Hemodynamic Study Of Pump-cardiovascular System And Aortic Dissection Using Lumped Parametric Models

The research of the cardiovascular system is a key direction at the intersection of medicine and fluid mechanics.In the field of cardiovascular system simulations,the lumped parameter modeling approach is widely used,with the advantage of being able to describe changes in hemodynamic parameters quantitatively and can quickly perform sensitivity analysis on a single parameter in the system,minimizing the need for complex physical models or in vitro experiments,and providing diagnostics and references for medical research.In this study,based on the analogous relationship between hydrodynamics and electrical networks,the lumped parameter model was used to explore the mechanism of hemodynamic changes in the cardiovascular system and type B aortic dissection.The effects of changes in pumping speed on cardiac output waveforms were investigated,and the hemodynamic characteristics of type B aortic dissection with different rupture characteristics were analyzed based on imaging data.The main contents are described as follows:Using Matlab,the lumped parameter model of the fifth-order cardiovascular system was established,and then the hemodynamic information in line with the physiological norms of the body can be obtained.By varying cardiac preload and afterload values,the model was verified to correctly reflect the pressure-volume changes in the left ventricle during the cardiac cycle.The changes of physiological parameters in heart failure could be simulated by changing the left ventricular volume parameters.Based on the pressure-flow relationship,the cardiac blood pump is coupled in the cardiovascular system,and the coupling model analyzes the compensatory effect of the blood pump on the heart failure state under constant speed operation.Based on increasing the speed linearly by an open-loop control,the critical point of rotational speed in the suction condition can be analyzed when the human body’s motion state changes.Then,the theoretical basis and safety threshold are provided for the control strategy of the blood pump.In the study of B-type aortic dissection,based on the CT scan image data of confirmed cases,Simpleware was applied to establish seven personalized models of B-type aortic dissection with preserved dissection features.Physical parameters,including the length,wall thickness,and cross-sectional area of each segment of the aorta,were measured by extracting the centerline.A statistical analysis of the tear characteristics between the actual and false lumens of aortic dissections was performed to obtain the size of the rupture and the law of relative position on the descending aorta.Statistical results showed that for type B aortic dissection,the tear size distribution was 4～12 mm.The average length between the original tear and the distal tear was 206 mm,and 57% of cases had a single tear entrance and exit.Based on type B aortic dissection data in actual cases,a lumped parameter model of type B aortic dissection with double tears was built through Simulink.A variety of simulation conditions were designed.The hemodynamic parameters in the true lumen and the false lumen,the geometric parameters of the blood vessel,and the biomechanical characteristics of the blood vessel wall were discussed.In the simulation of the aorta segment,the dilation will cause more pronounced changes in aortic blood pressure than elongation.Multiple combinations of tear size were set,and simulations revealed that the tear size affects the pressure gradient between the actual and false lumen,which is an essential factor in tear expansion.The flow and pressure change curve of the false lumen were observed by changing the compliance of the false lumen,which indirectly reflects the relationship between the biomechanical properties of the blood vessel wall and the chronic expansion of the dissection.The hemodynamic parameters in each area of the aorta were simulated when there are multiple tears while the risk indicators of the aortic morphology were further summarized,providing a guide for the grading treatment strategy of clinical patients.