Balloon Valvuloplasty to Predict X-ray Projection Angles that are Perpendicular to Cardiovascular Structures: A TAVI Patient Feasibility Study

Objectives: The purpose of this work is to describe methods to measure the 3D angular orientation of cardiovascular structures based on a planar image of a valvuloplasty balloon. These methods facilitate X-ray beam alignment with respect to the anatomy of interest. Background: X-ray beam projections which are perpendicular to the long axis of cardiovascular structures are required to support interventional procedures, including transcatheter aortic valve implant (TAVI). Methods: During the TAVI procedure, the 3D angular orientation of the LVOT of 10 patients was measured from a single planar image of an aortic valvuloplasty balloon and the continuous range of X-ray projection angles which are aligned with the aortic valve plane were calculated (research method). Misalignment of the X-ray beam and TAVI valve frame was measured from images of the deployed valve. The accuracy of the research method was compared to clinical standard method to determine appropriate X-ray projection angles, which utilized CT and aortography. Results: Using the clinical standard method, the median misalignment of the X-ray beam and TAVI valve frame was 8.6° (range 2.6° to 21°). Misalignment was reduced to 2.5° (range 0° to 10°) using the research method. Conclusions: The 3D angular orientation of cardiovascular structures can be measured accurately from a single X-ray projection image of a known cardiovascular device contained within the anatomy of interest. For TAVI procedures, improved X-ray beam alignment may help facilitate procedural success.