Multimodality imaging results of TAP versus novel modified TAP stenting in coronary bifurcation: From bench testing to first-in-man investigation

OBJECTIVES

We investigated the results of T and small protrusion (TAP) versus a novel modification of TAP (mTAP) stenting by multimodality imaging in bench testing and in patients with coronary bifurcation lesions (CBL).

BACKGROUND

TAP stenting is a suboptimal technique for bailout side branch (SB) stenting.

METHODS

In a bench model, optical coherence tomography (OCT), microscopic examinations (ME), and computational fluid dynamics (CFD) were performed after TAP and mTAP stenting. In 20 patients with CBL, 80 intravascular ultrasound (IVUS) examinations were performed during mTAP stenting in which the SB stent was pulled-back to indent the inflated main vessel (MV) balloon and deployed while deflating it. For TAP stenting, the tip of the SB stent was positioned in the MV and deployed.

RESULTS

In bench testing, OCT showed neocarina length (NL) was shorter and minimum stent area (MSA) was larger after mTAP versus TAP stenting (2.84 ± 0.70 vs. 4.80 ± 020 mm; 6.75 ± 1.50 vs. 4.5 ± 2.2 mm² ; respectively; p < 0.05). By ME, NL was shorter and shear rate trended lower after mTAP versus TAP stenting. In patients, IVUS showed MSA was larger after versus before mTAP stenting (6.32 ± 0.58 vs. 5.21 ± 0.56 mm² ; p < 0.01); NL was 1.43 ± 0.22 mm with SB ostium coverage. The Seattle Angina questionnaire (SAQ) score was higher at 6 months versus baseline (85 ± 4.0 vs. 48 ± 6.0, respectively; p < 0.001).

CONCLUSIONS

This multimodality imaging study showed, for the first time, mTAP stenting resulted in larger stent area and shorter neocarina than TAP stenting in bench testing. In patients with CBL, mTAP stenting led to larger stent area, short neocarina with complete SB ostium coverage, and improved the SAQ score at follow-up.

Telemedicine: Benefits for Cardiovascular Patients in the COVID-19 Era

The recent pandemic with SARS-CoV-2 raises questions worldwide regarding telemedicine for housebound patients, including those with cardiovascular conditions. The need for further investigation, monitoring and therapeutic management are advancing practical issues which had not been identified for consideration prior to the pandemic. Using the marketing assessment, we identified the needs of the patients and evaluated the future steps necessary in the short term to meet them. The research found progress made via telemedicine in monitoring and conducting minor decisions (like up-titrating the doses of different medication regimens) in patients with several cardiovascular diseases (heart failure, atrial fibrillation, high blood pressure), as there is a worldwide trend to develop new telemonitoring biosensors and devices based on implantable delivered transcatheter. The worldwide telemedicine trend encourages a switch from small and hesitating steps to a more consistent assessment of the patients, based on high technology and Interventional Cardiology. Cardiovascular telemedicine, although made a sustainable effort in managing patients' health, has many obstacles to overcome before meeting all their needs. Data security, confidentiality and reimbursement are the top priorities in developing remote Cardiology. The regulatory institutions need to play an integrative role in leading the way for defining the framework of future telemedicine activities. The SARS-CoV-2 outbreak with all its tragedy served to reinforce the message that telemedicine services can be life-saving for cardiovascular patients. Once the Covid-19 era will fade away, telemedicine is likely to remain a complementary service of standard care. There is still room to improve the remote identification and investigation of heart disease, provide an accurate diagnosis and therapeutic regimen, and update regulations and guidelines to the new realities of technological progress in the field.

Polymer Coating Integrity, Thrombogenicity and Computational Fluid Dynamics Analysis of Provisional Stenting Technique in the Left Main Bifurcation Setting: Insights from an In-Vitro Model

Currently, the provisional stenting technique is the gold standard in revascularization of lesions located in the left main (LM) bifurcation. The benefit of the routine kissing balloon technique (KBI) in bifurcation lesions is still debated, particularly following the single stent treatment. We compared the latest-generation drug-eluting stent (DES) with no side branch (SB) dilatation “keep it open” technique (KIO) vs. KBI technique vs. bifurcation dedicated drug-eluting stent (BD-DES) implantation. In vitro testing was performed under a static condition in bifurcation silicone vessel models. All the devices were implanted in accordance with the manufacturers’ recommendations. As a result, computational fluid dynamics (CFD) analysis demonstrated a statistically higher area of high shear rate in the KIO group when compared to KBI. Likewise, the maximal shear rate was higher in number in the KIO group. Floating strut count based on the OCT imaging was significantly higher in KIO than in KBI and BD-DES. Furthermore, according to OTC analysis, the thrombus area was numerically higher in both KIO and KBI than in the BD-DES. Scanning electron microscopy (SEM) analysis shows the highest degree of strut coating damage in the KBI group. This model demonstrated significant differences in CFD analysis at SB ostia with and without KBI optimization in the LM setting. The adoption of KBI was related to a meaningful reduction of flow disturbances in conventional DES and achieved results similar to BD-DES.

Stent malapposition generates stent thrombosis: Insights from a thrombosis model

BACKGROUND

Currently, there exists differing conclusions on the role of acute stent malapposition and its role in stent thrombosis (ST). The European Association of Percutaneous Cardiovascular Interventions (EAPCI) consensus recommends that acute malapposition <0.4 mm with longitudinal extension <1 mm need not be corrected since there is no clear correlation of malapposition with adverse clinical outcomes. However, malapposition was identified as the main mechanism of ST in the Bern and PESTO registries, and one of the three leading mechanism in the PRESTIGE study.

METHODS

In this study, a validated perfused benchtop thrombosis model was deployed to evaluate the role of both stent under-expansion (UE) and acute stent malapposition (MA) on thrombus formation in vitro in a controlled reproducible environment.

RESULTS

The results showed that UE alone did not result in acute thrombus formation, but UE together with MA did. The data suggested that a MA distance of 0.25 mm led to significant thrombus formation; and a positive correlation exists between the longitudinal extension of the MA and the thrombus volume formed.

CONCLUSION

Experiments in this in vitro model demonstrated that platelets and a thrombosis cascade were activated and developed around large segments of malapposed stent. This was significantly more thrombus formation than in the under-expanded stent region.

Provisional Stenting for the Treatment of Bifurcation Lesions: In Vitro Insights

Provisional stenting is considered the gold standard approach for most bifurcation lesions, but the benefit of routine side branch (SB) strut dilatation has not been fully elucidated. A benchtop model was used to determine the benefits of routine side branch (SB) dilatation techniques on strut apposition, acute thrombogenicity, and flow disruption. Three different provisional bifurcation techniques were compared: no SB dilatation "keep it open" method (KIO), sequential balloon dilatation (SBD), and kissing balloon inflation (KBI). Stents were deployed in a silicon bifurcation model and perfused with blood at a flow rate of 200 ml/min for 60 min. Optical coherence tomography (OCT) pullbacks were obtained before and after flow perfusion to conduct strut analysis and acute thrombus measurement respectively. Computational fluid dynamics (CFD) models were created using OCT pullbacks and simulated based on experimental conditions to analyze flow disruption. The strut analysis showed that KBI had the lowest percentage of floating (10.6 ± 2.3%) (p = 0.0004) and malapposed (41.2 ± 8.5%) struts (p = 0.59), followed by SBD and then KIO. This correlated to KBI having the lowest amount of thrombus formed at the SB, followed by SBD, with KIO being the most thrombogenic (KBI: 0.84 ± 0.22mm², SBD: 1.17 ± 0.25mm², KIO: 1.31 ± 0.36mm², p = 0.18). CFD models also predicted a similar trend, with KBI having the lowest amount of area of high shear rate as well as flow recirculation. Based on this benchtop model, SB intervention strategies demonstrated a reduction in number of struts and resulting thrombogenicity at the bifurcation ostia. Graphical abstract.

T and Small Protrusion (TAP) vs Double-Kissing Crush Technique: Insights From In Vitro Models

BACKGROUND

Percutaneous coronary interventions on complex bifurcation lesions may require implantation of two stents to appropriately treat diffuse side-branch (SB) disease. Comparisons among different bifurcation stenting techniques are continuously attempted by various study designs (bench tests, computer simulations, clinical studies). Among different techniques, double kissing crush (DKC) represents the last evolution for "crushing" while T and small Protrusion (TAP) represents the evolution of "T stenting". Both techniques are actually gaining popularity, but head-to-head comparisons are lacking.

METHODS AND RESULTS

Two last generation drug-eluting stents (Synergy™, Boston Scientific, MA, USA and Ultimaster™,Terumo Corp., Japan) were implanted in left main bifurcation bench models using TAP (n = 6 sets) and DKC (n = 6 sets) techniques. A peristaltic pump with fresh porcine blood was used to perfuse the blood through the silicone model at a flow rate of 200 ml/min for 4 min. Optical coherence tomography (OCT) was used to assess stent struts geometry and thrombus formation. SB cross sectional area as well as SB obstruction did not significantly differ between the two techniques. Numerical (but not statistically significant) differences were found in terms of malapposed struts (fewer with TAP) and floating struts (fewer with DKC). Thrombus formation after blood perfusion was similar between TAP and DKC technique (1.53 ± 1.12 vs. 1.20 ± 1.01 mm², p = 0.6).

CONCLUSION

The result of the present in-vitro study shows the absence of significant difference between TAP and DKC in terms of stent struts apposition and acute thrombus formation potential. Despite the completely different technical steps required, both techniques have similar performance according to such articulated pre-clinical evaluation. WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT?: Due to its limited complexity, T and Protrusion (TAP) technique is considered the to-go technique for bifurcation lesions with good long-term results. Recently, double kissing crush (DKC) technique has been gaining popularity and demonstrated promising results in randomized clinical trials. WHAT DOES THIS STUDY ADD?: This in-vitro bench test study provides a unique detailed OCT comparison and local hemodynamic environment analysis of the two techniques. HOW MIGHT THIS IMPACT ON CLINICAL PRACTICE?: New insights of acute thrombogenicity and computational flow model simulation may guide percutaneous therapeutic strategies of bifurcation lesions.

Drug-coated balloons: Technical and clinical progress

The advancement of drug-coated balloons (DCB) presents an alternative nonstent method in the percutaneous treatment of atherosclerotic lesions. While the current generation of drug-eluting stents (DES) are the device of choice, especially in coronary artery disease (CAD), DCB has potential applications in the treatment of de novo lesions, in-stent restenosis (ISR), bifurcations, and in peripheral artery disease (PAD). In terms of coronary clinical experience, DCB is used most in ISR scenarios and more data are collected to support the use of DCB in de novo lesions compared to best-in-class DES. The use of DCB in bifurcation side branch treatment has demonstrated safety, and with good angiographic and clinical outcomes, but more data from randomized trials will be required to assess its clinical value. For PAD, the clinical outcomes of DCB with and without debulking devices in diseased femoropopliteal arteries and treatment of below-the-knee (BTK) vessels with DCB are discussed. Current data demonstrated conflicting long-term safety outcomes in the use of paclitaxel devices in the femoral and/or popliteal arteries, while the role of DCB in BTK disease remains uncertain due to a lack of randomized controlled trial data. In summary, this review provides an overall view of current DCB technologies and progress, followed by an update on DCB clinical data in the treatment of CAD and PAD.

Efficacy and Reproducibility of Attenuation-Compensated Optical Coherence Tomography for Assessing External Elastic Membrane Border and Plaque Composition in Native and Stented Segments - An In Vivo and Histology-Based Study

BACKGROUND

Attenuation-compensated (AC) technique was recently introduced to improve the plaque characterization of optical coherence tomography (OCT). Histological validation demonstrated promising results but the efficacy and reproducibility of this technique for assessing in-vivo tissue composition remains unclear.Methods and Results:OCT images portraying native (n=200) and stented (n=200) segments and 31 histological cross-sections were analyzed. AC-OCT appeared superior to conventional (C)-OCT in detecting the external elastic lamina (EEM) borders (76% vs. 65.5%); AC-OCT enabled larger EEM arc detection compared with C-OCT (174.2±58.7° vs. 137.5±57.9°; P<0.001). There was poor agreement between the 2 techniques for detection of lipid in native and lipid and calcific tissue in stented segments (κ range: 0.164-0.466) but the agreement of C-OCT and AC-OCT was high for calcific tissue in native segments (κ=0.825). Intra and interobserver agreement of the 2 analysts was moderate to excellent with C-OCT (κ range: 0.681-0.979) and AC-OCT (κ range: 0.733-0.892) for all tissue types in both native and stented segments. Ex-vivoanalysis demonstrated that C-OCT was superior to AC-OCT (κ=0.545 vs. κ=0.296) for the detection of the lipid component in native segments.

CONCLUSIONS

The AC technique allows better delineation of the EEM but it remains inferior for lipid pool detection and neointima characterization. Combined AC- and C-OCT imaging may provide additional value for complete assessment of plaque and neointima characteristics.

Drug-Coated Balloons: Technologies and Clinical Applications

The progress and development of drug-coated balloons (DCBs) represents an emerging alternative treatment in peripheral and coronary artery diseases, particularly when a non-stent approach is necessary. Several studies and meta-analyses have evaluated the clinical outcomes of DCBs in different lesions and this review aims to compile the progress and updated clinical data of DCB strategy in both peripheral artery diseases (PAD) and coronary artery diseases (CAD). The review highlights that clinical data has encouraged the use of DCB for applications in PAD and in the treatment of coronary in-stent restenosis (ISR). The employment of DCB in side branch treatment of bifurcation lesions has been reported to be feasible and safe, with good angiographic and clinical outcome. The use of DCB for arteriovenous fistula and grafts stenoses is a promising strategy, but more clinical data is required to draw reliable conclusions. The limitations and impact of the current generation of DCBs will be discussed and the clinical development of newer generation of the device is also covered in this review.

Independent Predictors of Cardiac Mortality and Hospitalization for Heart Failure in a Multi-Ethnic Asian ST-segment Elevation Myocardial Infarction Population Treated by Primary Percutaneous Coronary Intervention

We aimed to identify independent predictors of cardiac mortality and hospitalization for heart failure (HHF) from a real-world, multi-ethnic Asian registry [the Singapore Myocardial Infarction Registry] of ST-segment elevation myocardial infarction (STEMI) patients treated by primary percutaneous coronary intervention. 11,546 eligible STEMI patients between 2008 and 2015 were identified. In-hospital, 30-day and 1-year cardiac mortality and 1-year HHF rates were 6.4%, 6.8%, 8.3% and 5.2%, respectively. From the derivation cohort (70% of patients), age, Killip class and cardiac arrest, creatinine, hemoglobin and troponin on admission and left ventricular ejection fraction (LVEF) during hospitalization were predictors of in-hospital, 30-day and 1-year cardiac mortality. Previous ischemic heart disease (IHD) was a predictor of in-hospital and 30-day cardiac mortality only, whereas diabetes was a predictor of 1-year cardiac mortality only. Age, previous IHD and diabetes, Killip class, creatinine, hemoglobin and troponin on admission, symptom-to-balloon-time and LVEF were predictors of 1-year HHF. The c-statistics were 0.921, 0.901, 0.881, 0.869, respectively. Applying these models to the validation cohort (30% of patients) showed good fit and discrimination (c-statistic 0.922, 0.913, 0.903 and 0.855 respectively; misclassification rate 14.0%, 14.7%, 16.2% and 24.0% respectively). These predictors could be incorporated into specific risk scores to stratify reperfused STEMI patients by their risk level for targeted intervention.

Everolimus- vs. novolimus-eluting bioresorbable scaffolds in patients with acute coronary syndrome

BACKGROUND

Limited data exist on bioresorbable scaffolds (BRS) in patients with acute coronary syndrome (ACS). The aim of the present study was to evaluate novolimus-eluting BRS (DESolve) as interventional treatment for patients with ACS, and to compare its 12-month outcomes with the everolimus-eluting bioresorbable scaffolds (Absorb).

METHODS

In this retrospective study, patients with ACS (including unstable angina pectoris, ST-segment elevation myocardial infarction, or non-ST-segment elevation myocardial infarction) treated with either the Absorb or the DESolve BRS were evaluated in a 1:1 matched-pair analysis. Major adverse cardiac events (MACE), including death, myocardial infarction, and target lesion revascularization, were evaluated as a major endpoint. The occurrence of scaffold thrombosis was also assessed.

RESULTS

A total of 102 patients were eligible for this analysis. The rate of MACE at 12 months was comparable between the Absorb and the DESolve group (8.3% vs. 6.8%, p = 0.738). The occurrence of target lesion revascularization (6.2% vs. 4.7%; p = 0.700) and scaffold thrombosis (4.1% vs. 2.1%; p = 0.580) was comparable as well. All instances of scaffold thrombosis occurred within 30 days of the index procedure.

CONCLUSION

In this study, similar 12-month event rates were observed for both BRS types after implantation for the treatment of ACS.

Evaluation of an in vitro coronary stent thrombosis model for preclinical assessment

Stent thrombosis remains an infrequent but significant complication following percutaneous coronary intervention. Preclinical models to rapidly screen and validate therapeutic compounds for efficacy are lacking. Herein, we describe a reproducible, high throughput and cost-effective method to evaluate candidate therapeutics and devices for either treatment or propensity to develop stent thrombosis in an in vitro bench-top model. Increasing degree of stent malapposition (0.00 mm, 0.10 mm, 0.25 mm and 0.50 mm) was associated with increasing thrombosis and luminal area occlusion (4.1 ± 0.5%, 6.3 ± 0.5%, 19.7 ± 4.5%, and 92.6 ± 7.4%, p < 0.0001, respectively). Differences in stent design in the form of bare-metal, drug-eluting, and bioresorbable vascular scaffolds demonstrated differences in stent thrombus burden (14.7 ± 3.8% vs. 20.5 ± 3.1% vs. 86.8 ± 5.3%, p < 0.01, respectively). Finally, thrombus burden was significantly reduced when healthy blood samples were incubated with Heparin, ASA/Ticagrelor (DAPT), and Heparin+DAPT compared to control (DMSO) at 4.1 ± 0.6%, 6.9 ± 1.7%, 4.5 ± 1.2%, and 12.1 ± 1.8%, respectively (p < 0.01). The reported model produces high throughput reproducible thrombosis results across a spectrum of antithrombotic agents, stent design, and degrees of apposition. Importantly, performance recapitulates clinical observations of antiplatelet/antithrombotic regimens as well as device and deployment characteristics. Accordingly, this model may serve as a screening tool for candidate therapies in preclinical evaluation.

Regression of left ventricular hypertrophy provides an additive physiological benefit following treatment of aortic stenosis: Insights from serial coronary wave intensity analysis

AIM

Severe aortic stenosis frequently involves the development of left ventricular hypertrophy (LVH) creating a dichotomous haemodynamic state within the coronary circulation. Whilst the increased force of ventricular contraction enhances its resultant relaxation and thus increases the distal diastolic coronary "suction" force, the presence of LVH has a potentially opposing effect on ventricular-coronary interplay. The aim of this study was to use non-invasive coronary wave intensity analysis (WIA) to separate and measure the sequential effects of outflow tract obstruction relief and then LVH regression following intervention for aortic stenosis.

METHODS

Fifteen patients with unobstructed coronary arteries undergoing aortic valve intervention (11 surgical aortic valve replacement [SAVR], 4 TAVI) were successfully assessed before and after intervention, and at 6 and 12 months post-procedure. Coronary WIA was constructed from simultaneously acquired coronary flow from transthoracic echo and pressure from an oscillometric brachial cuff system.

RESULTS

Immediately following intervention, a decline in the backward decompression wave (BDW) was noted (9.7 ± 5.7 vs 5.1 ± 3.6 × 10³  W/m² /s, P < 0.01). Over 12 months, LV mass index fell from 114 ± 19 to 82 ± 17 kg/m² . Accompanying this, the BDW fraction increased to 32.8 ± 7.2% at 6 months (P = 0.01 vs post-procedure) and 34.7 ± 6.7% at 12 months (P < 0.001 vs post-procedure).

CONCLUSION

In aortic stenosis, both the outflow tract gradient and the presence of LVH impact significantly on coronary haemodynamics that cannot be appreciated by examining resting coronary flow rates alone. An immediate change in coronary wave intensity occurs following intervention with further effects appreciable with hypertrophy regression. The improvement in prognosis with treatment is likely to be attributable to both features.

Radiopaque Fully Degradable Nanocomposites for Coronary Stents

Bioresorbable scaffolds (BRS) were introduced to overcome limitations of current metallic drug-eluting stents and poly-L-lactide (PLLA) has been used in the fabrication of BRS due to its biodegradability and biocompatibility. However, such polymers have weaker mechanical properties as compared to metals, limiting their use in BRS. We hypothesized that nanofillers can be used to enhance the mechanical properties considerably in PLLA. To this end, polymer-matrix composites consisting of PLLA reinforced with 5-20 wt% barium sulfate (BaSO4) nanofillers as a potential BRS material was evaluated. Stearic-acid (SA) modified BaSO4 nanofillers were used to examine the effect of functionalization. Rigid nanofillers improved the tensile modulus and strength of PLLA (60% and 110% respectively), while the use of SA-BaSO4 caused a significant increase (~110%) in the elongation at break. Enhancement in mechanical properties is attributed to functionalization which decreased the agglomeration of the nanofillers and improved dispersion. The nanocomposites were also radiopaque. Finite element analysis (FEA) showed that scaffold fabricated from the novel nanocomposite material has improved scaffolding ability, specifically that the strut thickness could be decreased compared to the conventional PLLA scaffold. In conclusion, BaSO4/PLLA-based nanocomposites could potentially be used as materials for BRS with improved mechanical and radiopaque properties.

Biomechanical stress in coronary atherosclerosis: emerging insights from computational modelling

Coronary plaque rupture is the most common cause of vessel thrombosis and acute coronary syndrome. The accurate early detection of plaques prone to rupture may allow prospective, preventative treatment; however, current diagnostic methods remain inadequate to detect these lesions. Established imaging features indicating vulnerability do not confer adequate specificity for symptomatic rupture. Similarly, even though experimental and computational studies have underscored the importance of endothelial shear stress in progressive atherosclerosis, the ability of shear stress to predict plaque progression remains incremental. This review examines recent advances in image-based computational modelling that have elucidated possible mechanisms of plaque progression and rupture, and potentially novel features of plaques most prone to symptomatic rupture. With further study and clinical validation, these markers and techniques may improve the specificity of future culprit plaque detection.

Stent malapposition and the risk of stent thrombosis: mechanistic insights from an in vitro model

AIMS

The aim of this report was to examine the effect of underexpansion on stent thrombogenicity with an in vitro perfusion model.

METHODS AND RESULTS

Drug-eluting stent (DES) samples were partially underdeployed in silicone tubes and perfused with porcine blood containing 10% anticoagulant citrate dextrose solution for four minutes at a flow rate of 200 ml/min. Thrombus formation was evaluated and compared between the well-apposed and malapposed sections. The malapposed sections showed significantly more thrombus formation compared to the well-apposed sections (13.9 vs. 0.41 mm2, p<0.001).

CONCLUSIONS

Stent malapposition has a very direct impact on thrombus formation. Optimised stent implantation is required to minimise malapposition in DES and BVS to reduce thrombus formation.

Role of Proximal Optimization Technique Guided by Intravascular Ultrasound on Stent Expansion, Stent Symmetry Index, and Side-Branch Hemodynamics in Patients With Coronary Bifurcation Lesions

BACKGROUND

Bench models of coronary bifurcation lesions demonstrated that the proximal optimization technique (POT) expanded the stent and opened the side branch (SB). We investigated the role of POT guided by intravascular ultrasound on the main vessel (MV) stent expansion and SB fractional flow reserve (FFR) in patients with coronary bifurcation lesion.

METHODS AND RESULTS

In 40 patients with coronary bifurcation lesion, 120 intravascular ultrasound examinations of the MV were performed at baseline, after MV stenting, and POT followed by 95 FFR measurements of the SB. In the proximal stent segment, stent volume index and minimum stent area were larger after POT versus MV stenting (9.2±3.4 versus 7.40±2.0 mm³/mm and 7.65±1.8 versus 6.38±1.7 mm², respectively; P<0.01). In the bifurcation segment, minimum stent area was larger after POT versus MV stenting (6.45±2.1 versus 5.9±2.0 mm², respectively; P<0.05). POT expanded the stent symmetrically. After POT, SB FFR was <0.75 in 12 patients (30%), which improved to >0.75 after SB dilation or SB stenting+final POT. SB FFR was significantly higher after POT+SB dilation or SB stenting+final POT versus after MV stenting and POT.

CONCLUSIONS

This is the first study of POT guided by intravascular ultrasound in patients with coronary bifurcation lesion, demonstrating that POT symmetrically expanded the proximal and bifurcation segments of the stent. After POT, SB FFR was <0.75 in a third of patients, which improved to >0.75 after SB dilation or SB stenting+final POT.

Optimization of coronary optical coherence tomography imaging using the attenuation-compensated technique: a validation study

Aim

To optimize conventional coronary optical coherence tomography (OCT) images using the attenuation-compensated technique to improve identification of plaques and the external elastic lamina (EEL) contour.

Methods and Results

The attenuation-compensated technique was optimized via manipulating contrast exponent C, and compression exponent N, to achieve an optimal contrast and signal-to-noise ratio (SNR). This was applied to 60 human coronary lesions (38 native and 22 stented) ex vivo conventional coronary OCT images acquired from heart autopsies of 10 patients and matching histology was available as reference. Three independent reviewers assessed the conventional and attenuation-compensated OCT images blindly for plaque characteristics and EEL detection. Conventional OCT and compensated OCT assessment were compared against histology. Using an optimized algorithm, the attenuation-compensated OCT images had a 2-fold improvement in contrast between different tissues in both stented and non-stented epicardial coronaries (P < 0.05). Overall sensitivity and specificity for plaque classification increased from 84 to 89% and from 92 to 94%, respectively, with substantial agreement among the three reviewers (Fleiss' Kappa k, 0.72 and 0.71, respectively). Furthermore, operators were 2.5 times more likely to identify the EEL contour in the attenuation-compensated OCT images (k = 0.72) than in the conventional OCT images (k = 0.36).

Conclusion

The attenuation-compensated technique can be retrospectively applied to conventional OCT images and improves the detection of plaque characteristics and the EEL contour. This approach could complement conventional OCT imaging in the evaluation of plaque characteristics and quantify plaque burden in the clinical setting.

Serial 5-Year Evaluation of Side Branches Jailed by Bioresorbable Vascular Scaffolds Using 3-Dimensional Optical Coherence Tomography: Insights From the ABSORB Cohort B Trial (A Clinical Evaluation of the Bioabsorbable Everolimus Eluting Coronary Stent System in the Treatment of Patients With De Novo Native Coronary Artery Lesions)

BACKGROUND

The long-term fate of Absorb bioresorbable vascular scaffold (Abbott Vascular, Santa Clara, CA) struts jailing side branch ostia has not been clarified. We therefore evaluate serially (post-procedure and at 6 months, 1, 2, 3, and 5 years) the appearance and fate of jailed Absorb bioresorbable vascular scaffold struts.

METHODS AND RESULTS

We performed 3-dimensional optical coherence tomographic analysis of the ABSORB Cohort B trial (A Clinical Evaluation of the Bioabsorbable Everolimus Eluting Coronary Stent System in the Treatment of Patients With De Novo Native Coronary Artery Lesions) up to 5 years using a novel, validated cut-plane analysis method. We included 29 patients with a total of 85 side branch ostia. From the 12 ostia which could be assessed in true serial fashion, 7 showed a pattern of initial decrease in the ostial area free from struts, followed by an increase in strut-free ostial area toward the end of the 5 years of follow-up. In a repeated-measures analysis with time as fixed variable and ostial area free from struts as dependent variable, we showed a numeric decrease in the estimated ostial area free from struts from 0.75 mm² (baseline) to 0.68 mm² (first follow-up visit at 6 months or 1 year) and 0.63 mm² (second follow-up visit at 2 or 3 years). However, from the second visit to the 5-year follow-up visit, there was a statistically significant increase from 0.63 to 0.89 mm² (P=0.001). Struts overlying an ostium divided the ostium into compartments, and the number of these compartments decreased over time.

CONCLUSIONS

This study showed that in most cases, the side branch ostial area free from struts initially decreased. However, with full scaffold bioresorption, the ostial area free from scaffold increased between 2 to 3 years and 5 years in the vast majority of patients.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00856856.

Complex coronary bifurcation treatment by a novel stenting technique: Bench test, fluid dynamic study and clinical outcomes

OBJECTIVES

We assess the mid-term outcomes of ultrathin biodegradable polymer double stenting using a very minimal crushing (Nano-Crush) technique in large complex coronary bifurcation.

BACKGROUND

Complex bifurcations have been suggested to be better approached by a planned double stent technique.

METHODS

Two hundred and five consecutive patients (107 males and 98 females) referred for large complex coronary bifurcation percutaneous coronary interventions were enrolled. The technique was also evaluated by both a bench test with a silicon tubes phantom resembling a coronary bifurcation and a computed fluid dynamic (CFD) analysis.

RESULTS

Left main bifurcation accounted for 40.9% of cases (84 patients). Mean angles between main branch (MB) and side branch (SB) were 63.6 ± 21.3°. SB intravascular ultrasound-calculated MSA was 5.6 ± 1.5 mm² . Clinical follow-up was available for 100% of patients and at a mean follow-up of 16.2 ± 6.7 months 8 deaths, all due to cardiovascular reason, (3.9%, 4 patients for stroke, two for heart failure, one after surgical aortic valve substitution, and one after acute massive pulmonary embolism) and no presumptive stent thrombosis or target vessel induced ischemia were observed. Angiographic follow-up was available in 108 patients (52.7%) and showed a very low significant restenosis (5 patients, 4.6%). Bench study and CFD evaluation suggested a complete coverage of the SB ostium with a very high strut-free area at the SB.

CONCLUSIONS

The revascularization of complex large coronary bifurcation disease using the Nano-crush technique appeared promising thanks to the favorable fluid dynamic profile, complete coverage of the SD ostium, and very small metal amount at the carina.

Local Hemodynamic Forces After Stenting: Implications on Restenosis and Thrombosis

Local hemodynamic forces are well-known to modulate atherosclerotic evolution, which remains one of the largest cause of death worldwide. Percutaneous coronary interventions with stent implantation restores blood flow to the downstream myocardium and is only limited by stent failure caused by restenosis, stent thrombosis, or neoatherosclerosis. Cumulative evidence has shown that local hemodynamic forces affect restenosis and the platelet activation process, modulating the pathophysiological mechanisms that lead to stent failure. This article first covers the pathophysiological mechanisms through which wall shear stress regulates arterial disease formation/neointima proliferation and the role of shear rate on stent thrombosis. Subsequently, the article reviews the current evidence on (1) the implications of stent design on the local hemodynamic forces, and (2) how stent/scaffold expansion can influence local flow, thereby affecting the risk of adverse events.

Invasive Assessment of the Coronary Microcirculation in Reperfused ST-Segment-Elevation Myocardial Infarction Patients: Where Do We Stand?

For patients presenting with an acute ST-segment-elevation myocardial infarction, the most effective therapy for reducing myocardial infarct size and preserving left ventricular systolic function is primary percutaneous coronary intervention (PPCI). However, mortality and morbidity remain significant. This is partly attributed to the development of microvascular obstruction, which occurs in around 50% of ST-segment-elevation myocardial infarction patients post-PPCI, and it is associated with adverse left ventricular remodeling and worse clinical outcomes. Although microvascular obstruction can be detected by cardiac imaging techniques several hours post-PPCI, it may be too late to intervene at that time. Therefore, being able to predict the development of microvascular obstruction at the time of PPCI may identify high-risk patients who might benefit from further adjuvant intracoronary therapies, such as thrombolysis, vasodilators, glycoprotein IIb/IIIa inhibitors, and anti-inflammatory agents that may reduce microvascular obstruction. Recent studies have shown that invasive coronary physiology measurements performed during PPCI can be used to assess the coronary microcirculation. In this article, we provide an overview of the various invasive methods currently available to assess the coronary microcirculation in the setting of ST-segment-elevation myocardial infarction, and how they could potentially be used in the future for tailoring therapies to those most at risk.

Fibroatheroma identification in Intravascular Optical Coherence Tomography images using deep features

Identifying vulnerable plaque is important in coronary heart disease diagnosis. Recent emerged imaging modality, Intravascular Optical Coherence Tomography (IVOCT), has been proved to be able to characterize the appearance of vulnerable plaques. Comparing with the manual method, automated fibroatheroma identification would be more efficient and objective. Deep convolutional neural networks have been adopted in many medical image analysis tasks. In this paper, we introduce deep features to resolve fibroatheroma identification problem. Deep features which extracted using four deep convolutional neural networks, AlexNet, GoogLeNet, VGG-16 and VGG-19, are studied. And a dataset of 360 IVOCT images from 18 pullbacks are constructed to evaluate these features. Within these 360 images, 180 images are normal IVOCT images and the rest 180 images are IVOCT images with fibroatheroma. Here, one pullback belongs to one patient; leave-one-patient-out cross-validation is employed for evaluation. Data augmentation is applied on training set for each classification scheme. Linear support vector machine is conducted to classify the normal IVOCT image and IVOCT image with fibroatheroma. The experimental results show that deep features could achieve relatively high accuracy in fibroatheroma identification.

Mechanical behavior of polymer-based vs. metallic-based bioresorbable stents

Bioresorbable scaffolds (BRS) were developed to overcome the drawbacks of current metallic drug-eluting stents (DES), such as late in-stent restenosis and caging of the vessel permanently. The concept of the BRS is to provide transient support to the vessel during healing before being degraded and resorbed by the body, freeing the vessel and restoring vasomotion. The mechanical properties of the BRS are influenced by the choice of the material and processing methods. Due to insufficient radial strength of the bioresorbable material, BRS often required large strut profile as compared to conventional metallic DES. Having thick struts will in turn affect the deliverability of the device and may cause flow disturbance, thereby increasing the incidence of acute thrombotic events. Currently, the bioresorbable poly-l-lactic acid (PLLA) polymer and magnesium (Mg) alloys are being investigated as materials in BRS technologies. The bioresorption process, mechanical properties, in vitro observations and clinical outcomes of PLLA-based and Mg-based BRS will be examined in this review.

Extract-and-match geometric corner and step pattern approach for registration of fluoroscopic X-ray sequences

This paper presents a method to extract-and-match robust corner features based on connecting edges from the edge maps, mainly formed by coronary vascular junctions in fluoroscopic x-ray sequence images. Such images are challenging due to the aperture problem. To overcome this, existing approaches attempt to extract vessels for registration. However, they are ineffective in poor quality images. Our approach describes the extracted robust corner features in a rotation invariant manner using step patterns, followed by matching them effectively. Experimental results show that our approach performs very well (above 80%) in a dataset of poor quality fluoroscopic x-ray image sequences without extensive processing such as segmentation or learning.

Coronary covered stents

Covered stents offer an effective bail-out strategy in vessel perforations, are an alternative to surgery for the exclusion of coronary aneurysms, and have a potential role in the treatment of friable embolisation-prone plaques. The aim of this manuscript is to offer an overview of currently available platforms and to report results obtained in prior studies.

Invasive or non-invasive imaging for detecting high-risk coronary lesions?

INTRODUCTION

Advances in our understanding about atherosclerotic evolution have enabled us to identify specific plaque characteristics that are associated with coronary plaque vulnerability and cardiovascular events. With constant improvements in signal and image processing an arsenal of invasive and non-invasive imaging modalities have been developed that are capable of identifying these features allowing in vivo assessment of plaque vulnerability. Areas covered: This review article presents the available and emerging imaging modalities introduced to assess plaque morphology and biology, describes the evidence from the first large scale studies that evaluated the efficacy of invasive and non-invasive imaging in detecting lesions that are likely to progress and cause cardiovascular events and discusses the potential implications of the in vivo assessment of coronary artery pathology in the clinical setting. Expert commentary: Invasive imaging, with its high resolution, and in particular hybrid intravascular imaging appears as the ideal approach to study the mechanisms regulating atherosclerotic disease progression; whereas non-invasive imaging is expected to enable complete assessment of coronary tree pathology, detection of high-risk lesions, more accurate risk stratification and thus to allow a personalized treatment of vulnerable patients.

Evaluation of coronary flow conditions in complex coronary artery bifurcations stenting using computational fluid dynamics: Impact of final proximal optimization technique on different double-stent techniques

BACKGROUND/PURPOSE

Computational fluid dynamics (CFD) have been recently adopted in many fields of cardiovascular medicine and in interventional cardiology. Using CFD analysis we compared the use of different PCI procedures, with and without the utilization of a proximal optimization technique (POT), on a complex coronary artery bifurcation.

METHODS/MATERIALS

For the analysis, we considered a hypothetic model of a left anterior descending artery-diagonal Medina 1,1,1 bifurcation type with a diameter of the proximal main branch (MB) and the side branch (SB) set at 3.5mm and 2.5mm, respectively. The bifurcation angle has been set to 50°. For the stent simulation, we reconstructed a third-generation, ultra-thin strut everolimus-eluting stent (ORSIRO stent, Biotronik IC, Bulack, Switzerland).

RESULTS

The Nano-crush and the modified T techniques seem able to restore the most physiologic fluid dynamic profile. Conversely, the DK-crush and the culotte demonstrated an intermediate and worst effect, respectively. The addition of a final POT resulted favorably for both Nano-crush and reverse modified T techniques, whereas a neutral and lack of significant effects have been observed for the DK-crush and culotte technique, respectively.

CONCLUSION

Different double-stenting techniques (DST) have a different impact on coronary flow physiology. Both Nano-crush and modified T techniques achieved the most physiologic profile. The addition of a final POT appears to be a favourable step for both Nano-crush and modified T.

Bioabsorbable vascular scaffold overexpansion: insights from in vitro post-expansion experiments

AIMS

While bioresorbable vascular scaffolds (BVS) are increasingly used in clinical practice, their behaviour when post-dilated beyond their recommended maximum overexpansion diameter remains sparsely documented. We aimed to test the overexpansion of the BVS scaffold in vitro and evaluate the impact of excessive scaffold oversizing on focal point support.

METHODS AND RESULTS

We examined the post-expansion behaviour of the bioresorbable vascular scaffold (3.0 mm and 3.5 mm Absorb BVS; Abbott Vascular, Santa Clara, CA, USA) after overexpansion with non-compliant (NC) balloons of increasing diameters. After each oversizing step, the scaffolds were measured and inspected for strut disruption using microscope and optical coherence tomography imaging. Point force mechanical measurements on single scaffold struts were also performed to evaluate the impact of excessive scaffold overstretching on focal mechanical support. 3.0 mm and 3.5 mm scaffold sizes could be post-expanded up to 1 mm above their nominal diameters without any strut fracture when deployed without an external constraining model. Importantly, when overexpansion of both scaffold sizes was repeated using a constraining silicone lesion model, only post-expansion with an NC balloon size 0.5 mm larger than the scaffold nominal sizes could be performed without strut fractures. Point force compression analysis on single struts shows that overstretched struts with fractures provided lower focal strength compared to overexpanded ring segments without fractures and normal segments expanded at nominal pressure.

CONCLUSIONS

In our experiments, only overexpansion with an NC balloon 0.5 mm larger than the BVS size was feasible for BVS deployed inside an arterial lesion model. Overexpansion of the BVS scaffold beyond recommended post-dilation limits can lead to strut disconnections and focal loss of mechanical support.

A new novolimus-eluting bioresorbable coronary scaffold: Present status and future clinical perspectives

The DESolve® scaffold (Elixir Medical Corporation, Sunnyvale, California, USA) is manufactured from a poly-l-lactide based polymer and elutes an anti-proliferative, anti-inflammatory drug, Novolimus from a poly-l-lactide based topcoat mixture. The strut thickness is 150μm and the scaffold has platinum-iridium radiopaque markers at both ends. Radial support is available during the early time period to prevent recoil. The scaffold biodegrades within 1year (>90% reduction in molecular weight) and then completely bioresorbs within 2years. The DESolve® scaffold permits a wide range of expansion with a consequently reduced risk for strut fracture. Lumen and scaffold enlargement is observed within 3-6months in both preclinical and clinical studies potentially allowing for the scaffolded region to respond to vasoactive stimuli. The device has a unique property of self-correction observed in bench top studies, which in clinical practice has the potential to eliminate minor malapposition following deployment.

Endothelial repair in stented arteries is accelerated by inhibition of Rho-associated protein kinase

Aims

Stent deployment causes endothelial cells (EC) denudation, which promotes in-stent restenosis and thrombosis. Thus endothelial regrowth in stented arteries is an important therapeutic goal. Stent struts modify local hemodynamics, however the effects of flow perturbation on EC injury and repair are incompletely understood. By studying the effects of stent struts on flow and EC migration, we identified an intervention that promotes endothelial repair in stented arteries.

Methods and Results

In vitro and in vivo models were developed to monitor endothelialization under flow and the influence of stent struts. A 2D parallel-plate flow chamber with 100 μm ridges arranged perpendicular to the flow was used. Live cell imaging coupled to computational fluid dynamic simulations revealed that EC migrate in the direction of flow upstream from the ridges but subsequently accumulate downstream from ridges at sites of bidirectional flow. The mechanism of EC trapping by bidirectional flow involved reduced migratory polarity associated with altered actin dynamics. Inhibition of Rho-associated protein kinase (ROCK) enhanced endothelialization of ridged surfaces by promoting migratory polarity under bidirectional flow (P < 0.01). To more closely mimic the in vivo situation, we cultured EC on the inner surface of polydimethylsiloxane tubing containing Coroflex Blue stents (65 μm struts) and monitored migration. ROCK inhibition significantly enhanced EC accumulation downstream from struts under flow (P < 0.05). We investigated the effects of ROCK inhibition on re-endothelialization in vivo using a porcine model of EC denudation and stent placement. En face staining and confocal microscopy revealed that inhibition of ROCK using fasudil (30 mg/day via osmotic minipump) significantly increased re-endothelialization of stented carotid arteries (P < 0.05).

Conclusions

Stent struts delay endothelial repair by generating localized bidirectional flow which traps migrating EC. ROCK inhibitors accelerate endothelial repair of stented arteries by enhancing EC polarity and migration through regions of bidirectional flow.