Serial endovascular assessment of polytetrafluoroethylene-covered stent: Capabilities and limitations of intravascular imaging modalities affected by a temporal factor

Abstract

A 47-year-old male who previously underwent coronary bypass graft surgery was transferred to our hospital for treatment of bare metal in-stent restenosis (ISR) of severely calcified left main (LM) coronary lesion. During a repeat coronary intervention, LM coronary perforation occurred after rotational atherectomy followed by balloon dilatation. Hemostasis was successfully achieved by implantation of a single polytetrafluoroethylene (PTFE)-covered stent. Although intravascular ultrasound (IVUS) and optical coherence tomography (OCT) were documented, any additional information was not obtained except stent expansion. Routine 6-month follow-up angiography revealed no findings of restenosis. Three representative imaging modalities, IVUS, OCT, and angioscopy were applied to visualize and differentiate any structures within the PTFE-covered stent. Intravascular findings included, (1) vascular structures outside the covered stent could be observed sufficiently by both IVUS and OCT at this time that could not be seen at all just after implantation, (2) neointimal hyperplasia distributed dominantly at both stent edges, and (3) in-stent micro thrombi still existed even 6 months after implantation. Intravascular findings of PTFE-covered stent may vary between the observational periods. Furthermore, vascular healing process of this special stent may be different from those of non-covered mesh stents. <Learning objective: Even with the use of IVUS and OCT, it may be difficult to evaluate apposition of PTFE-covered stent just after implantation. However, it could be visualized as being sufficiently similar to the other common stents at 6-month follow-up. Unique longitudinal NIH distribution (bilateral edge dominant) was evaluated, and existence of micro thrombi within PTFE-covered stent even at 6 months.>.

Keywords: Angioscopy; IVUS; OCT; Polytetrafluoroethylene-covered stent.

Fig. 1

A repeat coronary intervention was performed for left main lesion with severe calcification. After rotational atherectomy (burr 1.5 mm) and plain old balloon angioplasty, coronary perforation occurred. Red arrows show perforation site of left main lesion. As a result, a polytetrafluoroethylene (PTFE)-covered stent was implanted from left main lesion to proximal of left circumflex artery. Yellow arrows show range of PTFE-covered stent. After 6-month follow-up angiography, there was no in-stent restenosis in PTFE-covered stent. PCI, percutaneous coronary intervention.

Fig. 2

Apposition of polytetrafluoroethylene (PTFE)-covered stent by optical coherence tomography (OCT) and intravascular ultrasound (IVUS) just after stent implantation into perforated left main trunk and follow-up at 6 months after implantation of PTFE-covered stent. In the acute period, the outside of a stent cannot be observed. However, it was possible to have observed with IVUS and OCT the outside of PTFE after 6 months without high-intensity image of PTFE.

Fig. 3

Follow-up optical coherence tomography (OCT) and angioscopy of polytetrafluoroethylene (PTFE)-covered stent after 6 months. Yellow arrow shows range of PTFE-covered stent, yellow asterisk is angioscopy wire. Neointimal hyperplasia (NIH) at stent proximal and distal edge was observed in PTFE-covered stent by OCT from short-axis and longitudinal images. NIH at stent mid lesion was not observed by OCT and struts were visible by angioscopy (NSC grade 0 or 1).

Fig. 4

Follow-up coronary optical coherence tomography (OCT) after 6 months. Micro thrombi (A to C) were observed in mid lesion of polytetrafluoroethylene-covered stent by OCT. They were identified as low-backscattering projections in the lumen of the artery and without distal shadowing. Therefore these structures were identified as white thrombus.

Fig. 5

Average neointimal hyperplasia (NIH) thickness at every frame from the proximal lesion to distal lesion of polytetrafluoroethylene-covered stent. Analysis object was total of 720 struts at 56 frames (12.9 ± 1.55 struts/frame). White thrombi (Fig. 4) were observed for NIH around thin frame 35.