Which cardiovascular magnetic resonance planes and sequences provide accurate measurements of branch pulmonary artery size in children with right ventricular outflow tract obstruction?

Children with right ventricular outflow tract obstructive (RVOTO) lesions require precise quantification of pulmonary artery (PA) size for proper management of branch PA stenosis. We aimed to determine which cardiovascular magnetic resonance (CMR) sequences and planes correlated best with cardiac catheterization and surgical measurements of branch PA size. Fifty-five children with RVOTO lesions and biventricular circulation underwent CMR prior to; either cardiac catheterization (n = 30) or surgery (n = 25) within a 6 month time frame. CMR sequences included axial black blood, axial, coronal oblique and sagittal oblique cine balanced steady-state free precession (bSSFP), and contrast-enhanced magnetic resonance angiography (MRA) with multiplanar reformatting in axial, coronal oblique, sagittal oblique, and cross-sectional planes. Maximal branch PA and stenosis (if present) diameter were measured. Comparisons of PA size on CMR were made to reference methods: (1) catheterization measurements performed in the anteroposterior plane at maximal expansion, and (2) surgical measurement obtained from a maximal diameter sound which could pass through the lumen. The mean differences (Δ) and intra class correlation (ICC) were used to determine agreement between different modalities. CMR branch PA measurements were compared to the corresponding cardiac catheterization measurements in 30 children (7.6 ± 5.6 years). Reformatted MRA showed better agreement for branch PA measurement (ICC > 0.8) than black blood (ICC 0.4-0.6) and cine sequences (ICC 0.6-0.8). Coronal oblique MRA and maximal cross sectional MRA provided the best correlation of right PA (RPA) size with ICC of 0.9 (Δ -0.1 ± 2.1 mm and Δ 0.5 ± 2.1 mm). Maximal cross sectional MRA and sagittal oblique MRA provided the best correlate of left PA (LPA) size (Δ 0.1 ± 2.4 and Δ -0.7 ± 2.4 mm). For stenoses, the best correlations were from coronal oblique MRA of right pulmonary artery (RPA) (Δ -0.2 ± 0.8 mm, ICC 0.9) and sagittal oblique MRA of left pulmonary artery (LPA) (Δ 0.2 ± 1.1 mm, ICC 0.9). CMR PA measurements were compared to surgical measurements in 25 children (5.4 ± 4.8 years). All MRI sequences demonstrated good agreement (ICC > 0.8) with the best (ICC 0.9) from axial cine bSSFP for both RPA and LPA. Maximal cross sectional and angulated oblique reformatted MRA provide the best correlation to catheterization for measurement of branch PA's and stenosis diameter. This is likely due to similar angiographic methods based on reformatting techniques that transect the central axis of the arteries. Axial cine bSSFP CMR was the best surgically measured correlate of PA branch size due to this being a measure of stretched diameter. Knowledge of these differences provides more precise PA measurements and may aid catheter or surgical interventions for RVOTO lesions.

Antithrombotic strategies in children receiving long-term Berlin Heart EXCOR ventricular assist device therapy.

BACKGROUND: Thromboembolic events while receiving ventricular assist device (VAD) support remain a significant cause of morbidity and mortality despite standard anti-coagulation and anti-platelet therapies. The use of bivalirudin and epoprostenol infusions as an alternate anti-thrombotic (AT) regimen in pediatric VAD patients was reviewed. METHODS: This was a retrospective record review of 6 pediatric patients (aged ≤17 years) at 2 institutions treated with bivalirudin and epoprostenol infusions while being supported with the Berlin Heart EXCOR (Berlin Heart GmbH, Berlin, Germany) VAD. RESULTS: Six patients (age, 0.8-14 years; weight, 6.7-29.7 kg) were treated. Diagnoses included cardiomyopathy in 2 and congenital heart disease in 4. VAD support was left VAD in 2 and bi-VAD in 4, with duration of support of 21 to 155 days. Three patients required extracorporeal membrane oxygenation before VAD support. Bivalirudin/epoprostenol was used after recurrent thromboses on conventional medication in 3 patients, heparin-induced thrombocytopenia in 2, and in 1 patient considered high risk with a prosthetic mitral valve. The bivalirudin dose was titrated to partial thromboplastin time (PTT) of 1.5- to 2-times baseline (0.1-0.8 mg/kg/hour); the epoprostenol dose was 2 to 10 ng/kg/min. Additional anti-platelet agents included acetylsalicylic acid, dipyridamole, and clopidogrel in 5 patients each. No bleeding complications occurred. One patient sustained a cerebrovascular infarct on therapy, with subsequent complete recovery. No other complications occurred. Five patients underwent successful transplantation, and 1 patient died of multisystem organ failure. CONCLUSIONS: This report provides data on estimated safety and efficacy of bivalirudin and epoprostenol as an AT strategy in pediatric patients on extended VAD support. The short drug half-life and predictable AT response facilitated conversion to standard AT regimens at the time of transplantation (heparin-induced thrombocytopenia-negative patients). These agents should be considered for management of pediatric VAD patients when standard regimens fail.

Fast-track extubation after modified Fontan procedure.

OBJECTIVE: In 2007, we introduced a policy to plan to extubate all patients after a modified Fontan procedure in the operating room. Our objective was to review the feasibility, safety, and clinical outcomes of this approach. METHODS: Patients who underwent a modified Fontan operation between May 2004 and May 2010 were reviewed. RESULTS: Ninety-seven patients underwent a modified Fontan operation (mean age, 3.9 ± 2.2 years; mean weight, 15.1 ± 5.0 kg); 46 patients (47%) were extubated in the operating room (group A). Nineteen patients were extubated in the intensive care unit within 24 hours (group B), and 32 patients had delayed extubation (group C). The 3 groups were not significantly different with respect to preoperative characteristics. Twenty-four hours postoperatively, group A had a lower mean central venous pressure compared with patients in group B or C (13 vs 14 vs 17 mm Hg, respectively, P < .001); a higher base excess (0.4 vs -1.3 vs -3.4, P < .001); a lower fluid balance (234 vs 514 vs 730 mL, P < .001); and a lower inotrope score (4.6 vs 6.7 vs 10.8, P < .001). Group C had a longer median intensive care unit length of stay (2 vs 3 vs 6 nights, P = .01), kept their chest tubes longer (8 vs 9 vs 15 days, P = .001), and had a longer median hospital length of stay (9 vs 11 vs 21 days, P = .001). CONCLUSIONS: Extubation in the operating room after a modified Fontan procedure seems feasible. This approach is associated with improved early postoperative hemodynamics, earlier time to chest tube removal, and shorter intensive care unit and hospital lengths of stay.

Failure of prophylactic intravenous immunoglobulin to prevent sensitization to cryopreserved allograft tissue used in congenital cardiac surgery.

OBJECTIVE: Cryopreserved allograft tissue used in the Norwood procedure for infants with hypoplastic left heart syndrome causes profound immunologic sensitization, which may complicate future transplantation. Intravenous immunoglobulin has been shown to reduce sensitization after it has developed, allowing successful transplantation. The purpose of this pilot trial was to determine whether intravenous immunoglobulin given before and after the procedure could prevent sensitization to cryopreserved allograft patches used in the initial repair of hypoplastic left heart syndrome. METHODS: Intravenous immunoglobulin (2 g/kg) was given preoperatively, 3 weeks postoperatively, and 4 months postoperatively to 7 infants undergoing the Norwood procedure. Panel-reactive antibodies were measured with flow cytometry preoperatively and at 1, 4, 6, and 12 months postoperatively and compared with values from a contemporary cohort of 12 infants undergoing the Norwood procedure who did not receive intravenous immunoglobulin. RESULTS: The groups were well matched for length and weight at time of surgery. Control infants were somewhat younger than the cohort receiving intravenous immunoglobulin (8 +/- 5 vs 17 +/- 14 days, P = .021). There were no differences in transfusion requirements. There was no difference in the degree of sensitization between control and intravenous immunoglobulin groups at 1 month (class I panel-reactive antibodies 20% +/- 30% vs 4% +/- 9%, P = .443, class II panel-reactive antibodies 17% +/- 27% vs 20% +/- 17%, P = .400), 4 months (class I panel-reactive antibodies 62% +/- 40% vs 73% +/- 41%, P = .813, class II panel-reactive antibodies 49% +/- 42% vs 54% +/- 41%, P = .706), and 12 months (class I panel-reactive antibodies 49% +/- 42% vs 58% +/- 39%, P = .686, class II panel-reactive antibodies 44% +/- 36% vs 49% +/- 42%, P = .651). CONCLUSION: Despite studies showing intravenous immunoglobulin to reduce sensitization, we were unable to demonstrate that intravenous immunoglobulin prevented sensitization after exposure to allograft tissue in neonates undergoing congenital cardiac surgery.

Percutaneous coronary intervention for extrinsic coronary compression after pulmonary valve replacement.

Coronary artery compression is a rare and potentially fatal complication after pulmonary valve replacement. This report describes myocardial infarction from extrinsic left main coronary artery compression after pulmonary valve replacement in a 10-y-old boy. He was successfully treated with percutaneous coronary intervention.

Use of an allograft patch in repair of hypoplastic left heart syndrome may complicate future transplantation.

OBJECTIVE: Cryopreserved allograft tissue used in the Norwood procedure for infants with hypoplastic left heart syndrome (HLHS) has the potential to cause marked immunologic sensitization which may complicate potential future heart transplantation, if required. The purpose of this study was to assess the anti-HLA antibody response to allograft patches used in the initial repair of HLHS. METHODS: A prospective cohort study was conducted comparing the panel-reactive antibody levels (PRA) in 12 infants undergoing repair of HLHS with cryopreserved allograft patch to 10 infants undergoing arterial switch for transposition of the great arteries (no allograft tissue used). PRA for Class I (HLA-A, B, C) and Class II (HLA-DR, DQ) antibodies were assessed preoperatively and postoperatively using flow cytometry. RESULTS: The two groups were well matched at the time of surgery (age, weight, gender). Infants in both groups received blood from multiple donors; however, the allograft group received significantly more (12+/-10 vs. 5+/-1 units; P<0.001). By 4 months, most infants receiving allograft tissue had become highly sensitized for both Class I PRA (62+/-40 vs. 0; P=0.002) and Class II PRA (49+/-42 vs. 2+/-3; P=0.022). This response continued to increase at 12 months: Class I PRA (79+/-21 vs. 0; P=0.008) and Class II PRA (66+/-27 vs. 5+/-6; P=0.008). Specificity analysis confirmed antibodies were specific for the donor allograft HLA type. In addition, infants who were coincidently HLA-matched with their allograft did not develop an elevated PRA. CONCLUSIONS: Allograft tissue used in the repair of HLHS is associated with profound donor specific immunologic sensitization in the majority of recipients and may complicate or jeopardize future transplantation. Methods to reduce the immunogenicity of cryopreserved allograft tissue used for arch reconstruction requires further investigation.

Transcatheter closure of the patent ductus arteriosus.

Patent ductus arteriosus (PDA) is one of the most common congenital heart defects. Although surgery is still required in symptomatic neonates, the majority of older infants and children can undergo safe and effective transcatheter device closure on an out-patient basis. First described in 1967, over the past four decades, numerous devices have been specifically developed for this purpose. This article will review the current status of transcatheter therapy. The experience with each device is detailed and issues and controversies are reviewed.

Balloon dilation and stent implant through the side of a previously placed intravascular stent: a new option for the interventionalist.

Intravascular stent placement for relief of vascular stenoses often requires that a stent be positioned across the origin of side-branch vessels. Most currently available peripheral vascular stents have a closed-cell design that will not allow catheter manipulation, dilation, or stenting through the stent cells. Therefore, if a side branch arising off a previously stented vessel is stenotic or if its origin has been compromised, transcatheter dilation of the branch vessel has not been possible. We report a series of successful balloon dilation and stent placement through the sides (cells) of previously placed IntraStent DoubleStrut LD stents in the aortic arch and abdominal aorta of pigs.

Initial experience with intratherapeutics Intrastent Doublestrut LD stents in patients with congenital heart defects.

Limitations of the currently available balloon-expandable stainless steel (BE-SS) stents for use in patients with congenital heart defects (CHD) include inflexibility, significant shortening with expansion, sharp ends, and limited sizes. These limitations increase risk and greatly effect success of stent placement in these patients. The recently approved IntraStent DoubleStrut LD (IS-LD) stents are BE-SS stents designed to address such limitations. We report our initial experience with IS-LD stents in patients with CHD. Using standard techniques, 36 stents were implanted in 22 patients whose median age was 11 years (range, 1.4-35 years) and weight was 33 kg (range, 9-96.8 kg). Lesions stented included aortic coarctation (4), branch pulmonary arteries (19), inferior or superior vena cava (11), Mustard baffle (1), and Fontan baffle (1). All attempts at stent placement were successful. Hemodynamic assessment and angiography was performed pre- and poststent placement in all patients. Intravascular ultrasound was performed in four patients. Stenosis diameter increased from 5.7 +/- 0.6 mm (mean +/- SD) to 11.6 +/- 0.5 mm (P < 0.001). Stents did not shorten significantly with dilation (median percent shortening, 3.8%; P > 0.1). Complications included stent recoil (2), stent migration (1), and stent distortion (1). IS-LD stents are a safe and effective treatment for the majority of vascular stenoses in patients with CHD. Stent recoil at large diameters may limit its usefulness in selected lesions. Follow-up studies are required to determine the long-term performance of IS-LD stents.