Hybrid Palliation for Ductal-Dependent Systemic Circulation
Which patients with ductal-dependent systemic circulation (DDSC) may benefit from hybrid palliation?
Since 2007, the sole provider of congenital cardiac care in the state of Nevada had elected to perform hybrid palliation for all patients with DDSC and single ventricles (1V), including hypoplastic left heart syndrome, unbalanced atrioventricular (AV) canals, double outlet right ventricle with left ventricle hypoplasia, as well as high-risk DDSC two-ventricle (2V) patients, including hypoplastic aortic arch with coarctation with or without a ventricular septal defect, interrupted aortic arch, and aortic atresia. Post-procedure monitoring included B-type natriuretic peptide (BNP) and troponin I levels, electrocardiograms to assess for myocardial ischemia, and echocardiography to assess ventricular function, AV valve regurgitation, and Doppler gradients across the atrial septal defect, ductal stent, pulmonary artery band, and aortic isthmus. Hybrid conversion to a Norwood/shunt was performed as necessary, based on clinical status.
This single-center retrospective study analyzed data from 2007-2015, which included all 91 neonates in the state of Nevada with the above diagnoses who had undergone hybrid palliation. A summated risk factor score (RFS) was established for each patient: 2 points were assigned for a birth weight of <2.5 kg, and 1 point each for lung disease, noncardiac malformation or syndrome, atrial septal restriction (gradient >5 mm Hg), coronary artery stenosis or ostial atresia (in those with mitral stenosis and aortic atresia), an aortic isthmus less than -2 z scores by angiography, pulmonary venous abnormalities, and at least moderate AV valve regurgitation or ventricular dysfunction. Low risk (LR) and high risk (HR) 1V patients had a RFS of 0-1 and >1, respectively, while HR2V patients had borderline small left ventricles or a RFS of at least 2.
Of the 91 patients, 22% were 2V, while 35% and 43% were LR1V and HR1V, respectively. Mid-term survival (at least 48 months after initial hybrid) was 100% and 97% for HR2V and LR1V, with 38% survival at interstage 1, and more attrition at interstage 2 for HR1V, for an overall mid-term survival of approximately 15% in the HR1V group. Prenatal diagnosis and survival for all 1V patients improved in the recent era (since 2012). There is an inverse relationship between transplant-free midterm survival and RFS, with a breakpoint at a score of >2.
Initial hybrid palliation for HR2V and LR1V patients with DDSC has excellent mid-term results.
The hybrid palliation, first introduced in the 1990s as a way to avoid neonatal surgery and delay comprehensive open heart surgery until 6 months of age, has become a viable strategy in some centers, although most programs reserve it for HR1V DDSC. Small HR preterm neonates do poorly, and LR1V patients do better, whether they are palliated with the conventional surgical approach or the hybrid procedure. However, expanding the use of hybrid palliation to HR2V patients with DDSC is a novel, nonconventional approach that may be useful in centers that choose to defer neonatal surgery in small, preterm, HR infants. As this approach is utilized by more and more centers, its utility and efficacy, as well as the morbidities and complications of performing interventional procedures in this population, will come to light.
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