Complete Cypher‚Ñ¢ Stent Fracture and Migration in the Ostium of the Right Coronary Artery

Case Report. A 73-year-old female with hypertension and dyspnea on exertion underwent cardiac catheterization following an abnormal sestamibi stress test that showed inferior ischemia. Angiography revealed mild disease in the left anterior descending (LAD) coronary artery and a 70% stenosis at the ostium of the right coronary artery (Figure 1A). The patient was also noted to have moderate aortic stenosis by echocardiography and left heart catheterization.
Using a 6 Fr JR4 guiding catheter, an Asahi Prowater guidewire (Abbott, Redwood City, California) was used to cross the lesion at the ostium of the right coronary artery (RCA). A 3.5 x 18 mm Cypher stent was deployed at the ostium of the RCA at 16 atm with approximately 2 mm of stent visible in the aorta. Due to edge dissection, a second 3.5 x 13 mm Cypher stent was deployed at 14 atm in the proximal RCA, overlapping the ostial stent. A postdeployment inflation was performed with the second stent balloon at 16 atm at the overlap of the 2 stents in the RCA. Final angiography revealed a good result (Figure 1B). Note: both stents appear angiographically contiguous and intact at the end of the procedure. The patient’s angina resolved after the percutaneous coronary intervention.
Five months later, the patient returned to the catheterization laboratory due to a recurrence of angina. Repeat catheterization revealed the same mild left coronary disease and a new 50% stenosis in the mid RCA. The stent in the proximal RCA was widely patent, but the ostial portion of the RCA appeared to be unstented and mildly narrowed. Prior to injection of the RCA, the ostial portion of the stent was observed to be completely disarticulated from the proximal RCA stent (Figure 2A). Injection of the RCA demonstrated a completely fractured stent, out of plane, and extending into the aortic root (Figure 2B). Additionally, the patient was noted to have a 50 mmHg peak gradient across the aortic valve, consistent with progression to severe aortic stenosis (confirmed by echocardiography). In the setting of continued chest pain and dyspnea on exertion, the patient was referred for aortic valve replacement.
At the time of aortic valve surgery, the ostial portion of the Cypher drug-eluting stent was found connected to the aortic root by a single, thin, fibrous strand. It was mobile and noncontiguous with the ostium of the RCA. The 4 mm portion of the Cypher stent was manually removed from the ascending aorta (Figure 3). The removed portion of the stent represented less than 15% of the total length of the stents that were placed in the proximal RCA 5 months previously.

Discussion. To our knowledge, this is the first reported case of Cypher stent fracture leading to late migration of a stent portion into a non-stented area. In this case, the complete stent fracture and migration could have led to embolization to the noncardiac circulation, with devastating consequences such as stroke or limb ischemia. The necessity for aortic valve surgery obviated the need for a challenging percutaneous retrieval of an embolized stent.⁴ The uneventful surgery and recovery of this drug-eluting stent was fortuitous given the very mobile nature of this fractured stent in the aortic root.
Our review of the published literature and adverse event reporting to Cordis Corporation reveals that this is the second reported case of complete Cypher stent strut fracture with noncontiguous stent seen angiographically.² Incomplete Cypher stent fractures have been reported by both angiographic and intravascular ultrasound diagnosis as non-stented gaps associated with restenosis.^1–3 Multiple mechanisms of stent fracture have been proposed including overexpansion of the stent with high-pressure inflation, shear stress from vessel tortuosity, or overlapping of stents.⁵ In our case, the stent was inflated to only 16 atm and was postdilated with the stent balloon at a similar pressure. The stent was at the ostium of the vessel, not in a tortuous segment of the artery. Finally, the stent was overlapping another stent, but not at the area where the stent fracture occurred. Thus, the mechanical mechanism for Cypher stent fracture is unclear.
One hypothesis to explain the stent fracture is enhanced shear stress on the ostium of the RCA in relationship to the aortic root; to date, though, we are unaware of any other reports of stent fracture associated with stenting of the RCA ostium. Another possibility is that increased flow through the stenotic aortic valve could have caused increased shear forces on the portion of the stent in the aorta and thus caused the stent strut fracture.
The most unique finding in our case is stent migration into the aortic root. Drug-eluting stents are associated with a 5–10% incidence of late stent malapposition.^3,6 While intravascular ultrasound was not performed in this case, one plausible explanation of stent migration could involve the following: (a) a profound suppression of neointimal hyperplasia due to sirolimus; and (b) expansion of the external elastic membrane leading to unapposed fractured stent. This combination could lead to a fractured stent losing its “anchor” in the ostium of the RCA and migration either distally or proximally.
In conclusion, we report the first case of a fortunately uneventful complete stent fracture associated not only with physical discontinuity between Cypher stent segments, but also migration of the proximal fractured stent into the aorta. Further monitoring of drug-eluting stents for mechanical disruption and migration is warranted.

References

1. Halkin A, Carlier S, Leon MB. Late incomplete lesion coverage following Cypher stent deployment for diffuse right coronary artery stenosis. Heart 2004;90:e45.
2. Min PK, Yoon YW, Moon KH. Delayed strut fracture of sirolimus-eluting stent: A significant problem or an occasional observation? Int J Cardiol 2006;106:404–406.
3. Mintz GS, Weissman NJ. Intravascular ultrasound in the drug-eluting stent era. J Am Coll Cardiol 2006;48:421–429.
4. Guigauri P, Dauerman HL. A novel use for a distal embolic protection device: Stent retrieval. J Invasive Cardiol 2005;17:183–184.
5. Sianos G, Hofma S, Ligthart JM, et al. Stent fracture and restenosis in the drug-eluting stent era. Catheter Cardiovasc Interv 2004;61:111–116.
6. Kimura M, Mintz GS, Carlier S, et al. Outcome after acute incomplete sirolimus-eluting stent apposition as assessed by serial intravascular ultrasound. Am J Cardiol 2006;98:436–442.