Tutorial | Part 1: Definitions

Introduction

  • You get a more accurate score by doing this in a team (ideally a panel of 3 persons).
  • Focus on the coronary anatomy (do not think treatment).
  • For an accurate SYNTAX Score outcome, both the Left Coronary Artery as well as the Right Coronary Artery must be assessed.
Additional information is available under ‘References: SYNTAX Score’.

Which lesions should be scored?

Each coronary lesion with a Diameter Stenosis ≥50% in vessels ≥1.5 mm must be scored. Each lesion can involve ≥1 diseased segments.
If serial stenoses are less than 3 vessel reference diameters apart, they should be scored as one lesion. However, stenoses at a greater distance from each other (more than 3 vessel reference diameters), are considered as separate lesions.

* ≥3 vessel reference diameters.

This case should be described as two lesions:
  • one lesion involving segments 5, 6, and 11 and
  • one lesion involving segment 6.

* <3 vessel reference diameters.
 
This case should be described as one lesion:
  • one lesion involving segments 5, 6, and 11.

Dominance

Right dominance: the posterior descending coronary artery is a branch of the right coronary artery (segment 4).

Left dominance: the posterior descending artery is a branch of the left coronary artery (segment 15). Co-dominance does not exist as an option in the SYNTAX score.

Total occlusion

No intra-luminal antegrade flow (TIMI 0) beyond the point of occlusion. However, antegrade flow beyond the total occlusion might be maintained by bridging collaterals and/or ipsi collaterals.
At the question ‘Specify which segments are diseased for lesion X' one should only fill out the segment number of the start of the Total Occlusion. 

  • Blunt stump:


  •  Bridging collaterals:



Small channels running in parallel to the vessel and connecting proximal vessel to distal and being responsible for the ipsilateral collateralization.

Note: In case of a Total Occlusion, we will not score any lesion distally (if applicable) since we are not sure about the actual situation prior to total occlusion opening.

Trifurcation

A trifurcation is a division of a mainbranch into three branches of at least 1.5mm. Trifurcations are only scored for the following segment junctions: 3/4/16/16a, 5/6/11/12, 11/12a/12b/13, 6/7/9/9a and 7/8/10/10a.
‘Specify which segments are diseased for lesion X’: one should only fill out those segment numbers of the trifurcation that have a Diameter Stenosis ≥50% in direct contact with the trifurcation.


 
  • One lesion
  • Trifurcation: ‘Yes’
  • 1 diseased segment involved (= segment no.5).

Bifurcation

A bifurcation is a division of a main, parent, branch into two daughter branches of at least 1.5mm. Bifurcation lesions may involve the proximal main vessel, the distal main vessel and the side branch according to the Medina classification. The smaller of the two daughter branches should be designated as the ‘side branch’. In case of the main stem either the LCX or the LAD can be designated as the side branch depending on their respective calibres. Bifurcations are only scored for the following segment junctions: 5/6/11, 6/7/9, 7/8/10, 11/13/12a, 13/14/14a, 3/4/16 and 13/14/15.

Bifurcation (Medina) is classified when 50% lumen narrowing occurs within 3 mm of the bifurcation point. Bifurcations are only scored for existing SYNTAX Score segments, i.e. segments that have a segment number. In other words, bifurcation lesions within side branches of the intermediate branch, the diagonal branch, the obtuse marginal branch and the posterolateral branch are considered as bifurcation of second order and not scored.

Example 1


 
  • One lesion 
  • One segment number involved/diseased (= segment: 7)
  • Bifurcation ‘Yes’ 
  • Medina class: 0, 1, 0 

Example 2


 
  • One lesion
  • Three segment numbers involved/diseased (= segments: 6, 7 and 9)
  • Bifurcation ‘Yes’
  • Medina class: 1, 1, 1

Aorto ostial

A lesion is classified as aorto-ostial when it is located within 3 mm of 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 or a visible embolization of intraluminal material downstream.

Diffuse disease

Present when at least 75% of the length of any segment(s) proximal to the lesion, at the site of the lesion or distal to the lesion has a vessel diameter of
Note: In case of a Total Occlusion, Diffusely diseased and narrowed segment for this vessel should be scored 'No' since we are not sure about the actual situation prior to total occlusion opening.

APPENDIX I: Segment definitions

1 RCA proximal  From ostium to one half the distance to the acute margin of the heart.
2 RCA mid  From end of first segment to acute margin of heart.
3 RCA distal From the acute margin of the heart to the origin of the posterior descending artery.
4 Posterior descending Running in the posterior interventricular groove.
16 Posterolateral from RCA Posterolateral branch originating from the distal coronary artery distal to the crux.
16a Posterolateral from RCA  First posterolateral branch from segment 16.
16b Posterolateral from RCA  Second posterolateral branch from segment 16.
16c Posterolateral from RCA  Third posterolateral branch from segment 16.
5 Left main  From the ostium of the LCA through bifurcation into left anterior descending and left circumflex branches.
6 LAD proximal  Proximal to and including first major septal branch.
7 LAD mid  LAD immediately distal to origin of first septal branch and extending to the point where LAD forms an angle (RAO view). If this angle is not identifiable this segment ends at one half the distance from the first septal to the apex of the heart.
8 LAD apical Terminal portion of LAD, beginning at the end of previous segment and extending to or beyond the apex.
9 First diagonal  The first diagonal originating from segment 6 or 7.
9a First diagonal a Additional first diagonal originating from segment 6 or 7, before segment 8.
10 Second diagonal  Second diagonal originating from segment 8 or the transition between segment 7 and 8.
10a Second diagonal a  Additional second diagonal originating from segment 8.
11 Proximal circumflex  Main stem of circumflex from its origin of left main to and including origin of first obtuse marginal branch.
12 Intermediate/anterolateral  Branch from trifurcating left main other than proximal LAD or LCX. Belongs to the circumflex territory.
12a Obtuse marginal a  First side branch of circumflex running in general to the area of obtuse margin of the heart.
12b Obtuse marginal b  Second additional branch of circumflex running in the same direction as 12.
13 Distal circumflex  The stem of the circumflex distal to the origin of the most distal obtuse marginal branch and running along the posterior left atrioventricular grooves. Caliber may be small or artery absent.
14  Left posterolateral  Running to the posterolateral surface of the left ventricle. May be absent or a division of obtuse marginal branch.
14a Left posterolateral a  Distal from 14 and running in the same direction.
14b Left posterolateral b   Distal from 14 and 14 a and running in the same direction.
15 Posterior descending Most distal part of dominant left circumflex when present. Gives origin to septal branches. When this artery is present, segment 4 is usually absent.