Transcatheter Aortic Valve Implantation (TAVI)
Aortic valve stenosis is a severe complication which, if left untreated, can be fatal. Therefore, transcatheter aortic valve implantation (TAVI) has become the preferred treatment option for patients suffering from aortic valve stenosis who are at intermediate or high risk of complications from the traditional open-heart surgery. Although TAVI has matured drastically over the last decade or so, some significant post-surgical TAVI complications are attributed to altered hemodynamics due to this procedure. Such complications include valvular thrombosis, paravalvular flow, device migration and obstruction of blood flow to the coronary arteries. These complications require expensive medical reintervention(s) and present a very traumatic experience for the patients and, as such, must be avoided as much as possible.
While planning for TAVI, Physicians typically rely on data and observation made using echocardiography, computed tomography (CT), and magnetic resonance imaging (MRI). However, such techniques cannot predict the risk of developing the above-mentioned post-surgical complications. One of the most effective ways of predicting post-TAVI complications’ is through clinically realistic fluid-structure interaction (FSI) simulations. Patient-specific FSI simulations for TAVI start with the precise geometry of the aortic root (which can be extracted relatively quickly from the CT and MRI data) and the TAVI device. The second critical requirement for these simulations is the accurate boundary conditions that can be obtained from the echocardiography data. Once this data is obtained, TAVI FSI simulations can be performed relatively easily to obtain a detailed insight into the post-surgical hemodynamic environment within the aortic root.
Apart from a qualitative overview of the blood flow patterns in the aortic root, FSI simulations can also quantify fundamental quantities of interest, such as wall shear stress (WSS). For example, it is now well established that blood platelets, which plays a crucial role in the thrombosis cascade, get activated by high WSS. When these activated blood platelets reside for a long time in regions of low WSS, they initiate thrombus formation. Hence, if the detailed post-TAVI WSS patterns are available to the physicians, they can potentially predict the risk of developing post-surgical valvular thrombus. It is also worth mentioning that such FSI simulations can also be used during the planning phase to compare the hemodynamic efficacy of different devices, such as Edwards Sapien, Medtronic CoreValve, and pick the one with the best overall performance, as decided by the physicians. In summary, FSI simulations can facilitate an era of personalized cardiac surgeries such as TAVI by creating a digital avatar for a patient where physicians can perform virtual surgeries and predict the likely outcome of the surgical procedure.
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