Genetic and Developmental Contributors to Aortic Stenosis.

Aortic stenosis (AS) remains one of the most common forms of valve disease, with significant impact on patient survival. The disease is characterized by left ventricular outflow obstruction and encompasses a series of stenotic lesions starting from the left ventricular outflow tract to the descending aorta. Obstructions may be subvalvar, valvar, or supravalvar and can be present at birth (congenital) or acquired later in life. Bicuspid aortic valve, whereby the aortic valve forms with two instead of three cusps, is the most common cause of AS in younger patients due to primary anatomic narrowing of the valve. In addition, the secondary onset of premature calcification, likely induced by altered hemodynamics, further obstructs left ventricular outflow in bicuspid aortic valve patients. In adults, degenerative AS involves progressive calcification of an anatomically normal, tricuspid aortic valve and is attributed to lifelong exposure to multifactoral risk factors and physiological wear-and-tear that negatively impacts valve structure-function relationships. AS continues to be the most frequent valvular disease that requires intervention, and aortic valve replacement is the standard treatment for patients with severe or symptomatic AS. While the positive impacts of surgical interventions are well documented, the financial burden, the potential need for repeated procedures, and operative risks are substantial. In addition, the clinical management of asymptomatic patients remains controversial. Therefore, there is a critical need to develop alternative approaches to prevent the progression of left ventricular outflow obstruction, especially in valvar lesions. This review summarizes our current understandings of AS cause; beginning with developmental origins of congenital valve disease, and leading into the multifactorial nature of AS in the adult population.

Comparison of Evolution of Aortic Root Dilation and Ghent Criteria in Preadolescents and Adolescents with and without Marfan Syndrome.

OBJECTIVE: To determine whether the Ghent Criteria (2010) can be reliably used in evaluating preadolescents and adolescents for Marfan syndrome by comparing aortic growth, systemic scores, and anthropometric features in individuals with and without Marfan syndrome. STUDY DESIGN: A retrospective chart review was completed for patients less than 15 years of age referred for Marfan syndrome. Comparisons were made between the first and last visit. Paired t tests were used to compare Ghent systemic scores. Wilcoxon rank-sum test were used to compare age, aortic root z scores, height z scores, and body mass index z scores. Recursive partitioning was used to identify combinations of factors to distinguish Marfan syndrome. RESULTS: In total, 53 individuals met inclusion criteria (29 Marfan syndrome and 24 non-Marfan syndrome). Ghent systemic score increased in the Marfan syndrome group and declined in the non-Marfan syndrome. The non-Marfan syndrome group did not develop progressive aortic root dilation with age. Individuals with Marfan syndrome had higher median height z scores than non-Marfan syndrome, with no difference in median body mass index z score between groups. A combination of aortic root z score above 0.95 and Ghent systemic score above 3 was highly indicative of a Marfan syndrome diagnosis in children less than 15 years of age. CONCLUSION: The Ghent criteria (2010) can be used to reliably exclude a diagnosis of Marfan syndrome in individuals less than 15 years of age. Genetic testing should be used as an aide in confirming or excluding the diagnosis of Marfan syndrome in individuals with an aortic root z score above 0.95 in combination with a Ghent systemic score above 3 at initial visit.

Variants in ADRB1 and CYP2C9: Association with Response to Atenolol and Losartan in Marfan Syndrome.

OBJECTIVE: To test whether variants in ADRB1 and CYP2C9 genes identify subgroups of individuals with differential response to treatment for Marfan syndrome through analysis of data from a large, randomized trial. STUDY DESIGN: In a subset of 250 white, non-Hispanic participants with Marfan syndrome in a prior randomized trial of atenolol vs losartan, the common variants rs1801252 and rs1801253 in ADRB1 and rs1799853 and rs1057910 in CYP2C9 were analyzed. The primary outcome was baseline-adjusted annual rate of change in the maximum aortic root diameter z-score over 3 years, assessed using mixed effects models. RESULTS: Among 122 atenolol-assigned participants, the 70 with rs1801253 CC genotype had greater rate of improvement in aortic root z-score compared with 52 participants with CG or GG genotypes (Time × Genotype interaction P = .005, mean annual z-score change ± SE -0.20 ± 0.03 vs -0.09 ± 0.03). Among participants with the CC genotype in both treatment arms, those assigned to atenolol had greater rate of improvement compared with the 71 of the 121 assigned to losartan (interaction P = .002; -0.20 ± 0.02 vs -0.07 ± 0.02; P < .001). There were no differences in atenolol response by rs1801252 genotype or in losartan response by CYP2C9 metabolizer status. CONCLUSIONS: In this exploratory study, ADRB1-rs1801253 was associated with atenolol response in children and young adults with Marfan syndrome. If these findings are confirmed in future studies, ADRB1 genotyping has the potential to guide therapy by identifying those who are likely to have greater therapeutic response to atenolol than losartan.

Myofibroblast-Specific TGFß Receptor II Signaling in the Fibrotic Response to Cardiac Myosin Binding Protein C-Induced Cardiomyopathy.

RATIONALE: Hypertrophic cardiomyopathy occurs with a frequency of about 1 in 500 people. Approximately 30% of those affected carry mutations within the gene encoding cMyBP-C (cardiac myosin binding protein C). Cardiac stress, as well as cMyBP-C mutations, can trigger production of a 40kDa truncated fragment derived from the amino terminus of cMyBP-C (Mybpc340kDa). Expression of the 40kDa fragment in mouse cardiomyocytes leads to hypertrophy, fibrosis, and heart failure. Here we use genetic approaches to establish a causal role for excessive myofibroblast activation in a slow, progressive genetic cardiomyopathy-one that is driven by a cardiomyocyte-intrinsic genetic perturbation that models an important human disease. OBJECTIVE: TGFß (transforming growth factor-ß) signaling is implicated in a variety of fibrotic processes, and the goal of this study was to define the role of myofibroblast TGFß signaling during chronic Mybpc340kDa expression. METHODS AND RESULTS: To specifically block TGFß signaling only in the activated myofibroblasts in Mybpc340kDa transgenic mice and quadruple compound mutant mice were generated, in which the TGFß receptor II (TßRII) alleles ( Tgfbr2) were ablated using the periostin ( Postn) allele, myofibroblast-specific, tamoxifen-inducible Cre ( Postnmcm) gene-targeted line. Tgfbr2 was ablated either early or late during pathological fibrosis. Early myofibroblast-specific Tgfbr2 ablation during the fibrotic response reduced cardiac fibrosis, alleviated cardiac hypertrophy, preserved cardiac function, and increased lifespan of the Mybpc340kDa transgenic mice. Tgfbr2 ablation late in the pathological process reduced cardiac fibrosis, preserved cardiac function, and prolonged Mybpc340kDa mouse survival but failed to reverse cardiac hypertrophy. CONCLUSIONS: Fibrosis and cardiac dysfunction induced by cardiomyocyte-specific expression of Mybpc340kDa were significantly decreased by Tgfbr2 ablation in the myofibroblast. Surprisingly, preexisting fibrosis was partially reversed if the gene was ablated subsequent to fibrotic deposition, suggesting that continued TGFß signaling through the myofibroblasts was needed to maintain the heart fibrotic response to a chronic, disease-causing cardiomyocyte-only stimulus.

Left ventricular outflow tract obstruction: Uptake of familial cardiac screening and parental knowledge from a single tertiary care center.

Left ventricular outflow tract obstruction (LVOTO) malformations exhibit higher heritability than other cardiac lesions and cardiac screening is encouraged for first-degree relatives. This study sought to determine the uptake of familial cardiac screening in families with an infant with an LVOTO and assess parental knowledge regarding genetics and heritability of LVOTO. A chart review of the period 2010-2015 identified 69 families who received genetic counseling regarding a diagnosis of LVOTO in an infant. Surveys assessing familial cardiac screening and parental knowledge were completed by a parent in 24 families (completion rate of 35%). Forty percent (36/89) of all at-risk first-degree family members completed cardiac screening. The presence of additional congenital malformations in the affected infant was the only significant factor reducing the uptake of familial cardiac screening (p = 0.003). The reported uptake of screening for subsequent at-risk pregnancies was 11/12 (92%) compared to 25/77 (32%) of living at-risk relatives. Survey respondents answered seven knowledge questions with an average score of 5.2 and all correctly identified that LVOTO can run in families. Uptake of familial cardiac screening is occurring in less than half of at-risk individuals, despite parents demonstrating basic knowledge and receiving genetic counseling. Follow-up counseling in the outpatient setting to review familial screening recommendations should be considered to increase uptake and optimize outcomes.

Sickle cell anemia mice develop a unique cardiomyopathy with restrictive physiology.

Cardiopulmonary complications are the leading cause of mortality in sickle cell anemia (SCA). Elevated tricuspid regurgitant jet velocity, pulmonary hypertension, diastolic, and autonomic dysfunction have all been described, but a unifying pathophysiology and mechanism explaining the poor prognosis and propensity to sudden death has been elusive. Herein, SCA mice underwent a longitudinal comprehensive cardiac analysis, combining state-of-the-art cardiac imaging with electrocardiography, histopathology, and molecular analysis to determine the basis of cardiac dysfunction. We show that in SCA mice, anemia-induced hyperdynamic physiology was gradually superimposed with restrictive physiology, characterized by progressive left atrial enlargement and diastolic dysfunction with preserved systolic function. This phenomenon was absent in WT mice with experimentally induced chronic anemia of similar degree and duration. Restrictive physiology was associated with microscopic cardiomyocyte loss and secondary fibrosis detectable as increased extracellular volume by cardiac-MRI. Ultrastructural mitochondrial changes were consistent with severe chronic hypoxia/ischemia and sarcomere diastolic-length was shortened. Transcriptome analysis revealed up-regulation of genes involving angiogenesis, extracellular-matrix, circadian-rhythm, oxidative stress, and hypoxia, whereas ion-channel transport and cardiac conduction were down-regulated. Indeed, progressive corrected QT prolongation, arrhythmias, and ischemic changes were noted in SCA mice before sudden death. Sudden cardiac death is common in humans with restrictive cardiomyopathies and long QT syndromes. Our findings may thus provide a unifying cardiac pathophysiology that explains the reported cardiac abnormalities and sudden death seen in humans with SCA.

Age-dependent cardiac function during experimental sepsis: effect of pharmacological activation of AMP-activated protein kinase by AICAR.

Age represents a major risk factor for multiple organ failure, including cardiac dysfunction, in patients with sepsis. AMP-activated protein kinase (AMPK) is a crucial regulator of energy homeostasis that controls mitochondrial biogenesis by activation of peroxisome proliferator-activated receptor-γ coactivator-1α and disposal of defective organelles by autophagy. We investigated whether AMPK dysregulation contributes to age-dependent cardiac injury in young (2-3 mo) and mature adult (11-13 mo) male mice subjected to sepsis by cecal ligation and puncture and whether AMPK activation by 5-amino-4-imidazole carboxamide riboside affords cardioprotective effects. Plasma proinflammatory cytokines and myokine follistatin were similarly elevated in vehicle-treated young and mature adult mice at 18 h after sepsis. However, despite equivalent troponin I and T levels compared with similarly treated young mice, vehicle-treated mature adult mice exhibited more severe cardiac damage by light and electron microscopy analyses with more marked intercellular edema, inflammatory cell infiltration, and mitochondrial derangement. Echocardiography revealed that vehicle-treated young mice exhibited left ventricular dysfunction after sepsis, whereas mature adult mice exhibited a reduction in stroke volume without apparent changes in load-dependent indexes of cardiac function. At molecular analysis, phosphorylation of the catalytic subunits AMPK-α1/α2 was associated with nuclear translocation of peroxisome proliferator-activated receptor-γ coactivator-1α in vehicle-treated young but not mature adult mice. Treatment with 5-amino-4-imidazole carboxamide riboside ameliorated cardiac architecture derangement in mice of both ages. These cardioprotective effects were associated with attenuation of the systemic inflammatory response and amelioration of cardiac dysfunction in young mice only, not in mature adult animals. NEW & NOTEWORTHY Our data suggest that sepsis-induced cardiac dysfunction manifests with age-dependent characteristics, which are associated with a distinct regulation of AMP-activated protein kinase-dependent metabolic pathways. Consistent with this age-related deterioration, pharmacological activation of AMP-activated protein kinase may afford cardioprotective effects allowing a partial recovery of cardiac function in young but not mature age.

UBC9-Mediated Sumoylation Favorably Impacts Cardiac Function in Compromised Hearts.

RATIONALE: SUMOylation plays an important role in cardiac function and can be protective against cardiac stress. Recent studies show that SUMOylation is an integral part of the ubiquitin proteasome system, and expression of the small ubiquitin-like modifier (SUMO) E2 enzyme UBC9 improves cardiac protein quality control. However, the precise role of SUMOylation on other protein degradation pathways, particularly autophagy, remains undefined in the heart. OBJECTIVE: To determine whether SUMOylation affects cardiac autophagy and whether this effect is protective in a mouse model of proteotoxic cardiac stress. METHODS AND RESULTS: We modulated expression of UBC9, a SUMO E2 ligase, using gain- and loss-of-function in neonatal rat ventricular cardiomyocytes. UBC9 expression seemed to directly alter autophagic flux. To confirm this effect in vivo, we generated transgenic mice overexpressing UBC9 in cardiomyocytes. These mice have an increased level of SUMOylation at baseline and, in confirmation of the data obtained from neonatal rat ventricular cardiomyocytes, demonstrated increased autophagy, suggesting that increased UBC9-mediated SUMOylation is sufficient to upregulate cardiac autophagy. Finally, we tested the protective role of SUMOylation-mediated autophagy by expressing UBC9 in a model of cardiac proteotoxicity, induced by cardiomyocyte-specific expression of a mutant α-B-crystallin, mutant CryAB (CryAB(R120G)), which shows impaired autophagy. UBC9 overexpression reduced aggregate formation, decreased fibrosis, reduced hypertrophy, and improved cardiac function and survival. CONCLUSIONS: The data showed that increased UBC9-mediated SUMOylation is sufficient to induce relatively high levels of autophagy and may represent a novel strategy for increasing autophagic flux and ameliorating morbidity in proteotoxic cardiac disease.

Predictors of Rapid Aortic Root Dilation and Referral for Aortic Surgery in Marfan Syndrome.

Few data exist regarding predictors of rapid aortic root dilation and referral for aortic surgery in Marfan syndrome (MFS). To identify independent predictors of the rate of aortic root (AoR) dilation and referral for aortic surgery, we investigated the data from the Pediatric Heart Network randomized trial of atenolol versus losartan in young patients with MFS. Data were analyzed from the echocardiograms at 0, 12, 24, and 36 months read in the core laboratory of 608 trial subjects, aged 6 months to 25 years, who met original Ghent criteria and had an AoR z-score (AoRz) > 3. Repeated measures linear and logistic regressions were used to determine multivariable predictors of AoR dilation. Receiver operator characteristic curves were used to determine cut-points in AoR dilation predicting referral for aortic surgery. Multivariable analysis showed rapid AoR dilation as defined by change in AoRz/year > 90th percentile was associated with older age, higher sinotubular junction z-score, and atenolol use (R2 = 0.01) or by change in AoR diameter (AoRd)/year > 90th percentile with higher sinotubular junction z-score and non-white race (R2 = 0.02). Referral for aortic root surgery was associated with higher AoRd, higher ascending aorta z-score, and higher sinotubular junction diameter:ascending aorta diameter ratio (R2 = 0.17). Change in AoRz of 0.72 SD units/year had 42% sensitivity and 92% specificity and change in AoRd of 0.34 cm/year had 38% sensitivity and 95% specificity for predicting referral for aortic surgery. In this cohort of young patients with MFS, no new robust predictors of rapid AoR dilation or referral for aortic root surgery were identified. Further investigation may determine whether generalized proximal aortic dilation and effacement of the sinotubular junction will allow for better risk stratification. Rate of AoR dilation cut-points had high specificity, but low sensitivity for predicting referral for aortic surgery, limiting their clinical use. Clinical Trial Number ClinicalTrials.gov number, NCT00429364.

Metformin ameliorates gender-and age-dependent hemodynamic instability and myocardial injury in murine hemorrhagic shock.

Severity of multiple organ failure is significantly impacted by age and gender in patients with hemorrhagic shock. However, the molecular mechanisms underlying the enhanced organ injury are not fully understood. AMP-activated protein kinase (AMPK) is a pivotal orchestrator of metabolic responses during stress. We investigated whether hemorrhage-induced myocardial injury is age and gender dependent and whether treatment with metformin, an AMPK activator, affords cardioprotective effects. C57/BL6 young (3-5months) and mature (9-12months) male and female mice were subjected to hemorrhagic shock by blood withdrawing followed by resuscitation with blood and Lactated Ringer's solution. Vehicle-treated young and mature mice of both genders had a similar elevation of plasma inflammatory cytokines at 3h after resuscitation. However, vehicle-treated male mature mice experienced hemodynamic instability and higher myocardial damage than young male mice, as evaluated by echocardiography, histology and cardiovascular injury biomarkers. There was also a gender-dependent difference in cardiovascular injury in the mature group as vehicle-treated male mice exhibited more severe organ injury than female mice. At molecular analysis, vehicle-treated mature mice of both genders exhibited a marked downregulation of AMPKα activation and nuclear translocation of peroxisome proliferator-activated receptor γ co-activator α when compared with young mice. Treatment with metformin improved cardiovascular function and survival in mature animals of both genders. However, specific cardioprotective effects of metformin were gender-dependent. Metformin did not affect hemodynamic or inflammatory responses in young animals. Thus, our data suggest that targeting metabolic recovery with metformin may be a potential treatment approach in severe hemorrhage in adult population.

High fat diet-induced obesity increases myocardial injury and alters cardiac STAT3 signaling in mice after polymicrobial sepsis.

Little is known about how obesity affects the heart during sepsis and we sought to investigate the obesity-induced cardiac effects that occur during polymicrobial sepsis. Six-week old C57BL/6 mice were randomized to a high fat (HFD) (60% kcal fat) or normal diet (ND) (16% kcal fat). After 6weeks of feeding, mice were anesthetized with isoflurane and polymicrobial sepsis was induced by cecal ligation and puncture (CLP). Plasma and cardiac tissue were obtained for analysis. Echocardiography was performed on a separate cohort of mice at 0 and 18h after CLP. Following 6-weeks of dietary intervention, plasma cardiac troponin I was elevated in obese mice at baseline compared to non-obese mice but troponin increased only in non-obese septic mice. IL-17a expression was 27-fold higher in obese septic mice versus non-obese septic mice. Cardiac phosphorylation of STAT3 at Ser727 was increased at baseline in obese mice and increased further only in obese septic mice. Phosphorylation of STAT3 at Tyr705 was similar in both groups at baseline and increased after sepsis. SOCS3, a downstream protein and negative regulator of STAT3, was elevated in obese mice at baseline compared to non-obese mice. After sepsis non-obese mice had an increase in SOCS3 expression that was not observed in obese mice. Taken together, we show that obesity affects cardiac function and leads to cardiac injury. Furthermore, myocardial injury in obese mice during sepsis may occur through alteration of the STAT3 pathway.

Natural history of aortic root dilation through young adulthood in a hypermobile Ehlers-Danlos syndrome cohort.

Hypermobile Ehlers-Danlos syndrome (hEDS) is a common inherited connective tissue disorder characterized by joint hypermobility. The natural history of aortic root dilation (AoD), a potential complication of EDS, has not been well characterized in this population. We describe the natural history of aortic root size in a large cohort of patients with hEDS. A cohort of 325 patients with HEDS was identified at Cincinnati Children's Hospital Medical Center (CCHMC), including 163 patients from a previous study. Medical records were reviewed and each participant's height, weight, and aortic dimensions from up to four echocardiograms were documented. Aortic root z-scores were calculated using two established formulas based on age (Boston or Devereux). Overall prevalence of AoD and prevalence by age were calculated and longitudinal regression was performed. The prevalence of AoD with a z-score ≥ 2.0 was 14.2% (46/325) and with a z-score of ≥3.0 was 5.5% (18/325). No significant increases in z-score were seen over time for patients with multiple echocardiograms. Participants under the age of 15 years had an average decline of 0.1 standard deviations (SDs)/year. No significant change was found after 15 of age. Between the ages of 15 and 21 years, Boston z-scores were 0.96 higher than Devereux z-scores. The nearly 1 z-score unit difference between formulas indicates caution prior to diagnosing AoD in patients with hEDS. In light of the low prevalence and lack of progression of AoD, routine echocardiograms may not be warranted for pediatric patients with hEDS.

Fetal origins of adult cardiac disease: a novel approach to prevent fetal growth restriction induced cardiac dysfunction using insulin like growth factor.

BACKGROUND: Fetal growth restriction (FGR) is a risk factor for adult cardiovascular disease. Intraplacental gene transfer of human insulin-like growth factor-1 (IGF-1) corrects birth weight in our mouse model of FGR. This study addresses long term effects of FGR on cardiac function and the potential preventive effect of IGF-1. STUDY DESIGN: Laparotomy was performed on pregnant C57BL/6J mice at embryonic day 18 and pups were divided into three groups: Sham operated; FGR (induced by mesenteric uterine artery ligation); treatment (intraplacental injection of IGF-1 after uterine artery ligation). Pups were followed until 32 wk of life. Transthoracic echocardiography was performed starting at 12 wk. RESULTS: Systolic cardiac function was significantly impaired in the FGR group with reduced fractional shortening compared with sham and treatment group starting at week 12 of life (20 ± 4 vs. 31 ± 5 vs. 32 ± 5, respectively, n = 12 for each group; P < 0.001) with no difference between the sham and treatment groups. CONCLUSION: Intraplacental gene transfer of IGF-1 prevents FGR induced cardiac dysfunction. This suggests that in utero therapy may positively impact cardiac remodeling and prevent adult cardiovascular disease.

Tubulin hyperacetylation is adaptive in cardiac proteotoxicity by promoting autophagy.

Proteinopathy causes cardiac disease, remodeling, and heart failure but the pathological mechanisms remain obscure. Mutated αB-crystallin (CryAB(R120G)), when expressed only in cardiomyocytes in transgenic (TG) mice, causes desmin-related cardiomyopathy, a protein conformational disorder. The disease is characterized by the accumulation of toxic misfolded protein species that present as perinuclear aggregates known as aggresomes. Previously, we have used the CryAB(R120G) model to determine the underlying processes that result in these pathologic accumulations and to explore potential therapeutic windows that might be used to decrease proteotoxicity. We noted that total ventricular protein is hypoacetylated while hyperacetylation of α-tubulin, a substrate of histone deacetylase 6 (HDAC6) occurs. HDAC6 has critical roles in protein trafficking and autophagy, but its function in the heart is obscure. Here, we test the hypothesis that tubulin acetylation is an adaptive process in cardiomyocytes. By modulating HDAC6 levels and/or activity genetically and pharmacologically, we determined the effects of tubulin acetylation on aggregate formation in CryAB(R120G) cardiomyocytes. Increasing HDAC6 accelerated aggregate formation, whereas siRNA-mediated knockdown or pharmacological inhibition ameliorated the process. HDAC inhibition in vivo induced tubulin hyperacetylation in CryAB(R120G) TG hearts, which prevented aggregate formation and significantly improved cardiac function. HDAC6 inhibition also increased autophagic flux in cardiomyocytes, and increased autophagy in the diseased heart correlated with increased tubulin acetylation, suggesting that autophagy induction might underlie the observed cardioprotection. Taken together, our data suggest a mechanistic link between tubulin hyperacetylation and autophagy induction and points to HDAC6 as a viable therapeutic target in cardiovascular disease.

Assessment of the need for a cardiac morphology curriculum for paediatric cardiology fellows.

BACKGROUND: Expert knowledge of cardiac malformations is essential for paediatric cardiologists. Current cardiac morphology fellowship teaching format, content, and nomenclature are left up to the discretion of the individual fellowship programmes. We aimed to assess practices and barriers in morphology education, perceived effectiveness of current curricula, and preferences for a standardised fellow morphology curriculum. METHODS: A web-based survey was developed de novo and administered anonymously via e-mail to all paediatric cardiology fellowship programme directors and associate directors in the United States of America; leaders were asked to forward the survey to fellows. RESULTS: A total of 35 directors from 32 programmes (51%) and 66 fellows responded. Curriculum formats varied: 28 (88%) programmes utilised pathological specimens, 25 (78%) invited outside faculty, and 16 (50%) utilised external conferences. Director nomenclature preferences were split - 6 (19%) Andersonian, 8 (25%) Van Praaghian, and 18 (56%) mixed. Barriers to morphology education included time and inconsistent nomenclature. One-third of directors reported that <90% of recent fellow graduates had adequate abilities to apply segmental anatomy, identify associated cardiac lesions, or communicate complex CHD. More structured teaching, protected time, and specimens were suggestions to improve curricula. Almost 75% would likely adopt/utilise an online morphology curriculum. CONCLUSIONS: Cardiac morphology training varies in content and format among fellowships. Inconsistent nomenclature exists, and inadequate morphology knowledge is perceived to contribute to communication failures, both have potential patient safety implications. There is an educational need for a common, online cardiac morphology curriculum that could allow for fellow assessment of competency and contribute to more standardised communication in the field of paediatric cardiology.

In vivo definition of cardiac myosin-binding protein C's critical interactions with myosin.

Cardiac myosin-binding protein C (cMyBP-C) is an integral part of the sarcomeric machinery in cardiac muscle that enables normal function. cMyBP-C regulates normal cardiac contraction by functioning as a brake through interactions with the sarcomere's thick, thin, and titin filaments. cMyBP-C's precise effects as it binds to the different filament systems remain obscure, particularly as it impacts on the myosin heavy chain's head domain, contained within the subfragment 2 (S2) region. This portion of the myosin heavy chain also contains the ATPase activity critical for myosin's function. Mutations in myosin's head, as well as in cMyBP-C, are a frequent cause of familial hypertrophic cardiomyopathy (FHC). We generated transgenic lines in which endogenous cMyBP-C was replaced by protein lacking the residues necessary for binding to S2 (cMyBP-C(S2-)). We found, surprisingly, that cMyBP-C lacking the S2 binding site is incorporated normally into the sarcomere, although systolic function is compromised. We show for the first time the acute and chronic in vivo consequences of ablating a filament-specific interaction of cMyBP-C. This work probes the functional consequences, in the whole animal, of modifying a critical structure-function relationship, the protein's ability to bind to a region of the critical enzyme responsible for muscle contraction, the subfragment 2 domain of the myosin heavy chain. We show that the binding is not critical for the protein's correct insertion into the sarcomere's architecture, but is essential for long-term, normal function in the physiological context of the heart.

Accelerated cardiac remodeling in desmoplakin transgenic mice in response to endurance exercise is associated with perturbed Wnt/ß-catenin signaling.

Arrhythmogenic ventricular cardiomyopathy (AVC) is a frequent underlying cause for arrhythmias and sudden cardiac death especially during intense exercise. The mechanisms involved remain largely unknown. The purpose of this study was to investigate how chronic endurance exercise contributes to desmoplakin (DSP) mutation-induced AVC pathogenesis. Transgenic mice with overexpression of desmoplakin, wild-type (Tg-DSP(WT)), or the R2834H mutant (Tg-DSP(R2834H)) along with control nontransgenic (NTg) littermates were kept sedentary or exposed to a daily running regimen for 12 wk. Cardiac function and morphology were analyzed using echocardiography, electrocardiography, histology, immunohistochemistry, RNA, and protein analysis. At baseline, 4-wk-old mice from all groups displayed normal cardiac function. When subjected to exercise, all mice retained normal cardiac function and left ventricular morphology; however, Tg-DSP(R2834H) mutants displayed right ventricular (RV) dilation and wall thinning, unlike NTg and Tg-DSP(WT). The Tg-DSP(R2834H) hearts demonstrated focal fat infiltrations in RV and cytoplasmic aggregations consisting of desmoplakin, plakoglobin, and connexin 43. These aggregates coincided with disruption of the intercalated disks, intermediate filaments, and microtubules. Although Tg-DSP(R2834H) mice already displayed high levels of p-GSK3-ß(Ser9) and p-AKT1(Ser473) under sedentary conditions, decrease of nuclear GSK3-ß and AKT1 levels with reduced p-GSK3-ß(Ser9), p-AKT1(Ser473), and p-AKT1(Ser308) and loss of nuclear junctional plakoglobin was apparent after exercise. In contrast, Tg-DSP(WT) showed upregulation of p-AKT1(Ser473), p-AKT1(Ser308), and p-GSK3-ß(Ser9) in response to exercise. Our data suggest that endurance exercise accelerates AVC pathogenesis in Tg-DSP(R2834H) mice and this event is associated with perturbed AKT1 and GSK3-ß signaling. Our study suggests a potential mechanism-based approach to exercise management in patients with AVC.

FasL expression in cardiomyocytes activates the ERK1/2 pathway, leading to dilated cardiomyopathy and advanced heart failure.

Increase in the apoptotic molecule Fas ligand (FasL) in serum and cardiomyocytes has been shown to be associated with progressive dilated cardiomyopathy (DCM) and congestive heart failure (CHF) in humans. However, the underlying mechanism(s) of FasL-related deterioration of heart function remain obscure. The aim of the present study is to determine roles of myocardial FasL in the activation of alternative pathways such as extracellular-signal-regulated kinase 1/2 (ERK1/2), inflammation or fibrosis and to identify effective treatments of progressive DCM and advanced CHF. Transgenic mice with cardiomyocyte-specific overexpression of FasL were investigated and treated with an ERK1/2 inhibitor (U-0126), losartan (los), prednisolone (pred) or placebo. Morpho-histological and molecular studies were subsequently performed. FasL mice showed significantly higher mortality compared with wild-type (WT) littermates due to DCM and advanced CHF. Prominent perivascular and interstitial fibrosis, increased interleukin secretion and diffuse CD3-positive cell infiltration were evident in FasL hearts. Up-regulation of the short form of Fas-associated death domain (FADD)-like interleukin 1ß-converting enzyme (FLICE) inhibitory protein (s-FLIP), RIP (receptor-interacting protein) and ERK1/2 and down-regulation of transforming growth factor beta 1 (TGFß1) and nuclear factor-κB (NF-κB) was determined in the myocardium, whereas expression of ERK1/2, periostin (Postn) and osteopontin increased in cardiac fibroblasts. U-0126 and los increased CHF survival by 75% compared with pred and placebo groups. U-0126 had both anti-fibrotic and anti-apoptotic effects, whereas los reduced fibrosis only. Myocardial FasL expression in mice activates differential robust fibrotic, apoptotic and inflammatory responses via ERK1/2 in cardiomyocytes and cardiac fibroblasts inducing DCM and CHF. Blocking the ERK1/2 pathway prevented progression of FasL-induced DCM and CHF by reducing fibrosis, inflammation and apoptosis in the myocardium.

Sox17 is required for normal pulmonary vascular morphogenesis.

The SRY-box containing transcription factor Sox17 is required for endoderm formation and vascular morphogenesis during embryonic development. In the lung, Sox17 is expressed in mesenchymal progenitors of the embryonic pulmonary vasculature and is restricted to vascular endothelial cells in the mature lung. Conditional deletion of Sox17 in splanchnic mesenchyme-derivatives using Dermo1-Cre resulted in substantial loss of Sox17 from developing pulmonary vascular endothelial cells and caused pulmonary vascular abnormalities before birth, including pulmonary vein varices, enlarged arteries, and decreased perfusion of the microvasculature. While survival of Dermo1-Cre;Sox17Δ/Δ mice (herein termed Sox17Δ/Δ) was unaffected at E18.5, most Sox17Δ/Δ mice died by 3 weeks of age. After birth, the density of the pulmonary microvasculature was decreased in association with alveolar simplification, biventricular cardiac hypertrophy, and valvular regurgitation. The severity of the postnatal cardiac phenotype was correlated with the severity of pulmonary vasculature abnormalities. Sox17 is required for normal formation of the pulmonary vasculature and postnatal cardiovascular homeostasis.

Clinical Stratification of Pediatric Patients with Idiopathic Thoracic Aortic Aneurysm.

OBJECTIVES: To describe the global phenotypes of pediatric patients with thoracic aortic aneurysm (TAA) who do not have a clinical diagnosis of Marfan syndrome (MFS) or related connective tissue disorders. We hypothesized that the presence of noncardiovascular abnormalities correlate with TAA severity and that medical therapy reduces TAA progression. STUDY DESIGN: This is a retrospective case series of patients with TAA age ≤ 21 years evaluated in a cardiovascular genetics clinic. Patients meeting clinical criteria for MFS or related disorders were excluded. Repeated measures analyses of longitudinal echocardiographic measurements of the aorta were used to test associations between TAA severity and noncardiovascular phenotype and to assess the impact of medical therapy. RESULTS: Sixty-nine patients with TAA at mean age 12.5 ± 5.3 years were included. Noncardiovascular abnormalities, including skeletal (65%) or craniofacial (54%) findings, were frequently observed. Increased rate of aortic root enlargement was associated with ocular (P = .002) and cutaneous (P = .003) abnormalities, and increased rate of ascending aorta enlargement was associated with craniofacial (P < .001) abnormalities. Beta blocker or angiotensin receptor blocker therapy (n = 41) was associated with reduction in the rate of aortic root growth (P = .018). CONCLUSIONS: Children with TAA not satisfying diagnostic criteria for MFS or related disorders frequently have noncardiovascular findings, some of which are associated with TAA progression. Because therapy initiation may reduce risk of progression and long-term complications, comprehensive assessment of noncardiovascular findings may facilitate early risk stratification and improve outcomes.