Coronary stent fracture: The hidden truth of a problem more common than stent thrombosis

The report by Hetterich and Rieber in this issue of CCI adds additional focus on the problem of coronary stent, specifically strut, fracture [1]. Their case report illustrates fractures in long and overlapping sirolimus-eluting stents in an area of the coronary tree with above average angulation and flexion. From this report and others, there are some pressing questions that must be asked with the goal to further improve stent technology and its optimal use. 1. Are coronary stent fractures rare? Aoki detected fractures in 2.6% of lesions in patient undergoing routine follow-up angiography after stenting [2]. Shaifh reported that 20% of patients with DES in-stent restenosis have stent fractures [3]. 2. Are coronary stent fractures bad for the patient? The association between stent fracture and restenosis is strong. The numerous case studies illustrate the negative clinical consequences of stent fracture. What is unclear is whether there are many stent fractures that are undetected and without any clinical sequelae. 3. What is the best treatment for a stent fracture? It is remarkable, as in this case, how an additional stent is often placed to treat restenosis that may be a result of stent fracture. This may seem reasonable if restenosis is viewed in isolation without recognizing stent fracture or as a consequence of no drug-eluting struts in the area of the focal restenosis process. On the other hand, the local hostile mechanical environment causing the original fractures will still be present unless the underlying myocardium stops contracting and the artery is no longer subjected to these forces. 4. Are coronary stent fractures easily detected? The answer is clearly no and leads to the conclusion that stent fracture is underreported. This underreporting is not unexpected since current coronary stents are minimally radiopaque. Furthermore, coronary arteries and stents are small and move constantly such that visualization requires an imaging modality with very high spatial and temporal resolution. 5. Is stent fracture more common in SES? The answer to this question, based on literature reports is yes, but it is apparent that stent visibility for SES versus PES is better and thus there is an inherent bias against SES in the detection of fractures. True rates of fracture of different stent designs must await studies that include a surveillance technique applied to a larger number of patients with an imaging modality that will detect most if not all fractures even in stents with a low radiopacity. 6. What imaging modality should be used to detect stent fractures? The only modality that is widely available and has the potential for showing in vivo stent fractures is X-ray. Trehan nicely described the triad needed for stent fracture visualization with present day technology: the fracture must be moderate to severe, the stent must be reasonably radiopaque, and the patient cannot be too obese [4]. Of note is that standard IVUS is not suitable for detection of stent fracture despite its widespread use for assessment of stent expansion and apposition. 7. Since a much more sensitive means of detecting stent fracture is needed, what improvements in X-ray visualization are possible? Enhanced stent visualization has been pursued by development groups and studied clinically [5,6]. Unfortunately easily detectable markers, currently only on the delivery system, are needed for motion compensation to enhance stents and reduce quantum noise. This requirement makes the process only applicable to the minutes in the immediate post-implantation period. We need a technique that will allow enhancement of implanted stents in outpatient based surveillance studies. Permanent markers at the proximal and distal ends of stents could be used as one solution. Another limitation of current stent enhancement technologies is that they are 2D and thus