Is aspirin (acetylsalicylic acid) indicated for adults with non‑obstructive coronary artery disease?

Aspirin in Non-Obstructive CAD

Aspirin 75-100 mg daily may be considered in patients with non-obstructive coronary artery disease, but the evidence is weak and the benefit is uncertain—this is a Class IIb (may be considered) recommendation with low-quality evidence. 1

Guideline Recommendations

The 2024 ESC Guidelines provide the most recent guidance on this specific question 1:

• Class IIb, Level C: Aspirin 75-100 mg daily "may be considered" in patients without history of MI or revascularization but with definitive evidence of CAD on imaging
• This is the weakest level of recommendation, indicating uncertainty about the risk-benefit balance

The 2023 AHA/ACC Guidelines do not specifically address aspirin use in non-obstructive CAD, focusing instead on patients with prior MI or revascularization (Class I indication) 2.

Research Evidence on Outcomes

The research evidence reveals important nuances:

Mortality Benefit is Limited and Risk-Dependent

• In the CONFIRM Registry (5-year follow-up, n=6,386), aspirin was NOT associated with reduced MACE, mortality, or MI in patients with nonobstructive CAD 3

• Statins showed benefit, but aspirin did not 3

• A 2015 cohort study (n=8,372) found aspirin reduced all-cause mortality (adjusted HR 0.649) only in high-risk subgroups: age ≥65 years, diabetes, hypertension, decreased renal function, and elevated coronary calcium scores 4

Risk Stratification is Critical

• A 2019 risk prediction model demonstrated that aspirin may actually be harmful in low-risk patients with non-obstructive CAD (HR 2.57 for adverse outcomes) 5
• Only high-risk and very high-risk patients (risk score ≥7 out of 13) showed potential benefit from aspirin 5

Practical Algorithm for Decision-Making

Do NOT routinely prescribe aspirin for non-obstructive CAD. Instead:

Step 1: Assess Risk Profile

Calculate risk based on:

• Age ≥65 years
• Diabetes mellitus
• Hypertension
• Chronic kidney disease
• Elevated coronary artery calcium score
• Elevated LDL-C or hs-CRP
• Extent of non-obstructive disease (closer to 50% stenosis)

Step 2: Apply Treatment Strategy

• Low-risk patients (younger, few comorbidities): Avoid aspirin—may cause harm 5
• High-risk patients (multiple risk factors above): Consider aspirin 75-100 mg daily 4, 5
• ALL patients regardless of risk: Prioritize statin therapy—this has stronger evidence for benefit 3

Critical Caveats

1. Bleeding risk assessment is mandatory before prescribing aspirin—consider age >60, history of GI bleeding, concurrent anticoagulation, and NSAID use 6

2. Non-obstructive CAD is NOT the same as obstructive CAD—the evidence supporting aspirin in patients with prior MI or revascularization does NOT automatically apply here 1

3. Statins are more important than aspirin in this population—ensure optimal lipid management first 3

4. The benefit is marginal at best even in high-risk subgroups, so shared decision-making about bleeding vs. ischemic risk is essential

What Takes Priority

Focus on proven interventions first:

• Aggressive statin therapy (Class I evidence) 3
• Blood pressure control
• Diabetes management
• Smoking cessation
• Lifestyle modification

Reserve aspirin for:

• Patients with multiple high-risk features who understand the uncertain benefit
• Those who progress to obstructive disease or experience MI/revascularization (then it becomes Class I) 1