To the Editor:

Stent thrombosis (ST), especially in drug-eluting stents, is currently one of the large concerns in interventional cardiology.

We read with great interest the article by Gallego et al1 published in Revista Española de Cardiología, where they analyse the incidence of ST, its treatment and its prognosis in a sample of patients that underwent percutaneous coronary interventionism with conventional stents (CS) and drug-eluting stents (DES) from January of 1998 to December of 2007.

However, there are aspects regarding this study that we would like to mention.

The incidence of ST in CS and PAS is incredibly low (0.6%) and it is even lower than that documented in meta-analyses of clinical trials.2-4 In a realistic average, with more complex patients, a ST incidence greater than that observed in a clinical trial would be expected.5 Concerning the PAS, recently published observational studies have reported variable incidences of the ST (1.3%-3.3%).6-8 The authors have used the stent as a unit of follow-up instead of the patient, a fact that seems to underestimate the incidence of ST. If the angiographic definition represents the ideal method to document ST, it tends to underestimate the true magnitude of this problem as it does not include myocardial infarctions in the theoretical territory of a previously implanted stent that are reinfused with fibrinolysis nor the sudden deaths produced by thrombosis.5

The low mortality in ST may seem even more incredible in this series (5.2%), in spite of the fact that its most frequent form of clinical presentation was an acute myocardial infarction with ST elevation. This goes against our experience, according to which the late thrombosis of PAS is a serious event with elevated mortality (23.5%) and that it is associated with an elevated vital risk in the mid to long term.7

In this series, in up to 43% of the stents where a ST was produced, there was some kind of complication during the interventional procedure. The fact that the complications condition a greater risk of ST, especially acute and subacute ST, is well known. It would be interesting to use that they correlate these complications during the intervention compared to the chronological types of thrombosis.

Very late thrombosis was infrequent in the CS in this series (0.04%). Other studies have reported a greater incidence of ST in PAS after the first year.2-4 However, in this study the 2 very late thromboses were found in patients with CS (7.3 and 8.3 years after implantation). It is not necessary to know how the methodological problem was solved that considers the restenosis of a CS treated with a DES to quantify the incidence of ST. It is possible that some of the late thrombose took place after the implanting of a DES over a restenosis of the previously implanted CS.