Reference: Charlot et al. European Heart Journal 2012 (in press).
International guideline recommendations approve giving dual antiplatelet therapy for a period of not less than 12 months after acute myocardial infarction. However, the benefit is unknown if the therapy is extended beyond 12 months. Perhaps its extension could be particularly useful in patients receiving pharmacological stent implantation, due to the inherent risk of late thrombosis. A recent retrospective analysis of the Danish National Registry (2004-2009) assessed the risk of discontinuing dual antiplatelet therapy during the first three months after the monitoring year. From a total of 29,268 patients, 9,819 (33.6%) were treated conservatively and 19,449 (66.4%) by angioplasty. A total of 3,214 patients had a follow-up event (11%). After 12 months of infarction, patients treated conservatively had a similar risk (death or MI) when clopidogrel was discontinued in the first quarter compared with those in the second quarter: 1.07 (0.65-1.76, P = 0.79). In contrast, patients undergoing angioplasty had a higher risk when clopidogrel was discontinued in the first quarter, relative risk 1.59 (1.11-2.30, P = 0.013). For this subgroup, the risk of discontinuation was higher in patients with acute myocardial infarction with ST segment elevation, relative risk 2.65 (1.25-5.64, P = 0.011).
Comments:
Overall, patients where dual antiplatelet therapy is prolonged beyond the year of infarction constitute a risk group in themselves and can hardly be compared with patients who experience an early interruption of the drug.
To circumvent this problem and assess the need for prolonged therapy with clopidogrel, Danish researchers used the same patients as a reference, comparing the risk of discontinuing the drug in two consecutive periods which demonstrated the presence of a significant risk in the first 90 days after the year follow-up for patients undergoing angioplasty.
There is no doubt that no risk over the conservative group gives rise to speculation. Risk may be present due to late thrombosis, especially in patients receiving a first-generation stent drug. On the other hand, we cannot rule out the rebound effect, both in the territory treated as well as in other territories. Unfortunately, the study did not assess the causes of this excess risk. Although a hypothesis generator, the study suggests a different duration of dual antiplatelet therapy in patients treated with angioplasty to those treated conservatively. Future studies will need to confirm or disprove these findings.
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