DES decrease risk of stent thrombosis; questions remain about trial types
The widespread use of drug-eluting stents (DES) is associated with a decrease in repeat procedures and also does not appear to increase the risk of death, compared to bare-metal stents (BMS), according to a study published in the June 25 issue of the Journal of the American Medical Association.

“There has been a growing concern about the possibility of an increased risk of stent thrombosis (ST) associated with the use of DES compared with BMS,” the authors wrote. Despite several recent studies, there remains uncertainty about the trade-offs between the safety and effectiveness of DES.

This study is particularly important because it examines both the three-month and two-year outcomes for revascularization in a larger set of patients, Steven Bailey MD, president-elect of the Society of Cardiac Angiography and Interventions (SCAI), told Cardiovascular Business News.

David J. Malenka, MD, of Dartmouth-Hitchcock Medical Center in Lebanon, N.H., and colleagues performed an observational study to compare the rates of revascularization, heart attack and survival, before and after the availability of DES.

The authors noted that “observational studies have been better powered to detect a difference in stent thrombosis and better reflect on-label and off-label stent use.”

Most randomized trials take a low-risk population, so incidents are less likely to occur, Bailey said. He also concurred with the authors about the benefit of larger, observational trials because the researchers are able “to incorporate a higher-risk population, which is about 55 and 65 percent of patients, who have received stents for clinical indications. Given the low incidence of stent thrombosis—1 to 3 percent—it clearly takes very large population trials to demonstrate differences.”

The study included 38,917 Medicare patients who underwent elective PCI from October 2002 through March 2003 when only BMS were available and 28,086 similar patients, who underwent PCI from September through December 2003, when 61.5 percent of patients received a DES and 38.5 percent received a BMS. Follow-up data were available through December 2005. All patients treated with DES received Cordis’ Cypher sirolimus-eluting stent.

During the two years of observation, the investigators reported that 22.8 percent of patients in the BMS era group underwent a repeat revascularization (20 percent PCI; 4.2 percent CABG). In the DES era group, 19 percent of patients underwent a repeat revascularization (17.1 percent PCI; 2.7 percent CABG).

The authors wrote that a “small but statistically significant decrease in the unadjusted rate of STEMI in the DES era cohort began to emerge at three months and increased slightly through two years of follow-up,” which they said coincided with the lower rate of repeat PCI in the DES era cohort.

Researchers found that the risk of repeat revascularization decreased by approximately 18 percent in the DES era compared with the BMS era.

Malenka and colleagues also found that there was no difference in unadjusted mortality risks at two years (8.4 vs. 8.4 percent), but a small decrease in STEMI existed (2.4 vs. 2 percent). The adjusted risk of death or STEMI at two years was similar, the authors wrote.

“SCAAR [Swedish Coronary Angiography and Angioplasty Registry] ultimately pointed out that there is an important learning curve with these new technologies. In their original [negative] results, they reported early use of the new technologies. But when they reported their post-learning curve results in a larger population, their data repudiated their initial conclusions,” Bailey said. He added that that the Malenka et al. trial is consistent with the later 2006-2007 SCAAR data.

Malenka and colleagues noted that though the SCAAR three-year data was similar to their two-year observations, their three- and six-month data differed. “Unlike the Swedish registry, our landmark analysis showed no increased risk of death or STEMI in the drug-eluting stent era cohort [at three and six months],” according to the authors. “To what extent differences in patient selection, procedural practices or post-procedure medical management…explain why the results of our landmark analysis differed from that of the Swedish registry is unknown,” the researchers added.

Due to the limited nature of administrative data through the Medicare claims, the JAMA researchers could not assess the extent of temporal changes in patient characteristics; procedural characteristics; the use of antiplatelet agents; or the overall quality of cardiovascular care.

The study “is wonderful as a high-level view—the so-called 30,000-foot view. Most of the patients in the U.S., who receive stents are Medicare recipients, so it provides a broad look at the general population,” Bailey said.

“However, many of us are hoping that in the future, we will begin to focus on patients that may be at higher risk—such as diabetics and those who have a poor response to antiplatelet therapy—and alter that risk. This data doesn’t allow us to do that, but it does point us in the direction being able to do that,” Bailey added. 

Bailey concluded that this is another study involving large populations, showing that DES are not detrimental to patients. In fact, he said that the recent studies show that patients receiving DES actually have better outcomes. “It is very reassuring the practices that cardiologists have been in the best interest of patients,” he concluded.

Based on their findings, Malenka and colleagues concluded that although “other data may suggest some incremental risk of ST with the use of DES, we can detect no adverse consequence to the health of the population. We speculate that whatever the increased risk of ST associated with DES use is, it is more than offset by a decrease in the risk of developing restenosis and the attendant risk of a procedure to treat that restenosis.”