 An angiographic tool grading the complexity of coronary artery disease  A semiquantitative visual score that will help us to be aware of the anatomical complexity and to anticipate procedural difficulties

 One drawback in these comparisons is that there is heterogencity in the complexity of CAD of the patients enrolled.  Absence of grading of severity of CAD and lack of comparison of lesion complexity between various groups severely limits the interpretation of results.

 For example pts with distal LM trifurcation disease with occluded RCA is pooled together as TVD with patients with 3 focal lesions in midportion of the 3 coronary arteries.  The first has a greater therapeutic challenge for PCI and both have completely different prognosis regardless of revascularisation.

 SYNTAX (Synergy between PCI with TAXUS stent and cardiac surgery) trial was organised for patients with significant lesion in LM and /or TVD.  The syntax score has been used in this study to categorize the coronary vasculature with respect to the number of lesions their functional impact,location and complexity.

 The SYNTAX score has been developed based on the following:  1. The AHA classification of the coronary tree segments modified for the ARTS study  2. The Leaman score  3. The ACC/AHA lesions classification system  4. The total occlusion classification system  5. The Duke and ICPS classification systems for bifurcation lesions  6. Consultation of experts

 Arterial tree is divided into 16 segments  This system has been adopted for the syntax scoring.

 Based on severity of luminal diameter narrowing  Weighed according to usual blood flow to LV by each vessel

 significant lesion-50% reduction in lumen diameter by visual assessment in vessels >1.5mm in diameter.  Less severe lesions not included  Percent diameter stenosis is not included  Only occlusive lesions (100% stenosis)-MF 5  And non occlusive lesions (50-99% stenosis)- MF 2

 In right dominant system -RCA supplies 16% -LCA supplies 84% of flow to LV  Of the 84%,66% is by LAD and 33% by LCX.  The LM supplies approximately 5 times,the LAD app.3.5 times and LCX app.1.5 times blood as the RCA to the LV.

 For left dominant system -LM supplies 100%(hence multiplication factor 6) -LAD 58% (MF-3.5) -LCX 42% (MF-2.5)  The contribution is used as a multiplication factor -

 Type A (high success,low risk)  Type B (mod success,mod risk)  Type C (low success,high risk)

 No antegrade flow is visible distal to lesion  Distal segments may be filled via bridging,ipsilateral or contralateral collaterals.  Parameters included are -Age of occlusion -blunt stump -presence of bridging collaterals -presence of side branch -occlusion length

 Defined as junction of main vessel and a side branch (1.5mm)  Not involving ostium(A,B,C)  Involving ostium(D,E,F,G)

 5/6/11  6/7/9  7/8/10  11/13/12a  13/14/14a  3/4/16  13/14/15

 3/4/16/16a  5/6/11/12  11/12a/12b/13  6/7/9/9a  7/8/10/10a

 Aorto ostial: A lesion is classified as aorto- ostial when it is located immediately at the origin of the coronary vessels from the aorta (applies only to segments 1 and 5, or to 6 and 11 in case of double ostium of the LCA).  Severe tortuosity: One or more bends of 90° or more, or three or more bends of 45° to 90° proximal of the diseased segment.  Length >20mm: Estimation of the length of that portion of the stenosis that has ≥ 50% reduction in luminal diameter in the projection where the lesion appears to be the longest. (In case of a bifurcation lesion at least one of the branches has a lesion length of >20mm).

 Heavy calcification: Multiple persisting opacifications of the coronary wall visible in more than one projection surrounding the complete lumen of the coronary artery at the site of the lesion.  Thrombus: Spheric, ovoid or irregular intraluminal filling defect or lucency surrounded on three sides by contrast medium seen just distal or within the coronary stenosis in multiple projections

 The SYNTAX score is lesion based  A separate number calculated per lesion is Summed to generate the total SYNTAX score  Questions 1-3: determine dominance, total no. of lesions(max.12) and vessel segments/lesion  Questions 4-12: detail adverse lesion characteristics; are repeated for each lesion.  The SYNTAX score is calculated after answering a set of sequential, interactive self-guided questions

 Does not entail any clinical variable  Comorbidities are known to impact early outcomes of patients undergoing revascularisation.  Hence limited use in guiding decision making between CABG and PCI.  Relies on pure visual interpretation of lesion severity and subjective variables.

 Syntax score +  Age  Creatinine  EF

 Anatomical syntax score  Age  Creatinine clearance  LVEF  ULMCA  Peripheral Vascular Disease  Female sex  COPD

 broadly accepted instrument to help predict early outcomes in patients who undergo coronary artery bypass grafting (CABG).

MACCE to 5 years by Syntax Score Tercile Left Main Disease CABG PCI or CABG

The SYNTAX population represents the most complex patients ever studied for PCI in a randomised trial.  The more complex patients are better treated by CABG, but PCI is an acceptable alternative for those with less complex disease(ie, SYNTAX Scores 22 or less).

 The SYNTAX score is a new, innovative tool to describe the complexity of vasculature  The raw SYNTAX score is a good predictor of MACE  PCI patients with lower raw SYNTAX scores have similar 12-month MACE rates to CABG patients.  Increasing SYNTAX scores (and lesion complexity) are related to increased adverse outcomes in PCI, whereas outcomes of CABG are independent of SYNTAX score.

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