Abstract

Introduction There is a strong inverse relationship between final vessel diameter and subsequent risk of treatment failure after coronary stent deployment. We investigated the magnitude by which stent delivery balloon under-expansion and stent elastic recoil contributed to suboptimal final vessel geometry.

Methods We performed a prospective angiographic study recruiting 499 lesions (385 patients) undergoing coronary stent implantation. Quantitative coronary angiography (QCA) was used to measure the minimal lumen diameters of the delivery balloon during stent deployment (MLD1) and of the stented segment following balloon deflation (MLD2). The expected balloon diameter for the deployment pressure was determined from the manufacturer's reference chart. Delivery balloon deficit was measured by subtracting the MLD1 from the expected balloon size and stent recoil was calculated by subtracting MLD2 from MLD1. Delivery balloon deficit and stent recoil were examined as a function of reference vessel diameter (RVD) and balloon-vessel(BV) ratio.

Results The final stent MLD was a mean (SD) 27.2 (7.2) % less than the predicted diameter. The mean (SD) delivery balloon deficit was 0.65 (0.27) mm and the mean (SD) stent recoil was 0.28 (0.17) mm. Percentage delivery balloon deficit and stent recoil were independent of RVD. Delivery balloon deficit increased with higher BV ratios. Stent recoil was independent of BV ratio and the use of predilatation.

Conclusion Failure to achieve predicted final stent diameter is a real problem with contribution from delivery balloon under-expansion and stent recoil. On average the final stent MLD is only 73% of the expected diameter irrespective of vessel size.