Subintimal shift as mechanism for side-branch occlusion in percutaneous treatment of chronic total occlusions with bifurcation lesions

Background: The aim of this study was to describe the mechanism of subintimal shift (SIS), standardise diagnostic criteria and sensitise the interventional community to this phenomenon. The treatment of chronic total occlusions (CTO) by means of percutaneous coronary intervention (PCI) is complicated by bifurcation lesions involved in the CTO segment or adjacent to it. Extraplaque expansion of intracoronary devices during CTO PCI may extend the dissection plane over the bifurcation with the consequential side or main branch compression by an intimo-medial flap. This phenomenon is hereby described for the first time and named subintimal shift. Methods: Experienced CTO operators from 3 international high volume centers for CTO PCI retrospectively searched their personal records for paradigmatic cases of SIS, summarising key features and proposing diagnostic criteria. Results: The series comprised 7 demonstrative cases, illustrating SIS by intravascular imaging (2 cases) or indirect angiographic signs during CTO PCI (5 cases). Five cases were triggered by stent expansion, 1 by balloon inflation and 1 case was aborted after angiographic warning signs. In 4 cases, SIS resulted in total occlusion of a branch, refractory to ballooning whenever attempted. Four cases required bailout intervention and in 2 cases the branch was left occluded, resulting in a rise of cardiac markers. Conclusions: Subintimal shift is a noteworthy complication in CTO bifurcations, potentially resulting in occlusion of the relevant side or even the main branch. Intracoronary imaging prior to stenting is recommended to understand the tissue planes. Some counterintuitive peculiarities of this phenomenon, like its refractoriness to ballooning, must be known by CTO operators for its efficient resolution

Comprehensive appraisal of cardiac motion artefact in optical coherence tomography

Background: The relation between cardiac motion artefact (CMA) in optical coherence tomography (OCT) and the phases of cardiac cycle is unclear. Methods: Optical coherence tomography pullbacks containing metallic stents were co-registered with angiography and retrospectively analyzed. The beginning of three phases, namely ejection, rapid-inflow and diastasis, was identified in angiography. Rotation, shortening, elongation and repetition were qualitatively labelled as CMA artefacts. Platforms with coaxial longitudinal connectors (ML8 and Magmaris) entered a quantitative sub-study, consisting of measuring the length of their connector at the beginning of each phase. Results: A total of 261 stents (127 patients) were analyzed, including 105 stents for quantitative sus-tudy. CMA was detected in 61 (23.4%) stents: rotation in 6 (2.3%), shortening in 50 (19.2%), elongation in 51 (19.5%) and repetition in 12 (4.6%). Shortening was always observed during ejection phase, while elongation and repetition were always observed during rapid-inflow. Rotation occurred in both ejection and rapid-inflow phases, while no artefact was reported during diastasis. Longitudinal connectors measured in early ejection phase and in early rapid-inflow phase were shorter and longer, respectively, than those measured in diastasis, irrespective of the presence of CMA in the qualitative assessment. Conclusions: Cardiac motion artefact is prevalent in OCT studies, but shortening and elongation of vascular structures occur during early ejection and during early rapid-inflow, respectively, to a greater or lesser extent in all cases. Diastasis is free of CMA and hence the period in which longitudinal measurements can be more accurately quantified