Faculty Bibliography

Severe thrombosis of a mechanical valve is a rare complication in pediatric patients. Thrombolytic therapy as treatment of mechanical mitral valve thrombosis has rarely been reported in young infants. We report the successful treatment with recombinant tissue-type plasminogen activator of a mechanical mitral valve thrombus in a 7 month-old patient with trisomy 21, complete atrioventricular canal defect and pulmonary hypertension status post complete atrioventricular canal repair and subsequent prosthetic mitral valve replacement. He presented with respiratory decompensation and shock secondary to severe mechanical mitral valve stenosis. Serial echocardiograms showed significant resolution of the thrombus within 18 h of infusion with no major bleeding complications during the treatment course. Although a rare complication of mechanical valve placement in pediatrics, thrombosis of mechanical valves may result in severe hemodynamic and respiratory compromise. This case demonstrates that thrombolytic therapy is a feasible option for the treatment of critical thrombosis in pediatric patients after MVR.

OBJECTIVE:For infants with single ventricle malformations undergoing staged repair, interstage mortality is reported at 2% to 20%. The Single Ventricle Reconstruction trial randomized subjects with a single morphologic right ventricle undergoing a Norwood procedure to a modified Blalock-Taussig shunt (MBTS) or a right ventricle-to-pulmonary artery shunt (RVPAS). The aim of this analysis was to explore the associations of interstage mortality and shunt type, and demographic, anatomic, and perioperative factors. METHODS:Participants in the Single Ventricle Reconstruction trial who survived to discharge after the Norwood procedure were included (n = 426). Interstage mortality was defined as death postdischarge after the Norwood procedure and before the stage II procedure. Univariate analysis and multivariable logistic regression were performed adjusting for site. RESULTS:Overall interstage mortality was 50 of 426 (12%)-13 of 225 (6%) for RVPAS and 37 of 201 (18%) for MBTS (odds ratio [OR] for MBTS, 3.4; P < .001). When moderate to severe postoperative atrioventricular valve regurgitation (AVVR) was present, interstage mortality was similar between shunt types. Interstage mortality was independently associated with gestational age less than 37 weeks (OR, 3.9; P = .008), Hispanic ethnicity (OR, 2.6; P = .04), aortic atresia/mitral atresia (OR, 2.3; P = .03), greater number of post-Norwood complications (OR, 1.2; P = .006), census block poverty level (P = .003), and MBTS in subjects with no or mild postoperative AVVR (OR, 9.7; P < .001). CONCLUSIONS:Interstage mortality remains high at 12% and is increased with the MBTS compared with the RVPAS if postoperative AVVR is absent or mild. Preterm delivery, anatomic, and socioeconomic factors are also important. Avoiding preterm delivery when possible and close surveillance after Norwood hospitalization for infants with identified risk factors may reduce interstage mortality.

BACKGROUND:A major limitation of pediatric heart transplantation is scarcity of pediatric donor organs, leading to longer waiting times and higher waiting list mortality. Current practice is to match potential pediatric recipients with donors by weight; however, we hypothesize height to be a better predictor of heart size as estimated by left ventricular end-diastolic diameter (LVEDd), as well as a novel measurement from the superior vena cava-right atrium junction to inferior vena cava-right atrium junction (SVC-IVC distance). Our ultimate objective is to present a more effective means of size-matching for pediatric heart transplantation. METHODS:Measurements of LVEDd and SVC-IVC distance were taken from 254 normal echocardiograms performed on individuals aged 7 days to 22 years, and correlated with demographic variables, including height, weight, and body surface area. Simulations were conducted using echocardiographic measurements and size parameters of past recipients with hypothetic donors to demonstrate practicality. RESULTS:There was a linear relationship between height and SVC-IVC distance (R(2) = 0.904) and LVEDd (R(2) = 0.889), whereas the relationships with weight were logarithmic (SVC-IVC distance, R(2) = 0.855; LVEDd, R(2) = 0.880), and the relationships with body surface area were polynomial (SVC-IVC distance, R(2) = 0.880; LVEDd, R(2) = 0.884). Three simulations demonstrate improvements in efficiency of the size-matching process. CONCLUSIONS:The use of height and a novel SVC-IVC distance measurement to evaluate heart size in potential pediatric heart transplant recipients and donors may allow for broadening of the donor pool and creation of a more efficient and accurate size-matching process. The prospective evaluation of these novel methods with respect to clinical outcomes is necessary.

BACKGROUND:ABO incompatible (ABOi) heart transplantation is an accepted approach to increasing organ availability for young patients. Previous studies have suggested that early survival for ABOi transplants is similar to ABO compatible (ABOc) transplants. We analyzed the Pediatric Heart Transplant Study (PHTS) database from 1/96 to 12/08 to further assess this strategy. METHODS:We analyzed the numbers of ABOi and ABOc done at the PHTS centers. We then compared the clinical characteristics, and short-term freedom from death, rejection and infection in the ABOi patients with the patients that had an ABOc heart transplant during the same period. All patients were less than or equal to 15 months of age at listing (the age of the oldest ABOi patient). We adjusted for co-variates shown to increase risk for mortality (age less than 1 month, extracorporeal membrane oxygenation (ECMO), ventilator, previous sternotomy, and congenital heart disease). RESULTS:There were 931 total transplants done at 34 PHTS centers during the 12 year time period in patients ≤15 months of age. Of these, 502 transplants were performed at 20 PHTS centers that did at least one ABOi heart transplant. Eighty-five of the 502 (17%) were ABOi. At time of transplant, ABOi recipients compared with ABOc were more likely to be on a ventilator (49.4% vs 36.5%, p=0.025), and more often supported with ECMO (23.5% vs 13.4%, p=0.018). There was similar survival at 12 months (82% vs 84%, p=0.7). In risk adjusted analysis ABOi status was not associated with 1 year mortality (HR 0.85, 95% CI 0.45-1.6, p=0.61). The ABOi patients had greater freedom from rejection when compared with ABOc patients for all 34 centers (75% vs 62%, p=0.016), but the difference was not significant when limited only to the 20 centers doing ABOi transplants (75% vs 69%, p=0.4). The ABOi cohort had lower infection rates (23.5% vs 37.9%, p = 0.013). This difference remained after adjusting for center and other covariates. CONCLUSIONS:In center and risk adjusted analysis, young children who received an ABOi transplant had equivalent one-year survival and freedom from rejection compared with those who received an ABOc transplant. In spite of the favorable outcome for ABOi recipients, many centers appear to reserve ABOi transplantation for sicker patients. These data mandate reexamination of the current United Network for Organ Sharing (UNOS) policy that gives priority to ABOc over ABOi transplantation in the United States.

Left-ventricular noncompaction (LVNC) is an echocardiographic finding of increasing frequency in pediatrics; however, predictors of outcomes have been difficult to identify. We conducted a retrospective review of pediatric patients at the Morgan Stanley Children's Hospital of New York from January of 1993 to September of 2009 to identify predictors of the primary outcome of death or heart transplantation. LVNC was identified in 50 patients, 34 of them < 1 year of age. Death or transplantation occurred in 26 patients, with a median survival of 1.17 years after presentation. Patients surviving 1 year after presentation had 75% conditional survival, and patients surviving 2 years after presentation had 92% conditional survival. Hemodynamic instability, poor ventricular function, and LV dilatation were each independent predictors of poor outcome. Of the 21 patients who presented with hemodynamic instability, 17 died or underwent transplantation at a median of 0.08 years after presentation. In conclusion, LVNC is recognized more in younger patients; however, age is not a predictor of outcome. Patients who present with hemodynamic instability and poor ventricular function have decreased transplant-free survival, and most poor outcomes occur within the first year after presentation. Therefore, early listing for transplant may lead to better outcomes in this population.