Morphological and Physiological Characteristics of Ruptured Plaques in Native Arteries and Neoatherosclerotic Segments: An OCT-Based and Computational Fluid Dynamics Study.

Background: Intravascular imaging has been used to assess the morphology of lesions causing an acute coronary syndrome (ACS) in native vessels (NV) and identify differences between plaques that ruptured (PR) and caused an event and those that ruptured without clinical manifestations. However, there is no data about the morphological and physiological characteristics of neoatherosclerotic plaques that ruptured (PR-NA) which constitute a common cause of stent failure. Methods: We retrospectively analyzed data from patients admitted with an acute myocardial infarction that had optical coherence tomography (OCT) imaging of the culprit vessel before balloon pre-dilation. OCT pullbacks showing PR were segmented at every 0.4 mm. The extent of the formed cavity, lipid and calcific tissue, thrombus, and macrophages were measured, and the fibrous cap thickness (FCT) and the incidence of micro-channels and cholesterol crystals were reported. These data were used to reconstruct a representative model of the native and neoatherosclerotic lesion geometry that was processed with computational fluid dynamics (CFD) techniques to estimate the distribution of the endothelial shear stress and plaque structural stress. Result: Eighty patients were included in the present analysis: 56 had PR in NV (PR-NV group) and 24 in NA segments (PR-NA group). The PR-NV group had a larger minimum lumen area (2.93 ± 2.03 vs. 2.00 ± 1.26 mm2, p = 0.015) but similar lesion length and area stenosis compared to PR-NA group. The mean FCT (186 ± 65 vs. 232 ± 80 µm, p = 0.009) and the lipid index was smaller (16.7 ± 13.8 vs. 25.9 ± 14.1, p = 0.008) while the of calcific index (8.3 ± 9.5 vs. 2.2 ± 1.6%, p = 0.002) and the incidence of micro-channels (41.4 vs. 12.5%, p = 0.013) was higher in the PR-NV group. Conversely, there was no difference in the incidence of cholesterol crystals, thrombus burden or the location of the rupture site between groups. CFD analysis revealed higher maximum endothelial shear stress (19.1 vs. 11.0 Pa) and lower maximum plaque structural stress (38.8 vs. 95.1 kPa) in the PR-NA compared to the PR-NV model. Conclusion: We reported significant morphological and physiological differences between culprit ruptured plaques in native and stented segments. Further research is needed to better understand the causes of these differences and the mechanisms regulating neoatherosclerotic lesion destabilization.

Five-year follow-up of intracoronary autologous cell therapy in acute myocardial infarction: the REGENERATE-AMI trial.

AIMS: The long-term outcomes of the intracoronary delivery of autologous bone marrow-derived cells (BMCs) after acute myocardial infarction are not well established. Following the promising 1 year results of the REGENERATE-AMI trial (despite it not achieving its primary endpoint), this paper presents the analysis of the 5 year clinical outcomes of these acute myocardial infarction patients who were treated with an early intracoronary autologous BMC infusion or placebo. METHODS AND RESULTS: A 5 year follow-up of major adverse cardiac events (defined as the composite of all-cause death, recurrent myocardial infarction, and all coronary revascularization) and of rehospitalization for heart failure was completed in 85 patients (BMC n = 46 and placebo n = 39). The incidence of major adverse cardiac events was similar between the BMC-treated patients and the placebo group (26.1% vs. 18.0%, P = 0.41). There were no cases of cardiac death in either group, but an increase in non-cardiac death was seen in the BMC group (6.5% vs. 0%, P = 0.11). The rates of recurrent myocardial infarction and repeat revascularization were similar between the two groups. There were no cases of rehospitalization for heart failure in either group. CONCLUSION: This 5 year follow-up analysis of the REGENERATE-AMI trial did not show an improvement in clinical outcomes for patients treated with cell therapy. This contrasts with the 1 year results which showed improvements in the surrogate outcome measures of ejection fraction and myocardial salvage index.

A deep learning methodology for the automated detection of end-diastolic frames in intravascular ultrasound images.

Coronary luminal dimensions change during the cardiac cycle. However, contemporary volumetric intravascular ultrasound (IVUS) analysis is performed in non-gated images as existing methods to acquire gated or to retrospectively gate IVUS images have failed to dominate in research. We developed a novel deep learning (DL)-methodology for end-diastolic frame detection in IVUS and compared its efficacy against expert analysts and a previously established methodology using electrocardiographic (ECG)-estimations as reference standard. Near-infrared spectroscopy-IVUS (NIRS-IVUS) data were prospectively acquired from 20 coronary arteries and co-registered with the concurrent ECG-signal to identify end-diastolic frames. A DL-methodology which takes advantage of changes in intensity of corresponding pixels in consecutive NIRS-IVUS frames and consists of a network model designed in a bidirectional gated-recurrent-unit (Bi-GRU) structure was trained to detect end-diastolic frames. The efficacy of the DL-methodology in identifying end-diastolic frames was compared with two expert analysts and a conventional image-based (CIB)-methodology that relies on detecting vessel movement to estimate phases of the cardiac cycle. A window of ± 100 ms from the ECG estimations was used to define accurate end-diastolic frames detection. The ECG-signal identified 3,167 end-diastolic frames. The mean difference between DL and ECG estimations was 3 ± 112 ms while the mean differences between the 1st-analyst and ECG, 2nd-analyst and ECG and CIB-methodology and ECG were 86 ± 192 ms, 78 ± 183 ms and 59 ± 207 ms, respectively. The DL-methodology was able to accurately detect 80.4%, while the two analysts and the CIB-methodology detected 39.0%, 43.4% and 42.8% of end-diastolic frames, respectively (P < 0.05). The DL-methodology can identify NIRS-IVUS end-diastolic frames accurately and should be preferred over expert analysts and CIB-methodologies, which have limited efficacy.

Optical coherence tomography enables more accurate detection of functionally significant intermediate non-left main coronary artery stenoses than intravascular ultrasound: A meta-analysis of 6919 patients and 7537 lesions.

OBJECTIVE: Fractional flow reserve (FFR) is regarded as the gold standard for the physiological assessment of intermediate coronary artery stenoses. However, FFR does not allow assessment of plaque morphology and lesion geometry. Intracoronary imaging techniques such as intravascular ultrasound (IVUS) and optical coherence tomography (OCT) can help treatment planning by optimising stent implantation, which can improve patient outcomes. The aim of this meta-analysis is to compare the efficacy of IVUS and OCT-derived metrics in detecting flow limiting stenoses in non-left main stem lesions. METHODS: A systematic review of PubMed, Medline, and Cochrane databases was performed and identified studies examining the diagnostic accuracy of IVUS and OCT in detecting significant stenoses when compared to FFR. RESULTS: A total of 33 (7537 lesions) studies (24 IVUS, 7 OCT and 2 IVUS & OCT studies) were included in the meta-analysis. Pooled analysis showed that IVUS- and OCT-derived minimum lumen area (MLA) had a similar sensitivity in predicting haemodynamically significant lesions (IVUS-MLA: 0.747 vs OCT-MLA 0.732, p = 0.519). However, OCT-MLA had a higher specificity (0.763 vs 0.665, p < 0.001) and diagnostic accuracy in detecting flow-limiting stenoses than IVUS-MLA (AUC 0.810 vs 0.754, p = 0.045). Sub-analysis of the studies with the clinically significant FFR cut-off value of 0.80 yielded similar results demonstrating that OCT-MLA has a better accuracy than IVUS-MLA in detecting haemodynamically significant stenoses (AUC 0.809 vs 0.750, p = 0.034). CONCLUSIONS: OCT with its superior image resolution appears to be the preferable intravascular imaging modality for the detection of haemodynamically significant stenoses in non-left main stem lesions.

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.

Advanced Imaging Modalities to Monitor for Cardiotoxicity.

OPINION STATEMENT: Early detection and treatment of cardiotoxicity from cancer therapies is key to preventing a rise in adverse cardiovascular outcomes in cancer patients. Over-diagnosis of cardiotoxicity in this context is however equally hazardous, leading to patients receiving suboptimal cancer treatment, thereby impacting cancer outcomes. Accurate screening therefore depends on the widespread availability of sensitive and reproducible biomarkers of cardiotoxicity, which can clearly discriminate early disease. Blood biomarkers are limited in cardiovascular disease and clinicians generally still use generic screening with ejection fraction, based on historical local expertise and resources. Recently, however, there has been growing recognition that simple measurement of left ventricular ejection fraction using 2D echocardiography may not be optimal for screening: diagnostic accuracy, reproducibility and feasibility are limited. Modern cancer therapies affect many myocardial pathways: inflammatory, fibrotic, metabolic, vascular and myocyte function, meaning that multiple biomarkers may be needed to track myocardial cardiotoxicity. Advanced imaging modalities including cardiovascular magnetic resonance (CMR), computed tomography (CT) and positron emission tomography (PET) add improved sensitivity and insights into the underlying pathophysiology, as well as the ability to screen for other cardiotoxicities including coronary artery, valve and pericardial diseases resulting from cancer treatment. Delivering screening for cardiotoxicity using advanced imaging modalities will however require a significant change in current clinical pathways, with incorporation of machine learning algorithms into imaging analysis fundamental to improving efficiency and precision. In the future, we should aspire to personalized rather than generic screening, based on a patient's individual risk factors and the pathophysiological mechanisms of the cancer treatment they are receiving. We should aspire that progress in cardiooncology is able to track progress in oncology, and to ensure that the current 'one size fits all' approach to screening be obsolete in the very near future.

Implications of the local hemodynamic forces on the formation and destabilization of neoatherosclerotic lesions.

OBJECTIVE: To examine the implications of endothelial shear stress (ESS) distribution in the formation of neoatherosclerotic lesions. METHODS: Thirty six patients with neoatherosclerotic lesions on optical coherence tomography (OCT) were included in this study. The OCT data were used to reconstruct coronary anatomy. Blood flow simulation was performed in the models reconstructed from the stent borders which it was assumed that represented the lumen surface at baseline, immediate after stent implantation, and the estimated ESS was associated with the neointima burden, neoatherosclerotic burden and neointima characteristics. In segments with neointima rupture blood flow simulation was also performed in the model representing the lumen surface before rupture and the ESS was estimated at the ruptured site. RESULTS: An inverse association was noted between baseline ESS and the incidence and the burden of neoatherosclerotic (ß = -0.60, P < 0.001, and ß = -4.05, P < 0.001, respectively) and lipid-rich neoatherosclerotic tissue (ß = -0.54, P < 0.001, and ß = -3.60, P < 0.001, respectively). Segments exposed to low ESS (<1 Pa) were more likely to exhibit macrophages accumulation (28.2% vs 10.9%, P < 0.001), thrombus (11.0% vs 2.6%, P < 0.001) and evidence of neointima discontinuities (8.1% vs 0.9%, P < 0.001) compared to those exposed to normal or high ESS. In segments with neointima rupture the ESS was high at the rupture site compared to the average ESS over the culprit lesion (4.00 ±â€¯3.65 Pa vs 3.14 ±â€¯2.90 Pa, P < 0.001). CONCLUSIONS: Local EES is associated with neoatherosclerotic lesion characteristics, which suggests involvement of ESS in the formation of vulnerable plaques in stented segments.

Pericardial Disease in Cancer Patients.

PURPOSE OF REVIEW: To understand the variety of conditions in which the pericardium may be affected in cancer patients. RECENT FINDINGS: Cancer may affect the pericardium directly (primary cancer; uncommon) or through metastases (commoner). Cancer treatment (chemotherapy and radiotherapy) may affect the pericardium leading to pericarditis and myopericarditis. Pericardial effusions, tamponade and constrictive pericarditis are complications that can also occur. A variety of techniques (predominantly cardiac imaging related) are used to make the diagnosis with the treatment strategy dependent on whether the pericardial disease is due to cancer or as a result of cancer treatment. A variety of pericardial diseases may be caused by cancer and cancer treatment. Determining the aetiology and providing effective treatment can often be challenging.

Angiography-guided Multivessel Percutaneous Coronary Intervention Versus Ischemia-guided Percutaneous Coronary Intervention Versus Medical Therapy in the Management of Significant Disease in Non-Infarct-related Arteries in ST-Elevation Myocardial Infarction Patients With Multivessel Coronary Disease.

BACKGROUND: In ST-elevation myocardial infarction (STEMI) patients with multivessel (MV) disease, after primary percutaneous coronary intervention (PCI), emerging evidence suggests that significant disease in non-infarct-related coronary arteries (IRAs) should be routinely stented. Whether this procedure should be guided by angiography alone or ischemia testing is unclear. METHODS: All STEMI patients treated with primary PCI between January 1, 2005, and December 31, 2012, at a tertiary cardiology center were reviewed retrospectively. Inclusion criterion is patients with at least 70% stenosis in non-IRAs. There were 3 treatment groups: (1) angiography-guided MV-PCI, (2) ischemia-guided PCI, and (3) medical therapy. Primary endpoint is all-cause mortality, and secondary end point is major adverse cardiovascular events (MACE), including death, acute coronary syndrome, revascularization, or stent thrombosis. Event-free survivals were compared using multivariate Cox proportional-hazards analysis. A propensity score-adjusted analysis was performed. RESULTS: Four hundred forty-seven STEMI patients had >70% stenosis in non-IRAs. For all-cause mortality, the 3 strategies did not differ. For MACE, ischemia-guided PCI was associated with the lowest MACE rate, followed by angiography-guided PCI and medical therapy, which was associated with the highest MACE rate, driven by death and myocardial infarction. Hazard ratios (HRs) for MACE: angiography-guided MV-PCI versus ischemia-guided MV-PCI: HR = 2.23 [95% confidence interval (CI), 1.11-4.48; P = 0.023]; medical therapy versus angiography-guided MV-PCI: HR = 1.58 (95% CI, 0.99-2.63; P = 0.062); medical therapy versus ischemia-guided MV-PCI: HR = 1.72 (95% CI, 1.08-2.74; P = 0.022). Propensity score-adjusted analysis yielded similar results. CONCLUSIONS: After primary PCI, complete revascularization in STEMI multivessel disease is associated with lower MACE rates than medical therapy. However, ischemia-testing-guided rather than angiography-guided revascularization was associated with the lowest MACE. This study provides preliminary data and hypotheses for future randomized controlled studies.

Hemodynamic analysis of a novel bioresorbable scaffold in porcine coronary artery model

BACKGROUND: The shear stress distribution assessment can provide useful insights for the hemodynamic performance of the implanted stent/scaffold. Our aim was to investigate the effect of a novel bioresorbable scaffold, Mirage on local hemodynamics in animal models. METHOD: The main epicardial coronary arteries of 7 healthy mini-pigs were implanted with 11 Mirage Microfiber sirolimus-eluting Bioresorbable Scaffolds (MMSES). Optical coherence tomography (OCT) was performed post scaffold implantation and the obtained images were fused with angiographic data to reconstruct the coronary artery anatomy. Blood flow simulation was performed and Endothelial Shear Stress (ESS) distribution was estimated for each of the 11 scaffolds. ESS data were extracted in each circumferential 5-degree subunit of each cross-section in the scaffolded segment. The generalized linear mixed-effect analysis was implemented for the comparison of ESS in two scaffold groups; 150-mm strut thickness MMSES and 125-mm strut thickness MMSES. RESULTS: ESS was significantly higher in MMSES (150 mm) [0.85(0.49­1.40) Pa], compared to MMSES (125 mm) [0.68(0.35­1.18) Pa]. Both MMSES (150 mm) and MMSES (125 mm) revealed low recirculation zone percentages per luminal surface area [3.17% 6 1.97% in MMSES (150 mm), 2.71% 6 1.32% in MMSES (125 mm)]. CONCLUSION: Thinner strut Mirage scaffolds induced lower shear stress due to the small size vessels treated as compared to the thick strut version of the Mirage which was implanted in relatively bigger size vessels. Vessel size should be taken into account in planning BRS implantation. Small vessels may not get benefit from BRS implantation even with a streamlined strut profile. This pilot study warrants comparative assessment with commercially available bioresorbable scaffolds.

Intravascular imaging in cardiovascular ageing.

Ageing is related to complex molecular, inflammatory and biochemical changes that affect coronary pathology and often lead to coronary artery disease and cardiovascular events. Intravascular imaging is considered as the ideal technique to study coronary plaque morphology and assess its burden. Over the recent years several studies have been performed that investigated the association between pathophysiological mechanisms that promote vascular ageing and plaque morphology. In addition, several reports have compared plaque pathology in different age groups and a few studies included serial intravascular imaging to assess changes in the atheroma burden and compositional characteristics of the plaque. This review article summarizes the evidence derived from intravascular imaging studies about the implications of vascular ageing on coronary artery morphology and discusses the potential of coronary imaging in assessing atherosclerotic evolution.

Neointima and neoatherosclerotic characteristics in bare metal and first- and second-generation drug-eluting stents in patients admitted with cardiovascular events attributed to stent failure: an optical coherence tomography study.

AIMS: The aim of this study was to assess neoatherosclerotic plaque morphology in bare metal (BMS) and first- and second-generation drug-eluting stents (DES) in patients presenting with an event attributed to stent failure. METHODS AND RESULTS: Thirty-five patients (11 implanted with BMS, 13 with a first-generation and 11 with a second-generation DES) admitted with an event due to stent failure who had neoatherosclerotic lesions on optical coherence tomography were included in the analysis. The lumen and stent borders were detected and the lipid and calcific tissue were identified in the neointima and their burden was estimated. The neointima attenuation and backscatter indices were computed and compared between the different stent types. Although there were no differences in the neointima burden, the BMS group exhibited thinner fibrous caps (p<0.001), and a numerically increased incidence of lipid-rich plaques (p=0.052) and macrophage accumulation (p=0.012). Neointima discontinuities (p=0.009) and thrombus (p=0.032) were seen more often in first-generation DES. In all stent types, neoatherosclerosis had focal manifestations. In neoatherosclerotic lesions the attenuation and backscatter indices were increased in BMS (p=0.031 and p=0.018, respectively) compared to DES; however, there were no differences between stents in the attenuation indices in subsegments located distally to neoatherosclerotic lesions which had low values in all stent types. CONCLUSIONS: Although there are differences in lipid burden and neointima characteristics in different stent types, in all stents neoatherosclerosis has focal manifestations indicating that, irrespective of the stent type, focal triggers are involved in the generation of vulnerable neolesions.

Hemodynamic analysis of a novel bioresorbable scaffold in porcine coronary artery model.

BACKGROUND: The shear stress distribution assessment can provide useful insights for the hemodynamic performance of the implanted stent/scaffold. Our aim was to investigate the effect of a novel bioresorbable scaffold, Mirage on local hemodynamics in animal models. METHOD: The main epicardial coronary arteries of 7 healthy mini-pigs were implanted with 11 Mirage Microfiber sirolimus-eluting Bioresorbable Scaffolds (MMSES). Optical coherence tomography (OCT) was performed post scaffold implantation and the obtained images were fused with angiographic data to reconstruct the coronary artery anatomy. Blood flow simulation was performed and Endothelial Shear Stress(ESS) distribution was estimated for each of the 11 scaffolds. ESS data were extracted in each circumferential 5-degree subunit of each cross-section in the scaffolded segment. The generalized linear mixed-effect analysis was implemented for the comparison of ESS in two scaffold groups; 150-µm strut thickness MMSES and 125-µm strut thickness MMSES. RESULTS: ESS was significantly higher in MMSES (150 µm) [0.85(0.49-1.40) Pa], compared to MMSES (125 µm) [0.68(0.35-1.18) Pa]. Both MMSES (150 µm) and MMSES (125 µm) revealed low recirculation zone percentages per luminal surface area [3.17% ± 1.97% in MMSES (150 µm), 2.71% ± 1.32% in MMSES (125 µm)]. CONCLUSION: Thinner strut Mirage scaffolds induced lower shear stress due to the small size vessels treated as compared to the thick strut version of the Mirage which was implanted in relatively bigger size vessels. Vessel size should be taken into account in planning BRS implantation. Small vessels may not get benefit from BRS implantation even with a streamlined strut profile. This pilot study warrants comparative assessment with commercially available bioresorbable scaffolds.

Difference in haemodynamic microenvironment in vessels scaffolded with Absorb BVS and Mirage BRMS: insights from a preclinical endothelial shear stress study.

AIMS: In silico studies have provided robust evidence that stent design affects local haemodynamic forces, which appear as a major determinant of clinical outcomes following stent implantation. However, the implications of different stent/scaffold configurations on local haemodynamic forces have not yet been investigated in vivo in a comparative fashion. The aim of this study was to compare the ESS distribution in two differently shaped scaffolds using OCT-based modelling. METHODS AND RESULTS: Eight healthy mini pigs were implanted with six Absorb everolimus-eluting bioresorbable vascular scaffolds (Absorb BVS) and five Mirage sirolimus-eluting bioresorbable microfibre scaffolds (Mirage BRMS). Optical coherence tomography (OCT) was performed and strut protrusion was assessed post scaffold implantation. Following the reconstruction of coronary anatomy, blood flow simulation was performed and endothelial shear stress (ESS) was estimated on top of the struts and at luminal surface between the struts in each scaffold. The thicker struts in Absorb (152±140 µm) resulted in an increased protruded distance compared to Mirage (117±123 µm) (p=0.003). This had an effect on the local haemodynamic microenvironment. ESS at the top of the struts was higher in Absorb (1.69±1.20 Pa) than in Mirage (1.53±0.91 Pa) (p<0.001), but lower at inter-strut zones (0.60±0.51 Pa vs. 0.63±0.50 Pa; p<0.01) compared to Mirage. Both scaffold types revealed comparable percentages of vessel luminal surface exposed to recirculation. CONCLUSIONS: Absorb demonstrated higher shear stress on top of the struts compared to Mirage. However, in the inter-strut zones shear stress was higher in Mirage than in Absorb. Further research is required to examine the potential value of in vivo computational modelling in optimising scaffold configuration and clinical outcomes.

Prevalence and outcomes of coronary artery perforation during percutaneous coronary intervention.

AIMS: We aimed to examine the prevalence, clinical outcomes and procedural characteristics of percutaneous coronary intervention (PCI) complicated by coronary artery perforation (CAP) in a contemporary patient population. METHODS AND RESULTS: Procedural records of 39,115 patients undergoing PCI between 2005 and 2016 were reviewed. CAP affected 149 cases (0.37%). The prevalence of CAP increased from 0.31% in 2005 to 0.45% in 2016 (p=0.03), reflecting an increase in more complex PCI (from 14% in 2005 to 21% in 2016; p<0.0001). CAP was associated with increased all-cause mortality (23.1% vs. 9.4% in those without perforation; p=0.0054) and was an independent predictor of mortality (HR 2.55; 95% CI: 1.34-4.78). In-patient mortality was 4% (6/149). In 43 of 149 (28.9%) cases, a significant pericardial effusion ensued and mortality rates were higher in this subgroup. Thirty-one patients had covered stents (CS) inserted and five did not survive to discharge. Of the 26 patients with a CS who survived to hospital discharge, six (23.1%) had definite stent thrombosis, and two (7.7%) had possible/probable stent thrombosis. CONCLUSIONS: CAP remains uncommon but the prevalence is increasing. CAP is associated with significant short- and long-term mortality, particularly when there is haemodynamic compromise necessitating pericardiocentesis. Covered stents are a valuable tool but they are associated with a high risk of stent thrombosis.

Strut protrusion and shape impact on endothelial shear stress: insights from pre-clinical study comparing Mirage and Absorb bioresorbable scaffolds.

Protrusion of scaffold struts is related with local coronary flow dynamics that can promote scaffold restenosis and thrombosis. That fact has prompted us to investigate in vivo the protrusion status of different types of scaffolds and their relationship with endothelial shear stress (ESS) distributions. Six Absorb everolimus-eluting Bioresorbable Vascular Scaffolds (Absorb, Abbott Vascular) and 11 Mirage sirolimus-eluting Bioresorbable Microfiber Scaffolds (Mirage, Manli Cardiology) were implanted in coronaries of eight mini pigs. Optical coherence tomography (OCT) was performed post-scaffold implantation and obtained images were fused with angiographic data to reconstruct the three dimensional coronary anatomy. Blood flow simulation was performed and ESS distribution was estimated for each scaffold. Protrusion distance was estimated using a dedicated software. Correlation between OCT-derived protrusion and ESS distribution was assessed for both scaffold groups. A significant difference was observed in the protrusion distances (156 ± 137 µm for Absorb, 139 ± 153 µm for Mirage; p = 0.035), whereas difference remained after adjusting the protrusion distances according to the luminal areas. Strut protrusion of Absorb is inversely correlated with ESS (r = -0.369, p < 0.0001), whereas in Mirage protrusion was positively correlated with EES (r = 0.192, p < 0.0001). Protrusion distance was higher in Absorb than in Mirage. The protrusion of the thick quadratic struts of Absorb has a tendency to lower shear stress in the close vicinity of struts. However, circular shape of the less thick struts of Mirage didn't show this trend in creating zone of recirculation around the struts. Strut geometry has different effect on the relationship between protrusion and shear stress in Absorb and Mirage scaffolds.

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.

Intravascular multimodality imaging: feasibility and role in the evaluation of coronary plaque pathology.

Coronary artery disease remains the leading cause of death in the developed world. Over recent years, research has been focused on the development of diagnostic intravascular imaging techniques that enable assessment of plaque composition and morphology, and allow identification of vulnerable, high-risk lesions. Nevertheless recent studies of coronary atherosclerosis have shown that invasive modalities have a limited accuracy in detecting lesions that will progress and cause events, whilst histology-based studies also highlighted the limitations of invasive imaging in assessing plaque characteristics. To overcome these drawbacks, multimodality imaging has been proposed. Although it is apparent that coronary imaging with two or three imaging modalities is time consuming and is associated with a risk of complications, evidence from small clinical studies demonstrated that it provides incremental information about plaque pathology and biology and underscored the need to develop dual-probe hybrid imaging catheters that would enable complete and comprehensive assessment of plaque morphology. This paper reviews the current clinical evidence that supports the use of multimodality intravascular imaging in the study of atherosclerosis, summarizes the key findings of the first invasive imaging studies that utilize hybrid dual-probe catheters, and discusses the limitations of combined intravascular imaging that restrict its broad application in both the clinical and research arena.