麻豆传媒

In line with prior reports, a registry study found that scaffold thrombosis after implantation of bioresorbable vascular scaffolds (BVS) occurred frequently -- yet can be remedied with BVS-specific precautions, the authors said.

The registry study included 1,305 patients who received BVS implantation from 2012 to 2014; BVS thrombosis occurred in 1.8% of patients by 30 days, and in 3.0% within the first year.

On multivariable analysis, were implantation for ostial lesions (P=0.049) and an impaired left ventricular ejection fraction (P=0.019). Certain results of post-procedural angiography -- namely low minimum lumen diameters (P<0.0001) and small reference vessel diameters (P<0.0001) -- were also tied to scaffold thrombosis at 1 year.

A BVS-specific implantation strategy was tied to slashed rates of scaffold thrombosis at 1 year (1.0% post- vs 3.3% pre-implementation, HR 0.19, 95% CI 0.05-0.70), according to Tommaso Gori, MD, PhD, of Germany's University Medical Center Mainz, and colleagues.

"Although it is acknowledged that other possible predictors of scaffold thrombosis (e.g., malapposition) exist, the present data emphasize the importance of vessel sizing and of the implantation techniques in reducing the rate of this complication," Gori's group announced in the March 1, 2016 issue of the Journal of the American College of Cardiology. "Suboptimal post-procedural angiographic results, with even small deviations from the nominal BVS diameter, were associated with exponential increases in the risk of scaffold thrombosis," they added.

As such, scaffold thrombosis is "a particularly severe event with a 12-month incidence as high as 3%, but it can be addressed by taking particular precautions at the time of implantation," the authors concluded.

Writing in an accompanying editorial, , and , both of the German Heart Centre, suggested that current tools do allow operators to do just that.

"At the current stage, a more liberal use of intravascular imaging appears to be instrumental to anticipate, detect, and correct any possible technical shortcoming of current BVS technology and to further address whether the strut discontinuity in the absence of neointimal hyperplasia increases the thrombotic risk of this device," they wrote.

More than half of the scaffold thrombosis cases presented with ST-segment elevation myocardial infarction (52%), while 17% presented with sudden cardiac death.

Another 21% of BVS thrombosis occurrences arose after suspending dual antiplatelet therapy (DAPT). One-third of these patients developed very late scaffold thrombosis after completing a planned year-long course of DAPT.

"This analysis was limited to the patients treated by four operators," the authors noted, in addition to the nonrandomized nature of the retrospective study.

Given the results, however, "the interplay among BVS, DAPT, and thrombotic risk seems less predictable than with newer-generation metallic drug-eluting stents," Cassese and Kastrati wrote.

The strong link between BVS thrombosis and ostial lesions could be explained by the physical characteristics of the scaffold, the authors and editorialists agreed.

These "often calcific lesions located at hinge points in the coronary vasculature" can be tricky areas, especially when compounded by insufficient radial strength at implantation, resulting in "incomplete expansion and/or the loss of radial strength following BVS resorption," Gori and colleagues noted.

For Cassese and Kastrati, that means reaching a breaking point: implantation in ostial lesions can cause "acute distortions of polymeric struts, which break more readily that those of metallic stents. The loss of structural BVS integrity with subsequent malapposition and anomalous bioresorption kinetics likely influences the healing of the stented segment and inherent thrombotic risk," they explained.

With higher rates of scaffold thrombosis for BVS than for contemporary metallic drug-eluting stents, the editorialists warned of a "worrisome" future for the technology, particularly in higher-risk patients. Cassese and Kastrati noted that the current state of BVS technology is reminiscent of the early days of DES, when early enthusiasm was dampened by the emerging risk of adverse events first became apparent.

However, the lesson from that period was that only with "continuous iterations" was DES able to improve its safety and efficacy.

The editorialists suggested this will also be the case for BVS. "The combination of optimism with healthy skepticism will certainly push forward the progress in BVS technology," they concluded.