Scaffold thrombosis following implantation of the ABSORB BVS in routine clinical practice: Insight into possible mechanisms from optical coherence tomography

ObjectivesTo identify potential underlying mechanisms of early and (very) late scaffold thrombosis (ScT) by optical coherence tomography (OCT), in a frame-by-frame analysis. BackgroundThe absorb scaffold is associated with an increased risk of ScT compared with metallic stents. Several potential causes of bioresorbable ScT have been identified, however the precise etiology still remains unclear. MethodsBetween February 2013 and February 2016, 13 patients presenting with definite ScT underwent OCT imaging. After guidewire passage or balloon inflations, OCT images were acquired. Pullbacks were assessed offline at each 1mm longitudinal interval within the treated segment and the 5mm segments adjacent to both edges. Primary cause of ScT was assessed by reviewing medical records, baseline angiographic films, and OCT pullback and angiographic films at time of ScT. Results13 patients, with 14 thrombotic lesions presented either with early ScT (i.e., 30days) or very (late) (i.e., >30days). Analysis demonstrated a significantly smaller in-scaffold maximal lumen diameter in the early cases (2.750.85mm vs. 3.00 +/- 0.46mm; P=0.033) and a nonsignificant smaller minimal scaffold diameter (2.44 +/- 0.62mm vs. 2.58 +/- 0.37mm P=0.097). Per-strut analysis demonstrated significantly more malapposed scaffold struts in (very) late cases (6% versus 0.6%, P<0.001). Assessment of the predominate cause showed underexpansion as the dominant factor in the early cases, while malapposition was predominantly seen in the (very)late cases. ConclusionsOCT performed in patients presenting with Absorb ScT demonstrated that malapposition of scaffold struts was more prominent in patients presenting with (very) late ScT, while underexpansion was more frequent in the early cases.