Syntax Score in Coronary Artery Disease

Syntax Score in Coronary Artery Disease: A Detailed Guide

Introduction

When a patient is diagnosed with coronary artery disease (CAD), one of the most important questions for cardiologists is not only how many blockages are present, but also how complex those blockages are. Two patients may both have three blocked arteries, yet one may be easily treated with stenting while the other may benefit more from bypass surgery.

This is where the SYNTAX Score becomes extremely valuable.

The SYNTAX Score is an angiographic tool used to quantify the severity and complexity of coronary artery disease and helps guide decisions between Percutaneous Coronary Intervention (PCI) and Coronary Artery Bypass Grafting (CABG).

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What Does SYNTAX Stand For?

SYNTAX stands for:

Synergy Between Percutaneous Coronary Intervention with TAXUS and Cardiac Surgery

The score was originally developed during the landmark SYNTAX Trial.

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Why Was the SYNTAX Score Developed?

Traditional methods focused mainly on the number of diseased vessels:

Single vessel disease

Double vessel disease

Triple vessel disease

Left main disease

However, these categories do not account for lesion complexity such as:

Bifurcation lesions

Chronic total occlusions

Severe calcification

Long lesions

Vessel tortuosity

Diffuse disease

The SYNTAX Score was developed to objectively measure these complexities.

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What Does the SYNTAX Score Measure?

The score evaluates all coronary lesions that meet the following criteria:

Diameter stenosis ≥50%

Vessel diameter ≥1.5 mm

Each lesion receives points based on its anatomical characteristics.

The total score is the sum of all lesion scores.

A higher score indicates:

More complex coronary anatomy

Greater procedural difficulty

Higher risk of adverse outcomes after PCI

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Components of the SYNTAX Score

1. Number of Lesions

The more significant lesions present, the higher the score.

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2. Lesion Location

Lesions in strategically important locations receive more points.

Examples include:

Left main coronary artery

Proximal LAD

Proximal circumflex artery

Blockages in these areas jeopardize larger myocardial territories.

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3. Bifurcation Lesions

Lesions involving branch points are technically more challenging.

Examples include:

Medina 1,1,1 lesions

Left main bifurcation disease

These lesions often require:

Two-wire techniques

Complex stenting strategies

Additional procedural time

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4. Trifurcation Lesions

Disease involving three branches significantly increases procedural complexity and score.

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5. Chronic Total Occlusion (CTO)

A CTO is a complete occlusion lasting more than three months.

Additional factors increasing CTO score include:

Blunt stump

Length >20 mm

Severe calcification

Bridging collaterals

Vessel tortuosity

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6. Severe Calcification

Heavy calcium limits:

Balloon expansion

Stent delivery

Stent expansion

These lesions may require:

Rotational atherectomy

Orbital atherectomy

Intravascular lithotripsy

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7. Vessel Tortuosity

Marked vessel angulation and tortuous anatomy increase procedural complexity.

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8. Diffuse Disease and Small Vessels

Long segments of disease or small caliber vessels increase the score because complete revascularization becomes more difficult.

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9. Aorto-Ostial Lesions

Lesions at the origin of coronary arteries are technically demanding and associated with higher restenosis rates.

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10. Thrombus Presence

Visible intracoronary thrombus adds to lesion complexity and procedural risk.

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SYNTAX Score Categories

SYNTAX Score Complexity

0–22 Low complexity

23–32 Intermediate complexity

≥33 High complexity

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Clinical Interpretation

Low SYNTAX Score (0–22)

Coronary anatomy is relatively straightforward.

PCI generally provides outcomes comparable to surgery.

Drug-eluting stents are often preferred.

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Intermediate SYNTAX Score (23–32)

Decision should involve a multidisciplinary Heart Team discussion.

Factors considered include:

Age

Diabetes

LV function

Frailty

Patient preference

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High SYNTAX Score (≥33)

Indicates highly complex disease.

CABG usually provides superior long-term outcomes.

PCI may result in higher rates of repeat revascularization.

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Role in Left Main Coronary Artery Disease

The SYNTAX Score plays a major role in left main disease management.

Low to Intermediate Score

PCI may be considered if anatomy is suitable.

High Score

CABG is generally preferred because of improved long-term outcomes.

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Role in Multivessel Disease

In patients with:

Triple vessel disease

Diabetes mellitus

Reduced LV function

Higher SYNTAX scores tend to favor CABG over PCI.

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SYNTAX Score II

The original SYNTAX score only evaluated coronary anatomy.

The newer SYNTAX Score II combines anatomical and clinical variables such as:

Age

Gender

Creatinine clearance

Left ventricular ejection fraction

COPD

Peripheral vascular disease

Presence of left main disease

This provides a more individualized prediction of outcomes with PCI versus CABG.

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Variables Included in SYNTAX Score II 2020

Anatomical Variables

Original anatomical SYNTAX score

Presence of left main disease

Three-vessel disease

Clinical Variables

Age

Sex

Creatinine clearance

Left ventricular ejection fraction

COPD

Peripheral arterial disease

These variables help predict long-term mortality after either PCI or CABG.

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Advantages of the SYNTAX Score

Standardized assessment of CAD complexity

Assists in revascularization planning

Improves Heart Team decision-making

Predicts procedural risk

Predicts long-term outcomes

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Limitations

Requires coronary angiography.

Interobserver variability exists.

Does not assess plaque composition.

Functional significance of lesions is not considered.

FFR and intracoronary imaging may alter treatment decisions.

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Practical Clinical Use

The SYNTAX Score should not be used in isolation. Modern decision-making combines:

SYNTAX Score

Clinical characteristics

Surgical risk scores

Frailty assessment

Patient preference

Functional ischemia assessment

Intracoronary imaging findings

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Key Takeaway

The SYNTAX Score remains one of the most important tools in interventional cardiology for assessing the anatomical complexity of coronary artery disease.

Low scores favor PCI

High scores favor CABG

Intermediate scores require individualized Heart Team decisions

Rather than simply counting the number of blocked arteries, the SYNTAX Score helps clinicians understand the true complexity of coronary anatomy and select the most appropriate revascularization strategy for each patient.

Summary:

The #SYNTAX Score (Synergy Between PCI With Taxus and Cardiac Surgery) 

The SYNTAX Score is an angiographic scoring system used to quantify the complexity of coronary artery disease and to help determine whether a patient is more suitable for percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG).

Types of SYNTAX Scores

1. SYNTAX Score I (Anatomical Score)

Based only on coronary anatomy:

* Number of lesions

* Lesion location

* Total occlusions

* Bifurcation/trifurcation lesions

* Calcification

* Tortuosity

* Thrombus

* Diffuse disease/small vessels

Risk categories:

* Low: 0–22

* Intermediate: 23–32

* High: ≥33

Clinical implication:

* Low (0–22): PCI or CABG may both be reasonable depending on clinical factors.

* Intermediate (23–32): CABG is generally favored, especially in multivessel disease.

* High (≥33): CABG is strongly preferred because of better long-term outcomes.

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2. SYNTAX Score II

Combines anatomical complexity with clinical variables:

* Age

* Sex

* Creatinine clearance

* Left ventricular ejection fraction (LVEF)

* COPD

* Peripheral arterial disease

* Unprotected left main disease

* Anatomical SYNTAX Score

This score predicts:

* 4-year and 10-year mortality

* Expected outcomes with PCI versus CABG

* Individualized treatment recommendation

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Current Guideline-Based Role

According to recent European Society of Cardiology and European Association for Cardio-Thoracic Surgery guidelines:

Coronary Anatomy Preferred Revascularization

Three-vessel disease + SYNTAX ≥33 CABG (Class I)

Left main disease + high SYNTAX CABG preferred

Left main disease + low/intermediate SYNTAX PCI or CABG after Heart Team discussion

Diabetes with multivessel disease CABG generally preferred

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Why CABG Is Preferred in High SYNTAX Scores

Patients with high anatomical complexity have:

* More complete revascularization with CABG

* Lower rates of repeat revascularization

* Lower incidence of major adverse cardiac and cerebrovascular events (MACCE)

* Better long-term survival, particularly in three-vessel disease and diabetic patients

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Key Points for Clinical Practice

* SYNTAX 0–22: PCI is generally acceptable.

* SYNTAX 23–32: CABG is often preferred, particularly in three-vessel disease.

* SYNTAX ≥33: CABG is the recommended strategy in most patients.

* Decisions should always be made by a Heart Team, considering coronary anatomy, comorbidities, frailty, surgical risk, patient preference, and technical feasibility.

Note: The SYNTAX Score is one component of decision-making. Modern practice integrates anatomical complexity with clinical risk, surgical risk (e.g., STS or EuroSCORE II), and patient-centered factors rather than relying on the anatomical score alone.

#CABG #PCI #angioplasty #angiogram #CAG