Suboptimal final angiographic flow grade is the primary driver of restenosis after subintimal tracking and reentry (STAR) for chronic total occlusion (CTO) recanalization, according to a retrospective study published online August 26, 2015, ahead of print in Catheterization and Cardiovascular Interventions.

The elevated restenosis rate associated with the STAR strategy makes it a second-line strategy, but as many new techniques rely on the same principle, “we believe that it is important to understand the reason” behind the worse outcomes, say Mauro Carlino, MD, of the San Raffaele Scientific Institute (Milan, Italy), and colleagues.

Moreover, because STAR may restore vessel patency when other methods fail, the technique “should… be present in the interventionalist’s armamentarium,” they say.

The investigators evaluated 112 patients with 119 CTOs that had been successfully recanalized (TIMI flow ≥ 2) using the STAR technique after failed conventional PCI and then implanted with DES at 2 Italian centers between 2002 and 2013. All lesions underwent angiographic follow-up. 

Mean fluoroscopy time was 45 minutes and mean procedural time was 135 minutes. The only in-hospital complications were 1 NSTEMI and 1 coronary perforation, which was successfully treated with conservative management.

Restenosis Seen in Almost Two-Thirds of STAR-treated CTOs

The median time to angiographic follow-up was 8.5 months. Target-vessel restenosis was observed in 63% of lesions, with total occlusion in 27.7%, diffuse severe restenosis in 7.6%, and focal restenosis in 27.7%. Median time to restenosis was 179 days.

Restenosis was successfully treated in 72% of patients, although in one-quarter of those, repeat restenosis required a third intervention. At last angiographic follow-up, the target vessel was patent in 84% of lesions, either from the initial PCI or after 1 or more repeat procedures.

Baseline clinical characteristics were similar between patients with and without restenosis. The RCA was the target vessel in two-thirds of patients. Second-generation DES were used in only 18.5%.

Over follow-up, there was one instance of symptomatic acute vessel thrombosis, which was successfully treated with repeat PCI. In addition, 2 patients died and were classified as possible cases of stent thrombosis.

Final TIMI flow grade < 3 was the only procedural variable associated with TVR. Total stent length was similar between those with and without restenosis. In 8 of 9 patients with TIMI flow < 3 but no restenosis, flow improved to TIMI 3 at repeat angiography.

TIMI flow grade immediately after recanalization and after stenting were closely correlated. Reocclusion occurred in 19.8% of patients with final TIMI flow grade 3 vs 62% of those with a lower grade. Residual occlusion of a side branch of at least 2 mm tended to be more common in those who developed restenosis.

To assess the impact of evolving techniques and technology, the population was divided into quartiles based on the date of the index procedure. There was a trend toward a reduced rate of restenosis in the most recent quartile (March 2009-September 2013) compared with the previous time periods (41.9% vs 61.4%; P = .06), but this was confounded by a shorter time to angiographic follow-up and greater use of second-generation DES in the most recent quartile. Notably, TIMI flow grade < 3 was still associated with restenosis and reocclusion.

When final TIMI flow, use of second-generation DES, stent length, and diabetes were combined in a multivariate model, only final flow retained its predictive value (P < .05). The link was twice as strong when the model was applied to reocclusion only vs restenosis (HR 0.24 vs 0.48; P = .008). 

STAR Introduced Subintimal Recanalization—But Also Raised Concern

“The STAR technique was an important advance in the history of percutaneous CTO treatment as it demonstrated that the subintimal space could be used therapeutically to recanalize the vessel,” the authors observe. Since then, STAR has been integrated into a retrograde approach and a dedicated dissection/reentry system, contributing to increased success for CTO PCI, they add.

Concern has been raised that the high restenosis rate after STAR may be a direct consequence of subintimal stenting, Dr. Carlino and colleagues observe. But if that were so, then newer CTO techniques that involve subintimal dissection and reentry would be expected to have the same problem, and studies have not borne that out, they say. Moreover, the current study “strongly suggests that the final TIMI flow in the target vessel at procedural end is a major determinant of long-term patency,” they add.

Dr. Carlino and colleagues suggest that suboptimal flow after STAR may be explained by:

• The presence of a flow-limiting dissection flap
• A reentry site so distal that the volume of myocardium supplied by the recanalized artery is diminished
• Residual dissections in side branches that interfere with downstream circulation
• Residual trauma, causing microvascular obstruction 

Limiting Stenting May Help

“In situations when flow is compromised, it… may be appropriate to defer stenting and consider a ‘second look’ in order to assess the vessel healing at the dissection site after 2-3 months,” Dr. Carlino and colleagues say. Then, depending on the findings, a stent can be implanted at the site of the original occlusion or another recanalization can be attempted. “In this regard, STAR might be considered a ‘2-step procedure,’ with the first step aimed at obtaining vessel patency and the second [at] treating restenosis,” they say.

Despite its limitations, as a bailout technique, “STAR results in an excellent acute success rate with good safety and acceptable long-term results,” the authors conclude.

According to David E. Kandzari, MD, of Piedmont Heart Institute (Atlanta, GA), the technique is declining in popularity. In a telephone interview with TCTMD, he said this is due in part to its high restenosis risk and in part to the availability of newer technologies enable more-targeted dissection and reentry.

Nonetheless, in the hands of very experienced operators, STAR remains a valuable last option when all other methods of CTO crossing have failed, Dr. Kandzari said. Moreover, a strategy that limits extensive stenting and potentially allows the dissected vessel to heal and side branches to reopen may help reduce target vessel failure after STAR, he added.

Note: Two study coauthors are faculty members of the Cardiovascular Research Foundation, which owns and operates TCTMD.

Source: 
Carlino M, Figini F, Ruparelia N, et al. Predictors of restenosis following contemporary subintimal tracking and reentry technique: the importance of final TIMI flow grade. Catheter Cardiovasc Interv. 2015;Epub ahead of print.

Related Stories:

• Short-term Outcomes Worse After Failed CTO PCI
• Long-term Survival After PCI for CTO Linked with Procedural Success, Completeness of Revascularization
• Study Explores Procedural Success, Failure of Hybrid Approach to PCI in Chronic Total Occlusions