David Michael McMullan

Surgeon and Center Volume Influence on Outcomes After Arterial Switch Operation: Analysis of the STS Congenital Heart Surgery Database

BACKGROUND The relative impact of center volume and of surgeon volume on early outcomes after the arterial switch operation (ASO) is incompletely understood. METHODS Neonates in the Society of Thoracic Surgeons Congenital Heart Surgery Database (2005-2012) undergoing ASO for transposition of the great arteries were included in the analysis. Multivariable logistic regression with adjustment for patient factors and ventricular septal defect closure was used to evaluate relationships between annual center and surgeon volume and a composite end point (in-hospital mortality or major complications). RESULTS The study included 2,357 patients (84 centers, 155 surgeons). Median annual ASO center volume was 4 (range, 1 to 18). Median annual surgeon volume was 2 (range, 0.1 to 11). In-hospital mortality was 3.4%; 14.7% had major morbidity and 15.5% met the composite end point. Analyzed individually, lower center and surgeon volumes were each associated with the composite end point (odds ratios for centers with 2 versus 10 cases/y, 1.92; 95% confidence interval, 1.23 to 2.99); odds ratios for surgeons with 1 versus 6 cases/y, 2.16; 95% confidence interval, 1.42 to 3.26). When analyzed together, the addition of surgeon volume to the center volume models attenuated but did not completely mitigate the association of center volume with outcome (relative attenuation of odds ratio = 31%). Addition of center volume to surgeon volume models attenuated the association of surgeon volume with outcome to a lesser degree (relative attenuation of odds ratio = 11%). CONCLUSIONS Center and surgeon volume each influence early outcomes after ASO; however, surgeon volume appears to play a more prominent role. Surgeon and center ASO volume should be considered in the context of initiatives to improve outcomes from ASO for transposition of the great arteries.

Minimizing bleeding associated with mechanical circulatory support following pediatric heart surgery

OBJECTIVE The use of extracorporeal membrane oxygenation (ECMO) to support patients with early postcardiotomy heart failure may be associated with catastrophic bleeding, making its use undesirable. However, postcardiotomy mechanical circulatory assistance is necessary in some patients to allow for myocardial recovery. We have assembled a centrifugal pump system (CPS) that does not require early systemic anticoagulation. This study compares postoperative bleeding in pediatric patients placed on standard ECMO versus CPS within 24h of cardiotomy. METHODS Between November 2002 and February 2007, 25 patients (age 0 days-1.72 years) received postcardiotomy mechanical support. Fourteen patients were placed on ECMO and 11 patients were placed on CPS within 24h of surgical repair. Retrospective analysis was performed of chest-tube drainage at multiple time points following initiation of mechanical support. Additional variables, including Risk Adjustment for Congenital Heart Surgery-1 (RACHS-1) score, total time on mechanical support, 30-day mortality, activated clotting time, blood-product administration, circuit-related complications, and circuit changes were also analyzed. RESULTS Patients on ECMO (0.30 ± 0.39 years) and CPS (0.40 ± 0.56 years) were of similar age (p = 0.64). Patients on ECMO (0.3 ± 0.1m(2)) and CPS (0.3 ± 0.1m(2)) had similar body surface areas (p = 0.46). Patients placed on CPS had significantly less chest-tube drainage during the first 4h of support. Activated clotting times appeared to be higher during the first 12h of ECMO versus CPS. There was no statistical difference between ECMO and CPS with respect to the following variables: RACHS-1 score, time on support, 30-day mortality, circuit-related complications, and circuit changes. Blood-product administration at 24h of support was significantly less (p = 0.04) for patients on CPS versus ECMO. CONCLUSIONS Mechanical circulatory support can be provided without the complication of clinically significant bleeding if a specialized circuit is used. This has important implications for the decision to use mechanical support in the immediate postoperative period in the face of ventricular failure. In addition, early mechanical support can be used with a low incidence of circuit-related complications.

Extracorporeal life support for the neonatal cardiac patient: Outcomes and new directions

Extracorporeal life support is an important therapy for neonates with life-threatening cardiopulmonary failure. Utilization of extracorporeal life support in neonates with congenital heart disease has increased dramatically during the past three decades. Despite increased usage, overall survival in these patients has changed very little and extracorporeal life support-related morbidity, including bleeding, neurologic injury, and renal failure, remains a major problem. Although survival is lower and neurologic complications are higher in premature infants than term infants, cardiac extracorporeal life support including extracorporeal cardiopulmonary resuscitation is effective in preventing death in many of these high-risk patients. Miniaturized ventricular assist devices and compact integrated extracorporeal life support systems are being developed to provide additional therapeutic options for neonates.

Association of thymectomy with infection following congenital heart surgery.

Background: Congenital absence of the thymus can lead to profound immunodeficiency, suggesting that thymic function during fetal development is essential to normal lymphocyte development. How vital the thymus after birth is to human immune competence and regulation is not known. Routine thymectomy, especially at an early age, may influence immunity, and therefore the risk of infection, autoimmunity, or malignancy. Methods: A retrospective review of cardiac surgery patients followed at Seattle Children’s Hospital was performed. The primary outcome was rate of serious infections requiring hospitalization. Secondary analyses included age, type of infection, cardiac diagnosis, surgical procedure, and comorbidities. Results: Patients fell into 2 groups: 60 with complete thymectomy and 35 with partial or no thymectomy. There was no statistical difference between groups in the overall prevalence of serious infections (16.7% vs 17.2%, P = 1.0). There was a nonsignificant trend toward reduced time between surgery and onset of first infection in patients in the total thymectomy group versus those without thymectomy (1.7 years vs 4.6 years, P = .07). Total thymectomy before 6 months of age also tended to increase infection rate, but the effect was not significant (0.09/year vs 0.02, P = .14). Gastroesophageal reflux in patients with total thymectomy increased the risk of infection (P = .013), suggesting a cumulative effect. Conclusions: Though infections occurred frequently in the childhood cardiac surgery population, total thymectomy was not associated with increased risk of serious infection. Comorbid conditions may be more important contributing factors increasing the risk of infection in this complex and vulnerable population.

Embryology and Anatomy of Intrapulmonary Shunts

Pulmonary vascular shunting poses a major clinical risk. In this brief overview, we discuss the morphological aspects of shunting vessels in the lung, their development, and the regulation of their patency.

Risk of extracorporeal life support circuit-related hyperkalemia is reduced by prebypass ultrafiltration.

Objectives: Pediatric patients who receive large volume blood transfusions are at risk for experiencing transfusion-related hyperkalemic cardiac arrest. Prebypass ultrafiltration of blood used to prime cardiopulmonary bypass circuits is commonly used in pediatric cardiac surgery to create a more physiologic and electrolyte balanced priming solution prior to initiation of cardiopulmonary bypass. This study was undertaken to determine the efficacy of prebypass ultrafiltration in normalizing extracorporeal life support circuit priming solution before initiating extracorporeal life support. Design: Prospective study. Setting: PICU and neonatal ICU in a tertiary academic center. Patients: Patients requiring venovenous extracorporeal life support. Interventions: Prebypass ultrafiltration of extracorporeal life support circuits. Measurements and Main Results: Hematocrit, electrolyte, and lactate concentrations were measured in blood-primed extracorporeal life support circuits before and after ultrafiltration and in blood collected from patients before and after initiation of extracorporeal life support. Clinically significant elevation of K+ concentration was observed in all extracorporeal life support circuits prior to prebypass ultrafiltration, despite the fact that 93% of red blood cell units were collected ⩽ 7 days prior to use. Prebypass ultrafiltration significantly reduced concentrations of K+ (10.9 vs 6.0 mEq/L, p = 0.001) and lactate (7.0 vs 3.6 mmol/L, p < 0.001) and increased hematocrit (37% vs 48%, p < 0.001) and concentrations of ionized calcium (0.64 vs 1.16 mg/dL, p < 0.001) and Na+ (129 vs 144 mEq/L, p < 0.001). Serum electrolyte concentrations remained within the normal physiologic range in all patients following initiation of venovenous extracorporeal life support with circuits that underwent prebypass ultrafiltration. Conclusions: Prebypass ultrafiltration normalizes the electrolyte balance of blood-primed extracorporeal life support circuits. Prebypass ultrafiltration processing may reduce the risk of transfusion-related hyperkalemic cardiac arrest in small children who require venovenous extracorporeal life support.

Tricuspid Valve Replacement With a Melody Stented Bovine Jugular Vein Conduit

Atrioventricular valve replacement options are limited in infants and small children. The Melody stented bovine jugular vein conduit is being used with increasing frequency for percutaneous pulmonary valve replacement. The Melody valve can be serially dilated over time to accommodate the somatic growth of pediatric patients. We report the initial experience of using the Melody valve as a surgical tricuspid valve replacement in an infant.

Challenging Argatroban Management of a Child on Extracorporeal Support and Subsequent Heart Transplant.

A 6-year-old child developed heparin-induced thrombocytopenia while on extracorporeal life support. Hours after a difficult transition from heparin to argatroban for anticoagulation therapy, the child underwent heart transplantation. Intraoperative management was plagued with circuit thrombus formation while on cardiopulmonary bypass and subsequent massive hemorrhage after bypass. We review the child’s anticoagulation management, clinical challenges encountered, and review current literature related to the use of argatroban in pediatric cardiac surgery.

Fatal Spontaneous Dissection of a Contegra Conduit in a Child

The Contegra bovine jugular vein conduit (Medtronic, Minneapolis, MN) is one of the most widely used grafts for surgical reconstruction of the right ventricular outflow tract in both pediatric and adult patients with congenital heart disease. In this report, we describe a case of acute dissection of a neointimal peel in a Contegra conduit resulting in conduit stenosis and death of a child.

Long-term Outcomes After Transplantation Following Support with a Pulsatile Pediatric Ventricular Assist Device

BACKGROUND There has been increasing use of durable ventricular assist devices (VAD) in children as a bridge to transplantation (BTT). The Berlin Heart investigational device exemption (IDE) trial was the first pediatric VAD trial to demonstrate excellent survival outcomes as a BTT. OBJECTIVES Our aim was to compare the expanded post-transplant outcomes for children enrolled in the Berlin Heart IDE trial to a matched Pediatric Heart Transplant Study (PHTS) cohort not requiring mechanical circulatory support (MCS). SETTING University Hospitals. METHODS This was a retrospective review of linked PHTS and Berlin Heart IDE databases for pediatric (≤18 years) recipients transplanted from 2007-2011. Subjects with <5 years of follow up were excluded. VAD supported patients were matched 1:2 to non-VAD supported controls from the PHTS database. RESULTS Among 109 Berlin Heart IDE study enrollees, 83 were merged with the PHTS database and matched to 166 non-MCS supported patients. There was no difference in diagnosis, status at listing, and age between groups with the expected difference in inotrope use in the non-MCS supported patients. Compared to their matched cohort, there was no statistical difference in 5-year patient survival between VAD and non-VAD patients (81% vs 88%; p = 0.09) nor was there a difference in freedom from rejection or infection. CONCLUSIONS This data suggests that children supported with a Berlin Heart VAD had similar survival, infection and rejection rates compared to those not requiring MCS support. Continued surveillance of the Berlin Heart IDE trial population post heart transplantation is warranted.