Revisit of the CatLet (Hexu) angiographic scoring system: a narrative review

BACKGROUND AND OBJECTIVE: We have recently developed the Coronary Artery Tree description and Lesion EvaluaTion (CatLet or Hexu, invented by He and Xu) angiographic scoring system, which, considering the coronary anatomy in its diversity, the stenosis degree of a coronary artery, and the myocardial territory subtended by the diseased coronary artery, can be utilized to predict clinical outcomes for patients with acute myocardial infarction (available at www.catletscore.com). Its values for clinical practice and coronary artery disease research are building upon. Over the past two years, the principles underlying this novel angiographic scoring system do not materially change although slight adjustments have really happened. Given these adjustments and the scoring experience gained in daily use, we think that it is necessary to elaborate on these points so that readers with interest are capable to better use this CatLet or Hexu angiographic scoring system both in clinical practice and in scientific research. METHODS: The principles underlying this novel angiographic scoring system include the 17-myocardial segmental model, law of competitive blood supply, and law of flow conservation. KEY CONTENT AND FINDINGS: The adjustments made to this novel angiographic scoring system include: (I) the short axis of the left ventricle at the basal level is used to characterize the six types of right coronary artery size; (II) segments marked with ’X and ’S have a unified preset difference of one segment as adopted in the characterization of left anterior descending artery; (III) segments marked with ’+ have been added to explain the rare variability in the obtuse marginal branches or in the posterolateral vessels in some cases. The CatLet or Hexu angiographic scoring system strictly follows the law of flow conservation in weighting assignment, and the lesion scoring correction has been additionally emphasized and detailed. CONCLUSIONS: The elaboration on these adjustments and scoring experience gained on the CatLet or Hexu angiographic scoring system will help to boost its use in cardiovascular field. The utilities of this novel angiographic scoring system have been preliminarily validated and its future is deserving of being anticipated.