Additional stent implant strongly predicts recurrent stent thrombosis
CHICAGO—One in six patients can expect to experience at least one repeat stent thrombosis episode. Among the strongest predictors of recurrent stent thrombosis is implantation of an additional stent during emergency treatment of the first episode, according to a late-breaking clinical trials session at the 2008 American College of Cardiology (ACC) Scientific Sessions on Saturday.

Jochem Wouter van Werkum, MD, a cardiologist at St Antonius Hospital, Nieuwegein, the Netherlands, and colleagues enrolled 431 consecutive patients who had a first definite stent thrombosis confirmed by angiography between January 2004 and February 2007.

The Dutch Stent Thrombosis Registry is a multicenter observational study. It is the largest data base (21,000) and has longest follow-up (three years) for stent thrombosis patients, according to Werkum.

Of the 421 emergent PCIs, 203 were balloon angioplasty alone and 214 were PCI with additional stent placement. Four were aspiration only.

Of the 10 nonemergent patients, the target artery was too small in four; emergency bypass surgery was performed in two; the balloon failed passage in two; and two died before reperfusion.

The researchers found that 75 patients experienced multiple episodes of stent thrombosis. Of these, 61 patients had two episodes of stent thrombosis, 12 patients had three episodes and one patient had four episodes.

Further analysis revealed three independent predictors of repeat stent thrombosis. Patients who had an additional stent implanted during emergency treatment for the first episode of stent thrombosis were 4.2 times as likely as other patients to experience a repeat episode of stent thrombosis (p<0.0001). Patients with a previous heart attack faced 2.6 times the usual risk of repeat stent thrombosis (p<0.001), and patients who developed late stent thrombosis faced 2.1 times the usual risk of a repeat episode (p=0.0127).

Other predictors of unfavorable outcomes included:
  • Diabetes mellitus
  • Left ventricular ejection fraction less than 45%
  • Severe lesion calcification
  • Complex lesion stenting
  • Longer stent length
  • Left anterior descending stenting
  • TIMI flow post ST<3
Researchers concluded that additional stent placement at the time of emergency treatment for the first stent thrombosis should be avoided.

In her comment, Roxana Mehran, MD, from Columbia University Medical Center, said it’s important to consider the timing of stent thrombosis as it relates to the mechanism of stent thrombosis. Acute stent thrombosis occurs within 24 hours and is usually related to procedural issues, device or drugs issues, or complications during the procedure. It generally occurs in the hospital and is treated quickly.

Subacute stent thrombosis occurs within 30 days of the procedure and can present as sudden death. Late and very late stent thromboses were first described with brachytherapy and are now associated with drug-eluting stents, and there may be some healing issues associated with late thrombosis, she said

“It’s important to remember that there are different mechanistic approaches as we look at a stent thrombosis registry of this size,” Mehran said.

Mehran noted that in Werkum’s study, a small percentage of patients had late (13 percent) and very late (13 percent) stent thrombosis.

“The acute and subacute stent thrombosis patients were overrepresented and this aspect may have led to the observed high recurrence of stent thrombosis,” she said.

Mehran suggested that death and MI would have been good primary endpoints to know. The impact of antiplatelet therapy, adherence, and resistance is key to know—drawn out from the entire pool of 21,000 patients in the registry.

Other data she encouraged the Dutch authors to collect are the differences between drug-eluting stents and bare-metal stents. In this study, the authors found no difference, but Mehran said the number of patients receiving DES was too small to provide any real power.

She also would like to see an analysis of the impact of clinical syndrome and procedural variables at the time of original stent implantation in the entire population.

The take-home message, she said, is that stent thrombosis is a significantly morbid event and the recurrence is not rare. In this study, most events were acute and subacute in patients with acute or subacute original stent thromboses. The mechanics of stent thrombosis, predictors and outcomes may warrant further investigation.