Validation of numerical flow simulations against in vitro phantom measurements in different type B aortic dissection scenarios

An aortic dissection (AD) is a serious condition defined by the splitting of the arterial wall, thus generating a secondary lumen [the false lumen (FL)]. Its management, treatment and follow-up are clinical challenges due to the progressive aortic dilatation and potentially severe complications during follow-up. It is well known that the direction and rate of dilatation of the artery wall depend on haemodynamic parameters such as the local velocity profiles, intra-luminal pressures and resultant wall stresses. These factors act on the FL and true lumen, triggering remodelling and clinical worsening. In this study, we aimed to validate a computational fluid dynamic (CFD) tool for the haemodynamic characterisation of chronic (type B) ADs. We validated the numerical results, for several dissection geometries, with experimental data obtained from a previous in vitro study performed on idealised dissected physical models. We found a good correlation between CFD simulations and experimental measurements as long as the tear size was large enough so that the effect of the wall compliance was negligible.Postprint (published version

A web-based tool for cardiac dyssynchrony assessment on ultrasound data

Comunicació presentada al congrés Eurographics Workshop on Visual Computing for Biology and Medicine que va tenir lloc el 7 i 8 de setembre a Bremen, Alemanya.Cardiac resynchronization therapy (CRT) is a broadly used therapy in patients that suffers from heart failure (HF). The positive outcome of CRT depends strongly on the parameters criteria used to select patients and a lot of research has been done to introduce new and more reliable parameters. In this paper we propose an interactive tool to perform visual assessment and measurements on cardiac ultrasound images of patient with cardiac dyssynchrony. The tool is developed as a web application, allowing doctors to remotely access images and measurements.The authors acknowledge the European Union’s Seventh Framework Programme for research, technological development and demonstration (VP2HF FP7-2013-611823 and MEDIA FP7- HEALTH- 2010-261409), the Spanish Ministry of Economy and Competitiveness (TIN2012-35874) and the Maria de Maeztu Units of Excellence Programme (MDM-2015-0502)

A web-based tool for cardiac dyssynchrony assessment on ultrasound data

Comunicació presentada al congrés Eurographics Workshop on Visual Computing for Biology and Medicine que va tenir lloc el 7 i 8 de setembre a Bremen, Alemanya.Cardiac resynchronization therapy (CRT) is a broadly used therapy in patients that suffers from heart failure (HF). The positive outcome of CRT depends strongly on the parameters criteria used to select patients and a lot of research has been done to introduce new and more reliable parameters. In this paper we propose an interactive tool to perform visual assessment and measurements on cardiac ultrasound images of patient with cardiac dyssynchrony. The tool is developed as a web application, allowing doctors to remotely access images and measurements.The authors acknowledge the European Union’s Seventh Framework Programme for research, technological development and demonstration (VP2HF FP7-2013-611823 and MEDIA FP7- HEALTH- 2010-261409), the Spanish Ministry of Economy and Competitiveness (TIN2012-35874) and the Maria de Maeztu Units of Excellence Programme (MDM-2015-0502)

Assessment of wall elasticity variations on intraluminal haemodynamics in descending aortic dissections using a lumped-parameter model

Descending aortic dissection (DAD) is associated with high morbidity and mortality rates. Aortic wall stiffness is a variable often altered in DAD patients and potentially involved in long-term outcome. However, its relevance is still mostly unknown. To gain more detailed knowledge of how wall elasticity (compliance) might influence intraluminal haemodynamics in DAD, a lumped-parameter model was developed based on experimental data from a pulsatile hydraulic circuit and validated for 8 clinical scenarios. Next, the variations of intraluminal pressures and flows were assessed as a function of wall elasticity. In comparison with the most rigid-wall case, an increase in elasticity to physiological values was associated with a decrease in systolic and increase in diastolic pressures of up to 33% and 63% respectively, with a subsequent decrease in the pressure wave amplitude of up to 86%. Moreover, it was related to an increase in multidirectional intraluminal flows and transition of behaviour as 2 parallel vessels towards a vessel with a side-chamber. The model supports the extremely important role of wall elasticity as determinant of intraluminal pressures and flow patterns for DAD, and thus, the relevance of considering it during clinical assessment and computational modelling of the disease.This study was partially supported by the Subprograma de Proyectos de Investigación en Salud (FIS), Instituto de Salud Carlos III, Spain (ref. PI108/0608, PI11/01709); the Programa de ayudas destinadas a universidades, centros de investigación y fundaciones hospitalarias para la contratación de personal investigador novel (FI-DGR 2011), Spain; and the EU FP7 for research, technological development and demonstration under grant agreement VP2HF (no 611823)

Understanding the aortic isthmus Doppler profile and its changes with gestational age using a lumped model of the fetal circulation

Objective: The aortic isthmus (AoI) blood flow has a characteristic shape with a small end-systolic notch observed during the third trimester of pregnancy. However, what causes the appearance of this notch is not fully understood. We used a lumped model of the fetal circulation to study the possible factors causing the end-systolic notch and the changes of AoI flow through gestation. Methods: A validation of the model was performed by fitting patient-specific data from two normal fetuses. Then, different parametric analyses were performed to evaluate the major determinants of the appearance of the end-systolic notch. The changes in the AoI flow profile through gestation were assessed. Results: Our model allows to simulate the AoI waveform. The delay in the onset of ejection together with the longer ejection duration of the right ventricle are the most relevant factors in the origin of the notch. It appears around 25 weeks of gestation and becomes more pronounced with advancing gestation. Discussion: We demonstrated that the end-systolic notch on the AoI flow occurs mainly as a result of a delayed and longer ejection of the right ventricle. Our findings improve the understanding of hemodynamic changes in the fetal circulation and the interpretation of clinical imaging.This study was partly supported by grants from Ministerio de Economia y Competitividad (ref. SAF2012-37196, TIN2014-52923-R); the Instituto de Salud Carlos III (ref. (PI11/01709, PI12/00801, PI14/00226) integrado en el Plan Nacional de I+D+I y cofinanciado por el ISCIII-Subdirección General de Evaluación y el Fondo Europeo de Desarrollo Regional (FEDER) “Otra manera de hacer Europa”; the 1 EU FP7 for research, technological development and demonstration under grant agreement VP2HF (no 611823); The Cerebra Foundation for the Brain Injured Child (Carmarthen, Wales, UK); Obra Social "la Caixa” (Barcelona, Spain); Fundació Mutua Madrileña and Fundació Agrupació Mutua (Spain) and AGAUR 2014 SGR grant nº 928 (Barcelona, Spain). P.G.C. was supported by the Programa de Ayudas Predoctorales de Formación en investigación en Salud (FI12/00362) from the Instituto Carlos III, Spain. M.C.L. and B.V.A. wish to express her gratitude to the Mexican National Council for Science and Technology (CONACyT, Mexico City, Mexico) for supporting her predoctoral stay at Hospital Clinic, Barcelona, Spain

Relative root square mean error (rRMSE) between predicted and measured pressures at the proximal and distal tears, for each scenario.

<p><i>TL</i>, True lumen; <i>FL</i>, False lumen</p><p>Relative root square mean error (rRMSE) between predicted and measured pressures at the proximal and distal tears, for each scenario.</p

Intraluminal pressure indexes with changes in Young’s modulus.

<p>Values of predicted true (TL) and false lumen (FL) systolic pressure (SP), diastolic pressure (DP) and pulse pressure (PP), computed for different values of Young’s modulus for scenarios <i>S_4,4</i> and <i>S_10,10</i>. The value of <i>E = E^ref</i> corresponds to the reference Young’s modulus of the lumen wall, resulting from the calibration of the computational model to the experimental one.</p

Estimated parameters’ values of the lumped-parameter model.

<p><i>PT</i>: proximal tear; <i>DT</i>: distal tear; <i>TL</i>: true lumen; <i>FL</i>: false lumen; <i>PH</i>: peripheral</p><p>Estimated parameters’ values of the lumped-parameter model.</p

Experimental versus predicted intraluminal pressures and velocities across the tears.

<p>Comparison at the proximal and distal sites of the model, for scenarios <i>S_4,4</i> and <i>S_10,10</i>. Doppler positive velocities are directed from the TL to the FL and negative velocities the other way around.</p

Proposed experimental representation of a clinical aortic dissection and its equivalent lumped-parameter model.

<p>(a) Clinical appearance of a descending aortic dissection in the longitudinal plane. Transversal plane showing the distinction between TL and FL (Bottom right) (b-c) Proposed anatomic representation of a descending aortic dissection. Longitudinal diagram of the experimental model (b) and cross-sectional plane of the dissected segment (c). (d) Schema of the lumped-parameter model. The dissected region was modelled as two parallel compartments communicated by resistances (rigid tears). Dashed lines enclose the different compartments of the model: Proximal tear (PT), false lumen (FL), true lumen (TL), distal tear (DT) and peripheral (PH) bed.</p