Maximum calcium thickness is a useful predictor for acceptable stent expansion in moderate calcified lesions

Prediction of stent under-expansion in calcified coronary arteries using machine learning on intravascular optical coherence tomography images

It can be difficult/impossible to fully expand a coronary artery stent in a heavily calcified coronary artery lesion. Under-expanded stents are linked to later complications. Here we used machine/deep learning to analyze calcifications in pre-stent intravascular optical coherence tomography (IVOCT) images and predicted the success of vessel expansion. Pre- and post-stent IVOCT image data were obtained from 110 coronary lesions. Lumen and calcifications in pre-stent images were segmented using deep learning, and lesion features were extracted. We analyzed stent expansion along the lesion, enabling frame, segmental, and whole-lesion analyses. We trained regression models to predict the post-stent lumen area and then computed the stent expansion index (SEI). Best performance (root-mean-square-error = 0.04 ± 0.02 mm2, r = 0.94 ± 0.04, p < 0.0001) was achieved when we used features from both lumen and calcification to train a Gaussian regression model for segmental analysis of 31 frames in length. Stents with minimum SEI > 80% were classified as "well-expanded;" others were "under-expanded." Under-expansion classification results (e.g., AUC = 0.85 ± 0.02) were significantly improved over a previous, simple calculation, as well as other machine learning solutions. Promising results suggest that such methods can identify lesions at risk of under-expansion that would be candidates for intervention lesion preparation (e.g., atherectomy).

Optical coherence tomography-derived predictors of stent expansion in calcified lesions

BACKGROUND

Severe coronary artery calcification is associated with stent underexpansion and subsequent stent failure.

AIMS

We aimed to identify optical coherence tomography (OCT)-derived predictors of absolute (minimal stent area [MSA]) and relative stent expansion in calcified lesions.

METHODS

This retrospective cohort study included patients who underwent percutaneous coronary intervention (PCI) with OCT assessment before and after stent implantation between May 2008 and April 2022. Pre-PCI OCT was used to assess calcium burden and post-PCI OCT was used to assess absolute and relative stent expansion.

RESULTS

A total of 361 lesions in 336 patients were analyzed. Target lesion calcification (defined as OCT-detected maximum calcium angle ≥ 30°) was present in 242 (67.0%) lesions. Following PCI, median MSA was 5.37 mm² in calcified lesions and 6.24 mm² in noncalcified lesions (p < 0.001). Median stent expansion was 78% in calcified lesions and 83% in noncalcified lesions (p = 0.325). In the subset of calcified lesions, average stent diameter, preprocedural minimal lumen area, and total calcium length were independent predictors of MSA in multivariable analysis (mean difference 2.69 mm² /mm² , 0.52 mm² /mm, and -0.28 mm² /5 mm, respectively, all p < 0.001). Total stent length was the only independent predictor of relative stent expansion (mean difference -0.465% per mm, p < 0.001). Calcium angle, thickness, and the presence of nodular calcification were not significantly associated with MSA or stent expansion in multivariable analyses.

CONCLUSION

Calcium length appeared to be the most important OCT-derived predictor of MSA, whereas stent expansion was mainly determined by total stent length.

Comparison of long-term outcome in patients with calcified stenosis treated with intravascular lithotripsy or with modified balloon angioplasty: a propensity score-adjusted study

Background

The aim of this two-center, all-comers registry was to compare the effectiveness and safety of intravascular lithotripsy (IVL) to that of modified balloon angioplasty (MB). MB angioplasty using a cutting or scoring balloon is commonly used in patients with calcified coronary arteries. IVL is a new technology for lesion preparation. This is the first study to compare MB with IVL.

Methods

The cohort included all patients treated by MB angioplasty or IVL between 2019 and 2021. The primary endpoint was strategy success (<20% residual stenosis). The secondary endpoint was long-term safety outcomes [cardiac death, acute myocardial infarction (AMI), target lesion failure/revascularization (TVR)]. Quantitative coronary angiography (QCA) was performed in all patients. Primary and secondary endpoints were compared using inverse probability of treatment weighting (IPTW) for treatment effect estimation.

Results

A total of n = 86 patients were treated by IVL and n = 92 patients by MB angioplasty. The primary endpoint was reached in 152 patients (85.4%). Patients in the IVL group had less residual stenosis (5.8% vs. 22.8%; p = 0.001) in QCA. Weighted multivariable regression analysis revealed that IVL had a significant positive effect on reaching the primary endpoint of strategy success [odds ratio (OR) 24.58; 95% confidence interval (95% CI) 7.40-101.86; p = 0.001]. In addition, severe calcification was shown to result in a lower probability of achieving the primary endpoint (OR 0.08; 95% CI 0.02-0.24; p = 0.001). During the follow-up period (450 days) there was no difference in cardiovascular mortality rate [IVL (n = 5) 2.8% vs. MB (n = 3) 1.7%; p = 0.129]. Patients with unstable angina at the time of the index procedure had the highest probability of cardiovascular death [hazard ratio (HR) 7.136; 95% CI 1.248-40.802; p = 0.027]. No differences were found in long-term rates of AMI (IVL 1.7% vs. MB 2.8%; p = 0.399; IVL HR 2.73; 95% CI 0.4-17.0; p = 0.281) or TVR (IVL 5.6% vs. MB 9%; p = 0.186; IVL HR 0.78; 95% CI 0.277-2.166; p = 0.626).

Conclusion

IVL leads to a significantly better angiographic intervention outcome compared to MB angioplasty in our cohort. During long-term follow-up, no differences in cardiovascular mortality, rate of acute myocardial infarction, or target lesion failure/revascularization were observed.

A novel optical coherence tomography‑based calcium scoring system can predict the stent expansion of moderate and severe calcified lesions

Coronary calcified lesions can exert serious effects on stent expansion. A calcium scoring system, based on optical coherence tomography (OCT), has been previously developed to identify relatively mild calcified lesions that would benefit from plaque modification procedures. Therefore, the present study aimed to establish a novel OCT-based scoring system to predict the stent expansion of moderate and severe calcified lesions. A total of 33 patients who underwent percutaneous coronary intervention (PCI; 34 calcified lesions were observed using coronary angiography) were retrospectively included in the present study. Coronary angiography and OCT images were subsequently reviewed and analyzed. Furthermore, a calcium scoring system was developed based on the results of multivariate analysis before the optimal threshold for the prediction of stent underexpansion in patients with moderate and severe calcified lesions was determined. The mean age of the patients was 67±10 years. The present analysis demonstrated that the final post-PCI median stent expansion was 70.74%, where stent underexpansion (defined as stent expansion <80%) was observed in 23 lesions. The mean maximum calcium arc, length and thickness, which were assessed using OCT, were found to be 230˚, 25.10 mm and 1.18 mm, respectively. A multivariate logistic regression model demonstrated that age and the maximum calcium arc were independent predictors of stent underexpansion. A novel calcium scoring system was thereafter established using the following formula: (0.16 x age) + (0.03 x maximum calcium arc) according to the β-coefficients in the multivariate analysis, with the optimal cut-off value for the prediction of stent underexpansion being 16.87. Receiver operating characteristic curve analysis demonstrated that this novel scoring system yielded a larger area under the curve value compared with that from a previous study's scoring system. Therefore, in conclusion, since the calcium scoring system of the present study based on age and the maximum calcium arc obtained from OCT was specifically developed in the subjects with moderate and severe calcified lesions, it may be more accurate in predicting the risk of stent underexpansion in these patients.

Impact of ultrasound reverberation in calcified coronary arteries: Intravascular ultrasound study

BACKGROUND AND AIMS

Intravascular ultrasound (IVUS) often allows us to observe reverberations behind calcification in percutaneous coronary intervention (PCI) to heavily calcified lesions. However, clinical significance of reverberations remains unknown. The aim of this study was to assess the impact of reverberations on stent expansion and clinical outcomes after PCI with rotational atherectomy (RA) to heavily calcified lesions.

METHODS

We considered 250 calcified lesions that underwent IVUS-guided PCI with RA. According to the number of reverberations (NR), those lesions were divided into the high NR (≥3) group (n = 36) and the low NR (≤2) group (n = 214). Stent expansion and the cumulative incidence of ischemia-driven target lesion revascularization (ID-TLR) were compared between the high and low NR groups.

RESULTS

The high NR group showed significantly smaller stent expansion rate than the low NR group (67.7% vs. 75.9%, respectively, p=0.02). The multivariate logistic regression analysis showed that high NR and calcified nodule were significantly associated with stent underexpansion. The incidence of ID-TLR was significantly higher in the high NR group than in the low NR group (p=0.03). In multivariate Cox hazard analysis, high NR and acute coronary syndrome were significantly associated with ID-TLR.

CONCLUSIONS

High NR was significantly associated with stent underexpansion and ID-TLR. When high NR was detected by IVUS, the PCI strategy was be planned carefully to avoid stent underexpansion. The follow-up program of the patients with high NR might need to be scheduled prudently because of the high risk of TLR.

Experience with Optical Coherence Tomography Enhanced by a Novel Software (Ultreon™ 1.0 Software)-The First One Hundred Cases

Introduction: Optical coherence tomography (OCT) intravascular imaging including the latest version Ultreon™ 1.0 Software (Abbott Vascular, Santa Clara, CA, USA), not only improve patients prognosis, but also facilitates improved percutaneous coronary intervention (PCI). Objectives: The aim of the study was to compare procedure related decision making, procedural indices, clinical outcomes according to the extent of stent expansion and assess risk factors of underexpansion in patients treated with PCI using OCT. Methods: The study comprised 100 patients, which were divided in groups according to the extent of stent expansion: <90 (29 patients) and ≥90% (71 patients). Comparison of OCT parameters, selected clinical and procedural characteristics was performed between groups. We assessed clinical outcomes during the follow-up: major adverse cardiovascular events and risk factors of stent underexpansion. Results: Patients from the stent underexpansion group were treated more often in the past with percutaneous peripheral interventions (p=0.02), no other significant differences being noted in general characteristics, procedural characteristics or clinical outcomes comparing both groups. Significant predictors of stent underexpansion assessed by simple linear univariable analysis included: hypercholesterolemia, obstructive bronchial diseases and treatment with inhalators, family history of cardiovascular disease, PCI of other than the left main coronary artery, stent and drug-eluting stent implantation, PCI without drug-eluting balloon, paclitaxel antimitotic agent, greater maximal stent diameter and lower mean Euroscore II value. Univariable logistic regression analysis revealed a correlation between stent underexpansion and greater creatinine serum concentration before [OR: 0.97, 95%CI: 0.95-0.99, p=0.01] and after PCI [OR: 0.98, 95%CI: 0.96-0.99, p=0.02]. Conclusions: Based on the presented analysis, the degree of stent expansion is not related to the selected procedural, OCT imaging indices and clinical outcomes. Logistic regression analysis confirmed such a relationship for creatinine level.

Percutaneous management of calcified coronary arteries - review of atherectomy and lithotripsy devices and why it is important

PURPOSE OF REVIEW

Coronary artery calcification (CAC) predisposes to suboptimal revascularization outcomes after percutaneous coronary intervention (PCI). Despite the availability of several plaque modification devices, their rates of use remain low despite the prevalence of CAC encountered in clinical practice. It is important to understand how each device can be utilized in clinical practice in order to improve outcomes after PCI.

RECENT FINDINGS

This article summarizes the most recent clinical evidence for each plaque modification device. Although rotational atherectomy is the most frequently used device for plaque modification, the use of orbital atherectomy (OA) has been increasing. Balloon-based strategies including recent studies evaluating a novel intravascular lithotripsy balloon have shed light on the benefits of nonablative devices in modifying CAC during PCI.

SUMMARY

CAC poses significant technical challenges in achieving optimal stent results. Several intracoronary plaque modification devices are currently available and understanding the technical aspects, indications and contraindications to the use of each device is essential. Although rotational and OA are most commonly used, laser atherectomy and balloon-based devices may offer an advantage in certain lesion subsets.

Optical coherence tomography-versus intravascular ultrasound-guided stent expansion in calcified lesions

Optical coherence tomography (OCT) has a higher resolution than intravascular ultrasound (IVUS) and enables a more precise evaluation of calcium severity. We investigated the impact of the imaging method (OCT versus IVUS) on stent expansion during intravascular imaging-guided percutaneous coronary intervention (PCI) in calcified lesions. In this single-center, retrospective, observational study, 145 lesions with moderate to severe calcification were divided into four groups: 40 IVUS-guided rotational atherectomy (RA), 38 IVUS-guided non-RA, 35 OCT-guided RA, and 32 OCT-guided non-RA. Lesions without pre-procedural intravascular imaging were excluded. OCT-guided RA was associated with greater stent expansion at the target calcium compared with IVUS-guided RA (median 88.0%, interquartile range [78.0-96.0] vs. 76.5% [71.0-84.3], P = 0.008). Furthermore, stent expansion in OCT-guided non-RA was similar to OCT-guided RA. OCT-guided RA used a larger burr compared to IVUS-guided RA (1.75 mm [1.50-2.0] vs. 1.50 mm [1.50-1.75], P = 0.004). In OCT-guided RA, the median minimum calcium thickness was significantly reduced from 800 (640-980) µm to 550 (350-680) µm (P < 0.001). There was no significant difference in the incidence of ischemia driven target lesion revascularization between the four groups (P = 0.37). By determining the indication and endpoint of lesion modification by RA based on the thickness of calcium, OCT-guided PCI was associated with significantly greater stent expansion compared with IVUS-guided PCI.