TCT: Self-expanding stents trump balloon-expanding stents in APPOSITION II
Use of the Stentys nitinol self-expanding stent showed less incidence rates of malapposed struts with optical coherence tomography (OCT) compared to the use of balloon-expandable stents in acute MI patients, according to the results of the APPOSITION II study presented Sept. 22 at the annual Transcatheter Cardiovascular Therapeutics (TCT) scientific sessions in Washington, D.C.

“We have to realize that in treating STEMI patients with primary PCI we do great things for the patient. We have a good factor of mortality for these patients, which are known from the HORIZONS trial to have a pretty high risk of major adverse cardiovascular events (MACE) and high mortality risk. A significant part of that is stent thrombosis,” said Robert-Jan van Geuns, MD, of the Erasmus Medical Center in Rotterdam, the Netherlands, who presented the study.

Results in the HORIZONS trial showed that MACE and mortality rates in the bare-metal stent arm were 11.2 percent and 5.2 percent, respectively. Additionally, rates of stent thrombosis at 30 days and two years for this patient arm were 2.7 percent and 4.1 percent, respectively.

“Malapposition is a significant risk factor for stent thrombosis,” said van Geuns, which “occurs most often when there is incomplete stent apposition than in well-apposed stents, 20.6 percent versus 2 percent."

During the APPOSITION II trial, van Geuns and colleagues evaluated a self-expanding nitinol stent (Stentys) to understand whether self-expanding stents could reduce malapposition in acute MI patients when compared to balloon-expandable stents. Additionally, the trial assessed whether use of these stents decreased the rates of stent thrombosis after long-term follow-up.

“In this idea of improving apposition and even maybe long term stent thrombosis, we designed the APPOSITION II trial, a prospective, randomized two-arm, multicenter study with the object to compare the self-expandable stent to the balloon-expandable stent in patients with acute MI,” said van Geuns.

The study randomized 80 STEMI patients to receive either a self-expanding stent (n=43 patients) or a Vision/ Driver balloon-expanding stent (n=37 patients) at nine European sites between December 2009 and June 2010. The researchers used stent strut apposition at three days by OCT as the study’s primary endpoint.

Over 80 percent of the patients were male and all had a mean age of 60 years old. Additionally, 44.2 percent of patients randomized to the self-expanding stent group had hypertension compared with 51.4 percent in the control group.

The device and procedural success rates were the same, 97.6 percent for the self-expanding stent group and 100 percent for the control group.

Additionally, the results showed that after three days of follow-up, in-stent lumen loss was negative in the self-expanding arm (-0.11), and was 0.04 in the control arm.

Post-PCI, the rate of stent strut malapposition was 2.20 percent for the self-expanding stent group compared to 5.99 percent in the control group. Three days following the procedure, these rates were reported to be 0.51 percent and 5.33 percent, respectively.

“In self-expandable stents, we did see a significantly lower number of malapposed struts, but the most impressive thing was that after three days, only about half of a percent of these stents were malapposed,” said van Geuns. “There is a significant reduction and difference in the self-expanding compared with the balloon-expandable stents, which equated to almost a 10-fold reduction in our primary endpoint.”

Additionally, the results showed that zero patients in the self-expanding arm had malapposed stents; however, 28 percent of patients in the control arm did have malapposed stents. At 30 days, all patients were free of any MACE rates and stent thrombosis.

“We come to the conclusion that the APPOSITION II study showed that only 0.51 percent of the struts of the self-expandable stents were malapposed compared to 5 percent of the balloon-expandable stents, which we present is a 10-fold reduction in the number of malapposed struts using a self-expandable stent.”

This gives us the confidence to conduct further studies to see whether this malapposed index will have an impact on clinical study and stent thrombosis,” van Geuns concluded.

Van Geuns also said that one disadvantage of the use of self-expanding stents within the coronaries is their higher crossing profile. Additionally, he said that debate still surrounds the idea of whether a drug-eluting stent should be created for the treatment of acute MI.