TCT: CT for chronic total occlusion guidance may be feasible, but should it be used?

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SAN FRANCISCO—A small single-center feasibility study concluded that multi-slice CT (MSCT) co-registration for guidance during chronic total occlusion (CTO) procedure is feasible, with “a trend toward higher procedural success.” However, the panelists who heard the results of the trial on Nov. 8 at the 23rd annual Transcatheter Cardiovascular Therapeutics (TCT) conference, questioned that conclusion due to the high complication rates in the CT arm.

The study’s lead author Ravit Barkama, MD, director of the Center for Interventional Vascular Therapy research unit at Columbia University Medical Center in New York City, started her presentation by listing the shortcomings of angiography (the current gold-standard), which included:
  • Difficulty estimating occlusion length and path;
  • Poor visualization of entry and trajectory worsened by side branch overlay;
  • Inability to assess plaque constituents and poor resolution of location and extent of calcification;
  • Frequent time-consuming assessment for “optimal” views;
  • High contrast use (especially with dual injections); and
  • High radiation doses especially with frequent location checks.
“Since traditional coronary angiography provides images of the coronary vessel lumen, CTO segments are not visible using this modality,” said Barkama, adding that all of these shortcomings are worsened by the “technical complexity of achieving wire crossing.” 

Conversely, she also spoke to the benefits of MSCT, namely that it provides information on the soft tissue surrounding the vessel lumen, so it can be used to identify morphological features such as actual length of the occluded segment, tortuosity and the amount of calcification and plaque.

Also, the ability to perform 3D reconstruction of MSCT “allows accurate measurements of length that do not suffer from calibration limitations and foreshortening,” she said. “It allows assessment of anatomy and pathology in various angles, and can assist in identifying the optimal projection (least foreshortening and branch overlay) for the intervention.” 

The objective of the study was to evaluate the feasibility and added value of a software prototype (GE Healthcare) that provides real-time fusion of MSCT images onto the live angiogram during CTO recanalization.

The researchers enrolled 27 study cases, which were compared to 50 historical controls and conducted during the same time period of 2008 to 2011 by the same operators.

Co-registration was successful in all 27 study patients, according to Barkama, who added that “it helped define the optimal projection for performing the intervention and served as a roadmap for wire guidance.” Wire crossing occurred in 77.8 percent of the CT co-registration arm and 74 percent in the control arm. Also, in the CT co-registration arm, the fluoroscopy time was slightly shorter by 1.6 minutes, radiation dose was higher by 510.5 mGy and contrast use was lower by 22.4 cc. Based on a post-procedure survey, the operators said that MSCT provided significant value in 63 percent of cases.

However, the TCT panelists were most concerned with the complication rates in the CT arm, with 25.9 percent of the patients having a dissection, as opposed to 6 percent in the control arm. Also, there were four perforations (14.8 percent) in the CT arm and one in the control arm (2 percent).

The panel’s co-moderator, Alfredo R. Galassi, MD, director of diagnostic and cardiovascular interventional laboratory at Ferrarotto Hospital University of Catania in Italy, said, “While [the study authors declared] procedural success, there are also a lot of complications.” Another panelist echoed his concerns about “the relatively high number of perforations.”

In response, Barkama suggested that the patients who were chosen for the CT arm “may have had more challenging anatomies,” but also acknowledged that the small size of the study is a limitation. 

Another panelist, Emmanouil S. Brilakis, MD, of University of Texas Southwestern Medical Center in Dallas, said that his facility used to employ MSCT for this procedure, but has since slowed its use because “it’s costly, takes time, [results in] more patient complications and it may not be needed.”

In response, Barkama said she and her colleagues are not recommending the use of CT routinely in these patients, particularly because of the reimbursement restrictions in the U.S.