Purpose Aortic dissection (AD) is a catastrophic disease with complex hemodynamic conditions, however, understandings regarding its perfusion characteristics were not sufficient. In this study, a mock circulation loop (MCL) that integrated the Windkessel element and patient-specific silicone aortic phantoms was proposed to reproduce the aortic flow environment in vitro. Materials and Methods Patient-specific normal and dissected aortic phantoms with 12 branching vessels were established and embedded into this MCL. Velocities for aortic branches based on 20 healthy volunteers were regarded as the standardized data for flow division. By altering boundary conditions, the proposed MCL could mimic normal resting and left-sided heart failure (LHF) conditions. Flow rates and pressure status of the aortic branches could be quantified by separate sensors. Results In normal resting condition, the simulated heart rate and systemic flow rate were 60 bpm and 4.85 L/minute, respectively. For the LHF condition, the systolic and diastolic blood pressures were 75.94±0.77 mmHg and 57.65±0.35 mmHg, respectively. By tuning the vascular compliance and peripheral resistance, the flow distribution ratio (FDR) of each aortic branch was validated by the standardized data in the normal aortic phantom (mean difference 2.4%±1.70%). By comparing between the normal and dissected aortic models under resting condition, our results indicated that the AD model presented higher systolic (117.82±0.60 vs 108.75±2.26 mmHg) and diastolic (72.38±0.58 vs 70.46±2.33 mmHg) pressures, the time-average velocity in the true lumen (TL; 36.95 cm/s) was higher than that in the false lumen (FL; 22.95 cm/s), and the blood transport direction between the TL and FL varied in different re-entries. Conclusions The proposed MCL could be applied as a research tool for in vitro hemodynamic analysis of the aorta diseases under various physical conditions.
BackgroundEndovascular repair of type B aortic dissection (TBAD) with aberrant right subclavian artery (ARSA) is challenging due to anatomical complexity. The embedded modular single-branched stent graft (EMSBSG) could solve this problem. However, the hemodynamic efficacy of this innovative technique has not been fully assessed. This study aimed to propose morphometric and functional indicators to quantify the outcomes of EMSBSG in treating TBAD with ARSA.Material and MethodsA patient who had TBAD with ARSA underwent EMSBSG implantation was admitted. Computational fluid dynamics (CFD) and three-dimensional structural analyses were conducted based on CTA datasets before the operation (Pre-1) and at 4 and 25 days after EMSBSG implantation (Post-1 and Post-2). Quantitative and qualitative functional analyses were conducted via pressure-, velocity- and wall shear stress (WSS) -based parameters, such as the luminal pressure difference (LPD), total energy loss, and flow distribution ratio. By precisely registering the aortas at the three time points, parameter variations in the EMSBSG region were also computed to investigate the prognostic improvement after EMSBSG implantation.ResultsThe first balance point of LPD distally shifted to the abdominal aorta in Post-1 by a distance of 20.172 cm, and shifted out of the dissected region in Post-2, indicating positive pressure recovery post EMSBSG. The flow distribution ratios of all aortic arch branches increased after EMSBSG implantation. A positive normal deformation index in the EMSBSG region confirmed true lumen expansion; dominant ARN (area ratio of negative value) of pressure and WSS-based parameters indicated an improved prognosis from Post-1 to Post-2.ConclusionsThe short-term results of EMSBSG in treating TBAD with ARSA proved to be promising, especially in EMSBSG region. Comprehensive evaluation could provide new insight into the therapy of TBAD with ARSA. Thus, it might guide the further management of complex aortic arch lesions.
The design of medical technologies for developing countries is a multidisciplinary process. We describe a model process for an appropriate medical device design. D-Lab Health combines real world projects and partners with a diverse student team to provide experiential educational opportunities in a developing country health care setting; in turn, the partners benefit from student medical device designs. In order to effectively communicate practical design strategies toward an appropriate design for medical technology, a series of accelerated technology learning modules was developed using commercially available and customized medical devices. Each module included a formal framework for the students to think about the competing priorities of the user, chooser, payer, and approver of such global health technologies, christened the “global health innovation compass.” These modules provided a hands-on laboratory experience that demystified the design process. This was particularly useful for nonengineering students who were able to add value to the project through their life-sciences background. An essential component of the course was a week-long visit to our field partners in Nicaragua to enable the students to get first hand experience and to identify a health need they could address with a technology solution. Subsequently, the students utilized their hands-on training to develop medical device prototypes within an abbreviated production schedule of 3 weeks. We describe the design process for one such prototype “a low cost glucometer.”
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