Theodore Blake MD, Presenter: Research support, Siemens AG Research support, Employee, General Electric Company

Catherine Dao MD, Abstract Co-Author: Nothing to Disclose

Franz Edward Boas MD, PhD, Abstract Co-Author: Nothing to Disclose

William Fearon MD, Abstract Co-Author: Nothing to Disclose

D. Craig Miller, Abstract Co-Author: Nothing to Disclose

Dominik Fleischmann MD, Abstract Co-Author: Research support, Siemens AG Research support, General Electric Company

Angiographic viewing angles for device deployment during transcatheter aortic valve repair (TAVR) can be derived from CT data. Not all predicted angles can used during the procedure, however, and potential errors due to patient rotation have not been assessed. We propose a simple calculation of viewing angles based on the 3D orientation of the aortic anulus axis, which can be interactively corrected for patient rotation in the procedure room.

CT datasets of 81 patients with severe aortic stenosis were retrospectively reviewed. The anulus plane was identified by aligning the nadirs of the three sinuses of Valsalva at the level of the valve hinges. The aortic anulus axis is described by its (LAO/RAO) rotation angle (ϴa) in the transverse plane and the vertical (CRA/CAU) tilt angle (ϕa) relative to the transverse plane. Patient rotation on the CT table was assessed using fluoroscopically amenable anatomic landmarks (sternum and to spinous process). The optimal angiographic deployment angles are calculated as the C-arm coordinates (ϴ, ϕ) perpendicular to the anulus axis and are given by: (ϕ = -(ϕa/|ϕa|)sin-1[{cosϕacos(ϴ - ϴa)}/√{cos2ϕa cos2(ϴ - ϴa) + sin2 ϕa}]).

In general the anulus axis (corrected for patient rotation) is oriented to the right, superiorly and slightly anteriorly or posteriorly, with a wide range: RAO 103° ±12° (range 68°-129°), CRA 45° ± 9° (range, 22°-69°). Patient rotation on the CT table was on average ±4°, but ranged from -9° to 22°. Optimal viewing angles can be calculated and updated instantaneously and displayed as a table and in graphical format on the monitor bank in the treatment suite.

In patients with severe aortic stenosis, the range of aortic anulus angles can vary greatly due to increased tortuosity of the thoracic aorta. A complete range of orthogonal viewing angles, corrected for patient rotation can be calculated instantaneously from the 3D orientation of the anulus axis during the procedure.

This simple spread-sheet based calculation allows calculation and instantaneous correction of CT based deployment angles;in the procedure room for patients undergoing TAVR.

Blake, T, Dao, C, Boas, F, Fearon, W, Miller, D, Fleischmann, D, CT-based Instantaneous Calculation of Viewing Angles for Device Deployment in Patients Undergoing Transcatheter Aortic Valve Replacement (TAVR).  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12037392.html