Criteria for Severe Coronary Artery Disease
Severe coronary artery disease is defined as having at least one coronary artery with ≥70% stenosis, left main coronary artery stenosis ≥50%, or three-vessel obstructive disease with >70% stenosis in all three major vessels. 1
Anatomical Criteria for Severity Classification
The severity of coronary artery disease is primarily classified based on the degree of luminal narrowing and the number of vessels affected:
CAD-RADS Classification System
The Coronary Artery Disease - Reporting and Data System (CAD-RADS) provides standardized reporting of coronary stenosis:
- CAD-RADS 0: Absence of atherosclerosis
- CAD-RADS 1-2: Minimal to mild stenosis (<50%)
- CAD-RADS 3: Moderate stenosis (50-69%)
- CAD-RADS 4A: Severe stenosis (70-99%) in a single vessel or two vessels
- CAD-RADS 4B: Left main stenosis ≥50% or three-vessel obstructive disease (>70%)
- CAD-RADS 5: Total occlusion (100%) of at least one vessel 1
Specific Criteria for Severe CAD
Severe coronary artery disease is characterized by:
- Single vessel with ≥70% diameter stenosis
- Left main coronary artery stenosis ≥50%
- Three-vessel disease with >70% stenosis in all three major vessels 1
Prognostic Implications
The CAD Prognostic Index correlates the extent of disease with 5-year survival rates:
| Extent of CAD | 5-Year Survival Rate (%) |
|---|---|
| 3-vessel disease, ≥95% proximal LAD artery | 59 |
| 3-vessel disease, 75% proximal LAD artery | 67 |
| 3-vessel disease, ≥95% in ≥1 vessel | 73 |
| 3-vessel disease | 79 |
| 2-vessel disease, ≥95% proximal LAD artery | 79 |
| 2-vessel disease, ≥95% LAD artery | 83 |
| 1-vessel disease, ≥95% proximal LAD artery | 83 |
This demonstrates that the prognosis worsens with increasing number of vessels affected and involvement of the proximal left anterior descending (LAD) artery 1.
Functional Assessment
Beyond anatomical criteria, functional assessment is important in determining the clinical significance of coronary stenosis:
- Fractional Flow Reserve (FFR) measurement
- CT-FFR (computed tomography-derived FFR)
- Stress testing with imaging (nuclear, echocardiography, or cardiac MRI)
Moderate to severe ischemia is defined as:
- ≥10% ischemic myocardium on stress nuclear imaging
- ≥3 of 16 newly dysfunctional segments during stress echocardiography
- ≥4 of 32 subsegments with ischemic perfusion defects on stress CMR 1
Clinical Risk Factors
Several clinical factors increase the likelihood of severe CAD:
- Age (increasing risk with advancing age)
- Male sex
- Diabetes mellitus (especially insulin-dependent)
- History of previous myocardial infarction
- Typical angina symptoms 1
Common Pitfalls in Diagnosis
Visual assessment overestimation: Visual assessment of coronary angiography tends to overestimate stenosis severity compared to quantitative coronary angiography 1, 2
Anatomical vs. functional significance: Not all anatomically severe stenoses are functionally significant. Conversely, some moderate stenoses may cause significant ischemia 1
Diffuse disease underestimation: In diffusely diseased coronary arteries, lack of a normal reference segment may lead to underestimation of lesion severity 1
Interobserver variability: Significant interobserver variability exists in the visual grading of coronary artery stenosis 1
For accurate assessment of coronary artery disease severity, both anatomical criteria (degree of stenosis, number of vessels) and functional significance (ischemia on stress testing or invasive physiological assessment) should be considered to guide appropriate management decisions.