Preop Aspirin in Cardiac Patients Lowers Postop Risk for Stroke and Infectious Endocarditis

Aspirin before cardiac surgery significantly reduced postoperative permanent stroke and infectious endocarditis, a benefit that was not associated with increased risks for other potential adverse events.

According to Vwaire J. Orhurhu, MPH, there is scant research in the effect of aspirin administration before cardiac surgery. He and his colleagues at Beth Israel Deaconess Medical Center and Harvard School of Public Health, both in Boston, studied the records of 7,599 patients who had undergone non-emergency cardiac surgery at the institution between January 2002 and December 2013; 4,159 patients were included in the final analysis (Table). Mr. Orhurhu is currently a medical student at Mayo Clinic.

Table. Relationships Between Patient Characteristics and Aspirin Use Characteristics Aspirin Use P Value No Yes Patients, n (%) 998 (24) 3,161 (76)   Age, y 59.59±15.89 66.52±11.45 <0.0001 Sex (% female) 416 (41.68) 866 (27.40) <0.0001 BSA <1.7 m2, n (%) 193 (19.34) 372 (11.77) <0.0001 BMI (kg/m2) 27.58±6.13 28.64±5.49 <0.0001 White race, n (%) 875 (87.68) 2,858 (90.44) 0.1080 Diabetes, n (%) 140 (14.03) 1,105 (34.96) <0.0001 Current smoker, n (%) 148 (20.41) 503 (19.24) 0.7770 Hypertension, n (%) 584 (58.52) 2,601 (82.28) <0.0001 Last creatinine level 1.10±1.00 1.15±0.89 0.1270 Diagnosis of PVD, n (%) 80 (8.02) 456 (14.43) <0.0001 Diagnosis of CHF, n (%) 192 (19.24) 576 (18.22) 0.4710 Chronic lung disease, n (%) None Mild Moderate Severe 867 (86.87) 90 (9.02) 33 (3.31) 8 (0.80) 2,797 (88.48) 286 (9.05) 52 (1.65) 26 (0.82) 0.0150 Ejection fraction, n (%) <40% ≥40% 72 (7.21) 926 (92.79) 411 (13.0) 2,750 (87.0) <0.0001 Left main disease ≥50%, n (%) 637 (63.83) 2,133 (67.48) 0.0330 Operative status, n (%) Urgent Elective 164 (16.43) 834 (83.57) 760 (24.04) 2,401 (75.96) <0.0001 Preoperative IABP, n (% yes) 10 (1.0) 36 (1.14) 0.719 Perfusion time, min 108.20±48.41 96.15±36.26 <0.0001 Cross-clamp time, min 87.13±37.04 73.87±29.97 <0.0001 β-blocker use, n (%) 461 (46.19) 2,351 (74.38) <0.0001 ACE inhibitor use, n (%) 296 (34.38) 1,302 (47.28) <0.0001 CABG, n (%) 235 (23.55) 2,208 (69.85) <0.0001 ACE, angiotensin-converting enzyme; BSA, body surface area; CABG, coronary artery bypass graft; CHF, congestive heart failure; IABP, intraaortic balloon pump; PVD, peripheral vascular disease

Aspirin exposure or non-exposure was documented based on a simple yes or no response. “So it’s a binary exposure arm,” Mr. Orhurhu said. A total of 3,161 patients were taking aspirin preoperatively; 998 were not. “We identified 16 preoperative variables that were significantly associated with preoperative aspirin,” he added. These variables were included in a logistic regression model and propensity scores were calculated. Preoperative aspirin exposure and the propensity score covariate were included in an additional logistic regression model to predict mortality and eight postoperative outcomes.

After propensity score adjustment, permanent stroke was found to be significantly less common in patients who took preoperative aspirin than in their non-aspirin counterparts (40 patients or 2.58% vs. 29 patients or 6.30%; propensity-adjusted odds ratio [OR], 0.52; 95% confidence interval [CI], 0.28-0.94; P=0.031).

Moreover, infectious endocarditis was also found to be significantly less common in aspirin patients than non-aspirin patients (60 patients or 1.90% vs. 79 patients or 7.92%; propensity-adjusted OR, 0.47; 95% CI, 0.30-0.75; P=0.001).

In contrast, operative mortality was comparable between groups, affecting 60 patients (1.9%) in the aspirin group and 20 patients (2.0%) in the non-aspirin group (OR, 1.23; 95% CI, 0.57-2.77;P=0.565). This ratio did not change after propensity score adjustment.

No significant association was seen between aspirin and other postoperative outcomes. “When we looked at outcomes like operative mortality, transient ischemic attack, bleeding, renal failure, pneumonia, hospital readmission and time on ventilation, we didn’t really find any significant association with aspirin use,” he said.

“So the good news here is that we found that permanent stroke and infectious endocarditis were both significantly lower among patients who were on preoperative aspirin,” said Mr. Orhurhu, who reported the findings at the annual meeting of the American Society of Anesthesiologists (abstract A2280).

Session moderator Brian S. Rothman, MD, asked if there is any evidence corroborating the study’s findings. “Obviously, stroke and infective endocarditis are unwelcome complications,” said Dr. Rothman, associate professor of anesthesiology at Vanderbilt University Medical Center, in Nashville, Tenn. “Is this consistent with other studies?”

“A recent large, randomized controlled study [N Engl J Med 2014;370:1494-1503] compared aspirin with placebo in non-cardiac surgery and found no association between preoperative aspirin administration and permanent stroke,” Mr. Orhurhu replied. “Nonetheless, we need to further investigate the temporality of infectious endocarditis to the time of preoperative aspirin administration to ascertain if this may actually be an unwelcome complication.”

Indeed, the 10,010 participants in that trial were stratified according to whether they had not been taking aspirin before the study (n=5,628) or were already on an aspirin regimen (n=4,382). The study’s primary outcome was a composite of death or nonfatal myocardial infarction at 30 days, which occurred in 7.0% of patients in the aspirin group and 7.1% in the placebo group. Despite this comparability, major bleeding was more common in the aspirin group (4.6% vs. 3.8%; P=0.04).