The relationship between plaque cap morphology and access technique in lower extremity chronic total occlusion.

OBJECTIVES: To evaluate access success according to plaque cap morphology in subjects with lower limb chronic total occlusion.

METHODS: A retrospective study was performed for a three-year period. Subjects with lower extremity chronic total occlusion (Rutherford category 3-6, ischaemia) were included in the study. Cap morphology was classified according to The chronic total occlusion crossing approach based on plaque cap morphology (CTOP) classification system. When describing the classification by a traditional antegrade approach, Types I, II, III and IV were defined as follows: Type I: concave proximal and distal caps; Type II: concave proximal and convex distal caps; Type III: convex proximal and concave distal caps; Type IV: convex proximal and distal caps. For the study, the data on demographics, access type, and direction crossed, access conversion, crossing success, crossing location, extravascular ultrasound guidance, catheter used, subjects, and localization of were recorded. The effect of cap morphology on crossing strategy and success was evaluated.

RESULTS: A total of 110 subjects were enrolled in this study. The type of chronic total occlusion was determined by angiography in 100% of the subjects. The number of the subjects according to CTOP morphology for Types I, II, III and IV were 22 (20%), 39 (35.5%), 23 (20.9%) and 26 (23.6%), respectively. Superficial femoral artery, popliteal, anterior tibial, posterior tibial localizations did not differ among the CTOP types ( p = 0.649, p = 0.831, p = 0.923 and p = 0.903, respectively). Among the pre-operation parameters, lesion length was the only one that is significantly shorter in Type I (14.23 ± 1.93 cm) subjects when compared with Types II (21.77 ± 3.78 cm), III (21.17 ± 2.31 cm) and IV (19.85 ± 3.29 cm) subjects ( p < 0.001, for all comparisons). Antegrade access was significantly higher in group I than in group III. Planned dual access was also significantly lower in CTOP Type I than in CTOP Types II, III and IV. Antegrade crossed direction was significantly higher in CTOP Type I than in CTOP Types II, III and IV ( p = 0.001, for all comparisons). True lumen crossing was significantly higher in CTOP Type I than in CTOP Type II ( p = 0.002). In univariate analysis, chronic total occlusion Type IV was the only significant factor for antegrade crossing ( p = 0.001). Multivariate analysis demonstrated that chronic total occlusion Type IV (OR = 0.09, p = 0.001) was an independent risk factor for antegrade crossing. The odds of antegrade crossing for chronic total occlusion Type IV was 0.190 times that of chronic total occlusion Types I-II-III combined (OR (95% CI): 0.190 (0.070, 0.519), p = 0.001).

CONCLUSIONS: CTOP Type I accesses with an antegrade access, and Type IV accesses with a retrograde strategy. Type II and Type III CTOP will need planned dual access in order to prevent device bending and subintimal access.