Study Supports Noninferiority of Dedicated Bifurcation Stent: But is That Good Enough for Adoption?

A two-stent approach for treating bifurcation lesions with the Tryton side branch stent seems to be at least as effective as provisional stenting—the default approach—in patients with large side branches, a single-arm, extension study has shown.

It’s unclear, however, whether there is truly a need for a dedicated side branch stent in patients with relatively simple bifurcation lesions of the type included in the study, Issam Moussa, MD (Robert Wood Johnson University Hospital, New Brunswick, NJ), who was not involved in the research, told TCTMD.

When weighing two options, it is important consider what the added value of a new device might be, Moussa said. “Because if at the end of the day, they’re equal, then physicians will most likely use the easiest approach that is less costly, and that would be the provisional approach.”

Investigators conducted the Tryton Confirmatory Study after the randomized TRYTON trial failed to show that the two-stent strategy was noninferior to provisional stenting in terms of target vessel failure in patients with true bifurcation lesions, despite showing a reduction in diameter stenosis at 9 months. The inability to demonstrate noninferiority was attributed to a higher rate of periprocedural MI with the dedicated device—the Tryton side branch stent (Tryton Medical).

Most patients in the trial (59%) did not actually meet entry criteria, however, because their side branches had diameters of less than 2.25 mm by quantitative coronary angiography (QCA), corresponding to less than 2.5 mm by visual assessment. When the analysis was restricted to patients with side branches with diameters of at least 2.25 mm, an approach using the Tryton was shown to be noninferior to provisional stenting.

But because that analysis was not prespecified, researchers launched the confirmatory study, which enrolled an additional 133 patients to be treated with the Tryton stent. All but one had side branches at least 2.25 mm in diameter by QCA.

The results, initially presented at TCT 2015 and now published in the July 11, 2016, issue of JACC: Cardiovascular Interventions, show that periprocedural MI was less frequent in these patients compared with those in the provisional arm of the original randomized trial (10.5% vs 11.9%). The upper end of the 95% confidence interval around the 10.5% value did not exceed the predefined performance goal of 17.9%, establishing the noninferiority of the side branch stent (P = 0.014).

Together, all of the studies demonstrate the safety and efficacy of the Tryton stent, Philippe Généreux, MD (Hôpital du Sacré-Coeur de Montréal, Canada), lead author of the latest analysis, told TCTMD.

Overall, 15% to 20% of all PCIs involve a bifurcation, he noted, adding that patients with large side branches (more than 2.5 mm in diameter on visual assessment) and true bifurcation lesions would be considered candidates for the Tryton side branch stent. That group encompasses between one-third and one-half of patients with bifurcation lesions, Généreux estimated.

“We need a reliable bifurcation technique, and I think Tryton offers one,” he said. “We are doing more and more patients that are turned down for surgery and we are doing more and more complex patients that prefer PCI to CABG, so I think it’s reasonable to see the Tryton stent as a good tool to enhance outcomes in this very complex patient [population].”

The results of the study, which was designed in collaboration with the US Food and Drug Administration (FDA), have been submitted to the agency as part of an application of approval for the stent, with a decision expected in the coming months.

Clinical Need

In their paper, Généreux et al note that provisional stenting should be the treatment of choice for patients with small side branches (less than 2.5 mm by visual assessment), but add that patency of larger side branches “could be seen as extremely important.”

The Tryton stent facilitates easy access to the side branch, allowing for additional stents as needed, and reduces the fear of losing the side branch during a case, which is potentially more important for larger side branches like those found in the left main, Généreux said. It should be noted that patients with left main disease were excluded from the Tryton studies.

Commenting on the study, Moussa said, “There is a need for this type of stent but not in the population where the stent was tested.”

The patients included in the randomized trial and extension study had relatively low-risk bifurcation lesions, which other studies—including those of the Tryton stent—have shown to be managed well with the provisional approach, he told TCTMD.

Dedicated devices would be most useful for bifurcations involving severe disease or long lesions in the side branch, Moussa said. Some bifurcations have so much plaque, he added, that if the side branch is not treated effectively it can close up, causing MIs if occlusion happens acutely and recurrent angina if it happens over the long term.

Most clinical trials evaluating approaches and devices for treating bifurcations have not included such high-risk lesions, so ideally, Moussa said, further randomized trials will be conducted to establish the benefits of the Tryton stent in more complex patients.

“I’m uncertain whether if it’s approved it will make headway in the marketplace without more dedicated data in complex bifurcations,” he said, noting that it will be more expensive than existing technology.

Next Steps

Future studies are needed on whether bioresorbable scaffolds could be added to the bifurcation toolbox and on a drug-eluting version of the Tryton stent, which is currently bare metal, Généreux said, adding, however, that it will be difficult to show incremental value over the already good results that have been achieved.

Moussa agreed that a drug-eluting bifurcation stent may provide a benefit and is worth exploring. “If you have a drug-eluting version and that can be tested in complex bifurcation lesions, that would certainly be very exciting and that would most likely add the value people are looking for in new technology for complex bifurcations,” he said.

In an accompanying editorial, Antonio Colombo, MD, and Francesco Giannini, MD (San Raffaele Scientific Institute, Milan, Italy), suggest that the superior angiographic results seen with the Tryton stent might translate into a clinical benefit when larger numbers of patients are included in the analyses.

“Moreover, these differences may further magnify if we assume that future iterations of the Tryton stent may become drug eluting,” they write. “In addition, a longer ‘Tryton drug-eluting stent’ may be implanted to treat bifurcation lesions involving [side branches] with long lesions, thus simplifying the procedure when a two-stent strategy is required as intention to treat.”

Moving forward, “specific devices facilitating a two-stent strategy should be compared with a two-stent approach using contemporary DES in complex bifurcation lesions in which an a priori two-stent approach is the appropriate treatment,” Colombo and Giannini write.

But they concur with Moussa in saying “we are not completely sure if there is room to compete with the provisional approach for most of the bifurcation lesions appearing suitable for [a] one-stent approach.”

Note: Généreux and Colombo are faculty members of the Cardiovascular Research Foundation, which owns and operates TCTMD.

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• Study Validates Safety of Tryton Stent
• TRYTON Published: Noninferiority Not Shown for Dedicated Bifurcation Stent
• Despite Some Good News, Dedicated Stents Fail to Surpass Standard Care for Bifurcation Lesions