Massively Parallel Selection of NanoCluster Beacons.

NanoCluster Beacons (NCBs) are multicolor silver nanocluster probes whose fluorescence can be activated or tuned by a proximal DNA strand called the activator. While a single-nucleotide difference in a pair of activators can lead to drastically different activation outcomes, termed polar opposite twins (POTs), it is difficult to discover new POT-NCBs using the conventional low-throughput characterization approaches. Here, a high-throughput selection method is reported that takes advantage of repurposed next-generation-sequencing chips to screen the activation fluorescence of ≈40 000 activator sequences. It is found that the nucleobases at positions 7-12 of the 18-nucleotide-long activator are critical to creating bright NCBs and positions 4-6 and 2-4 are hotspots to generate yellow-orange and red POTs, respectively. Based on these findings, a "zipper-bag" model is proposed that can explain how these hotspots facilitate the formation of distinct silver cluster chromophores and alter their chemical yields. Combining high-throughput screening with machine-learning algorithms, a pipeline is established to design bright and multicolor NCBs in silico.

A kinetic model predicts SpCas9 activity, improves off-target classification, and reveals the physical basis of targeting fidelity.

The S. pyogenes (Sp) Cas9 endonuclease is an important gene-editing tool. SpCas9 is directed to target sites based on complementarity to a complexed single-guide RNA (sgRNA). However, SpCas9-sgRNA also binds and cleaves genomic off-targets with only partial complementarity. To date, we lack the ability to predict cleavage and binding activity quantitatively, and rely on binary classification schemes to identify strong off-targets. We report a quantitative kinetic model that captures the SpCas9-mediated strand-replacement reaction in free-energy terms. The model predicts binding and cleavage activity as a function of time, target, and experimental conditions. Trained and validated on high-throughput bulk-biochemical data, our model predicts the intermediate R-loop state recently observed in single-molecule experiments, as well as the associated conversion rates. Finally, we show that our quantitative activity predictor can be reduced to a binary off-target classifier that outperforms the established state-of-the-art. Our approach is extensible, and can characterize any CRISPR-Cas nuclease - benchmarking natural and future high-fidelity variants against SpCas9; elucidating determinants of CRISPR fidelity; and revealing pathways to increased specificity and efficiency in engineered systems.

Massively parallel kinetic profiling of natural and engineered CRISPR nucleases.

Engineered SpCas9s and AsCas12a cleave fewer off-target genomic sites than wild-type (wt) Cas9. However, understanding their fidelity, mechanisms and cleavage outcomes requires systematic profiling across mispaired target DNAs. Here we describe NucleaSeq-nuclease digestion and deep sequencing-a massively parallel platform that measures the cleavage kinetics and time-resolved cleavage products for over 10,000 targets containing mismatches, insertions and deletions relative to the guide RNA. Combining cleavage rates and binding specificities on the same target libraries, we benchmarked five SpCas9 variants and AsCas12a. A biophysical model built from these data sets revealed mechanistic insights into off-target cleavage. Engineered Cas9s, especially Cas9-HF1, dramatically increased cleavage specificity but not binding specificity compared to wtCas9. Surprisingly, AsCas12a cleavage specificity differed little from that of wtCas9. Initial DNA cleavage sites and end trimming varied by nuclease, guide RNA and the positions of mispaired nucleotides. More broadly, NucleaSeq enables rapid, quantitative and systematic comparisons of specificity and cleavage outcomes across engineered and natural nucleases.

HEDGES error-correcting code for DNA storage corrects indels and allows sequence constraints.

Synthetic DNA is rapidly emerging as a durable, high-density information storage platform. A major challenge for DNA-based information encoding strategies is the high rate of errors that arise during DNA synthesis and sequencing. Here, we describe the HEDGES (Hash Encoded, Decoded by Greedy Exhaustive Search) error-correcting code that repairs all three basic types of DNA errors: insertions, deletions, and substitutions. HEDGES also converts unresolved or compound errors into substitutions, restoring synchronization for correction via a standard Reed-Solomon outer code that is interleaved across strands. Moreover, HEDGES can incorporate a broad class of user-defined sequence constraints, such as avoiding excess repeats, or too high or too low windowed guanine-cytosine (GC) content. We test our code both via in silico simulations and with synthesized DNA. From its measured performance, we develop a statistical model applicable to much larger datasets. Predicted performance indicates the possibility of error-free recovery of petabyte- and exabyte-scale data from DNA degraded with as much as 10% errors. As the cost of DNA synthesis and sequencing continues to drop, we anticipate that HEDGES will find applications in large-scale error-free information encoding.

A metaanalysis of bat phylogenetics and positive selection based on genomes and transcriptomes from 18 species.

Historically, the evolution of bats has been analyzed using a small number of genetic loci for many species or many genetic loci for a few species. Here we present a phylogeny of 18 bat species, each of which is represented in 1,107 orthologous gene alignments used to build the tree. We generated a transcriptome sequence of Hypsignathus monstrosus, the African hammer-headed bat, and additional transcriptome sequence for Rousettus aegyptiacus, the Egyptian fruit bat. We then combined these data with existing genomic and transcriptomic data from 16 other bat species. In the analysis of such datasets, there is no clear consensus on the most reliable computational methods for the curation of quality multiple sequence alignments since these public datasets represent multiple investigators and methods, including different source materials (chromosomal DNA or expressed RNA). Here we lay out a systematic analysis of parameters and produce an advanced pipeline for curating orthologous gene alignments from combined transcriptomic and genomic data, including a software package: the Mismatching Isoform eXon Remover (MIXR). Using this method, we created alignments of 11,677 bat genes, 1,107 of which contain orthologs from all 18 species. Using the orthologous gene alignments created, we assessed bat phylogeny and also performed a holistic analysis of positive selection acting in bat genomes. We found that 181 genes have been subject to positive natural selection. This list is dominated by genes involved in immune responses and genes involved in the production of collagens.

Indel-correcting DNA barcodes for high-throughput sequencing.

Many large-scale, high-throughput experiments use DNA barcodes, short DNA sequences prepended to DNA libraries, for identification of individuals in pooled biomolecule populations. However, DNA synthesis and sequencing errors confound the correct interpretation of observed barcodes and can lead to significant data loss or spurious results. Widely used error-correcting codes borrowed from computer science (e.g., Hamming, Levenshtein codes) do not properly account for insertions and deletions (indels) in DNA barcodes, even though deletions are the most common type of synthesis error. Here, we present and experimentally validate filled/truncated right end edit (FREE) barcodes, which correct substitution, insertion, and deletion errors, even when these errors alter the barcode length. FREE barcodes are designed with experimental considerations in mind, including balanced guanine-cytosine (GC) content, minimal homopolymer runs, and reduced internal hairpin propensity. We generate and include lists of barcodes with different lengths and error correction levels that may be useful in diverse high-throughput applications, including >106 single-error-correcting 16-mers that strike a balance between decoding accuracy, barcode length, and library size. Moreover, concatenating two or more FREE codes into a single barcode increases the available barcode space combinatorially, generating lists with >1015 error-correcting barcodes. The included software for creating barcode libraries and decoding sequenced barcodes is efficient and designed to be user-friendly for the general biology community.

Massively Parallel Biophysical Analysis of CRISPR-Cas Complexes on Next Generation Sequencing Chips.

CRISPR-Cas nucleoproteins target foreign DNA via base pairing with a crRNA. However, a quantitative description of protein binding and nuclease activation at off-target DNA sequences remains elusive. Here, we describe a chip-hybridized association-mapping platform (CHAMP) that repurposes next-generation sequencing chips to simultaneously measure the interactions between proteins and ∼107 unique DNA sequences. Using CHAMP, we provide the first comprehensive survey of DNA recognition by a type I-E CRISPR-Cas (Cascade) complex and Cas3 nuclease. Analysis of mutated target sequences and human genomic DNA reveal that Cascade recognizes an extended protospacer adjacent motif (PAM). Cascade recognizes DNA with a surprising 3-nt periodicity. The identity of the PAM and the PAM-proximal nucleotides control Cas3 recruitment by releasing the Cse1 subunit. These findings are used to develop a model for the biophysical constraints governing off-target DNA binding. CHAMP provides a framework for high-throughput, quantitative analysis of protein-DNA interactions on synthetic and genomic DNA. PAPERCLIP.

Filovirus receptor NPC1 contributes to species-specific patterns of ebolavirus susceptibility in bats.

Biological factors that influence the host range and spillover of Ebola virus (EBOV) and other filoviruses remain enigmatic. While filoviruses infect diverse mammalian cell lines, we report that cells from African straw-colored fruit bats (Eidolon helvum) are refractory to EBOV infection. This could be explained by a single amino acid change in the filovirus receptor, NPC1, which greatly reduces the affinity of EBOV-NPC1 interaction. We found signatures of positive selection in bat NPC1 concentrated at the virus-receptor interface, with the strongest signal at the same residue that controls EBOV infection in Eidolon helvum cells. Our work identifies NPC1 as a genetic determinant of filovirus susceptibility in bats, and suggests that some NPC1 variations reflect host adaptations to reduce filovirus replication and virulence. A single viral mutation afforded escape from receptor control, revealing a pathway for compensatory viral evolution and a potential avenue for expansion of filovirus host range in nature.

Regional myocardial dysfunction following Norwood with right ventricle to pulmonary artery conduit in patients with hypoplastic left heart syndrome.

BACKGROUND: Improved early survival has led many centers to use the right ventricle-to-pulmonary artery (RVPA) conduit instead of the modified Blalock-Taussig shunt for Norwood palliation of hypoplastic left-heart syndrome. However, there is concern regarding the potential deleterious effects of the required right ventriculotomy for placement of the RVPA conduit on global and regional right ventricular (RV) function. The purpose of this study was to investigate global and regional RV wall motion abnormalities after Norwood palliation with RVPA conduit using Velocity Vector Imaging (VVI). METHODS: Thirty consecutive patients with hypoplastic left-heart syndrome who underwent stage 2 palliation between January 2007 and December 2009 were identified from the surgical database. VVI was performed on two-dimensional echocardiographic images obtained before second-stage palliation. Peak systolic circumferential and radial velocity, strain, and strain rate were measured from parasternal short-axis and apical four-chamber views. RV ejection fraction was measured using the biplane modified Simpson's rule. Regional RV systolic deformations were compared between different RV segments. VVI measures were also compared with RV systolic function. In a subgroup (n = 14), VVI was repeated on follow-up after stage 2 palliation to evaluate changes in regional and global RV deformation. RESULTS: A total of 30 patients (20 males) were studied. The median age at the time of interstage echocardiography was 12 weeks (range, 8-18 weeks). In the short axis, average peak systolic circumferential strain values for the anterior, posterior, septal, and RV free wall segments were 3.79 ± 2.52%, 11.4 ± 5.2%, 13.3 ± 6.5%, and 11.1 ± 5.0%, respectively. From the short-axis view, the anterior RV segment (ventriculotomy site) exhibited significantly reduced circumferential velocity, peak systolic strain, and strain rate (P < .0001). Mean global VVI measurements were correlated with RV ejection fraction. On follow-up after stage 2 palliation, the ventriculotomy region showed persistently reduced velocity, peak systolic strain, and strain rate compared with all other segments. CONCLUSIONS: In patients with hypoplastic left-heart syndrome after Norwood palliation with RVPA conduit, RV myocardial deformation was significantly reduced at the ventriculotomy site, which persisted after stage 2 palliation. VVI-derived measures demonstrating impairment of global systolic myocardial deformation were correlated with RV systolic function. Long-term multicenter studies to evaluate the effects of ventriculotomy scar on single systemic right ventricle are required.

Surgical management of complete atrioventricular septal defect: associations with surgical technique, age, and trisomy 21.

OBJECTIVES: We sought to evaluate the contemporary results after repair of a complete atrioventricular septal defect and to determine the factors associated with suboptimal outcomes. METHODS: The demographic, procedural, and outcome data were obtained within 1 and 6 months after repair of a complete atrioventricular septal defect in 120 children in a multicenter observational study from June 2004 to 2006. RESULTS: The median age at surgery was 3.7 months (range, 9 days to 1.1 years). The type of surgical repair was a single patch (18%), double patch (72%), and a single atrial septal defect patch with primary ventricular septal defect closure (10%). The incidence of residual septal defects and the degree of left atrioventricular valve regurgitation (LAVVR) did not differ by repair type. The median interval of intensive care stay were 4 days, ventilation use 2 days, and total hospitalization 8 days. All were independent of the presence of trisomy 21 (80% of the cohort). The in-hospital mortality rate was 2.5% (3/120). The overall 6-month mortality rate was 4% (5/120). The presence of associated anomalies and younger age at surgery were independently associated with a longer hospital stay. The age at repair was not associated with residual ventricular septal defect or moderate or greater LAVVR at 6 months. Moderate or greater LAVVR occurred in 22% at 6 months, and the strongest predictor for this was moderate or greater LAVVR at 1 month (odds ratio, 6.9; 95% confidence interval, 2.2-21.7; P < .001). CONCLUSIONS: The outcomes after repair of complete atrioventricular septal defect did not differ by repair type or the presence of trisomy 21. An earlier age at surgery was associated with increased resource use but had no association with the incidence of residual ventricular septal defect or significant LAVVR.

Bilateral Ductus Arteriosus With Isolated Right Pulmonary Artery: Long-term Results With Interposition Pulmonary Allograft.

Bilateral patent ductus arteriosus and isolated right pulmonary artery (RPA) is a rare anomaly often interpreted as congenital absence of the RPA. Recognized early, continuity between the main pulmonary artery and distal RPA can be established and long-term sequelae avoided. We report 2 patients who underwent neonatal repair using a nonvalved pulmonary artery allograft conduit placed anterior to the aorta to establish continuity between the main pulmonary artery and RPA. Both patients continue to do well 10 and 15 years postoperatively with good growth of the distal RPA and good exercise tolerance. This approach offers good long-term palliation.

Clinical performance of decellularized cryopreserved valved allografts compared with standard allografts in the right ventricular outflow tract.

BACKGROUND: Although decellularized cryopreserved valved allografts (DCAs) have reduced immunogenicity, proof of clinical superiority over standard cryopreserved allografts (SCAs) is lacking. To assess functional results and durability, we studied a group of patients with DCAs implanted between 2000 and 2005 and compared them with a similar group with SCAs. METHODS: From July 2000 until January 2005, 47 patients underwent insertion of a DCA between the right ventricle and pulmonary arteries. The DCA patients were compared with 47 age-matched and diagnosis-matched controls receiving SCAs. All patients received pulmonary allografts and were matched for valve position (orthotopic versus heterotopic). We analyzed each group for survival, reoperation, reintervention (surgical or catheter-based), stenosis, and regurgitation. RESULTS: There were no differences between groups with respect to weight, age, valve size, or survival. Actuarial freedom from reintervention at 8 years was 79% for DCAs as compared with 63% for SCAs (p = 0.31, log-rank). Echocardiogram in the DCA group (median 66 months) showed a slightly lower median peak gradient of 16 mm Hg (range, 0 to 82 mm Hg) as compared with 22 mm Hg (range, 0 to 63) in the SCA group (median 61 months, p = 0.051, Wilcoxon). However, when conduits 18 mm or less in diameter were compared, DCA patients had a median peak gradient of 10 mm Hg (range, 0 to 43) compared with 25 mm Hg in SCAs (range, 0 to 55 mm Hg, p = 0.03). There were no differences in the degree of allograft insufficiency in either group. CONCLUSIONS: Decellularized cryopreserved valved allografts have a nonsignificant trend toward lower peak valve gradient and reintervention in comparison with SCAs. Small valve sizes (18 mm or less) show a slight but significant improvement in peak gradient, but no advantage in valve insufficiency. These findings and a significantly higher cost (>$3,000) make further direct comparisons necessary before widespread use of DCAs can be justified.

Durability of truncal valve repair.

BACKGROUND: Truncus arteriosus associated with truncal valve dysfunction has been shown to increase the mortality and morbidity associated with repair and the various techniques employed for truncal valve repair continue to evolve. We sought to examine the durability of truncal valve repair in truncus arteriosus. METHODS: We reviewed all patients who underwent truncal valve repair at our institution from 1995 to 2008. Repair techniques included leaflet delamination, bicuspidization, commissuroplasty, annuloplasty, and leaflet augmentation. We examined long-term valve durability, function and need for valve replacement. RESULTS: A total of 17 patients underwent truncal valve repair, including 3 for predominant stenosis (>70 mm Hg gradient), 2 for mixed moderate stenosis (40 mm Hg gradient) and moderate regurgitation, and 12 for moderate or greater regurgitation. Of these, 14 patients (14 of 17, 82%) underwent valvuloplasty at the time of the initial truncus arteriosus repair. The median age at truncal valve repair was 24 days (range, 4 days to 42 years). Thirteen patients had 1 valvuloplasty, 3 patients had 2 valvuloplasties, and 1 patient had 3 valvuloplasties before undergoing a prosthetic valve replacement at age 13 years. Actuarial freedom from repeat truncal valve operation was 70% at 5 years and 50% at 7 years. Freedom from truncal valve replacement was 100% at 10 years. To date, only 1 patient (6%) has required a prosthetic valve. Echocardiography at 48 ± 33 (mean ± SD) months postoperatively showed a peak gradient of 11 ± 13 mm Hg; 6 patients have moderate regurgitation, and the rest have mild or less regurgitation. CONCLUSIONS: Truncal valve repair is a durable option with an acceptable reoperation rate, good function, and a low likelihood of needing truncal valve replacement. This is one of the largest series of truncal valve repairs and emphasizes that valve repair should remain the primary option.

Partial and transitional atrioventricular septal defect outcomes.

BACKGROUND: Surgical and perioperative improvements permit earlier repair of partial and transitional atrioventricular septal defects (AVSD). We sought to describe contemporary outcomes in a multicenter cohort. METHODS: We studied 87 patients undergoing primary biventricular repair of partial or transitional AVSD between June 2004 and February 2006 across seven North American centers. One-month and 6-month postoperative data included weight-for-age z-scores, left atrioventricular valve regurgitation (LAVVR) grade, residual shunts, and left ventricular ejection fraction. Paired methods were used to assess 6-month change. RESULTS: Median age at surgery was 1.8 years; median weight z-score was -0.88. Median days for ventilation were 1, intensive care 2, and hospitalization 5, all independent of age, with 1 in-hospital death. At 1 month, 27% (16 of 73) had ejection fraction less than 55%; 20% (17 of 87) had significant LAVVR; 2 had residual shunts; 1 each had subaortic stenosis and LAVV stenosis. At 6 months (n = 60), there were no interim deaths, reinterventions, or new development of subaortic or LAVV stenosis. Weight z-score improved by a median 0.4 units (p < 0.001), especially for underweight children less than 18 months old. Left atrioventricular valve regurgitation occurred in 31% (change from baseline, p = 0.13), occurring more frequently in patients repaired at 4 to 7 years (p = 0.01). Three patients had ejection fraction less than 55%, and 1 had a residual atrial shunt. CONCLUSIONS: Surgical repair for partial/transitional AVSD is associated with low morbidity and mortality, short hospital stays, and catch-up growth, particularly in underweight children repaired between 3 and 18 months of age. Left atrioventricular valve regurgitation remains the most common residual defect, occurring more frequently in children repaired after 4 years of age.

Long-term Outcome and Risk of Heart Block After Surgical Treatment of Subaortic Stenosis.

Although mortality following repair of subaortic obstruction is low, aggressive resection may increase morbidity. We sought to evaluate outcomes and risk of atrioventricular heart block (AVB) after subaortic resection in the current era. Simple obstruction was defined as a discrete subaortic membrane and complex as multilevel or diffuse narrowing. Limited resection included membranectomy and limited myomectomy. Aggressive resection included Konno, modified Konno, and Ross. Specified variables were obtained from a chart review. The 185 consecutive patients (1991-2008) ranged in age from 1 day to 21.8 years (5.1 ± 5.1 years) with 2 early and 4 late deaths. Actuarial survival was 97%, 95%, and 95% at 1, 5, and 10 years, respectively. Reoperations were required in 29 of 185 patients (15.7%); 2 required a third operation (1%). Freedom from reoperation in all patients was 97%, 83%, and 73% at 1, 5, and 10 years, respectively. Accessory mitral valve tissue (P < .001) and age <3 months (P = .004) predicted the need for reoperation. Transient or permanent high-degree AVB was documented in 33 of 185 patients (17.8%). Complex anatomy (P = .01) and aggressive resection (P < .001) increased the risk of acquiring AVB. The AVB was permanent in 21 of 185 (11.4%) patients, and pacemaker implantation was undertaken in 20 of 185 (10.8%) patients. Complex anatomy (P = .04) and modified Konno procedure (P = .03) increased the risk of acquiring a pacemaker. Aggressive resection lowered the frequency of recurrence but increased the risk of AVB. When aggressive resection is considered for long-term relief of subaortic obstruction, the risk of reobstruction must be balanced with the risk of AVB and the need for pacemaker implantation.

Simple versus complex truncus arteriosus: neutralization of risk but with increased resource utilization.

This study examined simple versus complex forms of truncus arteriosus (TA) results in the current era with regard to mortality, reintervention, and resource utilization. From 1999 to 2008, 42 infants underwent primary repair of TA, including 22 simple forms of TA without associated anomalies and 20 complex forms with risk factors such as interrupted aortic arch (n = 8), coarctation (n = 1), significant truncal valve regurgitation (n = 6), discontinuous pulmonary arteries (n = 3), and truncal valve stenosis (n = 2). There were 4 early deaths (4/42, 9.5%), with no difference between simple TA (2/22, 9.1%) and complex TA (2/20, 10%). Early mortality decreased to 1 patient (1/23, 4%) in the most recent era: 2003-2008. Late mortality occurred in 4 (4/38, 10.5%). Reintervention was required in 12 patients, a median of 2 years postoperatively: for conduit reasons in 8 and combined conduit and truncal valve insufficiency in 4. Actuarial survival was 82% ± 7% at 5 years and freedom from reintervention was 52% ± 17% at 5 years, which are not different between complex and simple forms. Complex TA, age, and weight were not predictors on multivariable analysis for early or late death or reintervention. Complex TA had significantly longer (P < .05) median length of stay (17 vs 13 days) and intensive care unit intubation times (8 vs 5 days) versus simple TA. Complex TA does not have a higher operative or late mortality risk or increased risk of reintervention compared with simple TA. However, complex patients can be expected to have increased resource utilization as compared with simple forms of TA.

Effect of ABO-incompatible listing on infant heart transplant waitlist outcomes: analysis of the United Network for Organ Sharing (UNOS) database.

BACKGROUND: Midterm heart transplant outcomes of ABO-incompatible (ABO-I) organ use in infants are favorable. ABO-I transplantation has resulted in reduced waitlist mortality in some countries. This study assessed the effect of an ABO-I listing strategy on pre-transplant outcomes in the United States. METHODS: The Organ Procurement and Transplantation Network (OPTN)/United Network of Organ Sharing (UNOS) database was used to identify infants aged younger than 1 year listed as status 1 for heart transplantation between January 1, 2001, and May 20, 2008. The cohort was divided into 2 groups: eligible for ABO-compatible (ABO-C) transplant and eligible for ABO-I transplant. Baseline characteristics, waitlist times, and outcomes were compared in univariate analysis. Competing risks analysis evaluated differences in time to transplant in the presence of other outcomes. RESULTS: Of 1,029 infants listed for transplant, 277 (27%) were listed for an ABO-I transplant. Overall, 92% of transplant recipients received an ABO-C organ regardless of listing type. Among recipients eligible for ABO-I, only 27% received an ABO-I organ. The percentage that underwent transplant in each group did not differ. Although infants listed for an ABO-I organ had a shorter wait time for transplant, waitlist mortality was similar. CONCLUSIONS: Despite the intended merits of ABO-I heart transplantation, ABO-I listing and organ acceptance have not yielded lower waitlist mortality in the United States under the current UNOS allocation algorithm. Consideration should be given to altering the allocation system to one that gives less preference toward blood group compatibility in hopes of improving organ use and reducing waitlist mortality.

Coarctation repair in neonates and young infants: is small size or low weight still a risk factor?

OBJECTIVE: Previous reports of neonatal coarctation repair demonstrate a high rate of recurrent arch obstruction in small neonates. This study assesses the effect of patient size on reintervention and survival in neonates and infants undergoing repair of simple aortic coarctation. METHODS: From 1996 to 2006, 167 neonates and infants younger than 90 days with simple coarctation underwent repair. Median patient age was 16 days (range, 1-85 days). Median patient weight was 3.4 kg (range, 0.8-6.0 kg), with 29 patients weighing less than 2.5 kg. All 167 patients included in the study underwent repair through a left thoracotomy. RESULTS: There was 1 early death (1/167, 0.6%). Median follow-up of 4.8 years (range, 0-11.8 years) demonstrated 2 late deaths unrelated to recurrent coarctation. Eighteen patients underwent intervention for recurrent arch obstruction a median of 0.48 years postoperatively (range, 0.14-9.8 years). All were treated with balloon angioplasty and have required no additional intervention. Actuarial freedom from reintervention was 90% at 1 year and 89% at 5 years for infants weighing more than 2.5 kg and 89% at 1 year and 86% at 5 years (P = .31) for infants weighing less than 2.5 kg. There was no difference between survival or reintervention for neonates 30 days of age or younger compared with infants 31 to 90 days of age. Use of polypropylene sutures and female sex did correlate with increased reintervention. CONCLUSIONS: Low weight does not affect survival or reintervention rates after coarctation repair in neonates and infants less than 3 months of age. Balloon angioplasty is an effective treatment for recurrent obstruction after coarctation repair in infancy. In the current era, timing of the operation should be based on clinical status.

Cardiovascular surgery in children with Marfan syndrome or Loeys-Dietz syndrome.

OBJECTIVE: This study was undertaken to assess the frequency and outcome of cardiovascular surgery in children with Marfan or Loeys-Dietz syndrome. METHODS: A retrospective review from 2 regional Marfan subspecialty clinics was performed. Between 1997 and 2007, 204 children with Marfan syndrome and 17 children with Loeys-Dietz syndrome were followed serially. Of these patients, 35 were identified who had undergone cardiovascular surgery at 18 years of age or less. Demographic, echocardiographic, and surgical data were collected. RESULTS: Surgery was performed at a median of 3 years (0-15 years) after diagnosis and a mean age of 11.5 +/- 6.2 years. Aortic root replacement was the initial surgery in 30 patients, and mitral valve surgery was the initial surgery in 8 patients, with 3 patients undergoing both. Aortic root replacement was performed using a composite root replacement in 9 patients and valve-sparing techniques in 21 patients (remodeling in 8 patients and reimplantation in 13 patients). Eight patients underwent reoperation at a mean of 4.7 +/- 3.0 years after aortic surgery: 3 for aortic insufficiency, 2 for dissection, 2 for valve thrombosis, and 1 for a distal aneurysm. Adverse outcomes included reoperation in 8 patients, aneurysm in 1 patient, and death due to dissection or stroke in 3 patients. Variables associated with an adverse outcome included preoperative aortic insufficiency, valve replacement, and absence of angiotensin-converting enzyme inhibitor therapy. CONCLUSION: Patients with Marfan or Loeys-Dietz syndrome requiring surgery during childhood have a favorable long-term outcome. Those undergoing valve-sparing root replacement or mitral valve repair have a low risk for reoperation. Postoperative angiotensin-converting enzyme inhibitor therapy confers clinical benefit.