New SCCT Guidelines Reflect Expanding Role for CT in TAVR

Patrice Wendling

January 18, 2019

Updated Society for Cardiovascular Computed Tomography (SCCT) guidelines on the use of CT imaging for transcatheter aortic valve replacement (TAVR) reflect its rapid transformation from second fiddle to central component of TAVR treatment.

"We don't have to convince our peers now that CT is of benefit, so the update is focusing really on standardization of measurement techniques, of nomenclature when, for example, it comes to describing adverse anatomies, and also standardization of grading systems," said the lead guideline author, Philipp Blanke, MD, University of British Columbia, Vancouver, Canada.

When SCCT published its first expert consensus statement on TAVR in 2012, there were data hinting that CT could provide more information than 2-dimensional echocardiography, "but not everyone was convinced," he said. CT was used primarily to assess peripheral access and perhaps for coronary artery height, but the further assessment of the aortic root, especially the intra-aortic dimensions that are important for valve sizing, was done by echocardiography.

The evidence supporting the role of CT in TAVR has grown significantly over time, and CT is now, for most people, the gold standard for assessing the aortic root, sizing of the TAVR valve, and providing coplanar fluoroscopic angle prediction before the procedure, Blanke said.

SCCT's new expert consensus document was published online January 7 in the Journal of Cardiovascular Computed Tomography.

It contains 11 recommendations for CT acquisition prior to TAVR, with "strong" grade evidence in support of imaging the aortic root using ECG-synchronized acquisition and including the aortic root, aortic arch, and iliofemoral access in imaging volume, and against the routine use of beta blockade in patients.

The recommendations emphasize the need for precise, robust assessment to achieve optimal valve sizing and to identify patients at higher anatomic risk for adverse events.

"If we have an adverse event and it is image related, it can be either due to improper data acquisition with poor image quality or improper anatomical measurements," Blanke said. "The current version of the guidelines really addresses those two issues — to be robust in regard to data acquisition and to be robust in terms of the measurement of anatomical assessment."

The new document includes scanner-specific recommendations for imaging the aortic root, and also suggests that image acquisition should cover the entire cardiac cycle to account for dynamic changes of aortic root geometry and dimensions throughout the cycle.

"There are enough data nowadays indicating that it is of benefit to have imaging data covering the entire cardiac cycle. For example, we have 4-dimensional CT covering the entire cycle and actually assessing the ventricle at the largest dimension," Blanke said.

Nevertheless, this recommendation might be somewhat controversial, he said, because more radiation is applied — a fact that has prompted "our European colleagues to limit the exposure to part of the cycle." This could come into greater play as the use of TAVR is expanded beyond high-risk septuagenarian and octogenarians into younger patients.

"We actually accounted for that in the updated version," Blanke said. "While we have a recommendation to cover the entire cardiac cycle, we also have a section on radiation protection, radiation dose, and provide recommendations on what to do if you come into a situation where you may have a younger patient. So the recommendations provide some guidance for our colleagues."

Also new in the 2019 document is a section on post-TAVR CT imaging, which has taken on greater import with increasing evidence, for example, of post-TAVR leaflet thrombosis.

"We still don't know whether there's any indication to perform a routine follow-up CT, so that's where I think we take a very conservative approach in the current version of the guidelines, stating that postprocedure CT can be used when there is suspicion of leaflet thrombosis or clinical evidence of leaflet thrombosis or concern," Blanke said.

Finally, the nine-member expert panel included a section on the role of CT for aortic valve-in-valve (ViV) procedures, which require special consideration and include the simulation of the procedure to assess anatomic risk. The new valve is frequently implanted in a somewhat canted position, which means it has the potential to come into close proximity to the coronary ostia, even if the aortic root is wide, explained Blanke.

A recent study showed that coronary obstruction after ViV procedures was more common in patients with a shorter virtual transcatheter valve to coronary ostium distance, or VTC, with the optimal cutoff being 4 mm.

"This is an entire new chapter in the document and pretty much answers a need because more and more centers are performing aortic valve-in-valve and the numbers are of course growing," he said.

Blanke is a consultant for Edwards Lifesciences and Circle Cardiovascular Imaging and provides CT core lab services for Edwards, Medtronic, Neovasc, and Tendyne Holdings, for which he receives no direct compensation.

J Cardiovasc Comput Tomogr. Published online January 7, 2019. Full text

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