Paravalvular Leakage(PVL)has been recognized as one of the most dangerous complications in relation to Transcathether Aortic Valve Implantation(TAVI)activities.However,data available in the literature about Fluid Stru...Paravalvular Leakage(PVL)has been recognized as one of the most dangerous complications in relation to Transcathether Aortic Valve Implantation(TAVI)activities.However,data available in the literature about Fluid Structure Interaction(FSI)for this specific problem are relatively limited.In the present study,the fluid and structure responses of the hemodynamics along the patient aorta model and the aortic wall deformation are studied with the aid of numerical simulation taking into account PVL and 100%TAVI valve opening.In particular,the aorta without valve(AWoV)is assumed as the normal condition,whereas an aorta with TAVI 26 mm for 100%Geometrical Orifice Area(GOA)is considered as the patient aorta with PVL complication.A 3D patient-specific aorta model is elaborated using the MIMICS software.Implantation of the identical TAVI valve of Edward SAPIEN XT 26(Edwards Lifes ciences,Irvine,California)is considered.An undersized 26 mm TAVI valve with 100%valve opening is selected to mimic the presence of PVL at the aortic annulus.The present research indicates that the existence of PVL can increase the blood velocity,pressure drop and WSS in comparison to normal conditions,thereby paving the way to the development of recirculation flow,thrombus formation,aorta wall collapse,aortic rupture and damage of endothelium.展开更多
The novel coronavirus responsible for COVID-19 has spread to several countries within a considerably short period.The virus gets deposited in the human nasal cavity and moves to the lungs that might be fatal.As per sa...The novel coronavirus responsible for COVID-19 has spread to several countries within a considerably short period.The virus gets deposited in the human nasal cavity and moves to the lungs that might be fatal.As per safety guidelines by theWorld Health Organization(WHO),social distancing has emerged as one of the major factors to avoid the spread of infection.However,different guidelines are being followed across the countries with regards to what should be the safe distance.Thus,the current work is an attempt to understand the virus deposition pattern in the realistic human nasal cavity and also to find the impact of distance that could be termed as a safety measure.This study is performed usingComputationalFluid Dynamics as a solution tool to investigate the impact of COVID-19 deposition(i)On a realistic 3D human upper airway model and(ii)2D social distancing protocol for a distance of 0.6,1.2,1.8,and 2.4 m.The results revealed that the regional deposition flux within the nasal cavity was predominantly observed in the external nasal cavity and nasopharyngeal section.Frequent flushing of these regions with saltwater substitutes can limit contamination in healthy individuals.The safe distancing limit estimated with 1 m/s airflow was about 1.8 m.The extensive deposition was observed for distances less than 1.8 m in this study,emphasizing the fact that social distancing advisories are not useful and do not take into account the external dynamics associated with airflow.展开更多
Cerebral intracranial aneurysms are serious problems that can lead to stroke,coma,and even death.The effect of blood flow on cerebral aneurysms and their relationship with rupture are unknown.In addition,postural chan...Cerebral intracranial aneurysms are serious problems that can lead to stroke,coma,and even death.The effect of blood flow on cerebral aneurysms and their relationship with rupture are unknown.In addition,postural changes and their relevance to haemodynamics of blood flow are difficult to measure in vivo using clinical imaging alone.Computational simulations investigating the detailed haemodynamics in cerebral aneurysms have been developed in recent times not only to understand the progression and rupture but also for clinical evaluation and treatment.In the present study,the haemodynamics of a patient-specific case of a large aneurysm on the left side internal carotid bifurcation(LICA)and no aneurysm on the right side internal carotid bifurcation(RICA)was investigated.The simulation of these patient-specific models using fluid–structure interaction provides a valuable comparison of flow behavior between normal and aneurysm models.The influences of postural changes were investigated during standing,sleeping,and head-down(HD)position.Significant changes in flow were observed during the HD position and quit high arterial blood pressure in the internal carotid artery(ICA)aneurysm model was established when compared to the normal ICA model.The velocity increased abruptly during the HD position by more than four times(LICA and RICA)and wall shear stress by four times(LICA)to ten times(RICA).The complex spiral flow and higher pressures prevailing within the dome increase the risk of aneurysm rupture.展开更多
基金Universiti Putra Malaysia,for providing funds for this project through Grant UPM GP-IPM/2019/9675000.
文摘Paravalvular Leakage(PVL)has been recognized as one of the most dangerous complications in relation to Transcathether Aortic Valve Implantation(TAVI)activities.However,data available in the literature about Fluid Structure Interaction(FSI)for this specific problem are relatively limited.In the present study,the fluid and structure responses of the hemodynamics along the patient aorta model and the aortic wall deformation are studied with the aid of numerical simulation taking into account PVL and 100%TAVI valve opening.In particular,the aorta without valve(AWoV)is assumed as the normal condition,whereas an aorta with TAVI 26 mm for 100%Geometrical Orifice Area(GOA)is considered as the patient aorta with PVL complication.A 3D patient-specific aorta model is elaborated using the MIMICS software.Implantation of the identical TAVI valve of Edward SAPIEN XT 26(Edwards Lifes ciences,Irvine,California)is considered.An undersized 26 mm TAVI valve with 100%valve opening is selected to mimic the presence of PVL at the aortic annulus.The present research indicates that the existence of PVL can increase the blood velocity,pressure drop and WSS in comparison to normal conditions,thereby paving the way to the development of recirculation flow,thrombus formation,aorta wall collapse,aortic rupture and damage of endothelium.
基金The authors are thankful to the Institute of Research and Consulting Studies at King Khalid University for supporting this research through Grant No.#34-67-S-2020.
文摘The novel coronavirus responsible for COVID-19 has spread to several countries within a considerably short period.The virus gets deposited in the human nasal cavity and moves to the lungs that might be fatal.As per safety guidelines by theWorld Health Organization(WHO),social distancing has emerged as one of the major factors to avoid the spread of infection.However,different guidelines are being followed across the countries with regards to what should be the safe distance.Thus,the current work is an attempt to understand the virus deposition pattern in the realistic human nasal cavity and also to find the impact of distance that could be termed as a safety measure.This study is performed usingComputationalFluid Dynamics as a solution tool to investigate the impact of COVID-19 deposition(i)On a realistic 3D human upper airway model and(ii)2D social distancing protocol for a distance of 0.6,1.2,1.8,and 2.4 m.The results revealed that the regional deposition flux within the nasal cavity was predominantly observed in the external nasal cavity and nasopharyngeal section.Frequent flushing of these regions with saltwater substitutes can limit contamination in healthy individuals.The safe distancing limit estimated with 1 m/s airflow was about 1.8 m.The extensive deposition was observed for distances less than 1.8 m in this study,emphasizing the fact that social distancing advisories are not useful and do not take into account the external dynamics associated with airflow.
文摘Cerebral intracranial aneurysms are serious problems that can lead to stroke,coma,and even death.The effect of blood flow on cerebral aneurysms and their relationship with rupture are unknown.In addition,postural changes and their relevance to haemodynamics of blood flow are difficult to measure in vivo using clinical imaging alone.Computational simulations investigating the detailed haemodynamics in cerebral aneurysms have been developed in recent times not only to understand the progression and rupture but also for clinical evaluation and treatment.In the present study,the haemodynamics of a patient-specific case of a large aneurysm on the left side internal carotid bifurcation(LICA)and no aneurysm on the right side internal carotid bifurcation(RICA)was investigated.The simulation of these patient-specific models using fluid–structure interaction provides a valuable comparison of flow behavior between normal and aneurysm models.The influences of postural changes were investigated during standing,sleeping,and head-down(HD)position.Significant changes in flow were observed during the HD position and quit high arterial blood pressure in the internal carotid artery(ICA)aneurysm model was established when compared to the normal ICA model.The velocity increased abruptly during the HD position by more than four times(LICA and RICA)and wall shear stress by four times(LICA)to ten times(RICA).The complex spiral flow and higher pressures prevailing within the dome increase the risk of aneurysm rupture.
