SAN FRANCISCO, CA — Two studies presented last week at TCT 2013 have shown that a two-stent strategy in bifurcation lesions does not improve clinical outcomes.

In the first trial, known as the Nordic-Baltic Study IV , the rate of major adverse cardiovascular events (MACE) was similar in patients randomized to a two-stent strategy and those randomized to a provisional approach that primarily involved stenting of the main vessel alone.

The second trial, known as the TRYTON bifurcation trial, tested a dedicated cobalt-alloy bare-metal stent (Tryton Medical, Durham, NC) designed specifically for side branches, and the results were similar. At nine months, there was a nonsignificant higher rate of target vessel failure (TVF) in patients who underwent stenting of the main vessel and side branch vs those who underwent stenting of the main vessel alone with a provisional strategy to stent the side branch if necessary. Overall, just 8% of patients in the provisional arm had the side branch stented.

The TRYTON study, said investigators, did not meet the primary end point of statistical noninferiority when comparing the two approaches.

Dr Martin Leon

"The primary end point at nine months, the composite end point of TVF, for the provisional arm was 12.8% and for the Tryton arm was 17.4%," said lead investigator Dr Martin Leon (Columbia University Medical Center, New York) during a press conference announcing the results. "The difference was not statistically significant, and when we break this down into its components, the [difference] was certainly driven by a relatively higher frequency of small, periprocedural CK-MB elevations."

Aside from the increase in target vessel MIs, which were defined as CK-MB elevations three times greater than normal, rates of clinically driven target vessel revascularization were similar in both stenting-strategy arms. The investigators did observe an angiographic improvement in the diameter stenosis of the side branch, a secondary end point, in those who received the Tryton side-branch stent.

The TRYTON Study

In TRYTON, 704 patients treated with a drug-eluting stent in the main vessel were randomized to provisional side-branch stenting or to receive the Tryton side-branch stent. The stent is designed with three components: an 8-mm main-branch zone; a 4.5-mm transition zone; and a 6.5-mm side-branch zone.

Presenting the results to the media, Leon said the trial was designed to enroll patients with large side branches. Despite the negative results, Leon said there did appear to be a trend toward benefit in terms of the composite end point of TVF in 40% of patients with side branches >2.25 mm. In these patients, the rate of TVF was 15.6% in the provisional stenting arm and 11.3% in the Tryton arm (p=0.383).

Speaking to the media, Dr Philippe Généreux (New York-Presbyterian Hospital/Columbia University Medical Center, New York, NY), who was not involved in the trial, looked on the bright side of the Tryton study, noting the benefit observed in large side branches and improvement in diameter stenosis as assessed by angiography. Dr Bernard Gersh (Mayo Clinic, Rochester, MN) added that studies have shown the periprocedural increases in CK-MB are not that important clinically.

"We have the data from ACUITY where it very clearly states that periprocedural CK-MB rises are of no prognostic significance, whether you call it three times or five times above normal," said Gersh. "Spontaneous MIs, those that occur after several days, they have a major prognostic significance. So the fact that there is a slightly higher rate [of periprocedural MIs] doesn't bother me at all."

Nordic-Baltic Bifurcation Study

As noted, the Nordic-Baltic Bifurcation Study, which included 405 patients with a large side branch, was also negative. Overall, the two-stent technique for the treatment of bifurcation lesions did not result in a significant difference in MACE (cardiac death, nonprocedural MI, target lesion revascularization, and definite stent thrombosis) at six months when compared with a provisional stenting approach. There was a trend favoring the two-stent strategy—the rate of MACE was 4.6% in the provisional stenting arm vs 1.8% in the two-stent arm (p=0.09)—but the difference did not reach statistical significance.

The researchers, led by Dr Indulis Kumsars (Latvian Cardiology Center, Riga), noted that the complex two-stent approach did not increase the rate of periprocedural MIs.

Dr James Hermiller (St Vincent Hospital/The Heart Center of Indiana, Indianapolis) said that bifurcation studies "often come down to what the lesion really looks like," meaning the length and complexity of the side-branch lesions. The take-away message, however, despite the presence of large side branches in patients treated in Nordic-Baltic IV, is that provisional stenting should remain the default strategy, said Hermiller.

Leon reports research support from Abbott, Boston Scientific, and Medtronic. Kumsars reports no conflicts of interest; the participating centers received unrestricted study grants from Cordis and Abbott.

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