NEW YORK (Reuters Health) – Stent fractures are not always associated with clinical sequelae, but they do increase the likelihood of in-stent restenosis (ISR) and target lesion revascularization (TLR), according to a new meta-analysis.

“Conversely, the probability of stent fractures is increased in lesions with ISR or TLR, thus raising the need for surveillance and management guidelines for at-risk patients,” Dr. Raj Makkar of Cedars Sinai Medical Center in Los Angeles and colleagues conclude.

Stent fracture was first reported in 2002, with the first instance of a fracture in a drug-eluting stent following 2 years later, Dr. Makkar and colleagues note in the October 15 issue of the American Journal of Cardiology. While a number of reports have since been published on stent fracture, the researchers add, these studies have typically been small or based at a single center, or both.

To better understand the incidence of stent fracture and variables associated with it, the researchers conducted a meta-analysis of eight studies including 108 stent fractures in 5,321 patients.

“Overall, the mean incidence per patient of stent fracture was 4%,” the team found.

Most (56.4%) of the stent fractures occurred in the right coronary artery, 30.4% in the left anterior descending coronary artery, 10.9% in the left circumflex coronary artery, 1.7% in saphenous vein grafts, and fewer than 0.01% in the left main coronary artery. Overlapping stents were more likely to fracture (7.5% versus 2.5% of non-overlapping stents), while fractured stents were longer on average than stents that didn’t fracture (46 mm vs. 32.5 mm).

ISR occurred in 38% of lesions with stent fractures, compared to 8.2% of lesions with intact stents. TLR occurred in 17% of lesions with fractured stents compared to 5.6% of lesions with intact stents. At the same time, stent fracture was more common in lesions with ISR (12.8% versus 2.1%) or TSR (8.8% versus 2.7%).

Fractures also occurred more commonly with sirolimus-eluting stents than paclitaxel-eluting stents; this may be due to the more rigid closed-cell design of sirolimus-eluting stents, the researchers suggest. At the same time, they add, paclitaxel-eluting stents show higher rates of restenosis and late luminal loss. “Thus, the different incidence of stent fracture does not necessarily translate into clinically significant differences,” they write.

Only technical and anatomic factors were associated with stent fracture risk, but clinical characteristics such as coronary artery disease risk factors, previous MI, or coronary artery bypass grafting were not. Vessel areas where stent fractures occur more frequently “may be subject to repetitive distorting forces,” Dr. Makkar and colleagues suggest.

This means that the risk of fracture could increase over time, the researchers say. The fact that intravascular ultrasound (IVUS) isn’t routinely used could lead to underestimation of the incidence of stent fracture, they add, while the fact that most repeat procedures in the study were “clinically driven” could lead to overestimation.

“It should be clear that the incidence of stent fracture can only be taken as an estimate and stated as a range,” the researchers conclude. “Furthermore, unless large trials of prespecified angiographic and IVUS follow-up are undertaken, this limitation will persist into the foreseeable future.”

Am J Cardiol 2010;106:1075-1080.