THE USE OF A TRANSCATHETER AORTIC VALVE TO REPLACE A DEFECTIVE AORTIC VALVE WITHOUT OPEN-HEART SURGERY Natalie Garda and Adam Cotter Heart disease is the leading cause of death in America, killing over 610,000 people a year [1]. Many of these deaths are contributed to a condition called aortic stenosis, which causes narrowing and calcification of the aortic valve as well as obstruction of blood flow [2]. An image of a normal versus a stenotic aortic valve is shown below in figure 1. FIGURE 1 [2] Normal aortic valve (left) and Stenotic aortic valve (right) TRANSCATHETER AORTIC VALVE IMPLANTATIONS (TAVIs) Transcatheter Aortic Valve Implantations (TAVIs) are biomedical- engineered devices that replace the biological function of the aortic heart valve without the need for an open heart surgery [3]. This valve is inserted in a minimally invasive manner through one of four arteries and only requires an incision in the more superficial layers of tissue [4]. The four different access points/arteries are shown in figure 2 and the advantages and disadvantages of each point are outlined in the chart below. FIGURE 2 [2] CHART 1 [5] TAVI Access Points Due to the fact that the transfemoral artery is the easiest to access and requires the least invasive procedure, the transfemoral approach tends to be the optimal choice [4[. THE SAPIEN AND THE COREVALVE Currently, two different types of TAVIs are commercially available for patient use. These two types include a balloon expandable model (Edwards SAPIEN) and a self-expandable model (MedTronic CoreValve) [6]. These two models are displayed in figure 3 FIGURE 3 [7] The Edwards SAPIEN device consists of a balloon inside of a stainless steel stent, all attached to a delivery catheter. The framework of the device is a tube with three attachment posts, all connected by beams arranged in a zigzag pattern for optimal support [14]. In addition, exactly like a human aortic valve, this artificial implant consists of three leaflets composed of bovine pericardium as a replacement for human tissue [7]. The MedTronic CoreValve also consists of three leaflets, however they are made from bovine pericardium. The difference between the SAPIEN and the CoreValve is that the latter is composed of a material called Nitinol which allows for self-expansion within the body. The Nitinol material is much more elastic and flexible than the stainless steel in the SAPIEN, which gives it its self- expanding ability [7]. TRANSAORIC VALVE IMPLANTATION (TAVI) VERSUS SURGICAL AORTIC VALVE REPLACEMENT (SAVR) No matter which device is used, the procedure remains generally the same. The only difference between the two devices is that, once into place in the aortic valve, a balloon has to be removed along with the catheter for the SAPIEN, but not for the CoreValve. In addition, there are no notable statistically differences between the use of one device over the other in patient trials [8]. Compared to open-heart surgery, referred to as surgical aortic valve replacement (SAVR), there are major statistical differences. Overall, there is more than a nineteen percent difference in mortality rate between the two procedures, which favors TAVI. There is also a thirteen percent difference in the need for a blood transfusion, again favoring TAVI. However, with the used of TAVI, the likelihood of having a stroke is two and a half times that for SAVR patients [3]. SUSTAINABILITY Over one third of the cases of aortic stenosis that are seen and reported by doctors are inoperable and require alternative measures. This means that by 2050, over 400,000 people per year will require an alternative method such as TAVI in order to replace a damaged aortic valve [3]. These statistics support the fact that TAVIs are vital and sustainable devices in the medical environment as they would provide an increased quality of life for hundreds of thousands of patients worldwide. The self-expanding Medtronic CoreValve (a) and the balloon- expandable Edwards SAPIEN (b) REFERENCES [ 1] CDC Division for Heart Disease and Stroke Prevention. (2015, February 19). “Heart Disease Fact Sheet.” Centers for Disease Control and Prevention. (Online Article). disease.htm [5] disease.htm [2]Medtronic. (2014, April). “CoreValve Transcatheter Aortic Valve Replacement (TAVR) Platform Patient Brochure.” CoreValve Procedure. (Online slideshow). cardio/documents/documents/corevalve_patient_booklet.pdf cardio/documents/documents/corevalve_patient_booklet.pdf [3] A. Pedersen. (2011, November 2). "FDA Approves First Catheter-Based Artificial Heart Valve in the U.S." U.S. Food and Drug Administration. (Online article). ents/ucm htm ents/ucm htm [4] S. Stortecky, C. J. O’Sullivan, L. Buellesfeld, et al. (2013, September 10). “Transcatheter Aortic Valve Implantation: the Transfemoral Access Route is the Default Access.” EuroIntervention. (Online article). pp. S14–S18 [5] “Sternotomy.” (2015). Cardiothoracic Surgery University of Southern California. (Image). sternotomy.htmlhttp:// sternotomy.html [6] Blue Cross Blue Shield (2015, January). “Transcatheter Aortic Valve Implantation for Aortic Stenosis.” Protocol. (Online article). Provider/Protocols/T/prov_prot_ pdf Provider/Protocols/T/prov_prot_ pdf [7] S. Tzamtzis, J. Viquerat, J. Yap, et al. (2013, January). “Numerical Analysis of the Radial Force Produced by the Medtronic-Corevalve and Edwards-SAPIEN after Transcatheter Aortic Valve Implantation (TAVI).” M edical Engineering & Physics. (Online article) pp pp [8] A. Chieffo, G. L. Buchanan, N. M. Van Mieghem, et al. (2013, February 26). “Transcatheter Aortic Valve Implantation with the Edwards SAPIEN versus the Medtronic CoreValve Revalving System Devices.” Journal of the American College of Cardiology. (Online article) pp pp

REFERENCES [ 1] CDC Division for Heart Disease and Stroke Prevention. (2015, February 19). “Heart Disease Fact Sheet.” Centers for Disease Control and Prevention. (Online Article). [5] [2]Medtronic. (2014, April). “CoreValve Transcatheter Aortic Valve Replacement (TAVR) Platform Patient Brochure.” CoreValve Procedure. (Online slideshow). [3] A. Pedersen. (2011, November 2). "FDA Approves First Catheter-Based Artificial Heart Valve in the U.S." U.S. Food and Drug Administration. (Online article). [4] S. Stortecky, C. J. O’Sullivan, L. Buellesfeld, et al. (2013, September 10). “Transcatheter Aortic Valve Implantation: the Transfemoral Access Route is the Default Access.” EuroIntervention. (Online article). pp. S14–S18 [5] “Sternotomy.” (2015). Cardiothoracic Surgery University of Southern California. (Image). [6] Blue Cross Blue Shield (2015, January). “Transcatheter Aortic Valve Implantation for Aortic Stenosis.” Protocol. (Online article). [7] S. Tzamtzis, J. Viquerat, J. Yap, et al. (2013, January). “Numerical Analysis of the Radial Force Produced by the Medtronic-Corevalve and Edwards-SAPIEN after Transcatheter Aortic Valve Implantation (TAVI).” Medical Engineering & Physics. (Online article). pp pp [8] A. Chieffo, G. L. Buchanan, N. M. Van Mieghem, et al. (2013, February 26). “Transcatheter Aortic Valve Implantation with the Edwards SAPIEN versus the Medtronic CoreValve Revalving System Devices.” Journal of the American College of Cardiology. (Online article). pp pp

 THE SAPIEN AND THE COREVALVE  Currently, two different types of TAVIs are commercially available for patient use. These two types include a balloon expandable model (Edwards SAPIEN) and a self-expandable model (MedTronic CoreValve) [12]. These two models are displayed in figure 3  The Edwards SAPIEN device consists of a balloon inside of a stainless steel stent, all attached to a delivery catheter. The framework of the device is a tube with three attachment posts, all connected by beams arranged in a zigzag pattern for optimal support [14]. In addition, exactly like a human aortic valve, this artificial implant consists of three leaflets composed of bovine pericardium as a replacement for human tissue [14].  The MedTronic CoreValve also consists of three leaflets, however they are made from bovine pericardium. The difference between the SAPIEN and the CoreValve is that the latter is composed of a material called Nitinol which allows for self-expansion within the body. The Nitinol material is much more elastic and flexible than the stainless steel in the SAPIEN, which gives it its self-expanding ability.