Novel Stent Promises to Reduce Long-Term Failure

WASHINGTON — A variety of stent designs have tried and failed to reduce the number of stent-related adverse events over time, but now a new device with a unique design has shown some initial promise in addressing that weakness.

A single-blind randomized trial of the DynamX Coronary Bioadaptor (Elixir Medical, Milpitas, California) found fewer adverse events after 12 months compared with a traditional drug-eluting stent, reported David Erlinge, MD, PhD, head of Cardiology at Skåne University Hospital in Lund, Sweden. In the first 6 months, the stents performed comparably, he said at the Transcatheter Cardiovascular Therapeutics (TCT) 2src24 conference.

And after 12 months, the bioadaptor was associated with significantly lower rates of target lesion failure and target vessel failure, he said.

The stent consists of three 71 µm helical strands coated with a polymer. The unique feature is that the coating is fully resorbed about 6 months after placed in a target lesion.

The strands are initially locked into position but are unlocked after the polymer is resorbed. This allows the device to adjust to normal vessel hemodynamics including pulsatility, compliance, and adaptive coronary flow, Erlinge explained. This greater adaptability is intended to avoid the problems associated with the way more rigid conventional stents disrupt vessel function.

Benefits Accrue Between 6 and 12 Months

The INFINITY-SWEDEHEART trial, conducted using Sweden’s SWEDEHEART online cardiac registry, enrolled more than 2srcsrcsrc patients. They were randomized to receive either the bioadaptor stent or the Resolute Onyx, a contemporary drug-eluding stent coated with zotarolimus.

After 12 months, just 2.35% of patients who received the bioreactor had experienced target lesion failure vs 2.77% of those given the standard drug-eluding stent, a difference that was statistically significant.

When stratified by the target lesion failure components, target vessel myocardial infarction (1.3% vs 1.5%) and ischemia-driven target lesion revascularization (1.3% vs 2.1%) were numerically lower in the bioadaptor group at 6 months. Cardiovascular death (src.6% vs src.5%) was slightly greater, but rates were very low in both arms. This meant that the new device easily met the primary endpoint of noninferiority.

It was after 6 months, the point at which the bioadaptor devices would be expected to unlock, that the difference between the devices began to become apparent.

At 7 months, the rates of target lesion failure were under src.2% in both groups. But by 12 months, they had climbed to nearly 1.5% in the drug-eluding stent group, while remaining essentially unchanged at src.3% in the bioadaptor group.

Similarly, the rates of target vessel failure, which were about src.5% in both groups at 9 months, had climbed to 2.5% in the drug-eluding stent group at 12 months but remained largely flat in the bioadaptor group, climbing to only src.8%.

When target lesion failure was examined in high-risk lesions from 6 to 12 months, the same plateauing was seen. The greater rate of target lesion failure among those in the drug-eluding stent group was significant for both left anterior descending lesions and small vessels (defined as <2.75 mm). The greater rate of target lesion failure among patients in the drug-eluding stent group with long lesions (defined as> 22 mm) did not quite reach statistical significance.

These differences between 6 and 12 months were highly consistent across subgroups defined by age, sex, comorbidities, type of acute coronary syndrome (STEMI vs NSTEMI) and lesion characteristics, such as bifurcation.

Longer Follow-Up Needed

Joanna J. Wykrzykowska, MD, PhD, associate professor of cardiology at University Medical Center Groningen, Groningen, the Netherlands, said the long-term rates of stent-related adverse events is a major problem “that needs solving,” and that these results were impressive.

“You cannot argue [with the fact that] the bioadaptor is performing better at 1 year,” she said.

However, she and others emphasized that it is hard to declare victory for any new stent design after just 12 months. She called for much longer follow-up of 5-1src years to accurately compare options.

Bon-Kwon Koo, MD, PhD, chair of Cardiology at Seoul National University Hospital in Seoul, Republic of Korea, said he does not think that late events unique to the bioadaptor device can be ruled out.

For example, he wondered if the constant motion of the device might eventually lead to stress and dissolution of its structure. If the device was available now, Koo said that he would not be comfortable using it routinely, but if the rate of failure remains low over the long term with no new complications, he thinks it