Mortality Reduced at Two Years in AMI Patients Treated With DES: Massachusetts Registry

Shelley Wood

April 03, 2008

April 3, 2008 (Chicago, IL) - Acute MI patients were less likely to die or have a repeat MI if they were treated with a drug-eluting stent (DES) instead of bare metal, two-year follow-up data from the observational Massachusetts registry suggest. According to Dr Laura Mauri (Harvard Medical School, Boston, MA), who presented the results during the American College of Cardiology 57th Annual Scientific Session/i2 Summit-SCAI Annual Meeting, the results were consistent for non-STEMI and STEMI patients. As in the randomized clinical trials that enrolled lower-risk, non-AMI patients, rates of target vessel revascularization (TVR) were also significantly reduced in DES-treated patients.

"There's has been concern about whether there are late events that might counterbalance the early benefits of DES; we saw no evidence of that," Mauri stated. "Although our aim was to detect whether there is a signal of harm, we actually observed lower two-year mortality in STEMI patients treated with DES."

As previously reported by heartwire , the Massachusetts registry includes all patients treated with stents between April 1, 2003 and September 30, 2004 at non-US government hospitals in the state; Mauri has previously presented two-year results for the entire registry population. For the current analysis, researchers looked specifically at acute MI patients--over 7000 patients in total--and used propensity-score matching to be able to evaluate outcomes in 2629 matched pairs of STEMI and non-STEMI patients.

Mauri et al report that mortality rates were reduced in DES-treated AMI patients, 10.6% as compared with 13.4% in bare-metal-stent-treated patients, a statistically significant difference. Death rates were also statistically lower in DES-treated STEMI patients; the reduced mortality in non-STEMI patients was not statistically significant. Recurrent MI rates also trended in favor of DES. Rates of TVR were also significantly lower at two years in DES-treated subjects (15.5% vs. 20.8%, p<0.001); statistically significant differences in TVR favoring DES were also seen in the non-STEMI and STEMI subsets.

Risk differences for propensity-matched MI patient groups: two-year results

Group Risk difference, death (%) p Risk difference, recurrent MI (%) p
All AMI -2.7 0.002 -1.5 0.08
NSTEMI -1.9 0.18 -2.4 0.07
STEMI -3.1 0.009 -1.6 0.127

In an interview with heartwire , Mauri hypothesized that the lower mortality seen in the DES-treated patients may have been driven by the lower rate of repeat revascularization procedures. "The other possible explanation is the differences in the rates of use of dual antiplatelet therapy, even though they were modest." The time period studied predated the guideline-recommended 12 months of dual antiplatelet therapy for DES-treated patients, but there were still differences between the two groups, she said. Clopidogrel tended to be used for three to six months in the DES-treated patients, as opposed to just one month in people treated with bare-metal stents.

Eliminating bias

Discussing the results after their presentation, Dr Bruce Brody (University of North Carolina, Greensboro) highlighted the size of the registry--the largest in the US to date--the relatively long follow-up, and the rigor used to adjust for differences in baseline risk between the two groups.

That said, Brody emphasized the difficulty of eliminating bias in an observational study. "Bare-metal stents are put into sicker patients, patients with severe comorbidities, who are not compliant not only with dual antiplatelet agents but also with other therapies and statins. There's a real bias in this and other registries that can't be accounted for by statistical adjustments."

But responding to the comment, Mauri countered that she and her coinvestigators had made "every effort" to control for these differences.

"If there is any bias, it's very small and doesn't account for the full magnitude of what we observed," she said. "That being said, I think the major finding is that there was no signal of harm, and that's robust."

But the lack of harm seen so far in the Massachusetts population is not, for the time being, enough to convince Brody.

"Our position, based on the data from this and other registries and from the small randomized controlled trials, is that the use of drug-eluting stents is supported in select patients with high risk of TVR who are good candidates for dual antiplatelet therapy. But otherwise, the benefits of DES are relatively small and the risks, particularly the risk of stent thrombosis, are unknown. Before we change clinical practice and start putting DES in the majority of our patients with STEMI, we should wait for the results of the HORIZONS trial."

One-year results from HORIZONS, he added, are due out at the TCT meeting later this year.

Others, however, believe the results may be enough to assuage stent-thrombosis fears and will lead to increased DES use. Dr Bill Knopf (Piedmont Hospital, Atlanta, GA), who moderated a press conference where the results were discussed, put the current DES use in AMI at around 45% but said results like Mauri's would inevitably lead to "higher penetration" of DES in AMI, currently an off-label practice.

Mauri disclosed receiving "modest" honoraria from Abbott, Boston Scientific, Cordis, Medtronic.

The complete contents of Heartwire , a professional news service of WebMD, can be found at www.theheart.org, a Web site for cardiovascular healthcare professionals.



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