US Patients Commonly Prescribed High-Dose Aspirin After MI

Marlene Busko

August 14, 2014

DALLAS, TX — American doctors may be unwittingly putting their MI patients at risk because they have not kept up with changes in practice guidelines pertaining to aspirin dose post-MI, a new study warns[1]. Many US patients who have an MI are discharged with high-dose aspirin, even though the latest evidence-based practice guidelines support the use of low-dose (81-mg) aspirin, since it is as effective as high-dose (325-mg) aspirin for secondary prevention of MI, with less bleeding risk.

These findings are from a study published August 12, 2014, in Circulation: Cardiovascular Quality and Outcomes.

Some of the use of high-dose aspirin agrees with PCI guidelines at the time of the study. However, surprisingly, "patients who did not get a stent who were managed medically . . . [as well as] many patients that we consider to be a higher bleeding risk—such as those with in-hospital bleeding events or those on concomitant blood thinners like warfarin—were also frequently discharged on high-dose aspirin," lead author Dr Hurst M Hall (University of Texas Southwestern Medical Center, Dallas) told heartwire .

The study also revealed that in any one hospital, less than 10% to as many as 100% of patients with STEMI or non-STEMI were being discharged with a prescription for high-dose aspirin, he noted.

To decrease this interhospital variation, registries could track aspirin doses on discharge as a quality measure. "Adding aspirin dosing to hospital-based quality reports may be an important strategy to rapidly align practice patterns with the current evidence basis and guideline recommendations," the researchers write. "Such changes would be expected to have favorable impact on bleeding complications in patients with MI."

Changes in Recommended Aspirin Dose

Aspirin is known to be effective for secondary prevention after an MI, and in Europe, guidelines have recommended a maintenance dose of 75 to 100 mg of aspirin for all patients with MI. Earlier US guidelines recommended higher doses, but the 2012–2013 guidelines now advocate low-dose aspirin.

The researchers aimed to evaluate what type of aspirin doses were being prescribed for US patients who had had an MI, based on data from the National Cardiovascular Data Registry's (NCDR's) Acute Coronary Treatment and Intervention Outcomes Network (ACTION) Registry-Get with the Guidelines (GWTG).

They identified 221 199 patients—40% with STEMI and 60% with non-STEMI—who were seen in 525 centers from 2007 to 2011 and received aspirin on discharge. Most patients (60.9%) received high-dose aspirin, and fewer (35.6%) received low-dose aspirin. The 3.5% of patients with doses other than 81 mg or 325 mg were excluded from subsequent analyses.

Patients receiving PCI had the highest prevalence of high-dose aspirin at discharge (73%), followed by patients receiving percutaneous transluminal coronary angioplasty alone (66%), CABG (48%), and medical management alone (44%).

"Despite the fact that post-CABG treatment is among the only cardiovascular situations where high-dose aspirin continues to be endorsed by guidelines (100–325 mg daily, class 1A), patients undergoing CABG in the present study were paradoxically more likely to be discharged on low-dose rather than high-dose aspirin," the researchers write.

Surprisingly, high-dose aspirin was prescribed for many patients with a high risk of bleeding—48% of patients who received a blood transfusion, 56.7% of those who had major bleeding, and 44% of the 9075 patients discharged on triple therapy (aspirin, thienopyridine, and warfarin).

"Major Changes Required in US Practice"

Previous US guidelines recommended high-dose aspirin at discharge for patients receiving intracoronary stents, based on protocols from early pivotal stent trials, and these "were likely a major contributor to the practice pattern we observed during the study period," the researchers write.

The 25-fold variation in prescribing across hospitals "suggest that local physician- or hospital-level practice habits, rather than individualized patient risk/benefit estimation, are the more important factors influencing aspirin prescribing patterns," they add.

Moreover, there is "a substantial gap" in the US between the 2012‐2013 guidelines based on data from studies such as CURRENT-OASIS 7 and the aspirin dosing patterns in 2007 to 2011 identified in the current study.

"Simply stated, post–acute coronary syndrome patients should no longer be prescribed high-dose aspirin at discharge, regardless of the approach to PCI," Hall and colleagues write.

"Because the large majority of US patients are currently discharged on high-dose aspirin, major changes are required in US practice. Because a major influence of aspirin dosing seems to be hospital-level variation, an important target for rapid quality improvement will be redesigning hospital-based treatment pathways."

ACTION Registry-GWTG is an initiative of the American College of Cardiology Foundation and the American Heart Association, with partnering support from the Society of Cardiovascular Patient Care, the American College of Emergency Physicians, and the Society of Hospital Medicine. The registry is funded in part by an independent grant from Merck and Bristol-Myers Squibb. The study was supported by the American College of Cardiology Foundation's NCDR. Hall has no disclosures. Disclosures for the coauthors are listed in the article.

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