Coronary Drug-eluting Stents
Figure 3: A Case of Late Drug-eluting Stent Thrombosis in Bifurcation Lesion
B
LCX E
LM DA D D
LAD F
LAX LAD A C
Although it is not fully understood why stent fractures cause adverse events, lack of stent integrity such as distortion or acquired underexpansion may play an important role in the occurrence of adverse events. Previous clinical studies have reported that the main risk factors for stent fracture are longer stent length, right coronary artery (RCA) or saphenous vein graft lesion location, lesion with high motion, overlapping stent and SES use.38,40,45
Our findings showed SES E G F H
A 55-year-old man with a history of smoking, hypertension and dyslipidaemia received two paclitaxel-eluting stents (PES) in the distal left main ostium of left anterior descending coronary artery (LAD) and left circumflex (LCX) with overlapping taxus stents placed in the LAD. The patient died suddenly two years after stent implantation. Radiograph shows mildly calcified coronary artery. Both stents are occluded with platelet-rich thrombus (Thr) at the ostium of LAD and LCX (A). High-magnification images demonstrated adherent thrombus in the region of the uncovered struts at the flow divider (B, C). Uncovered struts and adherent thrombus was also observed in all sections of the LCX stent (D, E, G). The middle to distal portion of the LAD stent showed absence of thrombus and healed luminal surface with mild neointimal thickening (D, F, H). Source: Nakazawa G, Yazdani SK, Finn AV, et al.35
with gap in the stent body). The incidence of adverse pathological findings (thrombosis and restenosis) was assessed histologically.
Stent fracture was documented in 51 lesions (29%; grade I=9, II=14, III=11, IV=6 and V=9). There was no significant difference in age, gender and cause of death between patients with fracture and those without. Lesions with stent fracture had longer duration of implant as compared with those without fracture (172 days [31–630] versus 44 days [7–270], p=0.004), whereas no statistical difference in duration of implant was identified between each grade of stent fracture (grade I: 31 days [5, 616], II: 105 days [27, 1,095], III: 376 days [72, 570], IV: 331 days [31, 833] and V: 172 days [44, 450], p=0.70). Furthermore, lesions with stent fracture showed a higher rate of SES usage (63% versus 36%, p=0.001), longer stent length (30.0mm [22.0–40.0] versus 20.0mm [14.0–27.3], p<0.0001), and a higher rate of overlapping stents (45% versus 22%, p=0.003) as compared with lesions without stent fracture. A forward stepwise logistic regression analysis demonstrated that longer stent length (OR: 1.07, 95% CI: 1.036–1.100, p<0.0001), use of SES (OR: 3.40, 95% CI: 1.57–7.33, p=0.002) and longer duration of implant (OR: 1.002, 95% CI: 1.001–1.003, p=0.002) were independent determinants of stent fracture.
Histological evaluation showed that neointimal thickness was similar between lesions with stent fracture and those without (0.11mm [0.06, 0.19] versus 0.11mm [0.03, 0.19], p=0.62). There was no significant difference in fibrin deposition (fibrin score, fracture [+]: 1.0 [0.1, 1.5] versus fracture [-]: 1.4 [0.4, 2.0]) and inflammation (inflammatory score, fracture [+]: 1.0 [0.5, 1.6] versus fracture [-]: 1.4 [0.4, 2.0]), including a similar degree of giant cell and eosinophil infiltration. Furthermore, there were no differences in these parameters among the various fracture grades (i.e. grade I–V). Six adverse events (five thrombosis and one restenosis) were associated with grade V fracture (67%), while there were no fracture-site-related adverse pathological findings in stents with grades I–IV except for one stented lesion with
32
were associated with higher incidence of stent fracture; the flexible ‘N’-shaped undulating longitudinal inter-sinusoidal ring linker segment was the most frequent location of the fractures, which are smaller in width than the sinusoidal ring portion. The relationship between longer implant duration and higher incidence of stent fracture suggests that stent fracture may result from continuous stress over time on the implant that leads to greater metal fatigue with eventual fracture. However, it should also be noted that stent fracture was seen even in the patients who died shortly after stent implantation, which is probably procedure related (high pressure and/or oversized balloon, overlapping stent, etc.).
In summary, the incidence of DES fracture is 29% of the stented lesions at autopsy, which is much higher than clinically reported. A high rate of adverse pathogical findings was observed in lesions with grade V fracture, while fracture with grades I–IV did not have a significant impact on the clinical outcome. Longer stent length, SES usage and longer duration of stent implant were identified as independent predictors of stent fracture.
Coronary Responses and Differential Mechanisms of Late Stent Thrombosis Attributed to Sirolimus-eluting and Paclitaxel-eluting Stents
Previous clinical trials have reported differences in angiographic late lumen loss in patients receiving SES or PES,46
whereas it remains
unclear whether the long-term histological responses to each stent type are different and how this relates to the time course of arterial healing and mechanism(s) of LST. Therefore, we evaluated vascular healing response and the mechanism(s) of LST in patients with first-generation DES.47
The overall analysis included 174 cases (230
DES lesions) from the CVPath autopsy registry, and histomorphometry was performed on coronary stents from 127 cases (171 lesions) who died ≥30 days after receiving stent implants. Analysis of individual lesions with duration of implant <30 days (SES=25 and PES=34) revealed that the incidence of early stent thrombosis was equivalent for lesions with SES and PES (44% versus 38%, p=0.79). Histologically, no differences in the extent of inflammation and fibrin deposition were noted between SES and PES implants <30 days.
Lesions with duration of implant ≥30 days comprised of 77 SES and 94 PES lesions: 40 SES (52%) and 53 PES (56%) lesions were treated for off-label indications, which included stents deployed for AMI or bifurcation lesions, left main artery, bypass graft, restenosis, chronic total occlusion or lesion lengths >30mm.48
There was no significant
difference in the incidence of LST between SES and PES (21% versus 27%, p=0.47). Neointimal thickness was significantly greater in PES as compared with SES (0.13mm [0.03, 0.20] versus 0.10mm [0.04, 0.15], p=0.04). Similarly, PES had greater maximum neointimal thickness than
INTERVENTIONAL CARDIOLOGY
grade IV that had a long overlapping stent (grade I–IV versus grade V, p<0.0001). A representative case of grade V fracture of DES is shown in Figure 4.
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