What are the ASCVD (Atherosclerotic Cardiovascular Disease) risk categories for low, medium, and high risk?

ASCVD Risk Categories: Low, Medium, and High

According to the American College of Cardiology/American Heart Association (ACC/AHA) guidelines, ASCVD risk categories are defined as: low risk (<10%), intermediate/medium risk (≥10%), and high risk (presence of established cardiovascular disease). 1

ACC/AHA Risk Categories

• Low Risk: 10-year ASCVD risk <10% and no clinical cardiovascular disease 1
• High Risk: Either:
  • Presence of clinical cardiovascular disease OR
  • 10-year ASCVD risk ≥10% using the ACC/AHA Pooled Cohort Equations 1

European Society of Cardiology/European Society of Hypertension (ESC/ESH) Risk Categories

For comparison, the European guidelines use a more granular approach:

• Low Risk: 10-year CVD mortality risk <1% 1
• Moderate Risk: 10-year CVD mortality risk 1% to <5% 1
• High Risk: 10-year CVD mortality risk 5% to <10% 1
• Very High Risk: 10-year CVD mortality risk ≥10% 1

Risk Assessment Tools

• The ACC/AHA uses the Pooled Cohort Equations for adults 40-79 years of age 1
• Risk factors included in calculation: age, sex, race, total cholesterol, HDL cholesterol, systolic blood pressure, treatment for hypertension, diabetes, and smoking status 1

Automatic High-Risk Qualifiers

Certain conditions automatically place patients in the high-risk category regardless of calculated risk score:

• Established cardiovascular disease 1
• Type 1 or Type 2 diabetes mellitus 1
• Grade 3 hypertension 1
• Chronic kidney disease stages 3-5 1
• Age ≥65 years 1

Risk Assessment for Younger Adults

• For adults <40 years of age, the ACC/AHA recommends lifetime risk assessment rather than 10-year risk 1
• The 2019 ACC/AHA guidelines suggest considering 30-year or lifetime ASCVD risk for adults 20-39 years and those 40-59 years with <7.5% 10-year risk 1

Risk Refinement Strategies

For borderline (5% to <7.5%) or intermediate (7.5% to <20%) risk patients, additional risk-enhancing factors can help refine risk assessment:

• Family history of premature ASCVD 1
• Chronic inflammatory conditions (rheumatoid arthritis, lupus, HIV) 1
• South Asian ancestry 1
• History of preeclampsia or preterm delivery 1
• Early menopause 1
• Erectile dysfunction 1
• Elevated lipoprotein(a) 2
• Elevated high-sensitivity C-reactive protein (≥2 mg/dL) 3, 2

Coronary Artery Calcium (CAC) Score for Risk Reclassification

• For intermediate-risk patients (7.5% to <20%) or selected borderline-risk patients (5% to <7.5%), CAC scoring can help guide treatment decisions 1
• CAC score ≥300 Agatston units or ≥75th percentile for age, sex, and ethnicity significantly increases ASCVD risk 3
• CAC=0 generally indicates lower risk, while CAC>100 indicates substantially higher risk 4

Clinical Implications

• Risk stratification is particularly important for treatment decisions in adults with stage 1 hypertension (SBP 130-139 mmHg or DBP 80-89 mmHg) 1
• Even without traditional risk factors, older adults with predicted ASCVD risk ≥7.5% still have significantly elevated risk compared to those with <7.5% risk 5

Common Pitfalls in Risk Assessment

• Risk calculators may become less accurate as population health changes over time 1
• Traditional risk factors are strong population-based markers but may be poor individual discriminators of coronary disease 1
• A significant proportion of ASCVD events (57% in one study) can occur in individuals with calculated risk <7.5% 3
• Risk assessment tools have limitations and should be considered alongside clinical judgment 1