Aspirin After CABG: Timing of Resumption
Aspirin should be initiated within 6 hours after CABG surgery and continued indefinitely—it should not be held at all postoperatively. 1
Postoperative Aspirin Initiation
The ACC/AHA guidelines provide a Class I recommendation (strongest level) that aspirin 100-325 mg daily should be initiated within 6 hours postoperatively if not given preoperatively, then continued indefinitely. 1 This recommendation is based on compelling evidence:
Graft patency is time-sensitive: Prospective controlled trials demonstrate that aspirin started at 1,7, or 24 hours after surgery maintains saphenous vein graft (SVG) patency, but this benefit is completely lost when aspirin is delayed until 48 hours post-surgery. 1
Early administration prevents thrombotic complications: When given within 48 hours after CABG, aspirin reduces mortality, myocardial infarction, stroke, renal failure, and bowel infarction. 1
Immediate postoperative aspirin is safe and effective: A landmark randomized trial showed that aspirin 324 mg given within 1 hour of CABG reduced early vein graft occlusion from 6.2% to 1.6% (p=0.004) and late occlusion from 11.6% to 5.8% (p=0.01), without significantly increasing bleeding complications. 2
Bleeding Risk Considerations
The 2022 CHEST guidelines examined perioperative aspirin use and found that in the ATACAS trial (>8,000 patients), aspirin use within 5 days prior to CABG was associated with reduced overall mortality without increased risk for reoperation due to bleeding or transfusion requirements. 1
While one study showed increased bleeding when aspirin was continued until surgery day (824.3 vs 492.1 mL, p<0.001), this addresses preoperative continuation, not postoperative resumption. 3 The postoperative context is fundamentally different—the surgical hemostasis has been achieved, and the thrombotic risk to grafts becomes the dominant concern.
Critical Timing Window
The 48-hour threshold is absolute: Beyond this window, aspirin loses its protective effect on graft patency. 1 Given that graft occlusion can lead to myocardial infarction and death, the risk-benefit calculation strongly favors early initiation.
Dosing
Acceptable aspirin doses range from 100-325 mg daily, with all doses in this range showing efficacy for graft patency. 1 Higher doses (up to 325 mg three times daily) have been studied, but 100-325 mg once daily is standard and sufficient. 1
Common Pitfall to Avoid
Do not confuse preoperative and postoperative management: The question of holding aspirin before surgery (typically 5-7 days for elective cases) is entirely separate from postoperative resumption. 1, 3, 4 Once CABG is completed, aspirin should be started immediately—within 6 hours—not held.