How is atherosclerotic cardiovascular disease (ASCVD) diagnosed?

Diagnosing Atherosclerotic Cardiovascular Disease (ASCVD)

ASCVD is diagnosed through clinical history identifying prior atherosclerotic events (myocardial infarction, acute coronary syndrome, stroke, TIA, peripheral artery disease, or arterial revascularization) combined with non-invasive imaging modalities to detect coronary stenosis, carotid disease, or subclinical atherosclerosis. 1

Clinical Diagnosis of Established ASCVD

Clinical ASCVD is definitively diagnosed when patients have documented history of:

• Acute coronary syndrome or myocardial infarction 1
• Stable or unstable angina 1
• Coronary or other arterial revascularization (PCI or CABG) 1
• Stroke or transient ischemic attack of atherosclerotic origin 1
• Peripheral artery disease including aortic aneurysm 1

These patients require no additional testing to establish the diagnosis of ASCVD, as they have already experienced clinical manifestations. 1

Diagnostic Imaging for Symptomatic Patients

For Patients with Chest Pain or Suspected Coronary Disease

Initial evaluation should use non-invasive functional imaging or coronary CT angiography (CCTA) as the primary diagnostic test. 1, 2

• Coronary CT angiography visualizes coronary stenosis severity (≥70% defines obstructive disease), atherosclerotic plaque composition, and high-risk features including positive remodeling and low attenuation plaque 1
• Stress imaging modalities (SPECT, PET, stress echo, or stress CMR) detect myocardial ischemia, with moderate-to-severe ischemia defined as ≥10% ischemic myocardium on nuclear imaging or ≥3 of 16 segments on stress echo 1
• Invasive coronary angiography remains the gold standard for defining obstructive stenosis (≥70% diameter stenosis or ≥50% left main stenosis) and is indicated when non-invasive tests are equivocal or when revascularization is being considered 1

For Patients with Neurological Symptoms

Patients with transient retinal or hemispheric neurological symptoms require immediate non-invasive imaging for extracranial carotid and vertebral artery disease. 1

• Duplex ultrasonography is the recommended initial test to detect hemodynamically significant carotid stenosis (>50%) in symptomatic patients 1
• MR angiography or CT angiography should be performed when ultrasonography yields equivocal or non-diagnostic results 1
• Echocardiography is indicated when cerebrovascular disease is not severe enough to account for symptoms, to search for cardioembolic sources 1

Screening for Subclinical ASCVD in Asymptomatic Patients

Carotid Artery Screening

Duplex ultrasonography is reasonable for detecting carotid stenosis in asymptomatic patients with:

• Carotid bruit on examination 1
• Symptomatic peripheral arterial disease, coronary artery disease, or atherosclerotic aortic aneurysm (though clinical benefit is uncertain) 1
• Two or more major risk factors (hypertension, hyperlipidemia, smoking, family history of premature atherosclerosis) though establishing this diagnosis may not affect outcomes 1

Carotid screening is NOT recommended for:

• Routine screening of asymptomatic patients without risk factors 1
• Neurological disorders unrelated to focal cerebral ischemia 1

Coronary Artery Calcium Scoring

Coronary artery calcium (CAC) scoring is a validated diagnostic test for detecting subclinical coronary atherosclerosis and predicting adverse outcomes beyond conventional risk factors. 3

• CAC scoring is recommended when risk-based treatment decisions are uncertain after calculating 10-year ASCVD risk 1, 3
• CAC score ≥300 Agatston units or ≥75th percentile for age, sex, and ethnicity is considered a risk-enhancing factor 1
• CAC score of 0 indicates very low risk, while scores of 1-10,11-299,300-999, and 1000+ represent progressively higher risk categories 4
• However, CAC alone should not be used to identify obstructive CAD, as it does not visualize luminal stenosis 2

Risk Assessment Tools

The Pooled Cohort Equations calculate 10-year ASCVD risk (first occurrence of nonfatal MI, CHD death, or fatal/nonfatal stroke) for non-Hispanic white and African-American adults aged 40-79 years. 1

This risk calculation guides:

• Statin therapy initiation (≥7.5% 10-year risk) 1, 5
• Antihypertensive medication decisions (≥10% risk with Stage 1 hypertension) 5
• Need for additional diagnostic testing with CAC scoring 1, 3

Risk-enhancing factors to consider when decisions are uncertain include: 1, 5

• Family history of premature ASCVD (men <55 years, women <65 years)
• Primary hypercholesterolemia (LDL-C 160-189 mg/dL)
• Metabolic syndrome
• Chronic kidney disease (eGFR 15-59 mL/min/1.73 m²)
• Chronic inflammatory conditions (psoriasis, rheumatoid arthritis, lupus, HIV/AIDS)
• High-sensitivity C-reactive protein ≥2 mg/L
• Elevated lipoprotein(a) ≥50 mg/dL
• Ankle-brachial index <0.9

Common Diagnostic Pitfalls

Do not rely solely on resting ECG for diagnosis, as more than 50% of patients with chronic stable angina have normal resting ECG. 2

Do not confuse subclinical atherosclerosis (detected by imaging) with clinical ASCVD (prior events). The presence of carotid plaque or coronary calcium indicates atherosclerosis but does not establish a diagnosis of clinical ASCVD unless accompanied by prior events. 1, 6

Recognize that ASCVD risk scores and imaging findings do not always correlate perfectly. Among patients with high calculated risk (≥7.5%), approximately 35% may have no arterial stenosis on imaging, while some low-risk patients may have significant plaque burden. 6

Avoid "triple rule-out" CT protocols. Use imaging protocols tailored to the most likely diagnosis rather than attempting to simultaneously evaluate coronary arteries, aorta, and pulmonary arteries. 1