Pre-procedural CT scans can predict optimal angiographic deployment projections for transcatheter aortic valve implantation (TAVI), according to a study in the November issue of the Journal of the American College of Cardiology: Cardiovascular Interventions.
Accurate device positioning during TAVI depends on valve deployment in angiographic projections perpendicular to the native valve plane, but these may be difficult to determine, the authors wrote. "If one or more of the aortic leaflets is 'off-axis,' accurate positioning is difficult to achieve, increasing the risk of malposition, embolization and procedural complications," they said.
To better understand the role CT imaging can play, Ronen Gurvitch, MBBS, from St. Paul's Hospital in British Columbia, Vancouver, and colleagues imaged 20 patients with CT before TAVI. They used a novel technique to determine multiple angiographic projections accurately representing the native valve plane in multiple axes.
They determined the accuracy of all predicted projections post-procedure using angiography according to new criteria, based on valve perpendicularity and the degree of strut overlap. Researchers compared the accuracy with a control group undergoing TAVI in which CT angle projection was not used.
They found that CT can correctly predict angiographic projection angles perpendicular to the aortic valve plane and help guide TAVI procedures. Correct final deployment projections were more frequent in the CT-guided group compared with non–CT-guided group: excellent or satisfactory projections (90 vs. 65 percent). The CT angle prediction was accurate but dependent on optimal images (optimal images: 93 percent of predicted angles were excellent or satisfactory; suboptimal images: 73 percent of predicted angles were poor).
Investigators said that CT's advantage is that images can be analyzed off-line. "Peripheral vasculature/femoral access, annular dimensions, extent and distribution of leaflet calcification, and coronary artery position and relationship to bulky calcified leaflets can be assessed concurrently."
Because CT images are taken before the procedure, there can be some difference between pre-imaged anatomy and real-time anatomy. Therefore, "CT is additive to aortography, especially in circumstances where the latter may be inadequate in confidently determining the valve plane. Eventually, real-time 4D co-registered CT may reduce the need for aortic root angiography," they concluded.
"Our center has a large experience with TAVI. Despite this experience, CT was able to improve the frequency of correct angle choice. Multislice CT may have an even greater impact on the results of groups beginning their experience with TAVI," they said.