.0+/- 13.3 days,11 patients (3.9%) died in post operative period. When comparing survivor and deceased groups, there was a significant difference in the mean value for max cTnI (16.7+/- 21.8 vs 59.2+/-41.4 mcg/l, p+0.0001), 48h AUC cTnI (82.0+/-110.7 vs 268.8+/-497.7 mcg/l, p+0.0001) and total AUC cTnI (623.8+/-1216.7 vs 2564+/-2826.0, p+0.0001). Analyses for duration of mechanical ventilation and duration of ICU stay by linear regression demonstrated a better correlation for 48h AUC cTnI (ventilation time r+0.82, p+0.0001 and ICU stay r+0.74, p+0.0001) then total AUC cTnI (ventilation time r+0.65, p+0.0001 and ICU stay r+0.60, p+0.0001) and max cTnI (ventilation time r+0.64, p+0.0001 and ICU stay r+0.60, p+0.0001). Conclusion: Cardiac Troponin I is a specific and sensitive marker of myocardial injury after congenital heart surgery and it may predict early in-hospital outcomes. Integration of post operative value of cTnI by calculation of AUC improves prediction of early in-hospital outcomes. It probably takes into account, not only the initial surgical procedure, but probably also incorporates the occurrence of hypoxic-ischemic phenomena in the post-operative period.

A key role of TRPC channels in the regulation of electromechanical activity of the developing heart.

Aims It is well established that dysfunction of voltage-dependent ion channels results in arrhythmias and conduction disturbances in the foetal and adult heart. However, the involvement of voltage-insensitive cationic TRPC (transient receptor potential canonical) channels remains unclear. We assessed the hypothesis that TRPC channels play a crucial role in the spontaneous activity of the developing heart.Methods and results TRPC isoforms were investigated in isolated hearts obtained from 4-day-old chick embryos. Using RT-PCR, western blotting and co-immunoprecipitation, we report for the first time that TRPC1, 3, 4, 5, 6, and 7 isoforms are expressed at the mRNA and protein levels and that they can form a macromolecular complex with the alpha 1C subunit of the L-type voltage-gated calcium channel (Cav1.2) in atria and ventricle. Using ex vivo electrocardiograms, electrograms of isolated atria and ventricle and ventricular mechanograms, we found that inhibition of TRPC channels by SKF-96365 leads to negative chrono-, dromo-, and inotropic effects, prolongs the QT interval, and provokes first-and second-degree atrioventricular blocks. Pyr3, a specific antagonist of TRPC3, affected essentially atrioventricular conduction. On the other hand, specific blockade of the L-type calcium channel with nifedipine rapidly stopped ventricular contractile activity without affecting rhythmic electrical activity.Conclusions These results give new insights into the key role that TRPC channels, via interaction with the Cav1.2 channel, play in regulation of cardiac pacemaking, conduction, ventricular activity, and contractility during cardiogenesis.

Subclinical hypothyroidism and the risk of coronary heart disease and mortality.

CONTEXT: Data regarding the association between subclinical hypothyroidism and cardiovascular disease outcomes are conflicting among large prospective cohort studies. This might reflect differences in participants' age, sex, thyroid-stimulating hormone (TSH) levels, or preexisting cardiovascular disease. OBJECTIVE: To assess the risks of coronary heart disease (CHD) and total mortality for adults with subclinical hypothyroidism. DATA SOURCES AND STUDY SELECTION: The databases of MEDLINE and EMBASE (1950 to May 31, 2010) were searched without language restrictions for prospective cohort studies with baseline thyroid function and subsequent CHD events, CHD mortality, and total mortality. The reference lists of retrieved articles also were searched. DATA EXTRACTION: Individual data on 55,287 participants with 542,494 person-years of follow-up between 1972 and 2007 were supplied from 11 prospective cohorts in the United States, Europe, Australia, Brazil, and Japan. The risk of CHD events was examined in 25,977 participants from 7 cohorts with available data. Euthyroidism was defined as a TSH level of 0.50 to 4.49 mIU/L. Subclinical hypothyroidism was defined as a TSH level of 4.5 to 19.9 mIU/L with normal thyroxine concentrations. RESULTS: Among 55,287 adults, 3450 had subclinical hypothyroidism (6.2%) and 51,837 had euthyroidism. During follow-up, 9664 participants died (2168 of CHD), and 4470 participants had CHD events (among 7 studies). The risk of CHD events and CHD mortality increased with higher TSH concentrations. In age- and sex-adjusted analyses, the hazard ratio (HR) for CHD events was 1.00 (95% confidence interval [CI], 0.86-1.18) for a TSH level of 4.5 to 6.9 mIU/L (20.3 vs 20.3/1000 person-years for participants with euthyroidism), 1.17 (95% CI, 0.96-1.43) for a TSH level of 7.0 to 9.9 mIU/L (23.8/1000 person-years), and 1.89 (95% CI, 1.28-2.80) for a TSH level of 10 to 19.9 mIU/L (n = 70 events/235; 38.4/1000 person-years; P <.001 for trend). The corresponding HRs for CHD mortality were 1.09 (95% CI, 0.91-1.30; 5.3 vs 4.9/1000 person-years for participants with euthyroidism), 1.42 (95% CI, 1.03-1.95; 6.9/1000 person-years), and 1.58 (95% CI, 1.10-2.27, n = 28 deaths/333; 7.7/1000 person-years; P = .005 for trend). Total mortality was not increased among participants with subclinical hypothyroidism. Results were similar after further adjustment for traditional cardiovascular risk factors. Risks did not significantly differ by age, sex, or preexisting cardiovascular disease. CONCLUSIONS: Subclinical hypothyroidism is associated with an increased risk of CHD events and CHD mortality in those with higher TSH levels, particularly in those with a TSH concentration of 10 mIU/L or greater.

Response of embryonic heart to hypoxia and reoxygenation: an in vitro model

OBJECTIVES: To define properly the consequences of oxygen deprivation and readmission for the functioning of the developing heart. METHODS: Spontaneously beating hearts excised from three-day-old chick embryos were loaded with a drop of viscous nontoxic silicone oil and cultured in a special chamber in which variations of PO2 at the tissue level could be strictly controlled. All parts of the hearts were simultaneously submitted to identical changes in PO2. Instantaneous heart rate, myocardial shortening, velocities of contraction and relaxation, and mechanical propagation along the heart tube were determined photometrically. RESULTS: The hearts, submitted to a PO2 ramp (0 to 9.3 kPa) or absolute anoxia, reacted rapidly, reversibly and reproducibly. Under sustained anoxia, ventricular activity stopped after 3.8±0.7 mins (n=4) and then resumed intermittently in the form of tachycardic bursts. Brief anoxia (1 min) provoked tachycardia followed by bradycardia, induced contracture, depressed contractility and retarded atrioventricular propagation. Upon reoxygenation, ventricular contractions ceased suddently for 20±11 s (n=5), whereas a residual atrial activity could persist. The duration of this arrest and the rate of recovery depended on duration of the preceding anoxia. Such a dysfunction constitutes the embryonic analogue of the oxygen paradox observed in adult hearts. Initial impulses, including arrhythmic activity, originated exclusively from the atrium, and no ventricular ectopic beats were detected whatever the conditions of oxygenation. CONCLUSIONS: This in vitro model seems promising for studying the pathophysiological mechanisms associated with hypoxia and reoxygenation in the developing heart.

Postischemic recovery of heart metabolism and function: role of mitochondrial fatty acid transfer.

Postischemic recovery of contractile function is better in hearts from fasted rats than in hearts from fed rats. In this study, we examined whether feeding-induced inhibition of palmitate oxidation at the level of carnitine palmitoyl transferase I is involved in the mechanism underlying impaired recovery of contractile function. Hearts isolated from fasted or fed rats were submitted to no-flow ischemia followed by reperfusion with buffer containing 8 mM glucose and either 0.4 mM palmitate or 0.8 mM octanoate. During reperfusion, oxidation of palmitate was higher after fasting than after feeding, whereas oxidation of octanoate was not influenced by the nutritional state. In the presence of palmitate, recovery of left ventricular developed pressure was better in hearts from fasted rats. Substitution of octanoate for palmitate during reperfusion enhanced recovery of left ventricular developed pressure in hearts from fed rats. However, the chain length of the fatty acid did not influence diastolic contracture. The results suggest that nutritional variation of mitochondrial fatty acid transfer may influence postischemic recovery of contractile function.

Resting heart rate and incident heart failure and cardiovascular mortality in older adults: role of inflammation and endothelial dysfunction: the PROSPER study.

AIMS: Resting heart rate is a promising modifiable cardiovascular risk marker in older adults, but the mechanisms linking heart rate to cardiovascular disease are not fully understood. We aimed to assess the association between resting heart rate and incident heart failure (HF) and cardiovascular mortality, and to examine whether these associations might be attributable to systemic inflammation and endothelial dysfunction. METHODS AND RESULTS: We studied 4084 older adults aged 70-82 years with known cardiovascular risk factors or previous cardiovascular disease, without pre-existing HF or beta-blockers in the PROSPER study. Over a 3.2-year follow-up period, we examined incident HF hospitalization and cardiovascular mortality according to resting heart rate, along with C-reactive protein (CRP), interleukin-6 (IL-6), tissue plasminogen activator (tPA), and von Willebrand factor (vWf). Mean heart rate was 67 b.p.m. for men and 70 b.p.m. for women. CRP, IL-6, tPA, and vWf levels were all positively correlated with heart rate. After multivariate adjustment, heart rate was associated with HF hospitalization [hazard ratio (HR) 1.78 for highest vs. lowest distribution third, 95% confidence interval (CI) 1.21-2.63, P= 0.003] and cardiovascular mortality (HR 1.74, 95% CI 1.23-2.47, P= 0.002). Further adjustment for both IL-6 and vWf levels decreased HR to 1.60 (95% CI 1.08-2.38, P= 0.020) for HF and to 1.50 (95% CI 1.04-2.15, P= 0.028) for cardiovascular mortality. CONCLUSION: Increased heart rate is associated with increased systemic inflammation and endothelial dysfunction. These factors are likely to contribute to, but do not fully explain, the risk of HF and cardiovascular death associated with increased heart rate in older age.

From diabetes to heart disease : studies on dyslipidemia-induced B-cell dysfunction, immunomodulation in heart transplantation, and cardiac stem cell therapy

Diabetes is a growing epidemic with devastating human, social and economic impact. It is associated with significant changes in plasma concentrations of lipoproteins. We tested the hypothesis that lipoproteins modulate the function and survival of insulin-secreting cells. We first detected the presence of several receptors that participate in the binding and processing of plasma lipoproteins and confirmed the internalization of fluorescent LDL and HDL particles in insulin-secreting β-cells. Purified human VLDL and LDL particles reduced insulin mRNA levels and β-cell proliferation, and induced a dose-dependent increase in the rate of apoptosis. In mice lacking the LDL receptor, islets showed a dramatic decrease in LDL uptake and were partially resistant to apoptosis caused by LDL. VLDL-induced apoptosis of β-cells involved caspase-3 cleavage and reduction in levels of the c-Jun N-terminal (JNK) Interacting Protein-1 (IB1/JIP-1). In contrast, the pro-apoptotic signaling of lipoproteins was antagonized by HDL particles or by a small peptide inhibitor of JNK. The protective effects of HDL were mediated, in part, by inhibition of caspase-3 cleavage and activation of the protein kinase Akt/PKB. Heart disease is a major cause of morbidity and mortality among patients with diabetes. When heart failure is refractory to medical therapy and cannot be improved by electrical resynchronization, percutaneous angioplasty or coronary graft bypass surgery, heart transplantation remains a "last resort" therapy. Nevertheless, it is limited by the side effects of immunosuppressive drugs and chronic rejection. Localized expression of immunomodulatory genes in the donor organ can create a state of immune privilege within the graft, and was performed in rodent hearts by infecting cells with an adenovirus encoding indoleamine 2,3-dioxygenase (IDO), the rate-limiting enzyme in the catabolism of tryptophane. Other strategies are based on genetic manipulation of dendritic cells (DCs) with immunosuppressive genes and in vitro exposure of DCs to agents that prevent their maturation by inflammatory cytokines. Finally, we used 5-bromo-2'-deoxyuridine, which is incorporated into DNA and diluted with cell division, to identify long-term label retaining cells in the adult rodent heart. The majority of these cells were positive for the stem cell antigen-1 (Sca-1) and negative for the endothelial precursor marker CD31. They formed cardiospheres in vitro and showed differentiation potential into mesenchymal cell lineages. When cultured in cardiomyogenic differentiation medium, they expressed cardiac-specific genes. Taken together, these data provide evidence of slow-cycling stem cells in the rodent heart. Chronic shortage of donor organs opens the way to cardiac stem cell therapy in humans, although the long way from animal experimentation to routine therapy in patients may still take several years. - Du diabète de type 2 à la maladie coronarienne : trois études sur les dysfonctions de la cellule sécrétrice d'insuline induites par les dyslipidémies, l'immunomodulation dans la transplantation cardiaque, et la thérapie par des cellules souches myocardiques. Le diabète de type 2 a pris les dimensions d'une épidémie, avec des conséquences sociales et économiques dont nous n'avons pas encore pris toute la mesure. La maladie s'accompagne souvent d'une dyslipidémie caractérisée par une hypertriglycéridémie, des taux abaissés de cholestérol HDL, et des concentrations de cholestérol LDL à la limite supérieure de ce qui est considéré comme acceptable. L'hypothèse à la base de cette étude est qu'une modification des taux plasmatiques de lipoprotéines pourrait avoir une influence directe sur la cellule β sécrétrice d'insuline en modifiant sa fonction, sa durée de vie et son taux de régénération. Dans un premier temps, nous avons mis en évidence, sur la cellule β, la présence de plusieurs récepteurs impliqués dans la captation des lipoprotéines. Nous avons confirmé la fonctionnalité de ces récepteurs en suivant l'internalisation de LDL et de HDL marqués. En présence de VLDL ou de LDL humains, nous avons observé une diminution de la transcription du gène de l'insuline, une prolifération cellulaire réduite, et une augmentation de l'apoptose, toutes fonctions de la dose et du temps d'exposition. L'apoptose induite par les VLDL passe par une activation de la caspase-3 et une réduction du taux de la protéine IB1/JIP-1 (Islet Brain1/JNK Interacting Protein 1), dont une mutation est associée à une forme monogénique de diabète de type 2. Par opposition, les HDL, ainsi que des peptides inhibiteurs de JNK, sont capables de contrer la cascade pro-apoptotique déclenchée, respectivement, par les LDL et les VLDL. Ces effets protecteurs comprennent l'inhibition du clivage de la caspase-3 et l'activation de la protéine kinase Akt/PKB. En conclusion, les lipoprotéines sont des éléments clés de la survie de la cellule β, et pourraient contribuer au dysfonctionnement observé dans le pancréas endocrine au cours du développement du diabète. La maladie cardiaque, et plus particulièrement la maladie coronarienne, est une cause majeure de morbidité et de mortalité chez les patients atteints de diabète. Plusieurs stratégies sont utilisées quotidiennement pour pallier les atteintes cardiaques: traitements médicamenteux, électromécaniques par resynchronisation électrique, ou communément appelés « interventionnels » lorsqu'ils font appel à l'angioplastie percutanée. La revascularisation du myocarde par des pontages coronariens donne également de très bons résultats dans certaines situations. Il existe toutefois des cas où plus aucune de ces approches n'est suffisante. La transplantation cardiaque est alors la thérapie de choix pour un nombre restreint de patients. La thérapie génique, en permettant l'expression locale de gènes immunomodulateurs dans l'organe greffé, permet de diminuer les réactions de rejet inhérentes à toute transplantation (à l'exception de celles réalisées entre deux jumeaux homozygotes). Nous avons appliqué chez des rongeurs cette stratégie en infectant le coeur greffé avec un adénovirus codant pour l'enzyme indoleamine 2,3-dioxygénase (IDO), une enzyme clé dans le catabolisme du tryptophane. Nous avons procédé de manière identique in vitro en surexprimant IDO dans les cellules dendritiques, dont le rôle est de présenter les antigènes aux lymphocytes Τ du receveur. Des expériences similaires ont été réalisées en traitant les cellules dendritiques avec des substances capables de prévenir, en partie du moins, leur maturation par des agents pro-inflammatoires. Finalement, nous avons exploré une stratégie utilisée couramment en hématologie, mais qui n'en est encore qu'à ses débuts au niveau cardiaque : la thérapie par des cellules souches. En traitant des rongeurs avec un marqueur qui s'incorpore dans l'ADN nucléaire, le 5-bromo- 2'-deoxyuridine, nous avons identifié une population cellulaire se divisant rarement, positive en grande partie pour l'antigène embryonnaire Sca-1 et négative pour le marqueur endothélial CD31. En culture, ces cellules forment des cardiosphères et sont capables de se différencier dans les principaux types tissulaires mésenchymateux. Dans un milieu de differentiation adéquat, ces cellules expriment des gènes cardiomyocytaires. En résumé, ces données confirment la présence chez le rongeur d'une population résidente de précurseurs myocardiques. En addenda, on trouvera deux publications relatives à la cellule β productrice d'insuline. Le premier article démontre le rôle essentiel joué par la complexine dans l'insulino-sécrétion, tandis que le second souligne l'importance de la protéine IB1/JIP-1 dans la protection contre l'apoptose de la cellule β induite par certaines cytokines.

Mirror image atrial dilatation in adult patients with atrial fibrillation and congenital heart disease.

BACKGROUND: Atrial fibrillation (AF) is largely regarded to be initiated from left atrial (LA) dilatation, with subsequent dilatation of the right atrium (RA) in those who progress to chronic AF. We hypothesized that in adult patients with right-sided congenital heart disease (CHD) and AF, RA dilatation will predominate with subsequent dilatation of the left atrium, as a mirror image. METHODS: Adult patients with diagnosis of right-sided, ASD or left-sided CHD who had undergone an echocardiographic study and electrocardiographic recording in 2007 were included. RA and LA area were measured from the apical view. AF was diagnosed from a 12-lead electrocardiogram or Holter recording. A multivariate logistic regression model was used to identify predictors of AF and linear regression models were performed to measure relationship between RA and LA area and AF. RESULTS: A total of 291 patients were included in the study. Multivariate analysis showed that age (p=0.0001), RA (p=0.025) and LA area (p=0.0016) were significantly related to AF. In patients with pure left-sided pathologies, there was progressive and predominant LA dilatation that paralleled the development of AF from none to paroxysmal to chronic AF. In patients with pure right-sided pathologies, there was a mirror image of progressive and predominant RA dilatation with the development of AF. CONCLUSION: We observed a mirror image atrial dilatation in patients with right sided disease and AF. This may provide novel mechanistic insight as to the origin of AF in these patients and deserves further studying in the form of targeted electrophysiological studies.