What are the guideline recommendations for aspirin (acetylsalicylic acid) therapy in primary and secondary prevention of cardiovascular disease?

Aspirin Guideline Recommendations for Cardiovascular Disease Prevention

For cardiovascular disease prevention, aspirin therapy is strongly recommended for secondary prevention in all patients with established cardiovascular disease (75-162 mg daily), while primary prevention requires careful risk assessment with aspirin generally recommended only for those at higher cardiovascular risk without increased bleeding risk. 1

Secondary Prevention Recommendations

Established Coronary Artery Disease

• Long-term single antiplatelet therapy with aspirin 75-100 mg daily is recommended for patients with established coronary artery disease (CAD), defined as:
  • Patients 1-year post-acute coronary syndrome (ACS)
  • Prior revascularization
  • Coronary stenoses >50% by angiogram
  • Evidence of cardiac ischemia on diagnostic testing 1

Post-Acute Coronary Syndrome (ACS)

• For patients in the first year after ACS without PCI:

  • Dual antiplatelet therapy (DAPT) with ticagrelor 90 mg twice daily plus low-dose aspirin (75-100 mg daily) or clopidogrel 75 mg daily plus low-dose aspirin 1
  • Ticagrelor plus aspirin is preferred over clopidogrel plus aspirin 1

• For patients in the first year after ACS with stent placement:

  • DAPT with ticagrelor 90 mg twice daily plus low-dose aspirin, clopidogrel 75 mg daily plus low-dose aspirin, or prasugrel 10 mg daily plus low-dose aspirin 1
  • Note: Prasugrel may cause harm in patients with body weight <60 kg, age >75 years, or previous stroke/TIA 1

Aspirin Allergy

• For patients with atherosclerotic cardiovascular disease and documented aspirin allergy, clopidogrel (75 mg/day) should be used 1

Primary Prevention Recommendations

Risk-Based Approach

• For adults aged 50 years or older without symptomatic cardiovascular disease:
  • Low-dose aspirin 75-100 mg daily may be considered for those at increased cardiovascular risk 1
  • This includes most adults with diabetes aged ≥50 years who have at least one additional major risk factor (family history of premature ASCVD, hypertension, dyslipidemia, smoking, or albuminuria) 1

Risk Assessment

• Risk assessment should include evaluation of:
  • Age and sex
  • Diabetes status
  • Total cholesterol and HDL levels
  • Blood pressure
  • Family history (especially in younger adults)
  • Smoking status 1
• Tools that incorporate multiple risk factors provide more accurate estimation of cardiovascular risk than simply counting risk factors 1

Age Considerations

• For patients over age 70 (with or without diabetes), the balance appears to have greater risk than benefit 1
• Aspirin is not recommended for low-risk individuals (such as men and women aged <50 years with diabetes with no other major ASCVD risk factors) 1
• Aspirin use in patients aged <21 years is generally contraindicated due to risk of Reye syndrome 1

Dosing Recommendations

Optimal Dosing

• For long-term prevention: 75-100 mg daily 1
• For acute coronary syndromes: Initial loading dose of 162.5-325 mg, followed by daily maintenance dose of 75-100 mg 2
• Lower doses (75-100 mg) appear as effective as higher doses for long-term use while causing fewer side effects 2, 3

Bleeding Risk Considerations

Major Bleeding Risk

• Aspirin increases rates of gastrointestinal bleeding (approximately 2-4 per 1,000 middle-aged individuals and 4-12 per 1,000 older individuals given aspirin for five years) 1
• Risk of hemorrhagic stroke increases by a small amount (0-2 per 1,000 individuals over five years) 1
• Factors that increase bleeding risk include:
  • Older age
  • Uncontrolled hypertension
  • Concomitant use of other NSAIDs or anticoagulants 1

Risk-Benefit Assessment

• In secondary prevention, the benefits of aspirin far outweigh the bleeding risks 3
• In primary prevention, the balance of benefits and harms is most favorable in high-risk persons (five-year risk >3%) 1
• For adults with ASCVD risk >1% per year, the number of ASCVD events prevented will be similar to the number of bleeding episodes induced 1
• Individual preferences regarding prevention of MI versus avoiding bleeding should be considered 1

Common Pitfalls and Caveats

1. Overuse in low-risk individuals: Aspirin should not be used for primary prevention in those at low cardiovascular risk where harms likely outweigh benefits
2. Inadequate loading dose in acute settings: For acute MI or stroke, a loading dose of 162.5-325 mg is necessary for rapid antithrombotic effect 2
3. Failure to consider bleeding risk factors: Always assess for history of GI bleeding, concurrent anticoagulant use, and uncontrolled hypertension
4. Inappropriate discontinuation: Abrupt discontinuation of aspirin in patients with established cardiovascular disease can trigger thrombotic events
5. Suboptimal dosing: Using doses higher than 100 mg daily for long-term prevention increases bleeding risk without additional cardiovascular benefit 2, 3