SAN FRANCISCO – Two separate randomized studies of treating coronary bifurcation lesions with a two-stent strategy rather than provisional stenting produced varying results that were reported at the Transcatheter Cardiovascular Therapeutics annual meeting.
The 450-patient BIF IV (Nordic-Baltic Bifurcation Study IV) found statistically comparable 6-month rates of major adverse cardiac events in the two-stent and provisional stenting groups for the treatment of bifurcation lesions involving a large side branch. The two-stent strategy failed to meet a noninferiority endpoint at 9 months, however, in the separate 704-patient TRYTON (Tryton Bifurcation) trial compared with provisional stenting, which is the conventional strategy of stenting the main vessel and only stenting the side branch if it is compromised.
Dr. Indulis Kumsars
In BIF IV, at the 6-month follow-up, 1.8% of 229 patients in the two-stent group and 4.6% of 221 patients in the provisional stenting group developed one of the major adverse cardiac events (MACEs) in the primary composite endpoint: cardiac death; non–index-procedure-related myocardial infarction (MI); target-lesion revascularization; or definite stent thrombosis. The difference was not statistically significant, Dr. Indulis Kumsars and his associates reported.
Rates for individual secondary outcomes also were similar between groups, including rates for the separate MACE components and for target-vessel revascularization or for angina.
The study randomized patients at 16 European centers who had angina or non-ST elevation MI with stenosis involving the main vessel (at least 3 mm) and a true bifurcation lesion (at least 2.75 mm) in a large side branch. Average side branch lesions were significantly longer in the two-stent group (8 mm) than in the provisional stenting group (7.4 mm). Compared with the provisional stenting procedures, the two-stent procedures were significantly longer (93 vs. 74 minutes), and required more contrast volume (238 vs. 187 mL) and fluoroscopy time (23 vs. 14 minutes).
Provisional stenting has been accepted for treating most bifurcation lesions, but it had not been known whether it would work equally well in true bifurcation lesions involving a large side branch, said Dr. Kumsars of Pauls Stradins Clinical University Hospital, Riga, Latvia. The investigators had expected the two-stent technique to produce superior results.
"Longer and more complex procedures in the two-stent group did not translate into more procedural MIs," he said. Perhaps longer follow-up will identify the optimal strategy for treating true bifurcation lesions, he added.
The TRYTON trial included patients at 58 international sites with symptoms or evidence of ischemia from true bifurcation lesions involving a main coronary artery (2.5-4.0 mm) and a side branch (2.5-3.5 mm). Patients were randomized to receive a drug-eluting stent in the main vessel and provisional stenting in the side branch or the Tryton bare-metal dedicated bifurcation stent in the side branch and a drug-eluting stent in the main vessel. The Tryton stent is approved in Europe but is investigational in the United States.
At 9 months of follow-up, 12.8% in the provisional stenting group and 17.4% in the two-stent group showed target vessel failure, defined as cardiac death, target vessel MI, or target vessel revascularization. The 4.6% difference in failure rates had an upper limit of a 10.3% difference in the confidence interval, and so did not fall within the prespecified 5.5% difference to show noninferiority of one technique over the other, Dr. Martin B. Leon and his associates reported at the meeting, which was cosponsored by the American College of Cardiology.
Dr. Martin B. Leon
The failure to reach clinical noninferiority was due mainly to relatively higher frequencies of small periprocedural creatinine kinase MB (CK-MB) elevations in the Tryton group, said Dr. Leon, professor of medicine at Columbia University, N.Y., and director of the Center for Interventional Vascular Therapy at New York-Presbyterian Hospital/Columbia University Medical Center. One of the components of the primary outcome of target vessel failure – target vessel MI – was defined as periprocedural CK-MB elevations greater than three times normal levels.
Definite or probable stent thrombosis rates were low at 9 months: 0.3% in the provisional stenting group and 0.6% in the Tryton group. Target vessel revascularization was needed in 3.6% of the provisional group and 4.7% of the Tryton group. The percent diameter stenosis in the side branch at 9 months was significantly lower in the Tryton group (31.6%) than in the control group (38.6%), a positive outcome in the main secondary outcome measure.
Eight percent of patients in the provisional stenting arm crossed over to treatment with a second stent, a relatively low proportion. "It means the site investigators adhered to rigorous crossover criteria," Dr. Leon said.