September 19th, 2012

Studies Examine Less Burdensome Dual Antiplatelet Regimens

Two new studies published in the Journal of the American College of Cardiology offer hope but not, yet, compelling evidence to support less burdensome requirements for dual antiplatelet therapy (DAPT) after drug-eluting stent (DES) implantation.

In the first study, Spanish investigators followed 1622 consecutive patients who received a DES for 1 year. They found that 10.6% of the patients interrupted at least one antiplatelet drug during the first year. Two-thirds (64.5%) of the  interruptions were temporary, lasting a median of 7 days. After discontinuation of therapy, 4.1% of patients had an acute coronary syndrome (ACS) — not significantly different from the 5.5% rate of major cardiac events in patients who remained on DAPT.

The authors conclude that early discontinuation of DAPT “is not exceptional and is usually temporary. Although further knowledge about individual risk is desirable, our results suggest that discontinuation for a few days (median: 7 days) of [DAPT] after the first month of DES implantation may be reasonably safe in terms of major cardiac events.”

In an accompanying editorial, Bernhard Witzenbichler points out several limitations of the study, and concludes that “the data can only suggest that a brief interruption of DAPT does not have a large impact on ischemic risk.”

In the second study, Korean investigators randomized 2117 patients to receive either the Endeavor zotarolimus-eluting (ZES) stent plus 3 months of DAPT therapy, or standard therapy consisting of another DES with a full year of DAPT. There was no difference between the two groups in the primary endpoint (the composite of CV death, MI, stent thrombosis, TVR, or bleeding), which occurred in 4.7% of patients in each group, and there were no significant differences in any of the components of the endpoint. The authors conclude that the Endeavor ZES plus 3 month DAPT “could be safe and beneficial for the selected patients with coronary artery disease who may need to stop DAPT early after DES implantation.”

In his editorial, however, Witzenbichler urges caution in interpreting the trial, noting, among other factors, that the trial was underpowered to demonstrate safety, and that the low overall event rate in the trial “makes it difficult to translate the findings to a broader all-comer population.”

Witzenbichler asks whether it is time to “slacken the reins” of DAPT after DES implantation, but concludes the evidence is still insufficient to change standards:

With newer-generation DES, 6 months DAPT might be sufficient, and 3 months not completely off the wall in low-risk groups. Brief interruption of DAPT beyond 4 weeks might not be associated with a dramatic risk increase. However, the patient- and device-related criteria safely allowing early DAPT withdrawal or interruption still have to be determined. Until then, we should be cautious and do our best to avoid unplanned discontinuation of DAPT.

Please click here for additional commentary about this topic by Deepak Bhatt, Rick Lange, and David Hillis.

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