SYNTAX Score: A Tool for Assessing Coronary Artery Disease Complexity
The SYNTAX (Synergy between PCI with Taxus and Cardiac Surgery) score is an angiographic grading system that quantifies the complexity of coronary artery disease based on anatomical characteristics to guide decision-making between coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI).
Definition and Components
The SYNTAX score evaluates coronary lesions with respect to:
- Number of lesions
- Location of lesions
- Functional impact
- Complexity factors including:
- Bifurcation or trifurcation involvement
- Total occlusions
- Thrombus
- Lesion length >20mm
- Heavy calcification
- Small vessel/diffuse disease
- Severe tortuosity
Calculation and Interpretation
The score is calculated by assigning points to each coronary lesion (defined as ≥50% diameter stenosis for left main and ≥70% for other vessels) based on its anatomical characteristics 1. The final score represents the sum of all lesion scores.
SYNTAX scores are typically categorized into three groups:
- Low: ≤22 points
- Intermediate: 23-32 points
- High: ≥33 points
Clinical Applications
1. Revascularization Decision-Making
The SYNTAX score is primarily used to guide the choice between CABG and PCI:
- Low SYNTAX score (≤22): PCI may be considered as an alternative to CABG 2
- Intermediate SYNTAX score (23-32): CABG generally preferred, but PCI may be reasonable in selected patients 2
- High SYNTAX score (≥33): CABG strongly recommended over PCI due to superior outcomes 2
The 2018 ESC/EACTS guidelines specifically recommend calculating the SYNTAX score to assess anatomical complexity and long-term risk in patients with left main or multivessel disease 2.
2. Prognostic Value
The SYNTAX score has demonstrated significant prognostic value:
- Higher scores correlate with increased risk of major adverse cardiac events (MACE) after PCI 3, 4
- In patients with three-vessel disease, those in the highest SYNTAX score tertile had significantly higher rates of MACE compared to those in lower tertiles (21.6% vs. 9.9% vs. 7.5%) 3
- In STEMI patients undergoing primary PCI, higher SYNTAX scores were associated with increased 30-day mortality (18.5% in high score group vs. 3.3% in mid-score group) 5
3. Risk Stratification
The score helps identify patients at higher risk for complications:
- Patients with high SYNTAX scores undergoing PCI require longer fluoroscopy time and greater contrast volume, indicating more complex procedures 6
- The SYNTAX score can predict completeness of revascularization, which impacts long-term outcomes 7
Limitations and Evolutions
The original SYNTAX score has some limitations:
- Does not incorporate clinical variables
- Some interobserver variability
- Requires invasive coronary angiography
Newer iterations have been developed:
- SYNTAX Score II: Incorporates clinical variables with the anatomical SYNTAX score
- CT-SYNTAX Score: Derived from coronary CT angiography rather than invasive angiography 6
- Functional SYNTAX Score: Incorporates functional assessment of lesions
Clinical Implementation
The SYNTAX score is now incorporated into major cardiovascular guidelines:
- The ESC/EACTS guidelines recommend calculating the SYNTAX score in patients with left main or multivessel disease to assess anatomical complexity and long-term risk 2
- The ACC/AHA guidelines recommend using the SYNTAX score as part of a heart team approach for revascularization decisions 2
The score should be calculated by trained personnel using the online calculator (www.syntaxscore.com) or dedicated software to ensure accuracy and consistency.