Aims: Immediately after stent/scaffold implantation, quantitative coronary angiography (QCA) in comparison to optical coherence tomography (OCT) more severely underestimates the lumen diameter (LD) in Absorb than in XIENCE. This OCT-QCA discrepancy has not been evaluated at long-term follow-up. The present study aimed to assess the accuracy of QCA with reference to OCT in Absorb as compared to XIENCE.
Methods and results: We assessed two-year QCA and OCT in the ABSORB Japan randomised trial (Absorb n=87, XIENCE n=44). The accuracy of QCA parameters was assessed with reference to OCT measurements. OCT-QCA luminal dimensions were compared in matched cross-sections at both edges of the scaffolds (n=127) and stents (n=78). OCT-QCA late lumen loss (LLL) was also assessed using the Bland-Altman method. The systematic error of LD on QCA in Absorb was -0.092 mm (relative difference -3.3%) with a random error of 0.473 mm, whereas in XIENCE the systematic error was -0.018 mm (-0.5%) with a random error of 0.477 mm. These OCT-QCA discrepancies did not differ between Absorb and XIENCE (p=0.275) at two-year follow-up. QCA tended to underestimate LLL more in Absorb than in XIENCE (QCA-LLL minus OCT-LLL: -0.180±0.308 mm vs. -0.058±0.322 mm, p=0.058) at two-year follow-up, although this comparison was not statistically powered.
Conclusions: The two-year dimensional measurements on QCA had minor and insignificant systematic errors between both devices. A discrepancy between QCA-LLL and OCT-LLL would raise a question as to whether this parameter is appropriate for the comparative assessment of device performance.