Evaluating threshold for donor fraction cell-free DNA using clinically available assay for rejection in pediatric and adult heart transplantation

BACKGROUND

The aims of the study were to assess the performance of a clinically available cell-free DNA (cfDNA) assay in a large cohort of pediatric and adult heart transplant recipients and to evaluate performance at specific cut points in detection of rejection.

METHODS

Observational, non-interventional, prospective study enrolled pediatric and adult heart transplant recipients from seven centers. Biopsy-associated plasma samples were used for cfDNA measurements. Pre-determined cut points were tested for analytic performance.

RESULTS

A total of 487 samples from 160 subjects were used for the analysis. There were significant differences for df-cfDNA values between rejection [0.21% (IQR 0.12-0.69)] and healthy samples [0.05% (IQR 0.01-0.14), p < .0001]. The pediatric rejection group had a median df-cfDNA value of 0.93% (IQR 0.28-2.84) compared to 0.09% (IQR 0.04-0.23) for healthy samples, p = .005. Overall negative predictive value was 0.94 while it was 0.99 for pediatric patients. Cut points of 0.13% and 0.15% were tested for various types of rejection profiles and were appropriate to rule out rejection.

CONCLUSION

The study suggests that pediatric patients with rejection show higher levels of circulating df-cfDNA compared to adults and supports the specific cut points for clinical use in pediatric and adult patients with overall acceptable performance.

Severe aortopulmonary collaterals are associated with lower transplant-free survival in patients undergoing staged single ventricle palliation

Objective

To identify risk factors for aortopulmonary collateral (APC) development and assess the impact of severe APCs in children undergoing staged single ventricle palliation.

Methods

Children undergoing a bidirectional Glenn operation between January 1, 2016, and March 31, 2021, at our center were included. All underwent angiography prior to Glenn and Fontan; APC flow was graded on a scale of 0 (no appreciable collateral flow) to 4 (severe burden). Demographic data, congenital diagnosis, clinical history, and outcomes were stratified by Glenn assessment; Fontan outcomes were stratified by pre-Fontan grade.

Results

Sixty patients met the inclusion criteria, all of whom had angiographic evidence of APCs. There were 7 transplants and 9 deaths in the cohort. There were no significant differences in demographics among the patients. Right ventricular morphology was more common in patients with severe pre-Glenn collaterals (24 of 44 vs 2 of 6 vs 7 of 8; P = .014). Longer stage 1 aortic cross-clamp duration was associated with greater severity pre-Glenn (44 minutes vs 34 minutes vs 66 minutes; P = .023). Patients with grade 3 pre-Glenn collaterals more commonly required transplantation than those with grade 1 collaterals (P < .001) and had lower overall transplant-free survival than those with grade 1 (P = .005) or grade 2 (P = .04) collaterals.

Conclusions

The ubiquity of APCs in this study demonstrates their prevalence in single ventricle disease. Right ventricular morphology and prolonged aortic cross-clamp duration are associated with higher burden. Greater severity was associated with decreased transplant-free survival. These data emphasize the negative long-term impact of these collaterals.

Impaired Reorganization of Centrosome Structure Underlies Human Infantile Dilated Cardiomyopathy

BACKGROUND

During cardiomyocyte maturation, the centrosome, which functions as a microtubule organizing center in cardiomyocytes, undergoes dramatic structural reorganization where its components reorganize from being localized at the centriole to the nuclear envelope. This developmentally programmed process, referred to as centrosome reduction, has been previously associated with cell cycle exit. However, understanding of how this process influences cardiomyocyte cell biology, and whether its disruption results in human cardiac disease, remains unknown. We studied this phenomenon in an infant with a rare case of infantile dilated cardiomyopathy (iDCM) who presented with left ventricular ejection fraction of 18% and disrupted sarcomere and mitochondria structure.

METHODS

We performed an analysis beginning with an infant who presented with a rare case of iDCM. We derived induced pluripotent stem cells from the patient to model iDCM in vitro. We performed whole exome sequencing on the patient and his parents for causal gene analysis. CRISPR/Cas9-mediated gene knockout and correction in vitro were used to confirm whole exome sequencing results. Zebrafish and Drosophila models were used for in vivo validation of the causal gene. Matrigel mattress technology and single-cell RNA sequencing were used to characterize iDCM cardiomyocytes further.

RESULTS

Whole exome sequencing and CRISPR/Cas9 gene knockout/correction identified RTTN, the gene encoding the centrosomal protein RTTN (rotatin), as the causal gene underlying the patient's condition, representing the first time a centrosome defect has been implicated in a nonsyndromic dilated cardiomyopathy. Genetic knockdowns in zebrafish and Drosophila confirmed an evolutionarily conserved requirement of RTTN for cardiac structure and function. Single-cell RNA sequencing of iDCM cardiomyocytes showed impaired maturation of iDCM cardiomyocytes, which underlie the observed cardiomyocyte structural and functional deficits. We also observed persistent localization of the centrosome at the centriole, contrasting with expected programmed perinuclear reorganization, which led to subsequent global microtubule network defects. In addition, we identified a small molecule that restored centrosome reorganization and improved the structure and contractility of iDCM cardiomyocytes.

CONCLUSIONS

This study is the first to demonstrate a case of human disease caused by a defect in centrosome reduction. We also uncovered a novel role for RTTN in perinatal cardiac development and identified a potential therapeutic strategy for centrosome-related iDCM. Future study aimed at identifying variants in centrosome components may uncover additional contributors to human cardiac disease.

Validation of donor fraction cell-free DNA with biopsy-proven cardiac allograft rejection in children and adults

OBJECTIVES

Donor-specific cell-free DNA shows promise as a noninvasive marker for allograft rejection, but as yet has not been validated in both adult and pediatric recipients. The study objective was to validate donor fraction cell-free DNA as a noninvasive test to assess for risk of acute cellular rejection and antibody-mediated rejection after heart transplantation in pediatric and adult recipients.

METHODS

Pediatric and adult heart transplant recipients were enrolled from 7 participating sites and followed for 12 months or more with plasma samples collected immediately before all endomyocardial biopsies. Donor fraction cell-free DNA was extracted, and quantitative genotyping was performed. Blinded donor fraction cell-free DNA and clinical data were analyzed and compared with a previously determined threshold of 0.14%. Sensitivity, specificity, negative predictive value, positive predictive value, and receiver operating characteristic curves were calculated.

RESULTS

A total of 987 samples from 144 subjects were collected. After applying predefined clinical and technical exclusions, 745 samples from 130 subjects produced 54 rejection samples associated with the composite outcome of acute cellular rejection grade 2R or greater and pathologic antibody-mediated rejection 2 or greater and 323 healthy samples. For all participants, donor fraction cell-free DNA at a threshold of 0.14% had a sensitivity of 67%, a specificity of 79%, a positive predictive value of 34%, and a negative predictive value of 94% with an area under the curve of 0.78 for detecting rejection. When analyzed independently, these results held true for both pediatric and adult cohorts at the same threshold of 0.14% (negative predictive value 92% and 95%, respectively).

CONCLUSIONS

Donor fraction cell-free DNA at a threshold of 0.14% can be used to assess for risk of rejection after heart transplantation in both pediatric and adult patients with excellent negative predictive value.

Relationship between donor fraction cell-free DNA and clinical rejection in heart transplantation

BACKGROUND

Clinical rejection (CR) defined as decision to treat clinically suspected rejection with change in immunotherapy based on clinical presentation with or without diagnostic biopsy findings is an important part of care in heart transplantation. We sought to assess the utility of donor fraction cell-free DNA (DF cfDNA) in CR and the utility of serial DF cfDNA in CR patients in predicting outcomes of clinical interest.

METHODS

Patients with heart transplantation were enrolled in two sequential, multi-center, prospective observational studies. Blood samples were collected for surveillance or clinical events. Clinicians were blinded to the results of DF cfDNA.

RESULTS

A total of 835 samples from 269 subjects (57% pediatric) were included for this analysis, including 28 samples associated with CR were analyzed. Median DF cfDNA was 0.43 (IQR 0.15, 1.36)% for CR and 0.10 (IQR 0.07, 0.16)% for healthy controls (p < .0001). At cutoff value of 0.13%, the area under curve (AUC) was 0.82, sensitivity of 0.86, specificity of 0.67, and negative predictive value of 0.99. There was serial decline in DF cfDNA post-therapy, however, those with cardiovascular events (cardiac arrest, need for mechanical support or death) showed significantly higher levels of DF cfDNA on Day 0 (2.11 vs 0.31%) and Day 14 (0.51 vs 0.22%) compared to those who did not have such an event (p < .0001).

CONCLUSION

DF cfDNA has excellent agreement with clinical rejection and, importantly, serial measurement of DF cfDNA predict clinically significant outcomes post treatment for rejection in these patients.

Increase in nuclear cell-free DNA is associated with major adverse events in adult and pediatric heart transplant recipients

BACKGROUND

Cell-free DNA is an emerging biomarker. While donor fraction may detect graft events in heart transplant recipients, the prognostic value of total nuclear cell-free DNA (ncfDNA) itself is largely unexplored.

OBJECTIVE

Explore the relationship between ncfDNA and clinical events in heart transplant recipients.

METHODS

We conducted a multi-center prospective study to investigate the value of cell-free DNA in non-invasive monitoring following heart transplantation. Over 4000 blood samples were collected from 388 heart transplant patients. Total ncfDNA and donor fraction were quantified. Generalized linear models with maximum likelihood estimation for repeated measures with subjects as clusters were used to explore the relationship of ncfDNA and major adverse events. Receiver operating characteristic curves were used to help choose cutpoints.

RESULTS

A ncfDNA threshold (50 ng/ml) was identified that was associated with increased risk of major adverse events. NcfDNA was elevated in patients who suffered cardiac arrest, required mechanical circulatory support or died post heart transplantation as well as in patients undergoing treatment for infection.

CONCLUSIONS

Elevated ncfDNA correlates with risk for major adverse events in adult and pediatric heart transplant recipients and may indicate a need for enhanced surveillance after transplant.

Autograft Root Dilation After the Ross Procedure Is Not Benign

Autograft root dilation is common after the unsupported Ross procedure. In the absence of valvar incompetence, and with the perception that dissection is exceedingly rare, expectant management of autograft aneurysm is common practice. Autograft dissection may not be as rare as thought though, as at this point 7 case reports have accrued that describe autograft dissection requiring urgent operative intervention. All had a bicuspid native aortic valve. Bicuspid aortic valve has been shown to be associated with an intrinsic, histologically demonstrated pulmonary arteriopathy, possibly contributing to autograft root dilation and dissection. Autograft root dilation can no longer be regarded as benign, especially in patients with bicuspid aortic valve. Mounting evidence further validates the practice of externally supporting the Ross autograft. For patients who have had an unsupported Ross procedure, mounting evidence may support earlier intervention for autograft root dilation and aneurysm.

No survival benefit associated with waiting for non-lung donor heart transplants for adult recipients with congenital heart disease

BACKGROUND

Adults with congenital heart disease (CHD) awaiting heart transplant (HT) have higher mortality and waitlist removal due to clinical deterioration than those without CHD. The selective use of non-lung donors (NLD) to recover donor pulmonary vasculature to assist in graft implantation may be a contributing factor and is supported by consensus statements despite the recent use of pericardium or graft material as an alternative in pulmonary vascular reconstruction. The impact of selecting NLD for CHD recipients on wait time and mortality has not been evaluated.

METHODS/RESULTS

In the United Network for Organ Sharing (UNOS) Registry, 1271 HT recipients age ≥ 18 with CHD were identified between 1987 and 2016, 68% of which had NLDs. Prior to HT, NLD recipients were significantly less likely to be listed UNOS Status 1A, require mechanical ventilation, or intra-aortic balloon pump support. There was no difference in mean waitlist time (254 vs. 278 days, p = .31), 1-year mortality (82% vs. 80%, p = .81; adjusted odds ratio 1.32, 95% confidence interval [CI] 0.96-1.83, p = .08), or overall mortality (adjusted hazard ratio 1.08, 95% CI 0.86-1.36, p = .48) between recipients from NLD and concomitant lung donors.

CONCLUSIONS

Adult CHD patients who are less critically ill or listed at a lower status are more likely to receive HT from NLD. There is no overall mortality benefit associated with this practice. While specific cases may necessitate waiting for NLD, programs need to re-evaluate whether this should remain a more widespread practice among CHD patients.

Vaping Contributing to Postoperative Acute Respiratory Distress Syndrome

We report the case of an 18-year-old male patient with a history of bicuspid aortic valve with severe aortic insufficiency who had undergone a Ross procedure 1 year prior but subsequently developed stenosis of the pulmonary homograft necessitating conduit replacement. His postoperative course was complicated by acute respiratory distress syndrome. Bronchoscopy revealed significant mucus plugging without identification of contributing pathogen. Further evaluation revealed a history of electronic cigarette use not identified preoperatively and thought to be largely contributory to his postoperative complications. This case highlights the importance of screening preoperatively for electronic cigarette use and counseling on cessation before surgical procedures.

Association of chest tube position with phrenic nerve palsy after neonatal and infant cardiac surgery

BACKGROUND

Diaphragm paralysis (DP) complicates the postoperative course of neonates and infants undergoing cardiac surgery. Events causing DP remain poorly understood, and preventive strategies remain elusive. This retrospective cohort analysis aims to test the hypothesis that chest tubes in contact with the phrenic nerve in the pleural apex may cause pressure palsy.

METHODS

In late 2018, the chest tube positioning strategy was changed so as to avoid a putative "danger zone" configuration, defined as (1) the chest tube looping apicomedially at the level of the second right intercostal space, and (2) wedging of chest tube tip against pericardium. A preintervention and postintervention analysis of 531 patients from 2012 to 2019 was performed to evaluate any association of chest tube position or duration in place with DP. Univariable and multivariable analyses were carried out, with significance set a priori at P < .05.

RESULTS

The preintervention group comprised 488 patients, of whom 32 (6.6%) had RDP. The postintervention group comprised 43 patients, none of whom had DP. Multivariable analysis of the entire cohort revealed chest tube positioning in the danger zone as the only significant association with RDP (odds ratio, 4.22; 95% confidence interval, 1.57-11.33; P < .05).

CONCLUSIONS

Chest tubes that occupy the right superior pleural space are associated with increased risk of DP.

Reintervention After Infant Aortic Arch Repair Using a Tailored Autologous Pericardial Patch

BACKGROUND

Aortic arch reobstruction is a common complication after aortic repair, with rates of reintervention varying from 0% to 40%, depending on the disease and the institution. This study aimed to determine the reintervention rate in children undergoing aortic arch repair using a tailored autologous pericardial patch at our center (Monroe Carell, Jr Children's Hospital at Vanderbilt, Nashville, TN).

METHODS

This retrospective study examined all patients operated on by a single surgeon for aortic arch reconstruction through sternotomy, from 2011 to 2018, with 1 year of follow-up. Our data set was analyzed for normality by using the Shapiro-Wilk test, and nonparametric statistical methods were used. Kaplan-Meier survival analysis was performed, IBM SPSS software version 23 was used to perform all statistical analysis.

RESULTS

A total of 171 patients met inclusion criteria. Twenty-three (13.5%) patients underwent aortic arch reinterventions during the study period, 17 (9.9%) catheter based and 3 (1.8%) surgical. Three patients (1.8%) had both. Freedom from reintervention at 1-year follow-up for the univentricular and biventricular patients was 82.1% and 89.4% (P = .174), respectively. To assess the growth of the aortic arch over time, cardiac catheterization measurements were used to index different parts of the aortic arch against the descending aorta. Ascending-to-descending aortic arch measurements revealed that the pre-Glenn median was 2.0 (interquartile range, 1.8 to 2.2), whereas the pre-Fontan median was 2.5 (interquartile range, 2.2 to 2.7) (P < .05).

CONCLUSIONS

There was no significant difference in reintervention rates between biventricular and univentricular arches, and catheterization measurements showed significant growth of the arch over time. The use of a tailored autologous pericardial patch for aortic arch repair is comparable to other reported methods of arch repair.

Donor fraction cell-free DNA and rejection in adult and pediatric heart transplantation

BACKGROUND

Endomyocardial biopsy (EMB) is the current standard for rejection surveillance in heart transplant recipients. The quantification of donor-specific cell-free DNA (cfDNA) may be an appropriate biomarker for non-invasive rejection surveillance. A multicenter prospective blinded study (DNA-Based Transplant Rejection Test, DTRT) investigated the value of donor fraction (DF), defined as the ratio of cfDNA specific to the transplanted organ to the total amount of cfDNA present in a blood sample.

METHODS

A total of 241 heart transplant patients were recruited from 7 centers. Age at transplant ranged from 8 days to 73 years, with 146 subjects <18 years and 95 ≥18 years. All the patients were followed for at least 1 year, with blood samples drawn at routine and for-cause biopsies. A total of 624 biopsy-paired samples were included for analysis through a commercially available cfDNA assay (myTAI_HEART, TAI Diagnostics Inc.). A blinded analysis of repeated measures compared the outcomes using receiver operating characteristic (ROC) curves. All primary clinical end-points were monitored at 100%. All analysis and conclusions were reviewed by both an independent external oversight committee and the National Institutes of Health-mandated DTRT steering committee.

RESULTS

DF in acute cellular rejection (ACR) 1R/2R (n = 15) was higher than ACR 0R (n = 42) (p = 0.02); DF in antibody-mediated rejection pAMR1 (n = 8) and pAMR2 (n = 12) (p = 0.05) were higher than pAMR0 (n = 466) (p = 0.04 and p = 0.05 respectively). An optimal DF threshold was determined by the use of an ROC analysis, which ruled out the presence of either ACR or antibody-mediated rejection.

CONCLUSIONS

The cell-free DNA DF holds promise as a non-invasive diagnostic test to rule out acute rejection in both adult and pediatric heart transplant populations.

Heart Transplantation in a Fontan Patient Using a Hepatitis C-Positive Donor

A 38-year-old female with tricuspid atresia and normally related great arteries, initially palliated with Björk modified Fontan, and ultimately converted to extracardiac conduit Fontan, with a history of ventricular tachycardia and hepatitis C virus (HCV) treated with sofosbuvir/ledipasvir, was referred to our center for consideration of combined heart and liver transplantation. The patient's blood group was O with panel reactive antibodies of 52%. She consented to consideration of HCV-positive donors. Fifteen days later, an HCV-positive donor was identified, and she underwent heart transplantation with pulmonary artery reconstruction performed jointly by adult and pediatric transplant surgeons. To our knowledge, this the first time an HCV-positive donor heart has been to transplant an adult with congenital heart disease.

Congenital Heart Surgery Outcomes in Turner Syndrome: The Society of Thoracic Surgeons Database Analysis

BACKGROUND

Turner syndrome (TS) is a genetic syndrome characterized by monosomy X (45,XO) in phenotypic females and is commonly associated with congenital heart disease. We sought to describe the distribution, mortality, and morbidity of congenital heart surgery in TS and compare outcomes to individuals without genetic syndromes.

METHODS

The Society of Thoracic Surgeons Congenital Heart Surgery Database was used to evaluate index cardiovascular operations performed from 2000 to 2017 in pediatric patients (aged 0-18 years) with and without TS. Analyses were stratified by the most common operations, including coarctation repair, aortic arch repair, partial anomalous pulmonary venous return repair, Norwood, superior cavopulmonary anastomosis (Glenn), and Fontan.

RESULTS

Included were 780 operations in TS and 62,659 operations in controls. The most common TS operations were coarctation repair in 274 (35%), aortic arch repair in 116 (15%), and Norwood in 59 (8%). Compared with controls, TS patients had lower weight-for-age Z-scores across all operations (P < .01 for all); however, operative mortality rates did not differ significantly. The chylothorax rate was higher in TS after coarctation repair (8.8% vs 2.8%, P < .001) and Norwood (22% vs 8.1%, P < .001). The median (interquartile range) postoperative length of stay was longer in TS for coarctation repair (6.5 [5.0-15.5] days vs 5.0 [4.0-9.0] days, P < .001), aortic arch repair (15.0 [8.0-27.5] days vs 11.0 [7.0-21.0] days, P = .004), and Glenn (9.0 [6.0-16.0] days vs 6.0 [5.0-11.0] days, P = .013).

CONCLUSIONS

Turner syndrome patients most commonly underwent operations for left-sided obstructive lesions. Despite increased morbidity for select operations, TS was not associated with increased operative mortality.

Direct Splanchnic Perfusion Safely Avoids Deep Hypothermia

Deep hypothermia for the operative correction of congenital cardiac lesions protects hypoperfused organs, mostly because of its effect on lowering metabolic demand and oxygen requirement. Deleterious cerebral and extracranial side effects of deep hypothermia itself calls for a reexamination of the therapeutic value of hypothermia, and has led to the development of alternative perfusion strategies. Here we describe the potential advantages of milder hypothermia over deep hypothermia and our method of a practical and reproducible implementation of multisite perfusion under mild hypothermia (32°C).

A Medium-Term Venous Access Alternative for Infants Undergoing Congenital Heart Surgery

We describe a strategy aimed at maximizing the safety and minimizing the thrombogenicity of central venous lines for neonates with congenital heart defects. Our method involves the use of a tunneled technique to place a 4.2 Fr single-lumen (Broviac) catheter in the subpericardial space, with minimal intravascular course and a tip placed in the lower right atrium. Using this technique, we potentially eliminated the requirement for percutaneous placement of central venous lines postoperatively as well as potentially decreased the risk of intrapericardial bleeding associated with transthoracic lines.

Bidirectional Inferior Cavopulmonary Anastomosis: Pre-Fontan Interim Palliation

We report a novel method of constructing an extracardiac bidirectional inferior cavopulmonary anastomosis. Our patient was a 4-month-old girl with complex single-ventricle anatomy and a small-caliber superior vena cava. A direct anastomosis from the inferior vena cava to the main pulmonary artery was constructed by using all autologous tissue. The resulting pathway remained patent and exhibited growth with age. Furthermore, a pulmonary arteriovenous malformation did not develop. This case demonstrates how a bidirectional inferior cavopulmonary anastomosis is feasible in the human and can provide similar hemodynamic results as the bidirectional superior cavopulmonary anastomosis.

Neonatal Aortic Arch Reconstruction With Direct Splanchnic Perfusion Avoids Deep Hypothermia

BACKGROUND

Neonatal aortic arch reconstruction, typically performed with deep hypothermia and selective cerebral perfusion, leaves splanchnic organ protection dependent on hypothermia alone. A simplified method of direct in-field descending aortic perfusion during neonatal arch reconstruction permits the avoidance of deep hypothermia. We hypothesize that direct splanchnic perfusion at mild hypothermia provides improved or equivalent safety compared with deep hypothermia and may contribute to postoperative extracardiac organ recovery.

METHODS

Included were 138 biventricular patients aged younger than 90 days undergoing aortic arch reconstruction with cardiopulmonary bypass. Patients were grouped according to perfusion method A (selective cerebral perfusion with deep hyperthermia at 18° to 20°C) or method B (selective cerebral perfusion and splanchnic perfusion at 30° to 32°C). Patient characteristics and perioperative clinical and serologic data were analyzed. Significance was assigned for p of less than 0.05.

RESULTS

Of the 138 survivors, 63 underwent method A and 75 underwent method B. The median age at operation was 8.5 days (range, 6 to 15 days), and median weight was 3.2 kg (range, 2.8 to 3.73 kg), with no significant differences between groups. Cardiopulmonary bypass times were comparable between the two perfusion methods (p = 0.255) as were the ascending aortic cross-clamp times (p = 0.737). The postoperative glomerular filtration rate was significantly different between our groups (p = 0.028 to 0.044), with method B achieving a higher glomerular filtration rate. No significant differences were seen in ventilator time, postoperative length of stay, fractional increase of postoperative serum creatinine over preoperative serum creatinine, and postoperative lactate.

CONCLUSIONS

A simplified method of direct splanchnic perfusion during neonatal aortic arch reconstruction avoids the use of deep hypothermia and provides renal protection at least as effective as deep hypothermia.

Identifying predictors of hospital readmission following congenital heart surgery through analysis of a multiinstitutional administrative Database

BACKGROUND

Despite resource burdens associated with hospital readmission, there remains little multiinstitutional data available to identify children at risk for readmission following congenital heart surgery.

METHODS AND RESULTS

Children undergoing congenital heart surgery and discharged home between January of 2011 and December 2012 were identified within the Pediatric Health Information System database, a multiinstitutional collection of clinical and administrative data. Patient discharges were assigned to derivation and validation cohorts for the purposes of predictive model design, with 17 871 discharges meeting inclusion criteria. Readmission within 30 days was noted following 956 (11%) of discharges within the derivation cohort (n = 9104), with a median time to readmission of 9 days (interquartile range [IQR] 5-18 days). Readmissions resulted in a rehospitalization length of stay of 4 days (IQR 2-8 days) and were associated with an intensive care unit (ICU) admission in 36% of cases. Independent perioperative predictors of readmission included Risk Adjustment in Congenital Heart Surgery score of 6 (odds ratio [OR] 2.6, 95% confidence interval [CI] 1.8-3.7, P < .001) and ICU length of stay of at least 7 days (OR 1.9 95% CI 1.6-2.2, P < .001). Demographic predictors included Hispanic ethnicity (OR 1.2, 95% CI 1.1-1.4, P = .014) and government payor status (OR 1.2, 95% CI 1.1-1.4, P = .007). Predictive model performance was modest among validation cohort (c statistic 0.68, 95% CI 0.66-0.69, P < .001).

CONCLUSIONS

Readmissions following congenital heart surgery are common and associated with significant resource consumption. While we describe independent predictors that may identify patients at risk for readmission prior to hospital discharge, there likely remains other unreported factors that may contribute to readmission following congenital heart surgery.

Abstract 122: A Novel Mutation in a X-linked Gene Causes Human Congenital Dilated Cardiomyopathy

Congenital dilated cardiomyopathy (cDCM) is a rare but often fatal disease. In most cases, there is no family history, and its etiology is unknown. A major hurdle to elucidating a mechanistic understanding of congenital cardiomyopathy, and primary cardiomyopathies in general, has been a lack of access to diseased human cardiac tissues. Recent advances in patient-derived induced pluripotent stem cells (iPSCs) now enable production of human cardiomyocytes (iPSC-CMs) and allows for a systematic study of normal and diseased cardiomyocytes. We hypothesize that cardiomyocytes generated from iPSCs derived from cDCM patients will exhibit cellular and molecular differences from those generated from healthy donor iPSCs and that a rare genetic mutation, or a collection of mutations, plays a critical role in cDCM pathogenesis. To test these hypotheses, we generated cardiomyocytes from iPSCs derived from a 7-month old male with cDCM using a robust cardiac induction protocol based on the “matrigel sandwich” method of Kamp and colleagues. With this remarkably robust induction method, iPSC-CMs from the cDCM patient and a healthy control donor exhibited proteomic profiles that were 99.7% superimposable. Despite the close similarity at the global proteome level, iPSC-CMs from the cDCM patient showed greatly reduced contractility and dramatic structural defects in the sarcomere and the mitochondria. Finally, bioinformatics analyses of the RNAseq data of the patient’s iPSC-CMs discovered a putative causal mutation in an evolutionarily conserved site in a X-linked gene with unknown function. In summary, our work demonstrates that iPSC-based approaches are particularly useful for the study of human congenital heart diseases. We plan to confirm the causality of this mutation using gene editing techniques such as CRISPR/Cas9 and explore the role of this novel gene in cardiomyocyte structure and function.

Occlusion of the left main coronary artery os by a tethered aortic valve cusp

We report a 4-month-old girl who presented with poor ventricular function and was found to have occlusion of the left main coronary artery os by a tethered aortic cusp. The patient underwent surgical delamination of the aortic valve leaflet, revealing a normal left coronary os. After operative repair, her left ventricular function improved significantly. This diagnosis should be included in the differential in all children presenting with cardiac dysfunction.

A common angiotensin-converting enzyme polymorphism and preoperative angiotensin-converting enzyme inhibition modify risk of tachyarrhythmias after congenital heart surgery

BACKGROUND

The angiotensin-converting enzyme insertion/deletion (ACE I/D) polymorphism is described in association with numerous phenotypes, including arrhythmias, and may provide predictive value among pediatric patients undergoing congenital heart surgery.

OBJECTIVE

The purpose of this study was to examine the role of a common polymorphism on postoperative tachyarrhythmias in a large cohort of pediatric patients undergoing congenital heart surgery with cardiopulmonary bypass (CPB).

METHODS

Subjects undergoing congenital heart surgery with CPB at our institution were consecutively enrolled from September 2007 to December 2012. In addition to DNA, perioperative clinical data were obtained from subjects.

RESULTS

Postoperative tachyarrhythmias were documented in 45% of 886 enrollees and were associated with prolonged mechanical ventilation (P <.001) and intensive care unit length of stay (P <.001). ACE I/D was in Hardy-Weinberg equilibrium (19% I/I, 49% I/D, 32% D/D). I/D or D/D genotypes were independently associated with a 60% increase in odds of new tachyarrhythmia (odds ratio [OR] 1.6, 95% confidence interval [CI] 1.1-2.3, P = .02). Preoperative ACE inhibitor administration was independently associated with a 47% reduction in odds of postoperative tachyarrhythmia in the entire cohort (OR 0.53, 95% CI 0.32-0.88, P = .01), driven by a 5-fold reduction in tachyarrhythmias among I/I genotype patients (OR 0.19, 95% CI 0.04-0.88, P = .02).

CONCLUSION

The risk of tachyarrhythmias after congenital heart surgery is independently affected by the ACE I/D polymorphism. Preoperative ACE inhibition is associated with a lower risk of postoperative tachyarrhythmias, an antiarrhythmic effect that appears genotype dependent. An understanding of genotype variation may play an important role in the perioperative management of congenital heart surgery.

Postoperative complications and association with outcomes in pediatric cardiac surgery

OBJECTIVE

Our primary aim was to study postoperative complications in pediatric cardiac surgery patients and their association with cardiopulmonary bypass (CPB) use. The secondary aim was to evaluate the association of postoperative complications with established outcome measures.

METHODS

A single-institution retrospective observational study was undertaken of consecutive pediatric cardiac surgery patients during a 1-year period. Five cardiac and 15 extracardiac complications were studied. CPB use, CPB parameters, demographics, and Risk Adjusted Classification for Congenital Heart Surgery (RACHS-1) levels were evaluated as risk factors for complications. Outcomes, including mechanical ventilation duration, pediatric cardiac intensive care unit stay, hospital stay, and mortality were studied.

RESULTS

A total of 325 patients were studied: 271 with CPB and 54 without CPB. Of the 325 patients, 141 (43%) had ≥1 complication (95% confidence interval, 38%-49%). Of the 325 patients, 82 (25%) developed cardiac and 120 (37%) developed extracardiac complications. The evidence from logistic regression analysis was insufficient to suggest a relationship between CPB support and the incidence of cardiac or extracardiac complications after adjusting for age, gender, previous sternotomy, and RACHS-1 levels. For patients receiving CPB, longer CPB times, higher RACHS-1 levels, and a lower temperature with CPB were associated with a greater number of cardiac complications (P < .01). Longer CPB times and higher RACHS-1 levels were associated with a greater number of extracardiac complications (P = .006). Postoperative complications were significantly associated with an increased mechanical ventilation duration, pediatric cardiac intensive care unit stay, and hospital stay and mortality (P < .01).

CONCLUSIONS

Postoperative complications occurred in 43% of pediatric cardiac surgeries performed both with and without CPB. The complications were associated with longer mechanical ventilation and pediatric cardiac intensive care unit and hospital stays, and increased mortality.

Template of patient-specific summaries facilitates education and outcomes in paediatric cardiac surgery units

OBJECTIVES

Few educational opportunities exist in paediatric cardiac critical care units (PCCUs). We introduced a new educational activity in the PCCU in the form of of patient-specific summaries (TPSS). Our objective was to study the role of TPSS in the provision of a positive learning experience to the multidisciplinary clinical team of PCCUs and in improving patient-related clinical outcomes in the PCCU.

METHODS

Prospective educational intervention with simultaneous clinical assessment was undertaken in PCCU in an academic children's hospital. TPSS was developed utilizing the case presentation format for upcoming week's surgical cases and delivered once every week to each PCCU clinical team member. Role of TPSS to provide clinical education was assessed using five-point Likert-style scale responses in an anonymous survey 1 year after TPSS provision. Paediatric cardiac surgery patients admitted to the PCCU were evaluated for postoperative outcomes for TPSS provision period of 1 year and compared with a preintervention period of 1 year.

RESULTS

TPSS was delivered to 259 clinical team members including faculty, fellows, residents, nurse practitioners, nurses, respiratory therapists and others from the Divisions of Anesthesia, Cardiology, Cardio-Thoracic Surgery, Critical Care, and Pediatrics working in the PCCU. Two hundred and twenty-four (86%) members responded to the survey and assessed the role of TPSS in providing clinical education to be excellent based on mean Likert-style scores of 4.32 ± 0.71 in survey responses. Seven hundred patients were studied for the two time periods and there were no differences in patient demographics, complexity of cardiac defect and surgical details. The length of mechanical ventilation for the TPSS period (57.08 ± 141.44 h) was significantly less when compared with preintervention period (117.39 ± 433.81 h) (P < 0.001) with no differences in length of PCICU stay, hospital stay and mortality for the two time periods.

CONCLUSIONS

Provision of TPSS in a paediatric cardiac surgery unit is perceived to be beneficial in providing clinical education to multidisciplinary clinical teams and may be associated with improved clinical outcome.

Residual lesions in postoperative pediatric cardiac surgery patients receiving extracorporeal membrane oxygenation support

OBJECTIVE

The objective of this study was to examine the incidence and clinical outcomes of residual lesions in postoperative pediatric cardiac surgery patients receiving extracorporeal membrane oxygenation (ECMO) support.

METHODS

A retrospective observational study was undertaken at a pediatric heart institution. Postoperative pediatric cardiac surgery patients receiving ECMO support within 7 days of surgery during the past 7 years (2005-2011) were studied. A hemodynamically significant cardiac lesion on ECMO support that required intervention to decannulate successfully was defined as a residual lesion. Demographic data, complexity of cardiac defect, surgical data, indications for ECMO, echocardiographic findings, and cardiac catheterization results were studied. Evaluation of residual lesions based on duration of ECMO support, interventions undertaken, and clinical outcomes were also examined.

RESULTS

Residual lesions were evaluated in 43 of 119 postoperative patients placed on ECMO support. Lesions were detected in 35 patients (28%), predominantly in branch pulmonary arteries (n = 10), shunts (n = 7), and ventricular outflow tracts (n = 9). Echocardiography detected 7 residual lesions (20%) and cardiac catheterization detected 28 residual lesions (80%). Earlier detection of residual lesions during the first 3 days of ECMO support in 24 patients improved their rate of decannulation significantly (P = .004) and survival to hospital discharge (P = .035), compared with later detection (after 3 days of ECMO support) in 11 patients.

CONCLUSIONS

Residual lesions are present in approximately one-quarter of postoperative cardiac surgery patients requiring ECMO support. All postoperative pediatric cardiac surgery patients unable to be weaned off ECMO successfully should be evaluated actively for residual lesions, preferably by cardiac catheterization imaging. Earlier detection of residual lesions and reintervention are associated with improved clinical outcome.