Why the ASCVD Risk Score Excludes Heart Failure, Atrial Fibrillation, and Pulmonary Embolism
The ASCVD risk score deliberately excludes heart failure, atrial fibrillation, and pulmonary embolism because it was specifically designed to predict atherosclerotic cardiovascular events (myocardial infarction, stroke, and cardiovascular death), not all cardiovascular conditions. 1
Design and Purpose of the ASCVD Score
The Pooled Cohort Equations were developed from 24,626 participants across multiple cohort studies (ARIC, Cardiovascular Health Study, CARDIA, and Framingham cohorts) who were explicitly free of previous myocardial infarction, stroke, heart failure, percutaneous coronary intervention, coronary artery bypass surgery, or atrial fibrillation at baseline. 1 This exclusion was intentional—the goal was to predict first hard atherosclerotic events in apparently healthy individuals.
Specific Reasons for Each Exclusion:
Heart Failure:
- The Work Group examined including heart failure as an outcome but found that study-by-study ascertainment and adjudication of heart failure varied considerably, making it impossible to include reliably. 1
- Heart failure represents a distinct pathophysiologic process that can occur independently of atherosclerosis (e.g., valvular disease, hypertensive cardiomyopathy, infiltrative diseases). 2, 3
- Including heart failure would conflate two different disease processes with different prevention strategies.
Atrial Fibrillation:
- Participants with atrial fibrillation were excluded from the derivation cohorts because AF represents a different cardiovascular endpoint with distinct risk factors and pathophysiology. 1
- AF increases stroke risk through cardioembolic mechanisms rather than atherosclerotic plaque rupture, requiring different risk stratification tools (CHA2DS2-VASc) and management strategies (anticoagulation). 4
Pulmonary Embolism:
- PE was never considered as an ASCVD outcome because it primarily results from venous thromboembolism, not arterial atherosclerosis. 5
- PE has entirely different risk factors (immobility, hypercoagulable states, malignancy) compared to atherosclerotic disease.
Clinical Implications and Limitations
The ASCVD score captures only about half of preventable cardiovascular events in contemporary practice. 6 In a population-based study of 7.5 million individuals, the rate of incident ASCVD events was 3.95 per 1000 person-years, while the rate of all global CVD events (including heart failure, revascularization, and other endpoints) was 6.67 per 1000 person-years—nearly double. 6
Important Caveats:
Heart failure is particularly underestimated in certain populations. Black women with diabetes are more likely to develop heart failure as their first cardiovascular event (28.4%) compared to ASCVD (26.4%), whereas other race-sex groups predominantly present with ASCVD first. 2
The 2019 ACC/AHA Primary Prevention Guidelines acknowledge this limitation by stating the guideline addresses not only ASCVD outcomes but also heart failure and atrial fibrillation as important prevention targets, even though they are not included in the risk calculator. 7
For patients with established ASCVD, additional factors matter. The SMART2 model for secondary prevention shows that adding heart failure history, atrial fibrillation, and biomarkers like NT-proBNP significantly improves risk prediction for recurrent events. 8
Practical Approach
When using the ASCVD risk score, recognize that:
- It predicts atherosclerotic events only: MI, stroke, and cardiovascular death from atherosclerotic causes. 1
- It does not predict heart failure, atrial fibrillation, venous thromboembolism, or non-atherosclerotic cardiovascular conditions.
- For comprehensive cardiovascular risk assessment, consider these conditions separately using appropriate tools (e.g., CHA2DS2-VASc for AF stroke risk, specific heart failure risk models). 7, 4
- In patients with diabetes, particularly Black women, maintain heightened awareness for heart failure risk even when ASCVD risk appears moderate. 2