Evolution and trends in a pediatric cardiac magnetic resonance imaging program in a tertiary hospital over a 14-year period. / Evolución y tendencias de un programa de resonancia magnética cardiaca pediátrica en un hospital terciario durante 14 años.

OBJECTIVES: 1. To review the activity in our hospital's pediatric cardiac magnetic resonance imaging (cMRI) program from its inception to the present. 2. To evaluate changes in the number of patients, in the number of studies done under anesthesia, in the number of studies done with contrast material (magnetic resonance angiography (MRA) and delayed enhancement), and in representative diseases studied. 3. To estimate trends in the parameters evaluated in objective 2. MATERIAL AND METHODS: The pediatric cMRI program at our hospital started on February 14, 2005. We assessed cMRI studies done between the inception of the program and December 31, 2018. The cases were entered in a calculation table that included sex, date of birth, date of examination, clinical presentation, radiologic diagnosis, sequences done, and anesthesia. For each year, we obtained data about patients' age, studies done under anesthesia, contrast-enhanced MRA, delayed enhancement studies, and postoperative studies. We also evaluated the evolution of the number of patients studied for a group of representative diseases (coarctation of the aorta; tetralogy of Fallot; dextro-transposition of the great arteries; corrections of univentricular heart; hypoplastic left heart syndrome; anomalous pulmonary venous return; and cardiomyopathy). We analyzed these data with bar graphs, evolutions of means, and logarithmic trend curves. RESULTS: A total of 2606 cases were included. The number of cases per year increased gradually. The mean age of all patients was 12.5 years, and the age of the patients studied also increased during the 14-year period. Anesthesia was used in 42%. Contrast-enhanced MRA was done in 57.6% and delayed enhancement in 42.13%. The most common condition was aortic coarctation (16.39%), although the frequency of aortic coarctation and hypoplastic left heart syndrome decreased slightly during the period. By contrast, the frequency of cardiomyopathy (7.25% of cases) increased slightly, to the point where it represented 9.35% in 2018. CONCLUSION: During the 14-year period in which pediatric cMRI has been done at our hospital, the conditions studied, the type of patients, and the techniques used has varied; the number of patients and patients' age has increased, where as the frequency of MRA studies has decreased. The prevalence of the different conditions studied has also changed.

Erosion of Transplantation Tolerance After Infection.

Recent clinical studies suggest that operational allograft tolerance can be persistent, but long-term surviving allografts can be rejected in a subset of patients, sometimes after episodes of infection. In this study, we examined the impact of Listeria monocytogenes (Lm) infection on the quality of tolerance in a mouse model of heart allograft transplantation. Lm infection induced full rejection in 40% of tolerant recipients, with the remaining experiencing a rejection crisis or no palpable change in their allografts. In the surviving allografts on day 8 postinfection, graft-infiltrating cell numbers increased and exhibited a loss in the tolerance gene signature. By day 30 postinfection, the tolerance signature was broadly restored, but with a discernible reduction in the expression of a subset of 234 genes that marked tolerance and was down-regulated at day 8 post-Lm infection. We further demonstrated that the tolerant state after Lm infection was functionally eroded, as rejection of the long-term surviving graft was induced with anti-PD-L1 whereas the same treatment had no effect in noninfected tolerant mice. Collectively, these observations demonstrate that tolerance, even if initially robust, exists as a continuum that can be eroded following bystander immune responses that accompany certain infections.

Adoptive Transfer of Tracer-Alloreactive CD4+ T Cell Receptor Transgenic T Cells Alters the Endogenous Immune Response to an Allograft.

T cell receptor transgenic (TCR-Tg) T cells are often used as tracer populations of antigen-specific responses to extrapolate findings to endogenous T cells. The extent to which TCR-Tg T cells behave purely as tracer cells or modify the endogenous immune response is not clear. To test the impact of TCR-Tg T cell transfer on endogenous alloimmunity, recipient mice were seeded with CD4+ or CD8+ TCR-Tg or polyclonal T cells at the time of cardiac allograft transplantation. Only CD4+ TCR-Tg T cells accelerated rejection and, unexpectedly, led to a dose-dependent decrease in both transferred and endogenous T cells infiltrating the graft. In contrast, recipients of CD4+ TCR-Tg T cells exhibited enhanced endogenous donor-specific CD8+ T cell activation in the spleen and accelerated alloantibody production. Introduction of CD4+ TCR-Tg T cells also perturbed the intragraft accumulation of innate cell populations. Transferred CD4+ TCR-Tg T cells alter many aspects of endogenous alloimmunity, suggesting that caution should be used when interpreting experiments using these adoptively transferred cells because the overall nature of allograft rejection may be altered. These results also may have implications for adoptive CD4+ T cell immunotherapy in tumor and infectious clinical settings because cell infusion may have additional effects on natural immune responses.

Tracking of TCR-Transgenic T Cells Reveals That Multiple Mechanisms Maintain Cardiac Transplant Tolerance in Mice.

Solid organ transplantation tolerance can be achieved following select transient immunosuppressive regimens that result in long-lasting restraint of alloimmunity without affecting responses to other antigens. Transplantation tolerance has been observed in animal models following costimulation or coreceptor blockade therapies, and in a subset of patients through induction protocols that include donor bone marrow transplantation, or following withdrawal of immunosuppression. Previous data from our lab and others have shown that proinflammatory interventions that successfully prevent the induction of transplantation tolerance in mice often fail to break tolerance once it has been stably established. This suggests that established tolerance acquires resilience to proinflammatory insults, and prompted us to investigate the mechanisms that maintain a stable state of robust tolerance. Our results demonstrate that only a triple intervention of depleting CD25+ regulatory T cells (Tregs), blocking programmed death ligand-1 (PD-L1) signals, and transferring low numbers of alloreactive T cells was sufficient to break established tolerance. We infer from these observations that Tregs and PD-1/PD-L1 signals cooperate to preserve a low alloreactive T cell frequency to maintain tolerance. Thus, therapeutic protocols designed to induce multiple parallel mechanisms of peripheral tolerance may be necessary to achieve robust transplantation tolerance capable of maintaining one allograft for life in the clinic.

Delayed Cytotoxic T Lymphocyte-Associated Protein 4-Immunoglobulin Treatment Reverses Ongoing Alloantibody Responses and Rescues Allografts From Acute Rejection.

Antibody-mediated rejection has emerged as the leading cause of late graft loss in kidney transplant recipients, and inhibition of donor-specific antibody production should lead to improved transplant outcomes. The fusion protein cytotoxic T lymphocyte-associated protein 4-immunoglobulin (CTLA4-Ig) blocks T cell activation and consequently inhibits T-dependent B cell antibody production, and the current paradigm is that CTLA4-Ig is effective with naïve T cells and less so with activated or memory T cells. In this study, we used a mouse model of allosensitization to investigate the efficacy of continuous CTLA4-Ig treatment, initiated 7 or 14 days after sensitization, for inhibiting ongoing allospecific B cell responses. Delayed treatment with CTLA4-Ig collapsed the allospecific germinal center B cell response and inhibited alloantibody production. Using adoptively transferred T cell receptor transgenic T cells and a novel approach to track endogenous graft-specific T cells, we demonstrate that delayed CTLA4-Ig minimally inhibited graft-specific CD4(+) and T follicular helper responses. Remarkably, delaying CTLA4-Ig until day 6 after transplantation in a fully mismatched heart transplant model inhibited alloantibody production and prevented acute rejection, whereas transferred hyperimmune sera reversed the effects of delayed CTLA4-Ig. Collectively, our studies revealed the unexpected efficacy of CTLA4-Ig for inhibiting ongoing B cell responses even when the graft-specific T cell response was robustly established.

Effect of mitochondrial ascorbic acid synthesis on photosynthesis.

Ascorbic acid (AA) is synthesized in plant mitochondria through the oxidation of l-galactono-1,4-lactone (l-GalL) and then distributed to different cell compartments. AA-deficient Arabidopsis thaliana mutants (vtc2) and exogenous applications of l-GalL were used to generate plants with different AA content in their leaves. This experimental approach allows determining specific AA-dependent effects on carbon metabolism. No differences in O2 uptake, malic and citric acid and NADH content suggest that AA synthesis or accumulation did not affect mitochondrial activity; however, l-GalL treatment increased CO2 assimilation and photosynthetic electron transport rate in vtc2 (but not wt) leaves demonstrating a stimulation of photosynthesis after l-GalL treatment. Increased CO2 assimilation correlated with increased leaf stomatal conductance observed in l-GalL-treated vtc2 plants.

What radiologists need to know about the pulmonary-systemic flow ratio (Qp/Qs): what it is, how to calculate it, and what it is for.

Cardiac magnetic resonance imaging (cMRI) provides abundant morphological and functional information in the study of congenital heart disease. The functional information includes pulmonary output and systemic output; the ratio between these two (Qp/Qs) is the shunt fraction. After birth, in normal conditions the pulmonary output is practically identical to the systemic output, so Qp/Qs = 1. In patients with « shunts ¼ between the systemic and pulmonary circulations, the ratio changes, and the interpretation of these findings varies in function of the location of the shunt (intracardiac or extracardiac) and of the associated structural or postsurgical changes. We review the concept of Qp/Qs; the methods to calculate it, with special emphasis on cMRI; and the meaning of the results obtained. We place special emphasis on the relevance of these findings depending on the underlying disease and the treatment the patient has undergone.

[Quality of 3D magnetic resonance imaging of coronary arteries in patients with D-transposition of the great arteries after the Jatene switch procedure]. / Calidad de la coronariografía 3D por resonancia magnética en los pacientes con D-transposición de las grandes arterias intervenidos con switch arterial de Jatene.

OBJECTIVES: To evaluate the quality of images obtained with 3D balanced fast-field echo whole heart (WH3D) MRI sequences for assessing the coronary anastomosis and coronary stenosis in patients with D-transposition of the great arteries who have undergone the Jatene switch procedure. MATERIAL AND METHODS: We retrieved 100 WH3D studies done in 83 patients who had undergone the Jatene switch procedure from our pediatric cardiac MRI database; 84 of these studies fulfilled the criteria for inclusion in the study. We evaluated coronary stenoses on WH3D MR images and their correlation with coronary CT or angiography images. We retrospectively studied the quality of the images of the proximal coronary arteries using a four-point scale and correlating the findings with age, heart rate, and heart size. RESULTS: Of the 84 studies, 4 (4.8%) were of a quality considered «insufficient for diagnosis¼, 7 (8.3%) were considered «fair¼, 23 (27.4%) «good¼, and 50 (59.5%) «excellent¼. The quality of the image of the coronary arteries was significantly correlated with heart rate. MRI detected stenosis in the origin of the coronary arteries in 9 (10.7%) studies. CONCLUSION: Images obtained with the WH3D MRI sequence in patients who had undergone the Jatene procedure were of diagnostic quality in most cases and were better in patients with lower heart rates. In 10.7%, stenosis in the origin of the coronary arteries that required new studies was detected.

The microbiota, the immune system and the allograft.

The microbiota represents the complex collections of microbial communities that colonize a host. In health, the microbiota is essential for metabolism, protection against pathogens and maturation of the immune system. In return, the immune system determines the composition of the microbiota. Altered microbial composition (dysbiosis) has been correlated with a number of diseases in humans. The tight reciprocal immune/microbial interactions complicate determining whether dysbiosis is a cause and/or a consequence of immune dysregulation and disease initiation or progression. However, a number of studies in germ-free and antibiotic-treated animal models support causal roles for intestinal bacteria in disease susceptibility. The role of the microbiota in transplant recipients is only starting to be investigated and its study is further complicated by putative contributions of both recipient and donor microbiota. Moreover, both flora may be affected directly or indirectly by immunosuppressive drugs and antimicrobial prophylaxis taken by transplant patients, as well as by inflammatory processes secondary to ischemia/reperfusion and allorecognition, and the underlying cause of end-organ failure. Whether the ensuing dysbiosis affects alloresponses and whether therapies aimed at correcting dysbiosis should be considered in transplant patients constitutes an exciting new field of research.

IL-6 induced by Staphylococcus aureus infection prevents the induction of skin allograft acceptance in mice.

Clinical correlations between bacterial infections and rejection suggest a hypothesis that innate immune stimulation by bacterial infections results in the production of inflammatory cytokine that facilitate bystander T-cell activation, increased alloreactivity and inhibition of tolerance induction. Previous studies demonstrated that IFNß produced during an infection with a model bacterium, Listeria monocytogenes, prevented the induction of transplantation tolerance in mice with anti-CD154 and donor-specific transfusion (DST) (1). We investigated the impact of two clinically relevant bacterial infections at the time of transplantation on the ability of anti-CD154 and DST to induce skin allograft acceptance in mice. Staphylococcus aureus (SA) infection prevented skin allograft acceptance whereas maximally tolerated doses of Pseudomonas aeruginosa infection had no effect. SA induced an acute production of IL-6, which was necessary and sufficient for the prevention of skin allograft acceptance. Furthermore, a single pulse of methylprednisolone modulated IL-6 production during SA infection and facilitated skin allograft acceptance in SA-infected recipients. Taken together, our results suggest that bacterial infections elicit specific proinflammatory cytokines signatures that can serve as barriers to tolerance induction, and that inhibiting the production of or neutralizing these inflammatory cytokines can synergize with costimulatory blockade-based therapies to facilitate the development of transplantation tolerance.

Infection with the intracellular bacterium, Listeria monocytogenes, overrides established tolerance in a mouse cardiac allograft model.

Infections and TLR signals at the time of transplantation have been shown to prevent the induction of tolerance, but their effect on allografts after tolerance has been established is unclear. We here report that infection with Listeria monocytogenes precipitated the loss of tolerance and the MyD88- and T cell-dependent rejection of accepted cardiac allografts in mice. This loss of tolerance was associated with increases in the numbers of graft-infiltrating macrophages and dendritic cells, as well as CD4(+)FoxP3(-) and CD8(+) T cells. Rejection was also associated with increased numbers of graft-infiltrating alloreactive as well as Listeria-reactive IFNgamma-producing T cells. Rejection of the established grafts required both IL-6 and IFNss, cytokines produced during acute Listeria infection. However, IL-6 and IFNss alone, even when present at higher concentrations than during Listeria infection, were insufficient to break tolerance, while the combination of IL-6 and IFNss was sufficient to break tolerance. These and in vitro observations that IL-6 but not IFNss enhanced T cell proliferation while IFNss but not IL-6 enhanced IFNgamma production support a hypothesis that these cytokines play nonredundant roles. In conclusion, these studies demonstrate that the proinflammatory effects of infections can induce the loss of tolerance and acute rejection of accepted allografts.

Ausencia de realce tardío por resonancia magnética en la no compactación del ventrículo izquierdo en lactantes y niños pequeños / Lack of MR late-enhancement in left ventricular non-compaction in infants and young children

Objetivo: La miocardiopatía no compactada o la no compactación del ventrículo izquierdo (NCVI) es una enfermedad rara y probablemente infradiagnosticada. El diagnóstico es ecográfico, si bien la resonancia magnética (RM) aporta importante información morfológica y funcional. El realce tardío es un hallazgo importante que refleja fibrosis o infarto en las zonas afectadas, y se refiere en adultos y niños mayores de forma generalizada. El objetivo de este trabajo es revisar el realce tardío en esta enfermedad en lactantes y niños pequeños. Material y métodos: En nuestra base de datos de RM cardíaca encontramos 5 pacientes (rango de edad: un mes a 5 años; media de 29,4 meses). Se revisaron los hallazgos morfológicos y funcionales, incluyendo el realce tardío de contraste. Resultados: Todos los pacientes se diagnosticaron previamente por ecocardiografía. Los hallazgos morfológicos y el cociente miocardio no compactado/miocardio compactado fueron compatibles con NCVI. Ninguno de los casos mostró realce tardío poscontraste. Conclusiones: Al contrario que en adultos y niños mayores, ninguno de nuestros pacientes mostró realce tardío. Este hallazgo podría reflejar la naturaleza evolutiva de la fibrosis subendocárdica en estos pacientes (AU)

Objective: Non compaction cardiomyopathy or left ventricular non compaction is a rare disease that is probably underdiagnosed. The diagnosis is reached by echocardiography, although MRI provides additional morphological and functional information. Late MRI enhancement is a hallmark of the disease that reflects fibrosis or infarction of affected areas in adults and older children. We aimed to review the presence of late enhancement in left ventricular non compaction in infants and young children. Material and methods: We found five very young patients (mean age, 29.4 months; range 1 month to 5 years) with left ventricular non compaction in our cardiac MRI database. We reviewed the morphological and functional findings, including late enhancement after the administration of contrast material. Results: All patients had been previously diagnosed by echocardiography. At MRI, the morphological findings and the ratio of non compacted myocardium to compacted myocardium were compatible with left ventricular non compaction. None of the cases showed late enhancement after the administration of contrast material. Conclusions: Unlike in adults and older children, none of the infants and young children we studied had late enhancement. This finding might reflect the natural history of the disease, with subendocardial fibrosis developing over time (AU)

[Lack of MR late-enhancement in left ventricular non-compaction in infants and young children]. / Ausencia de realce tardío por resonancia magnética en la no compactación del ventrículo izquierdo en lactantes y niños pequeños.

OBJECTIVE: Noncompaction cardiomyopathy or left ventricular noncompaction is a rare disease that is probably underdiagnosed. The diagnosis is reached by echocardiography, although MRI provides additional morphological and functional information. Late MRI enhancement is a hallmark of the disease that reflects fibrosis or infarction of affected areas in adults and older children. We aimed to review the presence of late enhancement in left ventricular noncompaction in infants and young children. MATERIAL AND METHODS: We found five very young patients (mean age, 29.4 months; range 1 month to 5 years) with left ventricular noncompaction in our cardiac MRI database. We reviewed the morphological and functional findings, including late enhancement after the administration of contrast material. RESULTS: All patients had been previously diagnosed by echocardiography. At MRI, the morphological findings and the ratio of noncompacted myocardium to compacted myocardium were compatible with left ventricular noncompaction. None of the cases showed late enhancement after the administration of contrast material. CONCLUSIONS: Unlike in adults and older children, none of the infants and young children we studied had late enhancement. This finding might reflect the natural history of the disease, with subendocardial fibrosis developing over time.

[Contrast-enhanced magnetic resonance angiography in congenital heart disease]. / Angiografía con contraste por resonancia magnética en las cardiopatías congénitas.

Contrast-enhanced MR angiography is one of the greatest achievements brought about by advances in body MRI. The noninvasive evaluation of arteries and veins can obviate heart catheterization, the administration of iodinated contrast, and exposure to ionizing radiation in many patients and spare them the risks associated with these factors. These gains are even more important in children with congenital heart disease, who will have to undergo numerous vascular studies in their lifetimes and are more susceptible to the effects of ionizing radiation. Contrast-enhanced MR angiography provides abundant information for diagnosis and postoperative follow-up in these patients, who reach advanced age thanks to advances in medical and surgical treatment and thus receive more and more imaging studies during their lifetimes. In this review, we analyze the contrast-enhanced MR angiography technique in these patients, the problems and precautions related to the use of gadolinium, the indications for the test, and the relevant imaging findings in patients with congenital heart disease.

Angiografía con contraste por resonancia magnética en las cardiopatías congénitas / Contrast-enhanced magnetic resonance angiography in congenital heart disease

El avance de la resonancia magnética (RM) de cuerpo ha visto en la angiografía con contraste por RM (ACRM) uno de sus mayores logros. La evaluación no invasiva de arterias y venas evita la realización de cateterismo, la administración de contraste yodado y la exposición a radiaciones ionizantes a un gran número de pacientes. Este hecho es, si cabe, de mayor relevancia en los niños con cardiopatías congénitas, al tratarse de pacientes a los que habrá que realizar numerosos estudios vasculares a lo largo de su vida, con los riesgos inherentes del cateterismo, los debidos al contraste yodado, y la mayor susceptibilidad de estos pacientes a los efectos de las radiaciones ionizantes. La ACRM aporta abundante información para el diagnóstico y seguimiento posquirúrgico en este grupo de pacientes que, con los avances terapéuticos médicos y quirúrgicos, hoy en día alcanzan edades avanzadas y reciben, cada vez más, numerosos estudios de imagen a lo largo de su vida. En esta revisión se analiza la técnica de la ACRM en estos pacientes, los problemas y precauciones relativas al uso del gadolinio, las indicaciones y los hallazgos radiológicos a los que hay que prestar especial atención en esta patología (AU)

Contrast-enhanced MR angiography is one of the greatest achievements brought about byadvances in body MRI. The non invasive evaluation of arteries and veins can obviate heartcatheterization, the administration of iodinated contrast, and exposure to ionizingradiation in many patients and spare them the risks associated with these factors. These gains are even more important in children with congenital heart disease, who will have toundergo numerous vascular studies in their life times and are more susceptible to theeffects of ionizing radiation. Contrast-enhanced MR angiography provides abundantinformation for diagnosis and postoperative follow-up in these patients, who reachadvanced age thanks to advances in medical and surgical treatment and thus receive moreand more imaging studies during their life times. In this review, we analyze the contrast-enhanced MR angiography technique in these patients, the problems and precautionsrelated to the use of gadolinium, the indications for the test, and the relevant imagingfindings in patients with congenital heart disease (AU)