The animated implantation of the aortic heart valve prosthesis

The transcatheter aortic valve implantation is the non-invasive alternative for the open heart surgery . The percutaneous beating heart interventional procedure for The Medtronic product , The CoreValve Revalving System , is 3D animated by Elite Imaging .

The procedure performed under fluoroscopy in the CathLab lasts for up to 2 - 3 hours . The self expanding multilevel frame containing the tri-leaflet porcine pericardial tissue prosthesis is specifically designed for retrograde percutaneous implantation via the 18Fr catheter .

Video 1 . The presentation of the loading procedure for the bioprosthetic valve
into the delivery catheter

If aortic stenosis is present then a single inflation of the valvuloplasty balloon is performed prior to implantation . The delivery system is advanced retrogradely over the guide wire , from the femoral artery , up to the native failing aortic valve . The catheter circular tip frame is positioned in the aortic valve annulus . The external sheath is progresively retracted . The framed valve is deployed , while pushing aside the native valve leaflets . The new prosthesis is securely anchored by the radial force of the self expanding Nitinol frame . It starts functioning immediately during placement .

Video 2 . The presentaton in detail for the implantation procedure
for the bioprosthetic valve

The side of the frame that expands in the ascending aorta optimises the hemodynamics of the blood flow system . The central level of the frame is calcaved to prevent obstruction of and allow access to the coronary artery ostia . The conforming side of the frame towards the annulus minimises the risk of paravalvular leaks . The tri-level aortic framed bioprosthesis provides secure anchoring , without migration , and with natural valve function , ensuring long term valve durability .

The results for the open heart surgery for aortic valve replacement are compared with the ones for the CoreValve Revalving System , for 795 high risk patients , two years after the clinical procedure . The non-invasive method provides improved outcomes and increased quality of life for the patient .

Hybrid bioprosthetic heart valve

The peer - reviewed publication Engineering of a bio – functionalized hybrid off – the – shelf heart valve caught my interest . The growth factor signalling mechanism inside the bioprosthetic heart valve is different from the native valve . The Young ' s modulus quantifies the remodeling behaviour after implantation .

The chosen method to generate the scaffold is the electrospinning of either poly - lactide acid ( PLA ) or equal amounts of it and poly - ethylene glycol dimethacrylate ( PEGdma ) . The performance of the polymeric scaffold is tested under physiological conditions . The blood is assumed to interact with the heart valve leaflet at large amplitude , in a laminar flow , under oscillatory shear stress . The nonlinear flow properties affect the response of the heart valve .

Valvular endothelial and interstitial cells are seeded in the scaffold . The protein configuration is visualised on the cell – seeded polymeric scaffolds using immunofluorescence staining . The cell viability is assessed with 3 - ( 4 , 5 - dimethyl – 2 - thiazolyl ) - 2 , 5 - diphenyl - 2 H - tetrazolium bromide ( MTT assay ) . The cells are compatible with both the PLA and the PEGdma – PLA scaffold . The valvular endothelial cells adhere in a greater amount onto the PEGdma – PLA scaffold than on the one with PLA fibres . The valvular interstitial cells adhere similarly on both polymeric scaffolds . The valvular actin cytoskeleton for both the endothelian and the interstitial cells is more visible in the PEGdma – PLA than in the plain PLA scaffold .

Native porcine aortic valve tissue , unseeded and cell – seeded polymeric scaffolds are analysed using the scanning electron microscopy ( SEM ) . The PLA scaffold has 30 times greater fibre diameter and 1160 times greater pore size than the native leaflet .

The atomic composition of the surfaces is determined using the electron spectroscopy for chemical analysis ( ESCA ) . The comparison of the data is made using literature values for single components . The PLA – PEGdma scaffold has both PLA and PEGdma groups on the analysed surface .

The mechanical properties of both native and polymeric scaffolds are using the atomic force microscopy ( AFM ) . The spongiosa is the softest layer of the native porcine leaflet , with a Young ' s modulus twice as small as the one for the ventricularis and fibrosa layer . The Young ' s modulus of the PLA – PEGdma scaffold is 10 times greater than the ventricularis and fibrosa native layer .

Uniaxial tensile testing provides information regarding the Young ' s modulus , the tensile strength and the elongation values . Both the PLA scaffold and the native leaflet is soft , with similar values for the Young ' s modulus . The computed Young ' s modulus for the PLA – PEGdma scaffold is twice the value for the PLA scaffold . The PLA scaffold is 55 times more expansible than the native leaflet . The tensile strength value is similar for both the PLA and PLA – PEGdma scaffold .

The polarity of the molecules on the surface is detected using the contact angle goniometry technique . The PLA scaffold is highly hydrophobic . The PEGdma scaffold is hydrophilic . The PLA – PEGdma scaffold is highly hydrophilic . The PLA – PEGdma is highly hydrophilic .

The capacity of water - holding of both the native and the polymeric scaffolds is compared . The PLA scaffold has 11 % water intake capacity , the PEGdma scaffold has high value , while the native leaflet has 90 % . The PLA – PEGdma scaffold has 5 times more water intake capacity than the PLA scaffold .

The protein expression patterns are revealed in the early development for the human heart tissue . Collagen type 1 is present in the leaflets , Versican in the atria – ventricular valves and in the outflow tract , in the first trimester of the fetal development . Collagen type 1 is present in the fibrosa layer of the aortic valve , Versican in the leaflet tip and close to the arterial wall , in the second semester of the fetal development . The valvular histoarchitecture in the 19 years old adolescent is similar to the one in the second semester of the fetal development .

The bio – functionalised prosthetic leaflet has PLA – PEGdma scaffold , Collagen type 1 gel layer , and Versican tip , in a proof – of – principle experiment . The polymeric scaffold requires further structural modifications to have a biocompatible material with a set of mechanical properties closer to the one of the human heart valve .

References :

Hinderer S . , Seifert J . , Votteler M . , Shen N . , Rheinlaender J . , Schaffer T . E . , Schenke – Layland K . ( 2014 ) “ Engineering of a bio – functionalized hybrid off – the – shelf heart valve ” , Biomaterials , 35 ( 7 ) , 2130 – 2139 .

Hyun K . , Wilhelm M . , Klein C . O . , Cho K . S . , Nam J . G . , Ahn H. , Lee S . J . , Ewoldt R . H . , McKinley G . H . ( 2011 ) “ Progress in Polymer Science ” , 36 ( 12 ) , 1697 – 1753 .