Image Predictors, Prevention And Treatment Of Stent Underexpansion

Background: Despite the substantial improvement in interventional procedures to improve the drug-eluting stent implantation, stent thrombosis remains a critical issue, which is associated with acute myocardial infarction and sudden death. Accurate coronary lesion assessment before the procedure, efficient stent deployment evaluation during the procedure and solving it in time, are key to make sure stent deployed well. Through three-dimensional rotation, dual axis rotational coronary angiography (DARCA) can expand the coronary tree well and minimize vessel foreshortening. Compared to standard coronary angiography,DARCA may have a better coronary lesion evaluation. But the study on the accuracy of DARCA for coronary lesion assessment is limited. With regard to the impact of plaque component on stent deployment, all the prior studies are intravascular ultrasound (IVUS)study. Compared to IVUS, virtual histology-IVUS (VH-IVUS) can evaluate the impact of plaque tissue morphology on stent expansion more effectively. Although IVUS and optical coherence tomography are gold standard for stent expansion evaluation, they are not widely used due to time-consuming, cost-ineffective, risk of procedural complications and can only be applied by specifically trained interventionalists. StentBoost imaging, which can enhance the visualization of coronary stents, is a quicker, cost-effective and safe method. It may improve stent deployment and further reduce the occrence of stent underexpansion for facilitating the percutaneous coronary intervention process. For the moment, there is a paucity of research on the issue. This study aimed to explore the image predictors of stent underexpansion with the use of multiple interventional imaging modalities, and try to find the strategy of minimizing insufficient stent deployment.Part ?: Accuracy of dual-axis rotational coronary angiography for coronary lesion assessment evaluated by intravascular ultrasoundObjective: To evaluate the accuracy of dual-axis rotational coronary angiography (DARCA)for coronary lesion assessment by directly comparing with intravascular ultrasound (IVUS).Methods: From October 2014 to December 2015, 44 patients who had undergone both DARCA and IVUS were included. Minimum lumen diameter (MLD), lesion length,reference vessel diameter (RVD) and percent diameter stenosis at the same lesion, were identified and assessed by quantitative coronary angiography and IVUS.Results: Of these patients, 4 patients were excluded from image analysis due to poor imaging quality. 40 patients (58 lesions) were finally assessed. Significant correlation with IVUS was found for DARCA in either lesion length (r = 0.90, P < 0.001) or RVD (r = 0.81,P < 0.001) comparison. DARCA had fair correlation with IVUS for both MLD (r = 0.65, P< 0.001) and diameter stenosis (r = 0.48, P < 0.001). From the Bland-Altman plots, there was a good agreement between DARCA and IVUS regarding MLD (mean difference: -0.23 mm, 95% limits of agreement: -0.96?0.50 mm) and RVD (mean difference: -0.15 mm,95%limits of agreement: -0.85 ?0.55 mm), while lesser agreement was found on lesion length(mean difference: -3.39 mm,95% limits of agreement: -12.63 ?5.85 mm) and diameter stenosis (mean difference: 4,82 %,95% limits of agreement: -17.05 ?26.68 %).Conclusions: There are good agreements between DARCA and IVUS in both MLD and RVD assessments. Although DARCA is associated with a shorter lesion length compared to that assessed by IVUS, there is good correlation between them.Part ?: Impact of atherosclerotic plaque components on stent deployment: a VH-IVUS studyObjective: To evaluate atherosclerotic plaque components on stent deployment with the use of virtual histology intravascular ultrasound (VH-IVUS).Methods: From October 2014 to March 2016, 29 patients who had undergone drug-eluting stent implantation and pre- and post-stenting virtual histology intravascular ultrasound (VH-IVUS) were evaluated. The primary end point was the correlation between VH-IVUS normalized plaque volume (absolute volume / analysis length) and stent expansion index(SEI) at minimum lumen area.Results: 29 patients (34 lesions) were assessed. The incidence of stent underexpansion was 62%(in 21 lesions), the mean SEI at minimum stent area was 0.76 ± 0.12. The SEI was inversely correlated to the VH-IVUS normalized calcium volume (r = -0.45, P = 0.008). No correlation was found for fibrotic, fibrofatty and necrotic core tissues (all P > 0.05). Based on receiver-operating characteristic curve analysis, a 0.79 mm2 normalized calcium volume was the corresponding cut-off point for stent underexpansion (area under the curve = 0.71,specificity: 100%, sensitivity: 33%, P=0.049). The SEI at the site of maximum calcification with luminal calcification was lower than that with non-luminal calcification (0.69±0.13 vs.0.78±0.12, P = 0.013). The luminal calcification was the only independent predictor of stent underexpansion on multivariate analysis (P = 0.009).Conclusions: There is significant correlation between calcification and stent expansion. The luminal calcification was the only independent predictor of stent underexpansion.Part III: Impact of StentBoost guidance during percutaneous coronary intervention on stent underexpansion: an OCT studyObjective: To compare stent expansion guided by StentBoost (SB) versus angiography alone during percutaneous coronary intervention assessed by optical coherence tomography(OCT).Methods: This is a prospective, randomized, controlled trial. 114 patients undergoing drug-eluting stent (DES) implantation were randomly assigned to SB guidance group (N=57) or non-SB guidance group (N=57). OCT was performed after the procedure immediately. The primary end point was stent underexpansion at lesion level. Stent underexpansion was defined as stent expansion index < 0.80.Results: 67 lesions in SB group (N=57) and 73 lesions in non-SB group (N=57) were implanted with DES. All the lesions were included in the final analysis. No difference in stent underexpansion at lesion level was found between the two groups (SB group vs, nono-SB group: 64% vs. 68%, P = 0.589). However, SB guidance was associated with higher minimum stent diameter (MSD) and minimum stent area (MSA) after the procedure immediately when compared with non-SB guidance (MSD: 2.87±0.42 mm vs. 2.56±0.44 mm,P<0.001; MSA: 7.55±2.37mm2 vs. 6.35±2.30 mm2,P=0.003).Conclusions: Compared with DES implantation guided by angiography alone, SB guidance can improve the MSD and MSA after the procedure immediately, but no difference was found in stent underexpansion.In general, coronary lesion assessment with multiple interventional imaging modalities before the procedure, to obtain enough anatomy and histology information, is a precondition for sufficient stent deployment; PCI guided by SB can improve the acute result at the end of the procedure, but further study is needed to prove its effect on stent underexpansion and patient prognosis.