Common deletion variants causing protocadherin-α deficiency contribute to the complex genetics of BAV and left-sided congenital heart disease.

Bicuspid aortic valve (BAV) with ~1%-2% prevalence is the most common congenital heart defect (CHD). It frequently results in valve disease and aorta dilation and is a major cause of adult cardiac surgery. BAV is genetically linked to rare left-heart obstructions (left ventricular outflow tract obstructions [LVOTOs]), including hypoplastic left heart syndrome (HLHS) and coarctation of the aorta (CoA). Mouse and human studies indicate LVOTO is genetically heterogeneous with a complex genetic etiology. Homozygous mutation in the Pcdha protocadherin gene cluster in mice can cause BAV, and also HLHS and other LVOTO phenotypes when accompanied by a second mutation. Here we show two common deletion copy number variants (delCNVs) within the PCDHA gene cluster are associated with LVOTO. Analysis of 1,218 white individuals with LVOTO versus 463 disease-free local control individuals yielded odds ratios (ORs) at 1.47 (95% confidence interval [CI], 1.13-1.92; p = 4.2 × 10-3) for LVOTO, 1.47 (95% CI, 1.10-1.97; p = 0.01) for BAV, 6.13 (95% CI, 2.75-13.7; p = 9.7 × 10-6) for CoA, and 1.49 (95% CI, 1.07-2.08; p = 0.019) for HLHS. Increased OR was observed for all LVOTO phenotypes in homozygous or compound heterozygous PCDHA delCNV genotype comparison versus wild type. Analysis of an independent white cohort (381 affected individuals, 1,352 control individuals) replicated the PCDHA delCNV association with LVOTO. Generalizability of these findings is suggested by similar observations in Black and Chinese individuals with LVOTO. Analysis of Pcdha mutant mice showed reduced PCDHA expression at regions of cell-cell contact in aortic smooth muscle and cushion mesenchyme, suggesting potential mechanisms for BAV pathogenesis and aortopathy. Together, these findings indicate common variants causing PCDHA deficiency play a significant role in the genetic etiology of common and rare LVOTO-CHD.

Mucociliary Clearance Scans Show Infants Undergoing Congenital Cardiac Surgery Have Poor Airway Clearance Function.

Background: Infants undergoing congenital cardiac surgery with cardiopulmonary bypass are at high risk for respiratory complications. As impaired airway mucociliary clearance (MCC) can potentially contribute to pulmonary morbidity, our study objective was to measure airway clearance in infants undergoing congenital cardiac surgery and examine correlation with clinical covariables that may impair airway clearance function. Materials and Methods: Airway clearance in infants was measured over 30 min using inhaled nebulized Technetium 99m sulfur colloid administered either via a nasal cannula or the endotracheal tube in intubated infants. This was conducted bedside with a portable gamma camera. No difficulty was encountered in positioning the gamma camera over the patient, and neither the camera nor the MCC scan interfered with routine medical care or caused any adverse events. Patient and perioperative variables were examined relative to the MCC measurements. Results: We prospectively enrolled 57 infants undergoing congenital cardiac surgery and conducted a single MCC scan per patient. MCC data from 42 patients were analyzable, including five pre-operative, 15 (40.5%) in the immediate post-operative period (days 1-2), and 22 (59.5%) were later post-operative (≥3 days). Pre-operative MCC was inversely proportional to days requiring post-operative mechanical ventilation (p = 0.006) and non-invasive positive pressure ventilation (p = 0.017). MCC was higher at later post-operative days (p = 0.002) with immediate post-operative MCC being lower (3%; 0-13%) than either pre-operative (21%; 4-25%) (p = 0.091) or later post-operative MCC (18%; 0-29%) (p = 0.054). Among the infants with low post-operative MCC, significantly more were pre-mature [5/19 (26%) vs. 0/18 (0%); p = 0.046], were intubated [14/19 (75%) vs. only 7/18 (39%); p = 0.033] and were receiving higher FiO2 (40%, 27-47% vs. 26%, 21-37%; p = 0.015). Conclusions: This is the first study to show that infants undergoing congenital cardiac surgery have impaired MCC. MCC appeared lowest in the immediate post-operative period. Worse MCC was associated with pre-maturity, mechanical ventilation, or receiving higher FiO2. These findings suggest MCC scans should be further explored for informing clinical decision making to improve post-surgical respiratory outcomes. The possible therapeutic benefit of airway clearance maneuvers for infants with poor MCC function should also be investigated.

Deposition studies of aerosol delivery by nasal cannula to infants.

AIM: Nasal cannulas are used to provide oxygen support for infants and have been considered as a means for delivering aerosols to the lungs. To measure mucociliary clearance in the lungs of infants with congenital heart defects, we delivered radiopharmaceutical aerosols via a nasal cannula. Here we report on the pulmonary and nasal deposition of these aerosols. METHOD: A total of 18 infants (median age = 26 days; quartiles = 11-74 days) performed clearance measurements soon before or after corrective cardiac surgery. The regional aerosol deposition was assessed using gamma camera imaging. RESULTS: Cannula flow rate significantly affected pulmonary dosing. Flow rates useful for oxygen support were associated with low pulmonary deposition (2 L/min; mean, 4.5% of deposited dose; range, 2%-9%; n = 7) and high nasal deposition. Much lower cannula flow rates increased the pulmonary deposition (0.2 L/min; mean, 33.5% of deposited dose; range, 15%-51%; n = 5; P = 0.005 vs 2 L/min). The ratio of nose/lung dosing was approximately 26:1 at 2 L/min and 2:1 at 0.2 L/min. Bench studies demonstrated cannula output rates of 10.2 ± 1.7% (2 L/min) and 3.3 ± 0.4% (0.2 L/min) of the loaded nebulizer dose during a 2-minute delivery. Combining in vitro and in vivo results, we estimate that 0.46% of the loaded nebulizer dose reaches the lungs at 2 L/min vs 1.10% at 0.2 L/min during a 2-minute delivery. CONCLUSION: With the delivery system used here, pulmonary aerosol delivery via nasal cannula was very inefficient at the flow rates required to provide oxygen support. Even at low flows, nasal deposition was substantial and local toxicity must be considered.

Ross Versus Non-Ross Aortic Valve Replacement in Children: A 22-Year Single Institution Comparison of Outcomes.

BACKGROUND: The Ross aortic valve replacement (AVR) has been the AVR of choice for children at our center since 1993. Absence or inadequate quality of the pulmonary valve or, less commonly, family or surgeon preference caused us to select an alternative AVR prosthesis for some children. This review compares the outcomes of 42 children who received a non-Ross AVR with 115 children undergoing Ross root replacement at our institution during the most recent 22 years. METHODS: A retrospective chart review of the 42 pediatric non-Ross AVRs was compared with 115 Ross AVRs. The mean age at AVR was 11.0 ± 6.5 years (range, 1 month to 18 years) for the non-Ross and 11.4 ± 5.5 years (range, 6 weeks to 18 years) for the Ross groups. Follow-up was 7.8 ± 6.2 years for the Ross group and 8.7 ± 6.5 years for the non-Ross group. The Ross AVR technique was modified in 2000; these modifications were applied to 72 patients (63%) of the total Ross AVR group. RESULTS: All-cause early and late mortality of the non-Ross AVR group was 17% compared with 4% for the Ross cohort (p = 0.017). The actuarial survival rate at 20 years for the non-Ross AVR group was 81% compared with 94% for the Ross group (p = 0.018). Reintervention rate was 29% (12/38) in the non-Ross group and 28% (32/115) in the entire Ross group (60% [26/43] before 2000, and 8% [6/72] after 2000). Thromboemboli, bleeding, and endocarditis occurred in 2.4%, 1.4%, and 10% in the non-Ross group compared with 0.9%, 2.6%, and 1.7% in the Ross AVR group (p = 0.46, 0.01, and 0.02), respectively. Patients in the non-Ross group had a significantly higher recurrent or persistent aortic valve gradient (>20 mm Hg) than did patients in the Ross group at most recent follow-up (p < 0.05). CONCLUSIONS: Lower mortality, valve-related complications, and better hemodynamics were seen after the Ross AVR than with other types of AVR prostheses. The Ross AVR remains the treatment of choice for children who have an adequate pulmonary valve. Reoperation for Ross root dilatation, regurgitation, or both (only 6% since our modifications in 2000) has markedly reduced the main drawbacks of this AVR technique. The Ross AVR affords the growing child the advantages of a growing, autologous, viable valve substitute and eliminates the lifelong disadvantages of mechanical and xenograft valves.

Mutations in the muscle LIM protein and alpha-actinin-2 genes in dilated cardiomyopathy and endocardial fibroelastosis.

Dilated cardiomyopathy (DCM) is a major cause of morbidity and mortality. Two genes have been identified for the X-linked forms (dystrophin and tafazzin), while mutations in multiple genes cause autosomal dominant DCM. Muscle LIM protein (MLP) is a member of the cysteine-rich protein (CRP) family and has been implicated in both myogenesis and sarcomere assembly. In the latter role, it binds zyxin and alpha-actinin, both of which are involved in actin organization. An MLP-deficient mouse has been described; these mice develop dilated cardiomyopathy and heart failure. Based upon these data, and the recent descriptions of mutations in MLP in patients with DCM or hypertrophic cardiomyopathy, we screened patients for mutations in the MLP and alpha-actinin-2 genes. We identified a patient with DCM and EFE, having a mutation in MLP with the residue lysine 69 substituted by arginine (K69R). This is within a highly conserved region adjacent to the first LIM domain involved in alpha-actinin binding. Analysis in cell culture systems demonstrated that the mutation abolishes the interaction between MLP and alpha-actinin-2 and the cellular localization of MLP was altered. In another individual with DCM, a W4R mutation was identified. However, this mutation did not segregate with disease in this family. In another patient with DCM, a Q9R mutation was identified in alpha-actinin-2. This mutation also disrupted the interaction with MLP and appeared to inhibit alpha-actinin function in cultured cells, in respect to the nuclear localization of actinin and the initiation of cellular differentiation.