The invention of bioresorbable vascular scaffolds was considered a revolution in the field of interventional cardiology due to the potential advantages of scaffold bioresorption.
To our knowledge, this is the first study to compare the influence of OCT on the operators’ decisions during deployment of Absorb BRS versus everolimus-eluted metallic stents.
Optimal scaffold placement entails a balance between perfect struts embedment and absence of edge dissection. Uncorrected residual stenosis, struts malapposition, and edge dissections increase the risk of future scaffold restenosis and thrombosis [2].
In the present study, there was a significant difference in the impact of OCT on intraoperative decision-making during implantation of BRS versus DES. Despite angiographic success, we reported a significantly higher rate of OCT detected device-related complications in the BRS arm (47.8%) compared to the DES arm (32.9%).
The detected complications necessitated further modifications such as further optimization in case of device underexpansion or struts malapposition, and even additional stenting in case of strut fractures, or significant edge dissection reaching up to 10.2% of bailout device use in the BRS arm versus 1.2% only in the DES arm.
In ABSORB cohort B substudy, OCT detected suboptimal deployment in more than 25% of patients with mainly type A lesions, and this number might have theoretically increased with the expanded BRS use into complex lesions [1, 14]. This theory was verified by our findings, where type B2/C lesion, moderate/severe lesion calcification, and overlapping stents had a positive relationship with the need for OCT-guided additional interventions, emphasizing the importance of lesion selection before BRS implantation. BRS scaffold was found to have a significant positive relationship with the OCT-based intraoperative modification, thus highlighting the value of OCT guidance for BRS optimization.
Even if not identified on angiography, the OCT-detected complications may have a critical impact on patients’ outcome if left untreated [13]. It is well known that the recent Absorb setback was mainly due to a higher tendency of very late scaffold thrombosis in the ABSORB trials [5, 15].
Increased rates of subacute scaffold thrombosis in ABSORB III trial were explained by the high rate of residual stenosis, while the high very late scaffold thrombosis rate in ABSORB II was attributed to underexpansion and incomplete coverage due to malapposition, as detected with intravascular ultrasound (IVUS) [3, 4]. In the ABSORB Japan trial, OCT showed incomplete coverage due to overhanging struts in very late scaffold thrombosis cases as malapposing struts prevent scaffold bioresorption and delay endothelialization, thus increasing the risk of thrombosis [7].
The difference in the rate of required interventions between both devices can be explained by the intrinsic biomechanical differences due to the eccentric expansion pattern of the Absorb scaffold that results into a higher rate of underexpansion and struts malapposition [2]. Moreover, the radiolucency of the scaffold to the conventional angiography renders underexpansion and fractures less likely to be spotted by this modality.
A significant difference in the implantation technique adopted by the operators during BRS versus DES deployment was noted, as post-dilatation balloon/device diameter ratio, inflation time, and pressure were higher in the BRS arm (1.10 ± 0.09 vs 1.08 ± 0.12, p = 0.025; 15.88 ± 6.22 s vs13.70 ± 3.44 s, p = 0.004; and 17.89 ± 4.04 atm vs 16.84 ± 4.03 atm, p = 0.028, respectively), most likely governed by OCT findings of malapposition and underexpansion.
OCT displayed intraoperative complications requiring further interventions in 32.9% of DES arm, in concordance with the CLI-OPCI study that reported a 34.7% rate of additional interventions based on OCT findings during PCI using metallic stents [13]. The current results highlight the value of OCT-guidance also during DES implantation.
Study limitations
The study has some limitations, including those typical of non-randomized studies; however, the retrospective design has some advantages in the present study, as it prevented the operators’ bias while studying the impact of OCT on intraprocedural operators’ behavior. Additionally, substantial discrepancies between groups could not be avoided due to the retrospective time-limited study design; nevertheless, despite higher lesions complexity in the DES group, a significantly lower rate of modifications was required and thus strengthens the study results; however, we should not forget that no method can accurately adjust for all known and unknown confounders. Besides, any malapposition not considering axial and/or longitudinal distance (axial distance > 300 μm and longitudinal extension > 1.0 mm, not associated with side branches) may lead to the overestimation of complications detected by OCT after device implantation because minor malapposition (< 0.35 mm) will be resolved with neointima at follow-up. Finally, despite that the intraprocedural OCT assessment was verified by a different team during the study, the lack of corelab analysis is considered a limitation.