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.

Successful Salvage of an Extracardiac Fontan in the Setting of Purulent Mediastinitis using Antibiotic-Impregnated Beads

Post-cardiotomy mediastinitis is an especially serious complication after the implantation of prosthetic vascular grafts. Standard of care is irrigation, debridement, and removal of all prosthetic material present in the surgical field. The use of antibiotic impregnated beads at the site of infection has been reported in the salvage of vascular grafts in the adult population. We present the case of a 3-year-old child with hypoplastic left heart syndrome who developed mediastinitis following the Fontan operation. In a nontraditional approach, the Fontan conduit, which was surrounded by gross purulence, was successfully salvaged with the adjunctive use of vancomycin-impregnated beads.

Vitamin D Status After Cardiopulmonary Bypass in Children With Congenital Heart Disease

Deficiency in 25-hydroxyvitamin D (25OHD) is associated with increased morbidity and mortality in the critically ill. Children who underwent surgery for congenital heart disease under cardiopulmonary bypass (CPB) are typically deficient in 25OHD. It is unclear whether this deficiency is due to CPB. We hypothesized that CPB reduces the levels of 25OHD in children with congenital heart disease. We conducted a prospective observational study on children aged 2 months to 17 years who underwent CPB. Serum was collected at 3 time points: immediately before, immediately after surgery, and 24 hours after surgery. 25-Hydroxyvitamin D, 1,25-dihydroxyvitamin D, 1,25(OH)₂D, vitamin D binding protein, and albumin levels were measured. Levels were compared using repeated measures analysis of variance. We enrolled 20 patients, 40% were deficient in 25OHD with levels <20 ng/mL prior to surgery. Mean (±standard deviation) of 25OHD at the 3 time points was 21.3 ± 8 ng/mL, 19 ± 5.8 ng/mL, and 19.5 ± 6.6 ng/mL, respectively ( P = .02). The decrease in 25OHD was observed primarily in children with sufficient levels of 25OHD, with mean levels at the 3 time points: 26.8 ± 4.2 ng/mL, 21.5 ± 5.7 ng/mL, and 23.0 ± 4.9 ng/mL, respectively ( P < .001). Calculated means of free fraction of 25OHD at the 3 time points were 6.2 ± 2.8 pg/mL, 5.8 ± 2.2 pg/mL, and 5.5 ± 2.4 pg/mL, respectively, ( P = .04). Mean levels of 1,25(OH)₂D were 63.7 ± 34.9 ng/mL, 53.2 ± 30.6 ng/mL, and 67.7 ± 23.5 ng/mL ( P = .04). Vitamin D binding protein and albumin levels did not significantly change. Cardiopulmonary bypass decreases 25OHD by reducing the free fraction. Current investigations are geared to establish whether vitamin D deficiency is associated with outcomes and if treatment is appropriate.

Left ventricular function improves after pulmonary valve replacement in patients with previous right ventricular outflow tract reconstruction and biventricular dysfunction

Congenital heart defects that have a component of right ventricular outflow tract obstruction, such as tetralogy of Fallot, are frequently palliated in childhood by disruption of the pulmonary valve. Although this can provide an initial improvement in quality of life, these patients are often left with severe pulmonary valve insufficiency. Over time, this insufficiency can lead to enlargement of the right ventricle and to the deterioration of right ventricular systolic and diastolic function. Pulmonary valve replacement in these patients decreases right ventricular volume overload and improves right ventricular performance. To date, few studies have examined the effects of pulmonary valve replacement on left ventricular function in patients with biventricular dysfunction. We sought to perform such an evaluation.Records of adult patients who had undergone pulmonary valve replacement from January 2003 through November 2006 were analyzed retrospectively. We reviewed preoperative and postoperative echocardiograms and calculated left ventricular function in 38 patients.In the entire cohort, the mean left ventricular ejection fraction increased by a mean of 0.07 after pulmonary valve replacement, which was a statistically significant change (P < 0.01). In patients with preoperative ejection fractions of less than 0.50, mean ejection fractions increased by 0.10.We conclude that pulmonary valve replacement in patients with biventricular dysfunction arising from severe pulmonary insufficiency and right ventricular enlargement can improve left ventricular function. Prospective studies are needed to verify this finding.

Closure of symptomatic ventricular septal defects: how early is too early?

With improvements in technology and surgical technique, pediatric cardiologists are challenging surgeons to close symptomatic ventricular septal defects (VSDs) in ever smaller patients. Although delaying surgery may facilitate operative repair, early intervention decreases the period of time these patients require therapy to prevent heart failure, maintains growth, and minimizes exposure to increased pulmonary pressures. To evaluate early intervention, we compare the outcomes of VSD closure in different-sized children. From December 2002 to July 2005, 225 patients underwent closure of a VSD. These patients were divided into four weight-based groups: <4 kg (group 1, n = 28), 4 to 6 kg (group 2, n = 93), 6 to 10 kg (group 3, n = 47), and >10 kg (group 4, n = 57). We reviewed operative and postoperative data, and comparisons were made between the groups. Median weights and ages at the time of surgery were 3.5 kg and 77 days (group 1), 4.9 kg and 128 days (group 2), 7.1 kg and 309 days (group 3), and 18.2 kg and 190 days (group 4). Operative data included cardiopulmonary bypass (CPB), aortic cross-clamp, and procedure times. CPB (p = 0.064), cross-clamp (p = 0.665), and procedure (p = 0.187) times were not significantly affected by decreasing weight. Postoperative continuous data included duration of ventilation and length of intensive care unit (ICU) and hospital stay. Ventilation (p = 0.667) and ICU (p = 0.976) times and length of hospital stay (p = 0.905) were also unaffected by decreasing weight. Postoperative catagoric data included complications and presence of a residual VSD. There was no significant difference in complications (p = 0.763) or residual VSD (p = 0.696) between groups. There was no mortality and no persistent heart block requiring placement of a permanent pacemaker. With improvements in technology and surgical technique, safe and effective VSD closure can be performed in increasingly smaller children. Earlier repair decreases the period of time these patients require aggressive medical therapy to prevent heart failure and maintain growth. It also decreases the period of time for which they are exposed to increased pulmonary pressures and are at risk for infectious respiratory complications. It does not appear to affect operative or postoperative outcomes.

Utility of intravenous catheters for femoral arterial cannulation in infants having complicated sternal re-entry

OBJECTIVE

Many children undergoing surgery for congenital heart disease have had prior operations. Reoperative sternotomy carries with it the risk of cardiac injury and the need for emergency peripheral cannulation. Unfortunately, in smaller children, many of the standard sites are occluded, stenosed, or too small for the smallest manufactured cannulas. Using a model, we evaluated the feasibility of using peripheral intravenous catheters for establishing cardiopulmonary support.

METHODS

A model cardiopulmonary bypass circuit was created. Catheters of varying diameter and length were used to simulate arterial cannulation. With each catheter, flows were incrementally increased until a maximum arterial line pressure was achieved. Data were recorded.

RESULTS

Catheter diameters increased from 24 to 14 gauge, and catheter lengths increased from 1 inch to 1.88 inches. Flow could not be established through the 24-gauge catheter without an unacceptably high arterial line pressure. From the next smallest catheter (22 gauge x 1 inch) to the largest catheter (14 gauge x 1.88 inches), maximum achievable flow rates ranged from 70 to 540 mL/min, respectively.

CONCLUSIONS

Peripheral arterial cannulation may be lifesaving in cases of complicated sternal re-entry in children. Intravenous catheters can be used when vessels are too small for standard cannulas. Flow rates that provide adequate support while maintaining acceptable arterial line pressures are achievable with peripheral intravenous catheters until central cannulation can be accomplished safely.

The short term effects of cardiopulmonary bypass on neurologic function in children and young adults

OBJECTIVE

Cognitive deficits are common in adults following surgery utilizing cardiopulmonary bypass (CPB). A previous retrospective study suggested that surgical closure of an ASD in children was associated with neurologic injury, while transcather therapy was not. In a prospective study, we sought to determine whether neurologic deficits occur following repair of non-complex congenital heart lesions in school-age children and young adults.

METHODS

Inclusion criteria were: age between 5 and 20 years, cardiac surgery utilizing CPB without deep hypothermic circulatory arrest, and no prior cardiac surgery. Patients underwent psychometric testing 1-3 days prior to surgery and re-evaluation 7-18 days after surgery. In order to determine the test/re-test effect an age-matched cohort of children undergoing transcather closure of ASD under general anesthesia was also evaluated. The primary outcome measures were verbal and picture memory. Additional psychometric tests included: computerized performance test (CPT) and Digit Span (DS). Forty-one patients were enrolled, 29 undergoing surgery with CPB and 12 controls. Surgical procedures included ASD closure (n=13), VSD closure (n=10), resection of sub-aortic stenosis (n=3), mitral valvuloplasty (n=3). Mild hypothermia was used in all cases. The mean duration of CPB was 54+/-22 min.

RESULTS

There was no significant difference in any of the psychometric test scores between subjects undergoing surgery with CPB or controls.

CONCLUSIONS

There are no marked adverse neurologic effects of CPB in school-age children and young adults undergoing non-complex open-heart surgery. These data are important in counseling patients and families and should be considered in the debate as to the relative merits of transcather versus open-heart repair of various heart lesions.

Mechanism of therapeutic effect of high-dose intravenous immunoglobulin. Attenuation of acute, complement-dependent immune damage in a guinea pig model

Studies were performed in in vitro and in vivo models to assess the effect of intravenous immunoglobulin (IVIG) on the development of acute complement-mediated tissue damage. IVIG significantly increased the duration of survival and frequently prevented the death of guinea pigs injected with anti-Forssman antiserum to cause lethal Forssman shock; no control animal treated with albumin and/or maltose vehicle survived. The most pronounced effect was achieve by delivering IVIG as one slow injection at 1,800 mg/kg 3 h before Forssman shock was elicited. Infusion of guinea pig IgG at the same dosage was similarly protective. A strong positive correlation was found between IgG plasma levels and survival time in guinea pigs treated with graded doses of IVIG. Therapy itself did not affect C3 and C4 levels nor the capacity to activate these components. In vitro studies showed almost complete inhibition of C3 uptake onto IgG-sensitized erythrocytes using serum from an IVIG-treated animal. We suggest that supraphysiologic levels of IVIG act in part by preventing active C3 fragments from binding to target cells. Infusion of high dose IVIG may be a rational approach to modulating acute, complement-dependent tissue damage in a variety of diseases in man.