Late Aspirin Use Before CABG Does Not Increase Ischemic Events

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Continuing to use aspirin within 5 days of coronary artery bypass graft (CABG) surgery does not result in worse postoperative cardiovascular outcomes compared with halting the drug earlier before the procedure, according to a single-center study published online January 31, 2011, ahead of print in Circulation.

Researchers led by Leslie Cho, MD, of the Cleveland Clinic (Cleveland, OH), looked at over 4,000 patients undergoing nonemergent CABG at their institution between January 1, 2002, and January 31, 2008, who were taking chronic aspirin therapy. Of these, 2,298 patients discontinued aspirin 6 or more days prior to surgery, and 1,845 continued to use the drug within 5 days of surgery. Propensity score analysis was used to adjust for differences between the groups, resulting in 1,519 matched patient pairs.

There was no difference in the primary endpoint (composite of in-hospital death, MI, and stroke) or the individual component endpoints in patients who stopped aspirin early compared with those who used the drug late (table 1).

Table 1. CV Outcomes Based on Timing of Aspirin Discontinuation Before CABG

Transfusion rates, however, were increased with late aspirin use, while reoperations for bleeding were equivalent between groups (table 2).

Table 2. Transfusions and Reoperations Based on Timing of Aspirin Discontinuation Before CABG

Abbreviation: RBC, red blood cell.

Median postoperative length of stay was 6 days in both groups (P = 0.50).

Guidelines Provide Conflicting Advice

The researchers note that the timing of aspirin discontinuation prior to CABG is controversial, with current guidelines presenting divergent recommendations. For instance, the American College of Cardiology (ACC)/American Heart Association (AHA) 2004 guideline update for CABG states that in stable patients, aspirin should be discontinued 7 to 10 days before elective surgery. In contrast, the Society of Thoracic Surgeons (STS) recommends discontinuing aspirin 3 to 5 days before elective CABG.

Both recommendations may be based on platelet biology, according to the study authors. For example, the lifespan of a platelet is about 7 to 10 days, which may have influenced the ACC/AHA recommendations. Meanwhile, it takes 3 to 5 days for half of the platelet pool to be replenished, thereby normalizing bleeding time. This, in turn, may have influenced the STS cutoff.

In light of the current findings regarding equivalent CV outcomes but increased transfusion requirements between the 2 groups, the researchers “recommend that clinicians weigh the risks and benefits of late [aspirin] use on the basis of the patient’s risk profile before CABG.”

Little Downside to Stopping Late

Still, since there was no difference in the rate of reoperations for bleeding, “we would support the late use of [aspirin] in high-risk patients to reduce the rate of preoperative cardiovascular events,” they write.

According to Robert A. Guyton, MD, of the Emory University School of Medicine (Atlanta, GA), the study demonstrates that there are few ill effects from continuing aspirin until shortly before elective CABG.

“The main message to me is there’s a relatively small downside to continuing aspirin up until surgery,” he told TCTMD in a telephone interview. “Even though there’s a significant difference in transfusions, the absolute difference is fairly small in the grand scheme of things and the number of patients is low.”

Unfortunately, he added, the downside to stopping aspirin earlier cannot be deduced from the study. “They didn’t monitor the negative sequelae,” Dr. Guyton said, pointing out that patients who suffered a preprocedural stroke or MI after stopping aspirin 6 or more days before surgery were taken out of the analysis. “So they disappeared from the database,” he said.

Value of Platelet Reactivity Data Debated

In an editorial accompanying the study, Paul S. Myles, MB, BS, MPH, MD, of Alfred Hospital (Victoria, Australia), writes that without platelet reactivity data, the results of the study are difficult to interpret. For instance, some patients in the late use group may have had minimal platelet inhibition and reduced bleeding risk while some in the early discontinuation group may have had persistent platelet inhibition. “This overlap of aspirin-platelet responsiveness will dilute the intergroup comparisons and reduce the capacity to characterize the true beneficial and adverse effects of aspirin in CABG,” Dr. Myles writes.

Lisa K. Jennings, PhD, of the University of Tennessee Health Science Center (Memphis, TN), concurred. “We really need to include some understanding of on-drug platelet reactivity as we try to address the benefits and risks associated with aspirin for CABG patients,” she told TCTMD in a telephone interview. “With these cut-points for aspirin discontinuation, lumping patients together off-drug from 6 to 10 days vs. looking at patients on-drug from 5 days or less makes it really difficult to know how the aspirin is actually contributing to the benefit or risk for these patients.”

Dr. Guyton disagreed. “Platelet reactivity assays have generally shown no particularly great benefits,” he said. “This kind of testing hasn’t really hit the mainstream because the specificity and sensitivity are not there. They sound good, but when you try to implement such testing, you still have patients in whom the platelet reactivity tests say they’re not going to bleed and they do bleed. And some tests say they are going to bleed, and it’s only true half the time.”

Should We Be Stopping Aspirin at All?

Drs. Guyton, Jennings, and Myles all agree that randomized, prospective data are necessary to truly determine how best to handle aspirin discontinuation prior to elective CABG. In the meantime, “it’s still a very patient-individualized situation,” Dr. Jennings said. “It’s what we’re facing with any use of anticoagulant or antiplatelet therapy, just balancing the reduction of ischemic events versus the risk of bleeding.”

At Dr. Guyton’s institution, that balance usually tilts toward staying on aspirin. “Most surgeons have gotten fairly used to operating on aspirin, and we certainly don’t stop it anymore,” he said. “In fact, in our patients who are having off-pump surgery who are not already on aspirin, we actually give them aspirin before we operate. We’re anxious to get it started pretty much at the time the grafts are put in.”

Along those lines, Dr. Myles noted that the bigger question raised by the study is “whether or not we should be stopping aspirin at all.”

 

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Sources:
1. Jacob M, Smedira N, Blackstone E, et al. Effect of timing of chronic preoperative aspirin discontinuation on morbidity and mortality in coronary artery bypass surgery. Circulation. 2011;123:577-583.

2. Myles PS. Stopping aspirin before coronary artery surgery: Between the devil and the deep blue sea. Circulation. 2011;123:571-573.

 

 

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