SYNTAX Scores

SYNTAX scores

SYNTAX score I is a scoring system for coronary lesions based on the online calculator available at https://syntaxscore.org/. It is a tool for assessing the complexity of coronary artery disease. The online version is updated when new data from the follow up of SYNTAX trial is available. Latest version is 2.28 as on 10th August, 2023. It has been recommended that scoring has to be done by a team, ideally a panel of three persons. Focus has to be on the coronary anatomy and not on the treatment, while scoring. For accurate SYNTAX Score outcome, both the left coronary artery and the right coronary artery must be assessed. Before using the online calculator, the online tutorial should be read.

All lesions in both coronary territories in vessels of at least 1.5 mm diameter and of 50% or more severity should be scored. If tandem lesions are more than three times the diameter of the reference vessel apart, they should be scored as separate; otherwise as a single lesion.

For the purpose of SYNTAX score, the vessel which gives rise to the posterior descending coronary artery is considered as the dominant vessel and there is no provision for co-dominance. Proximal, mid and distal right coronary artery segments are numbered 1-3 and posterior descending coronary artery as segment 4. Proximal segment is half way up to the acute margin. Rest of RCA up to acute margin is mid segment. From acute margin to PDA is distal RCA. Posterior left ventricular branch originating from the right coronary artery is numbered 16 and its branches as 16a, 16b, 16c, starting from proximal to distal.

Left main coronary artery is segment 5. Proximal, mid and apical left anterior descending coronary artery segments are numbered 6-8. Proximal LAD is up to and including first major septal branch. Mid LAD is beyond that, up to one half distance from first septal to the apex or the region where the LAD forms an angle in RAO view. 9 and 10 are diagonals. 11, 13 and 14 are for left circumflex coronary artery and its branches. When PDA arises from the LCX, it is designated as 15. Intermediate coronary artery is designated 12.

SYNTAX Score II has a different questionnaire which also includes SYNTAX Score I. There is a nomogram which predicts 4-year mortality as a function of the SYNTAX II Score for patients proposed to undergo myocardial revascularization with coronary artery bypass grafing or percutaneous coronary intervention. Other parameters in SYNTAX Score II questionnaire are age, creatinine clearance, left ventricular ejection fraction, left main disease, gender, chronic obstructive pulmonary disease and peripheral vascular disease.

Functional syntax score uses fractional flow reserve data in addition to provide a better scoring system.