Congenital heart disease occurs in one in 150 live births. Hypoplastic Left Heart Syndrome (HLHS), one of the most complex such defects, occurs in 4 to 5 percent of such infants. This proposal focuses on the novel Hybrid Norwood (HN) strategy which has emerged as an alternative first intervention for neonates with HLHS. The HN is a less invasive procedure that provides numerous surgical advantages over the conventional method, such as avoiding cardiopulmonary bypass during neonatal period. Our team has been successful in developing an in-house multi-scale computational fluid dynamics (CFD) model to elucidate the resulting complex and far from intuitive hemodynamics applied to a synthetic geometry representative of a neonate undergoing Hybrid Norwood palliation.
Specific Aims - Having proven our methodology to this initial case our present focus is to expand and evolve our current model to address the following specific aims: 1. Develop a patient-specific geometry simulation and establish the effects on coronary, pulmonary, and carotid blood flow of various degrees of distal aortic arch obstruction proximal to the ductus arteriosus stenting. 2. Explore the patient-specific HN topologies to identify an optimal size and possible placement of the reverse BT shunt that provides an increase in coronary and carotid circulation and mitigates the abnormal wall stresses, stagnation zones, and anomalous flow. 3. Develop a HN topology case incorporating the use of Fluid Structure Interaction to study the effect of vascular hyper-elastic compliance on hemodynamics and ventricular performance. A comparison of results from aims 1 and 2 to previous computations based on a synthetic HN topology will be made and results from aim 3 will pave the way for the future research of our group in state-of-the-art cardiovascular procedure simulations that eventually will become an invaluable step in surgical planning. Methods - It is proposed to utilize a multi-scale computational model of the HN circulation with the implementation of a patient-specific MRI-derived geometry to address critical issues outlined in the specific aims. Subsequently, vascular and shunt compliance will be fully modeled as "fluid-structure interaction" (FSI): the flow field is resolved by the finite volume method and provides the stress loads that result in the mechanical response of the compliant vessel walls that will be calculated by the finite element method. Compliance is accounted for via empirical stress-strain relationship of the vessels and shunt. The full modeling of compliant vessels has not been accounted for in prior CFD studies of the Norwood circulation, and this is a novelty of the proposed work.
Our goal is to develop a computational tool that can explain the complex blood flow prior to and resulting from interventions that treat cardiovascular disease. In the future, as our methods evolve, we would like to provide surgeons with an invaluable surgical planning tool that will afford virtual what-if scenarios. This capability will llow the surgeon to tailor the procedure, and thereby increase the probabilities of its success, before stepping into the operating room on a patient-to-patient basis.