SCCT Policy Statement Recommends CT Prior to TAVI/TAVR Procedures

January 11, 2013

ERLANGEN, Germany — The Society of Cardiovascular Computed Tomography (SCCT) has issued a consensus statement on the use of CT imaging before transcatheter aortic-valve implantation (TAVI)/transcatheter aortic-valve replacement (TAVR), highlighting the importance of the imaging modality for patients receiving the catheter-based aortic valve [1].

According to the SCCT, CT imaging should be performed in the evaluation process of all patients under consideration for TAVI/TAVR, except for those in whom CT is contraindicated. Also, the CT images should be interpreted with a member of the TAVI/TAVR procedural team or reviewed with the operator before the procedure.

"CT has been integrated into TAVI screening for femoral access and in the assessment of patients pre-TAVI for a number of years, but recently, based on a number of papers from our site and from others, it has becoming increasingly used for transcatheter heart-valve selection and for actually sizing the annulus," Dr Jonathon Leipsic (St Paul's Hospital, Vancouver, BC), senior author of the consensus statement, told heartwire . "This is where CT has really moved forward in the past 18 months."

Contrast-enhanced CT, according to the experts, offers detailed information on the suitability of the peripheral access vessels to handle the large sheaths needed to perform the procedure and provides accurate dimensions of the ascending aorta, aortic root, and aortic annulus, all of which are important for sizing the prosthetic valve.

The expert consensus statement, with first author Dr Stephan Achenbach (University of Erlangen, Germany), is published in the November 2012 issue of the Journal of Cardiovascular Computed Tomography.

Physicians Becoming Comfortable With CT for TAVI

To heartwire , Leipsic said the 3D aspect of CT imaging allows clinicians "a more granular assessment of the complex geometry of the aortic annulus." With echocardiography, there is a fair amount of extrapolation based on 2D imaging, which has limitations. With echocardiography, the first imaging modality used in TAVI/TAVR procedures, many physicians became comfortable with the modality, and it has taken some time to determine how to best integrate CT into the sizing and selection of the transcatheter heart valve, said Leipsic.

Imaging is a necessary component before the TAVI/TAVR procedure because there might not be a suitable valve available for some patients, such as those with an aortic annulus diameter of <18 mm. If the prosthesis is too small, embolization can occur and paravalvular regurgitation is more frequent. On the flip side, if the prosthesis is too large for the aortic annulus, rupture can occur, and these events are often fatal, according to the SCCT. The self-expanding Medtronic CoreValve is available in 23 mm, 26 mm, 29 mm, and 31 mm, while the Edwards Sapien valve is available in 23 mm and 26 mm in the US, with the 20-mm and 29-mm valves available elsewhere, including Europe.

In addition to valve sizing, CT allows clinicians to formulate a coaxial angle of valve deployment and provides a 3D evaluation of the access arteries, which allows physicians to determine the best access pathway, be it via the femoral artery vs apical, subclavian, or aortic arteries. CT also allows physicians to assess aortic-root features that might put the patient at risk of obstruction of the coronary arteries. And finally, contrast-enhanced CT also allows physicians to identify high-risk plaque features in the aortic arch or other variables that might lead to an increased risk of cerebrovascular events.

In the consensus statement, the experts point out that the volume of iodinated contrast medium can be a problem for some patients because some of these candidates for TAVI/TAVR also have impaired renal function. Radiation exposure, on the other hand, is less of a concern given the advanced age of the patients undergoing the procedure.

To heartwire , Leipsic said that CT is continuing to move to forefront of imaging modalities for TAVI/TAVR, with a number of clinical trials utilizing CT in ongoing TAVI/TAVR studies. "As with most policy statements, this policy statement is a conservative one, as it should be," said Leipsic. "We really tried to focus on best practice that's currently available, but I think it's an exciting future for TAVI and CT, that's for sure."

Achenbach has received speaker's honoraria from Siemens and Edwards Lifesciences and research grants from Siemens and Bayer Schering Pharma and serves as a consultant to Servier and Guerbet. Leipsic has received speaker's honoraria from Edwards Lifesciences. Disclosures for the coauthors are listed in the paper.