The SYNTAX Score is a comprehensive angiographic grading system used to quantify the complexity and severity of coronary artery disease, particularly in patients being considered for revascularization (either through PCI – Percutaneous Coronary Intervention or CABG – Coronary Artery Bypass Grafting).

What is the SYNTAX Score?

The SYNTAX Score was developed from the landmark SYNTAX Trial (Synergy between PCI with TAXUS and Cardiac Surgery), which compared outcomes between PCI and CABG in patients with complex coronary artery disease.

Unlike the J-CTO score which focuses on single chronic total occlusions, the SYNTAX Score provides a comprehensive assessment of overall coronary anatomy, considering:

• Number of lesions
• Location of lesions
• Complexity of each lesion
• Dominance of coronary circulation
• Presence of specific high-risk features

How is the SYNTAX Score Calculated?

The score is calculated using dedicated software that evaluates multiple angiographic variables:

Key Components Assessed:

1. Coronary Dominance (Right, Left, or Co-dominant)
2. Number of Lesions and their locations
3. Lesion Characteristics for each identified lesion:
   • Total occlusions (including duration, blunt stumps, bridging collaterals)
   • Trifurcations
   • Bifurcations
   • Aorto-ostial lesions
   • Severe tortuosity
   • Lesion length >20 mm
   • Heavy calcification
   • Thrombus
   • Diffuse disease/small vessels

Scoring Process:

• Each coronary segment is assigned a specific “weight” based on its importance
• Lesion-specific characteristics add additional points
• The final score is the sum of all individual lesion scores

Interpreting the SYNTAX Score

Clinical Applications

1. Revascularization Guidance

• Helps determine whether PCI or CABG is more appropriate
• Supported by major guidelines (ESC, ACC/AHA)

2. Risk Stratification

• Predicts procedural complexity and potential complications
• Estimates long-term outcomes

3. Research and Trials

• Standardized tool for patient selection in clinical trials
• Ensures comparable patient populations across studies

Evolution: SYNTAX Score II

The SYNTAX Score II incorporates clinical variables to provide more personalized recommendations:

• Age
• Gender
• Creatinine clearance
• Left ventricular function
• Chronic obstructive pulmonary disease (COPD)
• Peripheral vascular disease
• Unprotected left main disease

Limitations

1. Complex Calculation: Requires specialized software and training
2. Inter-observer Variability: Different operators may score the same anatomy differently
3. Angiographic Focus: Doesn’t incorporate intravascular imaging or physiological data
4. Dynamic Nature: Coronary disease can progress, making scores time-dependent

Clinical Impact

The SYNTAX Score has fundamentally changed how interventional cardiologists and cardiac surgeons:

• Collaborative Decision-Making: Promotes “Heart Team” approach
• Evidence-Based Selection: Moves beyond subjective assessment
• Patient Counseling: Provides objective data for shared decision-making
• Quality Assessment: Allows comparison of case complexity across institutions

Current Role in Practice

While initially developed for complex multi-vessel disease, the SYNTAX Score is now commonly used in:

• Left main coronary artery disease
• Multi-vessel coronary disease
• Chronic total occlusion interventions
• Pre-operative planning for complex PCI

The score continues to evolve with newer iterations incorporating fractional flow reserve (FFR) and intravascular imaging data to provide even more comprehensive assessment of coronary artery disease complexity.