What are the guidelines for starting aspirin (acetylsalicylic acid) therapy for primary and secondary prevention of cardiovascular events?

Guidelines for Starting Aspirin Therapy for Cardiovascular Disease Prevention

Aspirin therapy should be prescribed for all patients with established cardiovascular disease (secondary prevention) at a dose of 75-162 mg daily, while primary prevention requires careful risk assessment with aspirin generally recommended only for adults aged 40-59 years with a 10% or greater 10-year cardiovascular risk. 1, 2

Secondary Prevention Guidelines

Aspirin is strongly indicated for secondary prevention in patients with established cardiovascular disease:

• Dose: 75-162 mg daily 1, 3
• Indications:
  • History of atherosclerotic cardiovascular disease 3
  • 1-year post-acute coronary syndrome
  • Prior revascularization
  • Coronary stenoses >50% by angiogram
  • Evidence of cardiac ischemia on diagnostic testing 1

For patients with documented aspirin allergy, clopidogrel (75 mg/day) should be used as an alternative 3.

Post-Acute Coronary Syndrome or Stent Placement

• After ACS or stent placement: Dual antiplatelet therapy (DAPT) is recommended:
  • First 12 months: Aspirin (75-162 mg daily) plus a P2Y12 inhibitor (clopidogrel, ticagrelor, or prasugrel) 3
  • After 12 months: Single antiplatelet therapy is recommended over continuation of dual therapy 3

Primary Prevention Guidelines

The decision to use aspirin for primary prevention requires careful assessment of both cardiovascular risk and bleeding risk:

Age-Based Recommendations:

• Ages 40-59 years: Consider aspirin 75-100 mg daily if 10-year cardiovascular risk ≥10% and no increased bleeding risk 1, 2
• Ages ≥60 years: Aspirin is generally not recommended for initiating primary prevention 2
• Ages <40 years: Insufficient evidence to recommend aspirin 2
• Ages <21 years: Aspirin is contraindicated due to risk of Reye syndrome 1

Risk Assessment Factors:

• Consider aspirin if patient has multiple risk factors:
  • Diabetes with at least one additional major risk factor (family history of premature ASCVD, hypertension, dyslipidemia, smoking, or albuminuria) 3, 1
  • Well-controlled hypertension
  • High cardiovascular risk profile 3

Bleeding Risk Considerations

Aspirin increases bleeding risk, which must be weighed against cardiovascular benefits:

• Major gastrointestinal bleeding risk:

  • 2-4 per 1,000 middle-aged persons given aspirin for 5 years
  • 4-12 per 1,000 older persons given aspirin for 5 years 3, 1

• Hemorrhagic stroke risk:

  • 0-2 per 1,000 persons given aspirin for 5 years 3

• Avoid aspirin in patients with:

  • History of gastrointestinal ulcers
  • Recent bleeding
  • Concomitant use of other NSAIDs or anticoagulants
  • Uncontrolled hypertension 1

Dosing Recommendations

• Primary prevention: 75-100 mg daily 1
• Secondary prevention: 75-162 mg daily 3, 1
• Post-ACS or stent placement: Initially 75-325 mg daily (as part of DAPT), then 75-100 mg daily for long-term therapy 3

Clinical Pitfalls to Avoid

1. Don't use aspirin for primary prevention in low-risk individuals (such as adults <50 years with no major risk factors) as risks likely outweigh benefits 1

2. Don't initiate aspirin for primary prevention in adults ≥60 years as recent evidence shows no net benefit 2

3. Don't overlook bleeding risk assessment before recommending aspirin therapy, especially in older adults

4. Don't discontinue aspirin in secondary prevention without compelling reasons, as benefits clearly outweigh risks 3

5. Don't use high-dose aspirin for long-term prevention as higher doses increase bleeding risk without providing additional cardiovascular benefit 4