A case of very late stent thrombosis on the protruded struts at the left main coronary bifurcation

Abstract

A previous autopsy study has revealed that malapposed or protruded struts in the coronary bifurcation were a risk factor for very late stent thrombosis (VLST); however, a live clinical case has not yet been reported due to difficulty in observation at the VLST site. In this case, a 56-year-old male patient underwent a zotarolimus-eluting stent implantation in the proximal left anterior descending artery for acute myocardial infarction 3 years previously and had been treated with dual antiplatelet therapy. The patient experienced chest pain and suddenly collapsed due to acute coronary syndrome caused by a huge thrombus in the left main coronary bifurcation. After insertion of the intra-aortic balloon pump, kissing balloon inflation improved coronary flow and hemodynamics. Two weeks later, a 3-dimensional optical frequency domain imaging (3-D OFDI) revealed uncovered protruded struts on the ostium of the left circumflex artery (LCX). We removed the protruded struts using a double lumen catheter, for which the second wire was advanced to more distal cell along with the first wire located in the same LCX branch. 3-D OFDI clearly demonstrated that uncovered protruded struts at the LCX ostium were the cause of VLST and navigated optimal wiring with a double lumen catheter.

Learning objective: Existence of protruded struts at the coronary bifurcated branch ostium is a risk factor for very late stent thrombosis. Three-dimensional optical frequency domain imaging clearly demonstrates the protruded strut configuration at the side branch of ostium and facilitates optimal guide wire re-crossing for kissing balloon inflation. Usage of double lumen catheter increases the possibility of optimal side branch wiring.

Introduction

A previous autopsy study revealed that malapposed or protruded struts of drug-eluting stent implanted at the bifurcation are a risk factor for stent thrombosis in both very late and early phases [1]. However, a clinically alive case has not yet been reported because the confirmation of intimal uncoverage of these floating unopposed struts is difficult via angiography or intravascular ultrasound. The optical coherence tomography (OCT) and optical frequency domain imaging (OFDI) can visualize the extent and degree of floating struts as well as the guide wire (GW) crossing point at the side branch ostial dilation [2], [3]. We encountered a case of very late stent thrombosis (VLST) on the protruded struts in the left main (LM) coronary bifurcation and removed the protruded struts using a novel technique with a double lumen catheter (DLC) under the guidance of 3-dimensional (3-D) OFDI.

Case report

A 56-year-old male patient underwent a zotarolimus-eluting stent implantation in the proximal left anterior descending artery (LAD) for acute myocardial infarction 3 years previously and had been treated with dual antiplatelet therapy (aspirin and clopidogrel) since then. However, clopidogrel had been reduced from 75 to 25 mg from 1 year later. Although he had not experienced any significant chest-related symptoms, he felt chest pain while drinking at a party and collapsed suddenly. He was transferred to our hospital and presented with pre-shock vitals. His coronary risk factors were hypertension, dyslipidemia, and history of smoking. After insertion of intra-aortic balloon pump, coronary angiography (CAG) revealed a hazy image in the LM bifurcation (Fig. 1A–C, Video 1). The OFDI demonstrated a huge thrombus at the LM bifurcation (Fig. 1D, Videos 2 and 3). After a 7Fr guiding catheter engagement and insertion of the GW to both LAD and left circumflex artery (LCX), thrombus aspiration was performed, however, it failed. The thrombus was compressed by kissing balloon inflation (KBI), and the hazy image disappeared without any deterioration in coronary flow. He did not have any episode of atrial fibrillation or present any embolic events in the systemic survey after administration. Two weeks later, CAG did not show any hazy image in the LM bifurcation (Fig. 2A), whereas the OFDI demonstrated some overhanging struts without any intimal coverage on the LCX ostium (Fig. 2B and C, Video 4). We tried to cross a GW to the protruded strut. At first, the GW crossing to LCX failed from advancing to the protruded stent struts regardless of using a DLC [Fig. 2D(a)]. Then, the LAD GW was removed, and the DLC was set along the LCX GW [Fig. 2D(b)]. The second GW was aimed for reaching the more distal strut, and it successfully crossed to the more distal cell [Fig. 2D(c)]. GW crossing to another cell was confirmed by stack at the LCX ostium in advancing the DLC, because each GW was crossed to the separate cells [Fig. 2D(d) and E]. These protruded struts were removed with KBI to prevent the recurrence of VLST in the LM bifurcation (Fig. 3A–C, Video 5). A stretched strut remained at the proximal site of the LCX ostium within acceptable malapposition (maximal distance 320 μm, Fig. 3D and E, Video 6). Final CAG showed excellent coronary flow in both coronary branches without any carina shift or dissection in the LM bifurcation (Video 7).

Fig. 1.

Acute coronary syndrome due to very late stent thrombosis 3 years after ostial stenting in left anterior descending artery. Coronary angiography showed hazy images at the left main bifurcation (arrows) in antero-posterior caudal view (A), right anterior objection caudal view (B), and magnified view around left main bifurcation (C). Optical frequency domain imaging clearly demonstrated thrombus on the struts (*) at the distal left main (D), the left circumflex ostium (E), and 3-dimensional imaging (F).

Fig. 2.

Coronary angiography at 2-week follow-up did not show any thrombus (A). Optical frequency domain imaging showed uncovered jailed struts remained at the left circumflex (LCX) ostium in the 2-dimensional (B, arrows) and 3-dimensional images (C, arrows). Scheme of the method of more distal cell guide wire (GW) crossing using a double lumen catheter (DLC) (D). (a) GW crossing to LCX failed to be advanced in the protruded stent struts regardless of using a DLC. (b) The GW in left anterior descending artery (LAD) was removed, and the DLC was set along the LCX GW. The second GW aimed to a more distal strut. (c) Successful GW crossing to more distal cell. (d) GW crossing to another cell was confirmed by stack of DLC at the LCX ostium. (E, arrow).

Fig. 3.

Final coronary angiography (A), 2-dimensional (B), and 3-dimensional optical frequency domain imaging (OFDI) (C) showed that no jailed strut remained at the carinal site of the left circumflex ostium (asterisks). One stretched strut remained at the proximal site (C, arrows), maximal distance of malapposition was 320 μm in 2-dimensional OFDI images (D, E: pullback from left circumflex and anterior descending arteries, respectively, arrows).

Discussion

In this case, a huge thrombus located at the distal LM bifurcation caused acute coronary syndrome and the OFDI demonstrated the uncovered protruded struts of the zotarolimus-eluting stent at the LCX ostium placed three years previously. Since the patient had not presented with any atrial fibrillation or embolization, VLST was the most likely diagnosis. A technique using a DLC in which two GWs were advanced into the same branch was successfully performed under the guidance of the 3-D OFDI to obtain optimal GW crossing to the more distal cell.

Malapposed or protruded struts at the bifurcated branch ostium have been reported to be a risk factor for late stent thrombosis in a previous autopsy study [1], however, routine performance of KBI after main vessel stenting for side branch dilation and removal of jailed struts did not provide significant benefits in the clinical studies [4], [5]. The OCT/OFDI studies at mid-term follow-up period reveal the following: (1) Non-KBI treatment led to more thrombus formation on the jailed struts than seen by KBI treatment [6]. (2) Struts on the larger side branch ostium were more unlikely to be covered with intima [7]. (3) In the non-KBI treatment after LM-LAD stenting, number of struts overhanging the LCX ostium had a positive correlation with the LCX ostial narrowing at the time of follow-up [8]. A recent study of 3-D OCT demonstrated that suboptimal GW re-crossing, stent link-connection located at the carina, and a bifurcation with perpendicular bifurcation angle had more risk of floating struts at the bifurcation even after KBI [2]. Inappropriate side branch dilation also led to serious stent deformation [3]. DLC is useful to advance the GW to the optimal cell at the side branch ostium due to strong back up and a lower risk of twisting of two GWs when the first GW is usually advanced to the main vessel. In the present case, the first GW changed the position from the LAD to the LCX which was the same as the target branch, after failure of usual method. The more distal optimal cell could be aimed at, which was confirmed by the stack of DLC in advancing toward the LCX, because two GWs were in the separate cells. The success of this technique was confirmed by the 3-D OFDI and clear removal of the protruded struts at the carinal site of the LCX ostium was completed by the KBI. Since proximal part of zotarolimus-eluting stent had the limitation of cell expansion, one stretched strut remained at the proximal site of the LCX ostium within acceptable malapposition for the future intimal coverage. The optimal side branch dilation with less protruded struts under the 3-D OCT/OFDI guidance may promote complete intimal coverage of the stent at the bifurcation and shorten the period of dual anti-platelet therapy.

Conclusion

Protruded struts in the LCX ostium have a possible risk of VLST owing to the unlikeliness of being covered with intima. Using a DLC under the 3-D OCT/OFDI guidance is helpful for clear removal of the protruded struts.

Conflict of interest

None declared.

Funding

None declared.

Appendix A. Supplementary data

The following are Supplementary data to this article: