Tryton Bifurcation Stent Safe but Fails to Meet Non-Inferiority Endpoint Compared to Provisional Stenting


November 1, 2013
tryton stent, bifurcation stenting
November 1, 2013 — A clinical trial designed to measure the effectiveness of using a dedicated side branch-covering bare metal stent in true bifurcation coronary lesions found that that the strategy was safe, but the results did not establish non-inferiority compared to the currently accepted strategy of using a single stent with provisional use of a second side branch stent when indicated. The findings of the TRYTON trial were presented at the 25th annual Transcatheter Cardiovascular Therapeutics scientific symposium (TCT 2013).
The TRYTON trial compared a new specially designed bare metal bifurcation stent to standard practice of provisional stenting. The Tryton stent is placed in the proximal main vessel extending into the side branch. A standard drug-eluting stent (DES) is then placed in the main vessel through the proximal portion of the bifurcation stent into the distal main vessel. 
The multicenter international study randomized 704 patients with true coronary bifurcation lesions to receive the new bifurcation stent (355 patients) or provisional stenting (349 patients). The primary endpoint was target vessel failure (TVF), a composite of cardiac death, target vessel myocardial infarction or target vessel revascularization at nine months. 
At nine months, TVF was 12.8 percent in the provisional stenting group and 17.4 percent in the Tryton stent group. 
However, the strategy met the secondary superiority endpoint, improving the percent diameter stenosis of the side branch at nine months. In the provisional group, the percent diameter stenosis was 38.6 and in the bifurcation stent group, the percent diameter stenosis was 31.6. In a post-hoc analysis, the Tryton stent demonstrated improved angiographic outcomes with the bifurcation stent in larger side branches (> 2.25mm side branches = 39 percent of enrolled patients). The study demonstrated a disparity between binary restenosis and clinically driven TVR for both arms, indicating that side branch angiographic restenosis is uncommonly expressed clinically. 
“The two-stent strategy in true bifurcations compared with the provisional strategy did not meet the non-inferiority clinical endpoint (TVF), largely due to a relatively higher frequency of peri-procedural CK-MB elevations,” said Martin Leon, M.D., professor of medicine, Columbia University College of Physicians and Surgeons, director, Center for Interventional Vascular Therapy (CIVT) at NewYork-Presbyterian Hospital / Columbia University Medical Center, founder and chairman emeritus, Cardiovascular Research Foundation (CRF) and lead investigator. “However, both strategies were safe, resulting in rare clinically significant MIs and stent thrombosis. Both also had low nine-month clinically-driven TVR with 3.6 percent occurring in the provisional group and 4.7 percent in the bifurcation stent group."
Leon said bifucation stents are usually more difficult to implant, but found the Tryon was easier to use. However, he said many of the lesions that would have been ideal to include in this trial were not included because operators were concerned about subjecting these patients to randomization.
"On the efficacy side, what we learned was that unless you put the Tryton stent into larger side branches — 2.25 or larger — then you really aren't any better than a single stent provisional strategy," Leon concluded.  
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