JACC: Benefits of DES may not outweigh risks of very late stent thrombosis

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A small absolute increase in drug-eluting stents (DES) thrombosis compared with bare-metal stents (BMS) after one year would result in BMS being the preferred strategy for the overall PCI population, according to an analysis published in the May 13 issue of the Journal of the American College of Cardiology.
Paul Garg, MBBS, from divisions of cardiology and clinical biometrics at Brigham and Women's Hospital and Harvard Medical School in Boston, and colleagues undertook the study to define what incremental risk of very late stent thrombosis (VLST) in DES would outweigh the restenosis benefit.

The researchers developed a decision analytic Markov model comparing DES versus BMS strategies for a contemporary PCI population. Over a range of incremental risk and duration of risk of very late ST, Garg and colleagues identified the net benefit of DES versus BMS in terms of quality-adjusted life expectancy (QALE).

Under an assumption of equal stent thrombosis rates beyond one year, the investigators found that DES strategy was superior to BMS in terms of QALE (16.26 vs. 16.25 quality-adjusted life years).

Under the alternative assumption of an incremental risk difference of 0.13 percent per year, the net benefit was substantially reduced, according to the researchers.

The investigators found that the threshold excess risk of very late DES thrombosis compared with BMS, above which BMS would be the preferred strategy, was 0.14 percent per year (over four years of follow-up). The authors noted that this threshold increased as the population risk of restenosis increased and decreased as the vulnerable time-window lengthened.

Overall, the researchers “found, on the basis of the best data currently available, that the DES strategy was preferred for a prototypical PCI patient under the assumption of no difference in the rates of VLST.”

However, Garg and colleagues “found that even a small excess risk of VLST (more than 0.14 percent per year over four years) would be sufficient to negate any advantage of DES over BMS in terms of QALE. Furthermore, if the at-risk period extended beyond four years, the incremental annual risk that could be tolerated was even smaller.”

The researchers also noted that larger clinical trials and longer follow-up are needed to estimate the risk of late stent thrombosis with greater certainty for existing and new DES.