Gain-of-function mutations in SMAD4 cause a distinctive repertoire of cardiovascular phenotypes in patients with Myhre syndrome.

Myhre syndrome is a rare, distinctive syndrome due to specific gain-of-function mutations in SMAD4. The characteristic phenotype includes short stature, dysmorphic facial features, hearing loss, laryngotracheal anomalies, arthropathy, radiographic defects, intellectual disability, and a more recently appreciated spectrum of cardiovascular defects with a striking fibroproliferative response to surgical intervention. We report four newly described patients with typical features of Myhre syndrome who had (i) a mildly narrow descending aorta and restrictive cardiomyopathy; (ii) recurrent pericardial and pleural effusions; (iii) a large persistent ductus arteriosus with juxtaductal aortic coarctation; and (iv) restrictive pericardial disease requiring pericardiectomy. Additional information is provided about a fifth previously reported patient with fatal pericardial disease. A literature review of the cardiovascular features of Myhre syndrome was performed on 54 total patients, all with a SMAD4 mutation. Seventy percent had a cardiovascular abnormality including congenital heart defects (63%), pericardial disease (17%), restrictive cardiomyopathy (9%), and systemic hypertension (15%). Pericarditis and restrictive cardiomyopathy are associated with high mortality (three patients each among 10 deaths); one patient with restrictive cardiomyopathy also had epicarditis. Cardiomyopathy and pericardial abnormalities distinguish Myhre syndrome from other disorders caused by mutations in the TGF-ß signaling cascade (Marfan, Loeys-Dietz, or Shprintzen-Goldberg syndromes). We hypothesize that the expanded spectrum of cardiovascular abnormalities relates to the ability of the SMAD4 protein to integrate diverse signaling pathways, including canonical TGF-ß, BMP, and Activin signaling. The co-occurrence of congenital and acquired phenotypes demonstrates that the gene product of SMAD4 is required for both developmental and postnatal cardiovascular homeostasis. © 2016 Wiley Periodicals, Inc.

Role of pulse oximetry in examining newborns for congenital heart disease: a scientific statement from the American Heart Association and American Academy of Pediatrics.

BACKGROUND: The purpose of this statement is to address the state of evidence on the routine use of pulse oximetry in newborns to detect critical congenital heart disease (CCHD). METHODS AND RESULTS: A writing group appointed by the American Heart Association and the American Academy of Pediatrics reviewed the available literature addressing current detection methods for CCHD, burden of missed and/or delayed diagnosis of CCHD, rationale of oximetry screening, and clinical studies of oximetry in otherwise asymptomatic newborns. MEDLINE database searches from 1966 to 2008 were done for English-language papers using the following search terms: congenital heart disease, pulse oximetry, physical examination, murmur, echocardiography, fetal echocardiography, and newborn screening. The reference lists of identified papers were also searched. Published abstracts from major pediatric scientific meetings in 2006 to 2008 were also reviewed. The American Heart Association classification of recommendations and levels of evidence for practice guidelines were used. In an analysis of pooled studies of oximetry assessment performed after 24 hours of life, the estimated sensitivity for detecting CCHD was 69.6%, and the positive predictive value was 47.0%; however, sensitivity varied dramatically among studies from 0% to 100%. False-positive screens that required further evaluation occurred in only 0.035% of infants screened after 24 hours. CONCLUSIONS: Currently, CCHD is not detected in some newborns until after their hospital discharge, which results in significant morbidity and occasional mortality. Furthermore, routine pulse oximetry performed on asymptomatic newborns after 24 hours of life, but before hospital discharge, may detect CCHD. Routine pulse oximetry performed after 24 hours in hospitals that have on-site pediatric cardiovascular services incurs very low cost and risk of harm. Future studies in larger populations and across a broad range of newborn delivery systems are needed to determine whether this practice should become standard of care in the routine assessment of the neonate.

Cardiovascular magnetic resonance of pulmonary artery growth and ventricular function after Norwood procedure with Sano modification.

For hypoplastic left heart syndrome (HLHS), there have been concerns regarding pulmonary artery growth and ventricular dysfunction after first stage surgery consisting of the Norwood procedure modified with a right ventricle-to-pulmonary artery conduit. We report our experience using cardiovascular magnetic resonance (CMR) to determine and follow pulmonary arterial growth and ventricular function in this cohort. Following first stage palliation, serial CMR was performed at 1 and 10 weeks post-operatively, followed by cardiac catheterization at 4-6 months. Thirty-four of 47 consecutive patients with HLHS (or its variations) underwent first stage palliation. Serial CMR was performed in 20 patients. Between studies, ejection fraction decreased (58 +/- 9% vs. 50 +/- 5%, p < 0.05). Pulmonary artery growth occurred on the left (6 +/- 1 mm vs. 4 +/- 1 mm at baseline, p < 0.05) but not significantly in the right. This trend continued to cardiac catheterization 4-6 months post surgery, with the left pulmonary artery of greater size than the right (8.8 +/- 2.2 mm vs. 6.7 +/- 1.9 mm, p < 0.05). By CMR, 5 had pulmonary artery stenoses initially, and at 2 months, 9 had stenoses. Three of the 9 underwent percutaneous intervention prior to the second stage procedure. In this cohort, reasonable growth of pulmonary arteries occurred following first stage palliation with this modification, although that growth was preferential to the left. Serial studies demonstrate worsening of ventricular function for the cohort. CMR was instrumental for detecting pulmonary artery stenosis and right ventricular dysfunction.

Adenosine receptor-mediated coronary vascular protection in post-ischemic mouse heart.

This study evaluated the ability of A1 and A3 adenosine receptor (AR) agonism, and A1, A2A, A2B and A3AR antagonism (revealing "intrinsic" responses), to modify post-ischemic coronary dysfunction in mouse heart. Vascular function was assessed before and after 20 min global ischemia and 30-45 min reperfusion in Langendorff perfused C57/Bl6 mouse hearts. Ischemic insult impaired coronary sensitivity to the endothelial-dependent dilators ADP (pEC50=6.8+/-0.1 vs. 7.6+/-0.1, non-ischemic) and acetylcholine (pEC50=6.1+/-0.1 vs. 7.3+/-0.1 in non-ischemic), and for the mixed endothelial-dependent/independent dilator 2-chloroadenosine (pEC50=7.5+/-0.1 vs. 8.4+/-0.1, non-ischemic). Endothelium-independent dilation in response to nitroprusside was unaltered (pEC50=7.0+/-0.1 vs. 7.1+/-0.1 in non-ischemic). Pre-treatment with a selective A1AR agonist (50 nM CHA) failed to modify coronary dysfunction, whereas A1AR antagonism (200 nM DPCPX) worsened the effects of I/R (2-chloroadenosine pEC50=6.9+/-0.1). Conversely, A3AR agonism (100 nM Cl-IB-MECA) did reduce effects of I/R (pEC50s=8.0+/-0.1 and 7.3+/-0.1 for 2-chloroadenosine and ADP, respectively), whereas antagonism (100 nM MRS1220) was without effect. While A2AAR agonism could not be assessed (due to pronounced vasodilatation), A2AAR antagonism (100 nM SCH58261) was found to exert no effect, and antagonism of A2BARs (50 nM MRS1754) was also ineffective. The protective actions of A3AR agonism were also manifest as improved reactive hyperemic responses. Interestingly, post-ischemic coronary dysfunction was also limited by: Na+-H+ exchange (NHE) inhibition with 10 or 50 microM BIIB-513 (2-chloroadenosine pEC50s=7.8+/-0.1, either dose), an effect not additive with A3AR agonism; Ca2+ antagonism with 0.3 microM verapamil (2-chloroadenosine pEC50=7.9+/-0.1); and Ca2+ desensitization with 5 mM BDM (2-chloroadenosine pEC50=7.8+/-0.1). In contrast, endothelin antagonism (200 nM PD142893) and anti-oxidant therapy (300 microM MPG+150 U/ml SOD+600 U/ml catalase) were ineffective. Our data collectively confirm that ischemia selectively impairs endothelial function and reactive hyperemia independently of blood cells. Vascular injury is intrinsically limited by endogenous (but not exogenous) activation of A1ARs, whereas exogenous A3AR activation further limits dysfunction (improving post-ischemic vasoregulation). Finally, findings suggest this form of post-ischemic coronary injury is unrelated to endothelin or oxidant stress, but may involve modulation of Ca2+ overload and/or related ionic perturbations.

Effect of cardiac A(1) adenosine receptor overexpression on sarcoplasmic reticulum function.

OBJECTIVE: We investigated the effect of A(1) adenosine receptor overexpression, which has been reported to increase myocardial tolerance to ischemia-reperfusion injury, on sarcoplasmic reticulum (SR) Ca(2+) handling. METHODS: Transgenic mouse hearts (approximately 300-fold A(1) adenosine receptor overexpression) and wild-type mouse hearts were perfused in the Langendorff mode and subjected either to 80 min of aerobic perfusion or to 30 min of aerobic perfusion, 20 min of global ischemia and 30 min of reperfusion. The hearts were then homogenized and used to assay SR oxalate-supported 45Ca(2+) uptake and [3H]-ryanodine binding. RESULTS: Transgenic hearts showed increased resistance to ischemia-reperfusion, as shown by lower diastolic tension (1.5 +/- 0.2 vs. 2.6 +/- 0.1 g, P<0.05) and higher recovery of developed tension (45 +/- 3 vs. 30 +/- 4% of the baseline, P<0.05) following ischemia-reperfusion. Under baseline conditions, oxalate-supported 45Ca(2+) uptake was lower in transgenic hearts, owing to reduced V(max) (10.6 +/- 2.0 vs. 17.8 +/- 2.7 nmol/min per mg of protein, P<0.05), and the difference was preserved after ischemia-reperfusion (10.0 +/- 1.0 vs. 15.7 +/- 2.5 nmol/min per mg of protein, P<0.05). No significant difference in [3H]-ryanodine binding was observed. CONCLUSIONS: A(1) adenosine receptor overexpression is associated with a decreased rate of active Ca(2+) transport into the SR. We hypothesize that changes in SR function may cause a depletion of the SR Ca(2+) pool, which might protect from ischemic injury by delaying the development of cytosolic Ca(2+) overload during ischemia.

Altered signal transduction in cardiac ventricle overexpressing A(1)-adenosine receptors.

OBJECTIVE: The aim of the present study was to assess the effects of A(1)-adenosine receptor (A1-AR) stimulation in ventricle of A(1)-adenosine receptor overexpressing mice (transgenic mice, TG). METHODS: Effects of the A(1)-adenosine receptor agonist R-PIA ((-)-N(6)-phenylisopropyladenosine) on phosphorylation of phospholamban (PLB), Ca(2+) transients, Ca(2+) currents and cell shortening were studied in isolated ventricular cardiomyocytes. RESULTS: R-PIA alone did not affect contractility in isolated electrically stimulated cardiomyocytes from wild-type mice (WT) or TG. However, after pre-stimulation of beta-adrenoceptors by isoproterenol, R-PIA reduced contractility in cardiomyocytes from WT but increased contractility in TG. Under the same conditions, R-PIA reduced isoproterenol-stimulated currents through L-type Ca(2+) channels, Ca(2+) transients and phosphorylation of PLB in cardiomyocytes from WT. In contrast, R-PIA diminished phospholamban phosphorylation induced by isoproterenol but augmented isoproterenol-elevated currents through L-type Ca(2+) channels, and isoproterenol-heightened Ca(2+) transients in cardiomyocytes from TG. CONCLUSIONS: We suggest that A(1)-adenosine receptor overexpression reverses the interaction of beta-adrenergic and A(1)-adenosine receptor stimulation, at least in part. Hence, the receptor/effector coupling is dependent on receptor density in this model.

Gene expression profile of mouse myocardium with transgenic overexpression of A1 adenosine receptors.

Transgenic mice with cardiac-specific overexpression of adenosine A(1) receptors (A(1)AR) have demonstrated metabolic and functional tolerance to myocardial ischemia. We utilized cDNA microarrays to test the hypothesis that the cardioprotective mechanism(s) of A(1) overexpression involves altered gene expression. Total RNA extracted from the left ventricles from A(1) transgenic (n = 4) and wild-type (n = 6) mice was hybridized to Affymetrix mgU74A chips. Comparison of RNA expression levels in transgenic to wild-type myocardium revealed approximately 636 known genes with expression significantly altered by greater than 25%. We observed increased expressions of genes including NADH dehydrogenase, the GLUT4 glucose transporter, Na-K-ATPase, sarcolemmal K(ATP) channels, and Bcl-xl in A(1)AR-overexpressing hearts. We also observed decreased expression of pro-apoptotic genes including a 50% reduction in message level of caspase-8. Protein expression of GLUT4 and caspase-8 was also altered comparable to the differences in gene expression. These data illustrate genes with chronically altered patterns of expression in A(1) transgenic mouse myocardium that may be related to adenosine receptor overexpression-mediated cardioprotection.

Pertussis toxin sensitive and insensitive effects of adenosine and carbachol in murine atria overexpressing A(1)-adenosine receptors.

1 It was investigated how A(1)-adenosine receptor overexpression alters the effects of carbachol on force of contraction and beating rate in isolated murine atria. Moreover, the influence of pertussis toxin on the inotropic and chronotropic effects of adenosine and carbachol in A(1)-adenosine receptor overexpressing atria was studied. 2 Adenosine and carbachol alone exerted negative inotropic and chronotropic effects in electrically driven left atrium or spontaneously beating right atrium of wild-type mice. 3 These effects were abolished or reversed by pre-treatment of animals with pertussis toxin which can interfere with signal transduction through G-proteins. 4 Adenosine and carbachol exerted positive inotropic but negative chronotropic effects in atrium overexpressing A(1)-adenosine receptors from transgenic mice. 5 The positive inotropic effects of adenosine and carbachol were qualitatively unaltered whereas the negative chronotropic effects were abolished or reversed in atrium overexpressing A(1)-adenosine receptors after pre-treatment by pertussis toxin. 6 Qualitatively similar effects for adenosine and carbachol were noted in the presence of isoprenaline, beta-adrenoceptor agonist. 7 It is concluded that overexpression of A(1)-adenosine receptors also affects the signal transduction of other heptahelical, G-protein coupled receptors like the M-cholinoceptor in the heart. The chronotropic but not the inotropic effects of adenosine and carbachol in transgenic atrium were mediated via pertussis toxin sensitive G-proteins.

Ischemic and pharmacological preconditioning induces further delayed protection in transgenic mouse cardiac myocytes over-expressing adenosine A1 receptors (A1AR): role of A1AR, iNOS and K(ATP) channels.

In this study we examined the hypotheses that over-expression of the adenosine A(1) receptor (A(1)AR) in transgenic mouse cardiac myocytes (A(1)AR-tgm) induces cellular protection against subsequent sustained simulated ischemia (SI); that the cellular protection induced by over-expression of A(1)AR in A(1)AR-tgm is mediated through inducible nitric oxide synthase (iNOS) and K(ATP) channels. Sub-lethal simulated ischemia (SSI) and the A(1)AR agonists chloro- N(6)-cyclopentyl adenosine (CCPA) or (2 S)- N(6)-[2-endo-norbornyl]adenosine (S-ENBA) induce further, delayed cytoprotection, additional to the existing protection in A(1)AR-tgm. Cellular injury and cell viability was measured by the release of lactate dehydrogenase (LDH) or creatine kinase (CK) into the medium and the amount remaining in the cells. The cellular resistance acquired by cardiac myocytes due to the over-expression of A(1)AR was reflected by the reduced release of LDH (in units/liter) from 44.94+/-1.46 (wild-type mouse cardiac myocytes, wt) to 29.59+/-2.83 (A(1)AR-tgm, P<0.001). Conversely, LDH release from A(1)AR-tgm increased to 42.53+/-2.23 ( P<0.01) on exposure to 5-hydroxydecanoate (a mitochondrial K(ATP) channel blocker), to 45.93+/-2.90 ( P<0.01) on exposure to S-methylthiourea (an iNOS inhibitor) and to 56.04+/-3.00 ( P<0.01) on exposure to glibenclamide (a K(ATP) channel blocker). Treatment of A(1)AR-tgm is with SSI and the A(1)AR agonists chloro- N(6)-cyclopentyl adenosine (CCPA) or (2 S)- N(6)-[2-endo-norbornyl]adenosine (S-ENBA) decreased the release of LDH from 46.44+/-0.57 (A(1)AR-tgm) to 42.08+/-0.48 (A(1)AR-tgm plus SSI, P<0.05), 38.03+/-1.16 (A(1)AR-tgm plus CCPA, P<0.001) and 32.77+/-0.58 (A(1)AR-tgm plus S-ENBA, P<0.001). Our data suggest that the A(1)AR has a cytoprotective effect against subsequent sustained SI in A(1)AR-tgm and that the cellular protection induced by over-expression of A(1)AR in A(1)AR-tgm depends on iNOS and K(ATP) channels. Further, SSI and the A(1)AR agonists CCPA or S-ENBA induce further, delayed cytoprotection in A(1)AR-tgm.

Glucose regulation of load-induced mTOR signaling and ER stress in mammalian heart.

BACKGROUND: Changes in energy substrate metabolism are first responders to hemodynamic stress in the heart. We have previously shown that hexose-6-phosphate levels regulate mammalian target of rapamycin (mTOR) activation in response to insulin. We now tested the hypothesis that inotropic stimulation and increased afterload also regulate mTOR activation via glucose 6-phosphate (G6P) accumulation. METHODS AND RESULTS: We subjected the working rat heart ex vivo to a high workload in the presence of different energy-providing substrates including glucose, glucose analogues, and noncarbohydrate substrates. We observed an association between G6P accumulation, mTOR activation, endoplasmic reticulum (ER) stress, and impaired contractile function, all of which were prevented by pretreating animals with rapamycin (mTOR inhibition) or metformin (AMPK activation). The histone deacetylase inhibitor 4-phenylbutyrate, which relieves ER stress, also improved contractile function. In contrast, adding the glucose analogue 2-deoxy-d-glucose, which is phosphorylated but not further metabolized, to the perfusate resulted in mTOR activation and contractile dysfunction. Next we tested our hypothesis in vivo by transverse aortic constriction in mice. Using a micro-PET system, we observed enhanced glucose tracer analog uptake and contractile dysfunction preceding dilatation of the left ventricle. In contrast, in hearts overexpressing SERCA2a, ER stress was reduced and contractile function was preserved with hypertrophy. Finally, we examined failing human hearts and found that mechanical unloading decreased G6P levels and ER stress markers. CONCLUSIONS: We propose that glucose metabolic changes precede and regulate functional (and possibly also structural) remodeling of the heart. We implicate a critical role for G6P in load-induced mTOR activation and ER stress.

Use of an administrative database to determine clinical management and outcomes in congenital heart disease.

We review our 16-year experience using the large, multi-institutional database of the University HealthSystem Consortium to study management and outcomes in congenital heart surgery for hypoplastic left heart syndrome, transposition of the great arteries, and neonatal coarctation. The advantages, limitations, and use of administrative databases by others to study congenital heart surgery are reviewed.

Role of pulse oximetry in examining newborns for congenital heart disease: a scientific statement from the AHA and AAP.

BACKGROUND: The purpose of this statement is to address the state of evidence on the routine use of pulse oximetry in newborns to detect critical congenital heart disease (CCHD). METHODS AND RESULTS: A writing group appointed by the American Heart Association and the American Academy of Pediatrics reviewed the available literature addressing current detection methods for CCHD, burden of missed and/or delayed diagnosis of CCHD, rationale of oximetry screening, and clinical studies of oximetry in otherwise asymptomatic newborns. MEDLINE database searches from 1966 to 2008 were done for English-language papers using the following search terms: congenital heart disease, pulse oximetry, physical examination, murmur, echocardiography, fetal echocardiography, and newborn screening. The reference lists of identified papers were also searched. Published abstracts from major pediatric scientific meetings in 2006 to 2008 were also reviewed. The American Heart Association classification of recommendations and levels of evidence for practice guidelines were used. In an analysis of pooled studies of oximetry assessment performed after 24 hours of life, the estimated sensitivity for detecting CCHD was 69.6%, and the positive predictive value was 47.0%; however, sensitivity varied dramatically among studies from 0% to 100%. False-positive screens that required further evaluation occurred in only 0.035% of infants screened after 24 hours. CONCLUSIONS: Currently, CCHD is not detected in some newborns until after their hospital discharge, which results in significant morbidity and occasional mortality. Furthermore, routine pulse oximetry performed on asymptomatic newborns after 24 hours of life, but before hospital discharge, may detect CCHD. Routine pulse oximetry performed after 24 hours in hospitals that have on-site pediatric cardiovascular services incurs very low cost and risk of harm. Future studies in larger populations and across a broad range of newborn delivery systems are needed to determine whether this practice should become standard of care in the routine assessment of the neonate.