‘Virtual Stenting’ with CT-Derived FFR Could Revolutionize Procedure Planning
Virtual coronary stenting from coronary computed tomographic angiography (CTA)-derived imaging is feasible and may aid in planning optimal invasive strategies and predicting functional outcome, according to results of a study published online December 11, 2013, ahead of print in JACC: Cardiovascular Interventions.
Preliminary data were first presented in May 2012 at EuroPCR in Paris, France.
Researchers led by Bon-Kwon Koo, MD, of Seoul National University Hospital (Seoul, Korea), compared the accuracy of CT-derived FFR with conventional FFR before and after stenting in 44 stable patients (48 lesions) from 3 centers. To perform virtual stenting, the researchers modified the 3-D computational model generated from CT-derived FFR to restore the area of the treated coronary segment to that of the proximal and distal reference areas. The CT-FFR value was then recalculated.
Virtual View of Lesion
The median time between coronary CTA and invasive coronary angiography was 12 days (range, 2-40). FFR prior to intervention was 0.70 ± 0.14 and increased to 0.90 ± 0.05 after stenting. CT-FFR prior to intervention was 0.70 ± 0.15 and increased to 0.88 ± 0.05 after virtual coronary stenting. There was a positive correlation between FFR and CT-FFR before (P < 0.001) and after intervention (P < 0.001). The mean disagreement between CT-derived and conventional FFR was low (0.006 pre-intervention vs. 0.024 post-intervention).
CT-derived FFR led to 2 false positive predictions of residual ischemia after stenting. Diagnostic accuracy of the noninvasive FFR to predict or rule out myocardial ischemia was 96% (positive predictive value 50%, negative predictive value 100%) after stenting, as defined by a post-stent FFR of > 0.80. The mean difference between FFR after stenting and CT-FFR after virtual stenting was 0.02 ± 0.05.
To demonstrate the potential of the technology to aid in decision making, the study authors cite a case in which the operator needed to decide whether to implant a stent from the distal left main segment to cover fully the ostium of the left anterior descending artery (LAD) to relieve ischemia. A stent was implanted without covering the LAD ostium, and conventional FFR after stenting was 0.74. Consistent with this finding, CT-FFR after virtual stenting without covering the LAD ostial lesion was 0.76, which improved to 0.81 after virtual treatment of the whole LAD lesion including the ostium.
Many Potential Advantages
“It is important to note that virtual stenting is performed by modification of the computational model derived from the original [coronary CTA] taken before the invasive procedure, and that post-stent FFR can be predicted from this same model without any additional noninvasive or invasive procedures,” Dr. Koo and colleagues write. Furthermore, they say clinical application of such a noninvasive planning approach has the potential to reduce clinically unnecessary interventions, procedural time, radiation dose, and costs.
They add that while more data are needed in larger cohorts, comprehensive planning of a revascularization strategy and selection of the optimal target coronary lesions for revascularization appears possible with this new technology and may be especially helpful for deciding on revascularization strategies in patients with complex disease. Another possible use could be to identify lesions best treated by medical therapy and/or CABG, although that remains to be explored, they note.
Eliminating the Guess Work
In a telephone interview with TCTMD, Robert S. Schwartz, MD, of the Minneapolis Heart Institute Foundation (Minneapolis, MN), said the technology and its potential value to operators are “impressive.”
“As we get more and more comfortable with CT as a referral test to the cath lab, it’s an easy add-on to do something like what they describe in this paper,” he said. “You can really look at this as a freebie in terms of data.”
Dr. Schwartz said while there will be some extra computational time involved, “it won’t cost the patient additional contrast, testing, etc. You’re just crunching data that’s already there and getting what I think could be some very useful, clinically important information.” As for financial implications, he said while some additional cost is to be expected, it will likely pay for itself by “taking the guess work out of some of this” and predicting best-case treatment. Ultimately, he said if it becomes clinically available it could be required by some payers to prove that a patient needs a specific intervention.
Mean LVEF was 63.1 ± 7.4%, and 10% of patients had a history of previous MI. Mean stent diameter was 3.1 ± 0.4 mm and mean stent length was 26.0 ± 10.1 mm. All treated patients had TIMI flow grade 3 after stenting and improvements in angiographic percentage of diameter stenosis from 10.1 ± 8.5% from a pre-stent diameter stenosis of 64.5 ± 14.1%.
Kim K-H, Doh J-H, Koo B-K, et al. A novel noninvasive technology for treatment planning using virtual coronary stenting and computed tomography-derived computed fractional flow reserve. J Am Coll Cardiol Intv. 2013;Epub ahead of print.
- Drs. Koo and Schwartz report no relevant conflicts of interest.