Bioresorbable Scaffold Performs Well, But Thrombosis Raises Concerns

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Percutaneous coronary intervention (PCI) with an everolimus-eluting bioresorbable vascular scaffold (BVS) results in an “acceptable” rate of target lesion failure (TLF) through 6 months in a relatively unselected patient population, according to a registry study published online July 18, 2014, ahead of print in EuroIntervention. The rate of scaffold thrombosis, however, was higher than rates seen with second-generation drug-eluting stents (DES) in other studies. 

Successful Procedures, ‘Acceptable’ Outcomes

The total number of BVS used in the patients was 1,731 (average 1.5 per patient). Overlapping scaffolds were used in 17.3% of lesions, and roughly 1 in every 5 patients (18.4%) also received either a DES or a BMS. Technical success was achieved in 99.7% of cases. 

The primary outcome of TLF (composite of cardiac death, target-vessel MI, or clinically driven TLR) occurred in 67 patients at a median of 109 days after implantation. Rates through 30 days and 6 months were “acceptable… particularly when considering the complexity of the patients and lesions treated,” according to the authors (table 1).

Table 1. Outcomes at 30 Days, 6 Months

The only independent predictor of TLF was diabetes (HR 2.41; 95% CI 1.28-4.53).

Scaffold Thrombosis ‘Not Negligible’

Twenty-three patients developed definite/probable scaffold thrombosis, resulting in rates of 1.5% at 30 days and 2.1% at 6 months. Most of the cases (70%) occurred in the first 30 days—at a median of 5 days postprocedure. Also, 87% occurred while the patient was still taking dual antiplatelet therapy. 

The scaffold thrombosis rates were “larger than anticipated” and “exceed the incidences typically reported in contemporary all-comers registries and trials of second-generation DES,” the authors point out, adding that “to the best of our knowledge, the present study represents the first one reporting a nonnegligible rate of this outcome with the Absorb BVS.” They suggest that compared with second-generation DES, the thicker struts of the BVS might explain the elevation.

In addition, they write, “clustering of [scaffold thrombosis] within the early period suggests the need for scrupulous lesion selection and PCI techniques when using BVS, and the opportunity for systematic postimplantation assessment.” IVUS can bring about additional postdilatation, they say, noting that such imaging was performed in only 9 of 23 patients who developed scaffold thrombosis.

However, a randomized trial is needed to fully assess the relevance of the scaffold thrombosis findings, Dr. Capodanno and colleagues state. “Whether the apparent early detrimental effect of strut thickness is counterbalanced by later benefits occurring when the scaffold is biodegraded needs to be clarified by longer follow-up and randomized comparisons versus best-in-class DES,” they conclude.

Gregg W. Stone, MD, of Columbia University Medical Center (New York, NY), who is study chair of the ongoing United States-based ABSORB trials, agreed, saying in a telephone interview with TCTMD, “The important point is that without a concurrent control group we don’t know if these results are as good as, better, or worse than they might have been with metallic drug-eluting stents.” 

But, he added, “It’s something that we need to keep an eye on, and I think it also emphasizes the fact that with this device—given that it’s relatively new and relatively high profile with relatively thick struts—adequate lesion preparation and post-BVS implantation optimization is very important.” 

Outcomes Suffer as More Complex Patients Are Treated

Patients treated after centers had performed more than 50 BVS implantations—compared with patients treated at an earlier stage—were more likely to present with ACS and be treated for ostial and thrombotic lesions but less likely to have intravascular imaging and postdilation performed during the procedure. This “may reflect the increasing confidence [of] the operators in using the Absorb BVS in more complex patient and clinical scenarios,” the authors write.

However, experienced centers had higher rates of TLF (5.2% vs 3.2%) and definite/probable scaffold thrombosis (2.0% vs 0.7%) through 6 months.

“This reminds us that we still need to be particularly cautious when selecting the lesions and performing the procedure, as in the earliest experience, at least until studies will be available to elucidate what the most important angiographic and procedural predictors of scaffold failure are,” Dr. Capodanno explained in an email to TCTMD.

The take-away message from the study, he said, “is positive overall in terms of feasibility, in that this was a good demonstration of how BVS can be used successfully in patients and lesions whose complexity extends beyond the boundaries of the pivotal trials. However, considerations on the comparative safety and effectiveness of BVS versus best-in-class DES must necessarily rely on a randomized trial.” 

Note: Study co-author Antonio Colombo, MD, are faculty members of the Cardiovascular Research Foundation, which owns and operates TCTMD.

Source: Capodanno D, Gori T, Nef H, et al. Percutaneous coronary intervention with everolimus-eluting bioresorbable vascular scaffolds in routine clinical practice: early and midterm outcomes from the European multicenter GHOST-EU registry. EuroIntervention. 2014;Epub ahead of print.

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