Small Vessel Coronary Artery Disease: Rationale for Standardized Definition and Critical Appraisal of the Literature.

Small vessel coronary artery disease (CAD) is present in 30% to 67% of patients undergoing percutaneous coronary intervention according to different series, representing an unmet clinical need in light of an increased risk of technical failure, restenosis, and need for repeated revascularization. The definition of small vessel is inconsistent across trials, and no definite cutoff value has yet been determined. The lack of consensus on the definition of small vessel CAD has contributed to the high degree of heterogeneity in the safety and efficacy of the various revascularization options. Therefore, the aim of this article is to provide a critical appraisal of existing reports and to propose a reference vessel diameter of <2.5 ​mm definition of small vessel CAD to guide future clinical trials and clinical decision-making.