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OBJECTIVE: The use of contrast agents and high-pulsed fluoroscopy is mandatory for visualization of anatomical landmarks in transcatheter aortic valve implantation (TAVI). Renal failure or iodine intolerance may occur and radiation exposure for the interventional heart team is still remarkable. The use of intravascular ultrasound (IVUS) may provide a precise visualization and may help sparing contrast agent and radiation. The aim of our pilot study was to show feasibility of IVUS guided TAVI in a porcine model.
METHODS: Six pigs, weighing 60 to 70 kg, underwent a transapical TAVI under general anesthesia via median sternotomy. In control animals (n=3), the evaluation of the aortic annulus size was done by root angiography. A 26mm or 29mm TAVI prosthesis were used. Positioning and prostheses-application were done using conventional methods. In the study group (n=3) an 8.5 Fr IVUS catheter (max visualized diameter of 60mm) was inserted into the apex. Annulus size, valve position and the height of the coronary ostia were evaluated before implantation by IVUS. After retraction of the catheter a balloon-expandable prosthesis was implanted. Position of the prosthesis was assessed by IVUS and confirmed with root angiography, as well as in situ after explantation of the heart.
RESULTS: The procedure was successful and the valves could be evaluated in two animals of each group. It was possible to identify anatomical landmarks such as the nadir of the aortic sinus, the commissures, the coronary ostia and the anterior mitral valve leaflet. The annulus size and the height of both ostia can be assessed by IVUS before valve implantation. Both annulus size and the height of the coronary ostia were correctly measured by IVUS. Both valve position and the patency of the coronary ostia could be assessed by post-TAVI IVUS measurement. The results were confirmed both in fluoroscopy and after explantation of the heart.
CONCLUSIONS: IVUS guided TAVI without using contrast agents is feasible, pre- implantation and post- implantation evaluation paves the way towards a contrast-free valve implantation.