Recombinant porcine factor VIII for high-risk surgery in paediatric congenital haemophilia A with high-titre inhibitor

INTRODUCTION

High-titre factor VIII (FVIII) inhibitors complicate peri-operative haemostasis. Recombinant porcine FVIII (r-pFVIII) may provide an alternative haemostatic agent for high-risk procedures and allow FVIII activity monitoring.

AIM

Devise an effective haemostatic plan for repair of a progressively symptomatic aortic coarctation in a 5-year-old male with immune tolerance induction (ITI) refractory high-titre FVIII inhibitors.

METHODS

Preprocedure human FVIII inhibitor titre was 58 Bethesda Units mL^-1 (BU) and cross-reacted to neutralize porcine FVIII at 30 BU. Daily ITI with plasma-derived FVIII concentrate was supplemented with anti-B-cell and anti-plasma cell immunotherapy to reduce FVIII inhibitor titres. Potential haemostatic agents were evaluated in comparative ex vivo thrombin generation assays (TGA).

RESULTS

Four weeks after immunosuppression, human and porcine inhibitor titres declined to 16 and 2 BU respectively. TGA with r-pFVIII was less robust than with activated prothrombin complex concentrate (aPCC); however, r-pFVIII was selected for cardiac surgery to secure the ability to assay FVIII levels throughout this high-bleeding risk procedure. Haemostasis with r-pFVIII was excellent; initial trough FVIII activity levels ranged from 0.81-1.17 IU mL^-1 . On postoperative day 3, peak and trough levels markedly declined suggesting a rising porcine inhibitor titre. Postprocedure prophylaxis was transitioned to aPCC, informed by TGA.

CONCLUSIONS

R-pFVIII provided effective peri-procedural haemostasis with no adverse events. Rapid neutralization of r-pFVIII after the first 60 hours, despite intensive immune suppression, accentuates the importance of careful monitoring. Use of TGA can support bypassing agent selection for convalescence. The comparative cost of r-pFVIII may limit its use to high morbidity clinical scenarios.

Perinatal outcome after prenatal diagnosis of single-ventricle cardiac defects

OBJECTIVES

To investigate the perinatal outcome of cases with a prenatal diagnosis of single-ventricle cardiac defects, single ventricle being defined as a dominant right ventricle (RV) or left ventricle (LV), in which biventricular circulation was not possible.

METHODS

We reviewed patients with a prenatal diagnosis of single-ventricle cardiac defects, made at one institution between 1995 and 2008. Cases diagnosed with double-inlet LV, tricuspid atresia, pulmonary atresia with intact ventricular septum and severe RV hypoplasia and those with hypoplastic left heart syndrome (HLHS) were included in the study population. Patients with HLHS were identified prenatally as being standard risk or high risk (HLHS with highly restrictive or intact atrial septum, mitral stenosis with aortic atresia and/or LV coronary artery sinusoids). Patients with an address over 200 miles from the hospital, diagnosed with heterotaxy syndrome or referred for fetal intervention, were excluded.

RESULTS

We identified 312 cases of single-ventricle cardiac defect (208 dominant RV; 104 dominant LV) that were diagnosed prenatally. Most (96%) patients with a dominant RV had HLHS. Among the total 312 cases there were 98 (31%) elective terminations of pregnancy (TOP), 12 (4%) cases of spontaneous fetal demise, 12 (4%) cases lost to prenatal follow-up and 190 (61%) live births. Among the 199 patients that underwent fetal echocardiography before 24 weeks' gestation, there were 97 (49%) cases of elective TOP. There was no difference in prenatal outcome between those with a dominant RV and those with a dominant LV (P = 0.98). Of the 190 live births, five received comfort care. With an average of 7 years' follow-up (to obtain data on the Fontan procedure), transplantation-free survival was lower in those with a dominant RV than in those with a dominant LV (standard-risk HLHS odds ratio (OR), 3.0 (P = 0.01); high-risk HLHS OR, 8.8 (P < 0.001)).

CONCLUSIONS

The prenatal outcome of cases with single-ventricle cardiac defects was similar between those with a dominant RV and those with a dominant LV, however postnatal intermediate-term survival favored those with a dominant LV. High-risk HLHS identified prenatally was associated with the lowest transplantation-free survival.

Mitral valve chordal rupture masquerades as endocarditis

Mitral valve chordal rupture is often associated with an inciting event. There are very few reported pediatric cases of spontaneous mitral valve chordal rupture. We describe a 9-year-old boy with a history of mitral valve prolapse who developed spontaneous mitral valve chordal rupture without evidence of endocarditis or trauma.