Pulmonary Hemodynamics Simulations Before Stage 2 Single Ventricle Surgery: Patient-Specific Parameter Identification and Clinical Data Assessment

Abstract

Single ventricle heart defects involve pathologies in which the heart has only one functional pumping chamber. In these conditions, treatment consists of three staged procedures. At stage 1 pulmonary flow is provided through an artificial shunt from the systemic circulation. Representative hemodynamics models able to explore different virtual surgical options can be built based on pre-operative imaging and patient data. In this context, the specification of boundary conditions is necessary to compute pressure and flow in the entire domain. However, these boundary conditions are rarely the measured variables. Moreover, to take into account the rest of the circulation outside of the three-dimensional modeled domain, a number of reduced order models exist. A simplified method is presented to iteratively, but automatically, tune reduced model parameters from hemodynamic data clinically measured before stage 2 surgery. Patient-specific local hemodynamics around the distal systemic-to-pulmonary shunt anastomosis and the connected pulmonary arteries are also analyzed. Multi-scale models of pre-stage 2 single ventricle patients are developed, including a 3D model of shunt-pulmonary connection and a number of pulmonary arteries. For each pulmonary outlet a total downstream resistance is identified, consistent with measured flow split and pressures. Target pressures such as minimum, maximum or average over one or both lungs are considered, depending on the clinical measurement. When possible, both steady and pulsatile identifications are performed. The methodology is demonstrated with six patient-specific models: the clinical target data are well-matched, except for one case where clinical data were subsequently found inconsistent. Inhomogeneous pressure, swirling blood flow patterns and very high wall shear stress 3D maps highlight similarities and differences among patients. Steady and pulsatile tuning results are similar. This work demonstrates (1) how to use routine clinical data to define boundary conditions for patient-specific 3D models in pre-stage 2 single ventricle circulations and (2) how simulations can help to check the coherence of clinical data, or provide insights to clinicians that are otherwise difficult to measure, such as in the presence of kinks. Finally, the choice of steady vs. pulsatile tuning, limitations and possible extensions of this work are discussed.

Data assimilation and modelling of patient-specific single-ventricle physiology with and without valve regurgitation

“…They can be either coupled with 3D Navier-Stokes models, for e.g. to assist surgical planning (Vignon-Clementel et al, 2010;Baretta et al, 2011;Arbia et al, 2015;Corsini et al, 2014), employed for parameter estimation later used in 3D (Pant et al, 2014), or run independently, for e.g. to assess ranges of variation and the effect of functional parameters that are not easily measurable (Hann et al, 2011;Sughimoto et al, 2013).…”

Hemodynamics of patient-specific aorta-pulmonary shunt configurations

“…There are studies utilizing advanced boundary conditions assigned to 3D vascular geometries that have shunt connections, especially by MOCHA investigators (Esmaily-Moghadam et al, 2015a;Esmaily-Moghadam et al, 2015b;Schiavazzi et al, 2015). Among those, studies with patient specific outlet boundary conditions (Arbia et al, 2015) and a model that predicts the growth of the patient anatomy could also be highlighted. To our knowledge, this present manuscript describes the first truly patient-specific case where the entire anatomical data is acquired from a real patient and a large number of shunt configurations are compared.…”

Invited commentary: Personalized surgical planning by computational and visual methods in 21st‐century medical engineering

“…In the past few decades; however, computer processors and numerical methods have advanced, allowing for the use of CFD in a range of medical applications. Highly detailed patient‐specific models of physiological fluid flows (including cerebrospinal fluid, airflow in the lungs, lymph, and blood) can now be created, computed, and interpreted within hours, and several groups have demonstrated the ability of these techniques to provide meaningful clinical insight 4,5 . Similarly, FSI studies are being leveraged to model surgical tools and techniques to treat cardiovascular pathologies.…”

“…The CFD simulations of various interruption site options were an effective tool to optimize perfusion of all blood vessels. This is meaningful because even minor alterations in angle or length can have a significant impact on the hemodynamics 5 . Finally, the team used surgical field simulations to plan for the ideal angle of approach.…”

“…This is meaningful because even minor alterations in angle or length can have a significant impact on the hemodynamics. 5 Finally, the team used surgical field simulations to plan for the ideal angle of approach. By considering that the traditional approach used in infants may not be ideal in adults, the team substantially improved the thoroughness of their preparation.…”