The first 30 days after percutaneous coronary interventions are traditionally regarded as the window for stent thrombosis. Drug-eluting stents have reduced the risk, but outside of clinical trials, little is known about their long-term risk of stent thrombosis after that 30-day window has closed.
Researchers from Germany and Italy, conducting a study of 2,229 patients who underwent successful implantations, found a 1.3% incidence of stent thrombosis at nine months: in nine of 1,062 patients with sirolimus-eluting stents and in 20 of 1,167 patients with paclitaxel-eluting stents. Thirteen patients died.
Four sirolimus patients and 10 pacli-taxel patients had subacute thrombosis, and five sirolimus and 10 paclitaxel patients had late thrombosis. Half of the late thrombosis cases (eight of 15) occurred within three months (median, 57 days).
A 1.3% rate may seem low, but this figure is substantially higher than the rates reported in clinical trials—0.4% at one year for sirolimus and 0.6% at nine months for paclitaxel). The researchers note that the “scope of percutaneous coronary intervention has been expanded to more complex lesions and patients, as a result of the widespread availability of drug-eluting stents.”
In their study, 27% of the patients had diabetes and 79% of the lesions were complex. The clinical consequences were severe, with a case-fatality rate of 45%.
Premature discontinuation of the anti-platelet therapy was the most important predictor of stent thrombosis. Other key predictors were renal failure; bifurcation lesions; diabetes; low ejection fraction; and, for subacute thrombosis, stent length.
Although the stent type was not observed to be an independent predictor, the researchers were concerned by the almost double incidence of stent thrombosis after paclitaxel compared with sirolimus.