Coronary Bifurcation Lesions: A Current Update

Reasons and frequency of transition to a double-stent technique when correcting bifurcation lesions of the coronary arteries in patients with acute coronary syndrome

The objective was to estimate the risk and predictors of intraoperative transition from a single-stent technique of correction of bifurcation lesions of the coronary arteries to a double-stent technique.

METHODS AND MATHERIALS. The study included 49 patients (35 men – 71.4 % and 14 women – 28.6 %) with acute coronary syndrome, whose coronary angiography revealed non-stem bifurcation lesions of the coronary arteries. The patients were operated with single- (Provisional) and double- (Culotte and TAR) stent techniques. Three patients had two bifurcation lesions at once. Thus, 52 bifurcations were included in the study. The average age of patients was 62±8 years. The lateral branch was affected in 34.6 % of cases. A blood clot in the bifurcation area was visualized in 15.4 % of cases. The study is a prospective analytical one. Statistical data processing was carried out using the chi-square test. The statistically significant value was considered p<0.05.

RESULTS. In Y-type bifurcation, kissing dilation was performed in 50% of cases, and stent implantation into the lateral branch - in 23.8% of cases (47.6% of cases where kissing dilation was performed). In T-type bifurcation, kissing dilation was required in 33.3% of cases, and the transition to double-stent technique was required in 11.1% of cases (33.3% of cases where kissing dilation was performed (p=0.610)). With the initially affected lateral branch, kissing dilation was required in 88.2 % of cases, and stenting of the lateral branch was required in 47.1 % of cases (53.3% of cases where kissing dilation was performed). With an intact lateral branch, kissing dilation was required in 26.5 % of cases, the second stent was needed in 8.8 % of cases (33.3% of cases where kissing dilation was performed (p<0.001)). In the presence of a blood clot in the bifurcation area, the need for kissing dilation appeared in 75% of cases, and the need for double-stent technique – in 12.5% of cases (20% of cases where kissing dilation was performed).

CONCLUSIONS. When using the Provisional techniques, the kissing dilation was required in 47.1 % of cases. Expansion of the scope of surgical intervention to double-stent technique was required in 21.6 % of cases.

Protective ballooning technique for prevention of side branch occlusion in coronary nonleft main true bifurcation lesions: A single-center study

OBJECTIVES

We aimed to evaluate the efficacy of a protective ballooning technique in preventing side branch (SB) occlusion and to assess the long-term clinical outcomes for coronary nonleft main true bifurcation lesions.

BACKGROUND

SB occlusion is a major complication associated with percutaneous coronary intervention (PCI) for coronary bifurcation lesions.

METHODS

Patients were consecutively enrolled and randomly assigned to protective ballooning technique or jailed wire technique group. Periprocedural and long-term clinical outcomes were compared.

RESULTS

Patients in the protective ballooning technique (n = 173) and jailed wire technique (n = 167) groups were followed up for 12 months. SB occlusion occurred in one patient (0.6%) and nine patients (5.4%) in each group, respectively. The proportion of thrombolysis in myocardial infarction (TIMI) flow grade 3 of the SB was higher in the protective ballooning technique group (98.8% vs. 95.2%, p < 0.05). SB rewiring was necessary in one patient in the protective ballooning technique group (0.6%) with provisional stenting, significantly lower than that in the jailed wire technique group (seven patients, 4.2%; p = 0.03). Periprocedural myocardial infarction occurred in three (1.73%) and six (3.59%) patients in the protective ballooning technique and jailed wire technique groups without significant difference, respectively. Major adverse cardiovascular events at 12 months were similar in both groups.

CONCLUSIONS

Protective ballooning technique is effective for the prevention of SB occlusion in nonleft main true bifurcation lesions and had favorable long-term outcomes at the 12-month follow-up.

Effect of Drug-Coated Balloon in Side Branch Protection for de novo Coronary Bifurcation Lesions: A Systematic Review and Meta-Analysis

Background: At present, there are a variety of treatment strategies for percutaneous coronary intervention. The role of drug-coated balloon (DCB) in the treatment of side branch for de novo coronary bifurcated lesions (CBL) is unclear.

Objective: To examine the effect of DCB in side branch protection for de novo CBL.

Methods: Electronic databases, including Pubmed, Embase, the Web of science, Cochrance library, CNKI, CBM, WanFang Data and VIP were searched for studies that compared DCB with non-drug-coated balloon (NDCB) in side branch protection for de novo CBL from inception through July 7th, 2021. The primary outcome was target lesion revascularization (TLR). Secondary clinical outcomes included myocardial infarction (MI), cardiac death (CD). The angiographic outcomes included side branch late lumen loss (LLL), minimum lumen diameter (MLD), diameter stenosis (DS) and binary restenosis (BR). The target lesion failure (TLF) was also analyzed.

Results: A total of 10 studies, including 5 randomized controlled trials and 5 non-randomized observational studies, with 934 patients were included. Meta-analysis results of angiographic outcomes suggested that DCB group had the less LLL, DS and BR and the higher MLD compared with NDCB group at follow-up (P < 0.05). Meta-analysis results of clinical outcomes suggested that the significant difference in the TLR, MI and CD between DCB group and NDCB group has not been found yet (P > 0.05). However, the MACE of DCB group was significantly less than that of NDCB group at 9-month follow-up [OR = 0.21, 95%CI (0.05, 0.84), P = 0.03] and 12-month follow-up [OR = 0.45, 95%CI (0.22, 0.90), P = 0.02]. In addition, there was no significant difference in TLF between DCB group and NDCB group (P > 0.05).

Conclusions: DCB had great effect in side branch protection for de novo CBL at short and medium-term follow-up with no reduction in the procedural success rate.

Systematic Review Registration:https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=267426, PROSPERO [Identifier: CRD42021267426].

Management of calcified coronary artery bifurcation lesions

Calcified coronary artery bifurcation lesions (CBL) remain a challenge for the interventional cardiologist. Evidence regarding treatment of CBL is minimal. Optimal plaque modification is the most important step prior to stent deployment. Provisional stenting is the preferred strategy for most bifurcation lesions. However, two-stent strategy should be considered for BL with compromised large SB (>2.5 mm) supplying a large territory, >70% SB stenosis and lesions more than 5 mm long. In this contemporary review article, we present a simplified approach to treating CBL and demonstrate the approach to specific case examples using our newly developed mobile application, BifurcAID.

Usefulness of longitudinal reconstructed optical coherence tomography images for predicting the need for the reverse wire technique during coronary bifurcation interventions

OBJECTIVES

The aim is to investigate the usefulness of longitudinal reconstructed optical coherence tomography (OCT) images in selecting the reverse wire (RW) technique for inserting a guidewire into a side branch (SB).

BACKGROUND

It is sometimes necessary to protect the SB with a guidewire to prevent SB complications in PCI for bifurcation lesions. The RW is a novel method for guidewire insertion into an extremely angulated SB when the standard antegrade wire (AW) approach is difficult.

METHODS

This retrospective study included 46 consecutive patients who underwent OCT-guided PCI in bifurcation lesions with significant SB stenosis. Patients were divided into two groups: 36 patients with successful guidewire crossing using the AW (AW group) and 10 patients with unsuccessful AW but successful RW guidewire crossing (RW group). SB angle and branch point (BP) slope, defined as the angle between the line connecting the proximal and distal BPs and the vertical, were measured using longitudinal reconstructed OCT images.

RESULTS

The RW group had a significantly larger SB angle and higher BP slope than the AW group (108.7 ± 11.4° vs. 76.2 ± 14.9°; P < 0.0001, 128.7 ± 31.6° vs. 82.9 ± 33.6°; P = 0.0004, respectively). Receiver operating characteristic curve analysis indicated that SB angle ≥ 100° and BP slope ≥ 120° are optimal cutoff values for predicting the need for RW (area under the curve 0.97, sensitivity 90.0%, specificity 91.7%; area under the curve 0.83, sensitivity 80.0%, specificity 86.1%, respectively).

CONCLUSIONS

Longitudinal reconstructed OCT is useful for selecting the wiring technique for bifurcation lesions.

Balloon-stent kissing technique versus jailed wire technique for interventional treatment of coronary bifurcation lesions: Comparison of short- and long-term clinical outcomes

Side-branch occlusion is a serious complication of provisional one-stent strategies used to treat coronary bifurcation lesions. The aim of the study was to compare the short- and long-term clinical outcomes between the balloon-stent kissing technique (BSKT) and jailed wire technique (JWT) in patients with non-left coronary bifurcation lesions.This prospective, double-blinded, randomized controlled study enrolled 89 consecutive patients (aged 18-85 years) with 90 true bifurcation lesions (hemadostenosis ≥70%; bifurcation angle <90°; Medina classification 1.1.1, 1.0.1, or 0.1.1) who underwent percutaneous coronary intervention (PCI) at the Zhongshan Hospital Affiliated to Dalian University (China) between January 2013 and May 2016. The patients were randomly divided into the BSKT (44 patients, 45 lesions) and JWT (45 patients, 45 lesions) groups. The intervention was conducted according to technical requirements using a single-stent strategy. Operative success rate, occurrence of complications, postoperative quantitative coronary angiography, and incidence of perioperative and long-term major adverse cardiovascular events (MACEs) were compared between groups.The intervention success rate was 100% in both groups. After main-branch stenting, the BSKT was associated with significantly lower rates of side-branch occlusion (0% vs 15.6%, P < .05) and side-branch post-processing (8.9% vs 26.7%, P < .05) than the JWT. The BSKT was associated with significantly lower degrees of postoperative proximal main-branch residual stenosis (6.1 ± 5.1% vs 9.6 ± 8.6%, P < .05) and side-branch ostial stenosis (51.6 ± 20.6% vs 70.3 ± 20.8%, P < .05) than the JWT. The incidence of perioperative MACEs was significantly lower in the BSKT group than in the JWT group (0% vs 13.3%, P < .05). Patients were followed for a mean duration of 19.0 ± 6.1 months. The occurrence rates of long-term MACEs, angina of Canadian Cardiovascular Society grade ≥2, and severe heart failure were not significantly different between groups.The BSKT is a safe and effective technique that may have advantages over the JWT with regard to protection of the side-branch during PCI for bifurcation lesions.

Treatment strategies for coronary bifurcation lesions made easy in the current era by introduction of the BIFURCAID app

Coronary bifurcation lesions account for 15-20% of all percutaneous coronary interventions. Percutaneous revascularization of these lesions is technically challenging and results in lower success rates than nonbifurcation lesions. There are unique procedural considerations and techniques that are employed in the percutaneous revascularization of these lesions. Our objective is to define the procedural complexities of treating coronary bifurcation lesions and describe the leading provisional and dedicated two stent techniques used to optimize procedural and clinical results, as described in the BIFURCAID app.

Plaque morphology predictors of side branch occlusion after provisional stenting in coronary bifurcation lesion: Results of optical coherence tomography bifurcation study (ORBID)

OBJECTIVES

The aim of this study was to identify the predictors of side branch (SB) ostial stenosis developed after provisional stenting of the main vessel (MV) using optical coherence tomography (OCT).

BACKGROUND

Provisional stenting remains the main approach to treatment of bifurcation lesions; however, it may result in the narrowing of SB ostium. There is little information about underlying plaque morphology of the MV lesion and its potential impact on the SB after provisional stenting.

METHODS

Patients with stable coronary disease with angiographic MV lesion not involving SB were included in a prospective single center study. The primary outcome was significant SB ostium stenosis (SBOS), defined as residual stenosis of >50% after MV stenting.

RESULTS

Thirty bifurcation lesions in 30 patients were analyzed in the study. Poststenting significant SBOS was observed in 30% of patients. The MV lesions with SBOS > 50% were characterized by a higher prevalence of lipid rich plaques (100 vs. 64%, p = 0.040) and spotty calcifications (60 vs. 0%, p = 0.005). Maximal lipid arcs were greater (257° vs. 132°, p = 0.001) and lipid volume index was higher (1380 vs. 574, p = 0.012) in the SBOS >50% group. Multivariate logistic regression analysis identified maximal lipid arc (odds ratio (OR): 1.014, p = 0.038) and the presence of lipid plaque contralateral to SB ostium (OR: 8.14, p = 0.046) before stenting as independent predictors of significant SBOS after PCI.

CONCLUSIONS

High lipid content of the MV lesion and a contralateral location of lipid in the bifurcation area may contribute to SBOS after provisional stenting. © 2016 Wiley Periodicals, Inc.

A Novel Tram Stent Method in the Treatment of Coronary Bifurcation Lesions - Finite Element Study

A novel stent was designed for the treatment of coronary bifurcation lesion, and it was investigated for its performance by finite element analysis. This study was performed in search of a novel method of treatment of bifurcation lesion with provisional stenting. A bifurcation model was created with the proximal vessel of 3.2 mm diameter, and the distal vessel after the side branch (2.3 mm) was 2.7 mm. A novel stent was designed with connection links that had a profile of a tram. Laser cutting and shape setting of the stent was performed, and thereafter it was crimped and deployed over a balloon. The contact pressure, stresses on the arterial wall, stresses on the stent, the maximal principal log strain of the main artery and the side-branch were studied. The study was performed in Abaqus, Simulia. The stresses on the main branch and the distal branch were minimally increased after deployment of this novel stent. The side branch was preserved, and the stresses on the side branch were lesser; and at the confluence of bifurcation on either side of the side branch origin the von-Mises stress was marginally increased. The stresses and strain at the bifurcation were significantly lesser than the stresses and strain of the currently existing techniques used in the treatment of bifurcation lesions though the study was primarily focused only on the utility of the new technology. There is a potential for a novel Tram-stent method in the treatment of coronary bifurcation lesions.

Long-term outcomes of rotational atherectomy in coronary bifurcation lesions

The aim of the present study was to determine the long-term outcomes of bifurcation lesions following a rotational atherectomy (ROTA). In this retrospective study, patients that had undergone a ROTA of the bifurcation coronary lesions in Juntendo University Hospital (Tokyo, Japan) were enrolled between January 2007 and December 2009, and received follow-up for a median duration of 48 months (range, 12-84 months). A total of 337 patients were enrolled. Each patient was treated with an average of 1.2±0.4 ROTA burrs (mean size, 2.9±0.3 mm). Baseline lesion length, reference diameter, minimal lumen diameter (MLD) and percentage of diameter stenosis (%DS) prior to the procedure were comparable between the DM and non-DM patients. Furthermore, MLD, %DS and acute gain following the procedure were similar between the two groups. At follow-up, DM patients exhibited a significantly decreased MLD (1.97±0.92 vs. 2.26±0.73 mm; P=0.0038), increased %DS (27.9±21.3 vs. 20.2±13.3%; P=0.022) and late loss (0.70±0.45 vs. 0.42±0.36 mm; P=0.0047) compared with the non-DM patients. Follow-up examinations (mean duration, 52.2±19.4 months) revealed that the DM patients experienced significantly higher rates of target lesion revascularization (TLR) [28 (15.7%) vs. 8 (5.0%); P=0.0011], target lesion (TL) restenosis [46 (25.8%) vs. 20 (12.6%); P=0.0019] and major adverse cardiac events (MACE) [36 (20.2%) vs. 19 (12.0%), P=0.039] compared with the non-DM patients. Although the usage of ROTA and drug-eluting stent evidently improved long-term outcomes in patients with bifurcation lesions, DM remained an independent risk factor for TLR, TL restenosis and MACE. Therefore, the management of DM in bifurcation lesions treated with ROTA requires increased investigation in future clinical practice.

Shear-Dependent Interactions of von Willebrand Factor with Factor VIII and Protease ADAMTS 13 Demonstrated at a Single Molecule Level by Atomic Force Microscopy

Vital functions of mammals are only possible due to the behavior of blood to coagulate most efficiently in vessels with particularly high wall shear rates. This is caused by the functional changes of the von Willebrand Factor (VWF), which mediates coagulation of blood platelets (primary hemostasis) especially when it is stretched under shear stress. Our data show that shear stretching also affects other functions of VWF: Using a customized device to simulate shear conditions and to conserve the VWF molecules in their unstable, elongated conformation, we visualize at single molecule level by AFM that VWF is preferentially cleaved by the protease ADAMTS13 at higher shear rates. In contrast to this high shear-rate-selective behavior, VWF binds FVIII more effectively only below a critical shear rate of ∼30.000 s(-1), indicating that under harsh shear conditions FVIII is released from its carrier protein. This may be required to facilitate delivery of FVIII locally to promote secondary hemostasis.

Dedicated two-stent technique in complex bifurcation percutaneous coronary intervention with use of everolimus-eluting stents: the EES-bifurcation study

OBJECTIVES

To compare the outcomes of initial one-stent (1S) versus dedicated two-stent (2S) strategies in complex bifurcation percutaneous coronary intervention (PCI) using everolimus-eluting stents (EES).

BACKGROUND

PCI of true bifurcation lesions is technically challenging and historically associated with reduced procedural success and increased restenosis. Prior studies comparing initial one-stent (1S) versus dedicated two-stent (2S) strategies using first-generation drug-eluting stents have shown no reduction in ischemic events and more complications with a 2S strategy.

METHODS

We performed a retrospective study of 319 consecutive patients undergoing PCI at a single referral center with EES for true bifurcation lesions, defined by involvement of both the main vessel (MV) and side branch (SB). Baseline, procedural characteristics, quantitative coronary angiography and clinical outcomes in-hospital and at one year were compared for patients undergoing 1S (n=175) and 2S (n=144) strategies.

RESULTS

Baseline characteristics were well-matched. 2S strategy was associated with greater SB acute gain (0.65±0.41 mm vs. 1.11±0.47 mm, p<0.0001). In-hospital serious adverse events were similar (9% with 2S vs. 8% with 1S, p=0.58). At one year, patients treated by 2S strategy had non-significantly lower rates of target vessel revascularization (5.8% vs. 7.4%, p=0.31), myocardial infarction (7.8% vs. 12.2%, p=0.31) and major adverse cardiovascular events (16.6% vs. 21.8%, p=0.21).

CONCLUSION

In this study of patients undergoing PCI for true coronary bifurcation lesions using EES, 2S strategy was associated with superior SB angiographic outcomes without excess complications or ischemic events at one year.

Model generation of coronary artery bifurcations from CTA and single plane angiography

PURPOSE

To generate accurate and realistic models of coronary artery bifurcations before and after percutaneous coronary intervention (PCI), using information from two image modalities. Because bifurcations are regions where atherosclerotic plaque appears frequently and intervention is more challenging, generation of such realistic models could be of high value to predict the risk of restenosis or thrombosis after stent implantation, and to study geometrical and hemodynamical changes.

METHODS

Two image modalities have been employed to generate the bifurcation models: computer tomography angiography (CTA) to obtain the 3D trajectory of vessels, and 2D conventional coronary angiography (CCA) to obtain radius information of the vessel lumen, due to its better contrast and image resolution. In addition, CCA can be acquired right before and after the intervention in the operation room; therefore, the combination of CTA and CCA allows the generation of realistic preprocedure and postprocedure models of coronary bifurcations. The method proposed is semiautomatic, based on landmarks manually placed on both image modalities.

RESULTS

A comparative study of the models obtained with the proposed method with models manually obtained using only CTA, shows more reliable results when both modalities are used together. The authors show that using preprocedure CTA and postprocedure CCA, realistic postprocedure models can be obtained. Analysis carried out of the Murray's law in all patient bifurcations shows the geometric improvement of PCI in our models, better than using manual models from CTA alone. An experiment using a cardiac phantom also shows the feasibility of the proposed method.

CONCLUSIONS

The authors have shown that fusion of CTA and CCA is feasible for realistic generation of coronary bifurcation models before and after PCI. The method proposed is efficient, and relies on minimal user interaction, and therefore is of high value to study geometric and hemodynamic changes of treated patients.

Optical coherence tomography for guidance of distal cell recrossing in bifurcation stenting: choosing the right cell matters

AIMS

The aim of this study was to assess the ability of optical coherence tomography (OCT) to guide recrossing during percutaneous coronary interventions in bifurcations and to reduce strut malapposition.

METHODS AND RESULTS

Fifty-two patients undergoing elective treatment of bifurcation lesions using provisional stenting as default strategy were included in the study. Patients were divided into two groups: OCT-guided stent recrossing (group 1, n=12), and angiography-guided recrossing (group 2, n=40). Malapposition in the various bifurcation segments was compared in the two groups, using propensity score analysis to correct for confounders. In 4/12 patients (33%) of the OCT-guided group after the first attempt to recross the stent towards the SB the wire was found to have crossed in a proximal cell, requiring a second and in one case a third attempt to successfully cross through a distal cell. Patients who were treated using OCT-guided recrossing had a significantly lower number of malapposed stent struts, especially in the quadrants towards the SB ostium (9.5%[7.5-17.4%] vs 42.3%[31.2-54.7%] in the angiography-guided group, p<0.0001).

CONCLUSIONS

The rate of strut malapposition was significantly reduced when OCT was used to confirm that wire recrossing was performed in a distal cell of the SB ostium.

Modeling stented coronary arteries: where we are, where to go

In the last two decades, numerical models have become well-recognized and widely adopted tools to investigate stenting procedures. Due to limited computational resources and modeling capabilities, early numerical studies only involved simplified cases and idealized stented arteries. Nowadays, increased computational power allows for numerical models to meet clinical needs and include more complex cases such as the implantation of multiple stents in bifurcations or curved vessels. Interesting progresses have been made in the numerical modeling of stenting procedures both from a structural and a fluid dynamics points of view. Moreover, in the drug eluting stents era, new insights on drug elution capabilities are becoming essential in the stent development. Lastly, image-based methods able to reconstruct realistic geometries from medical images have been proposed in the recent literature aiming to better describe the peculiar anatomical features of coronary vessels and increase the accuracy of the numerical models. In this light, this review provides a comprehensive analysis of the current state-of-the-art in this research area, discussing the main methodological advances and remarkable results drawn from a number of significant studies.

Is there a higher risk of stent thrombosis in bifurcation lesion or is it related to the technique?

Bifurcation lesions and bifurcation stenting have been reported to be risk factors of stent thrombosis (ST). ST is a complex process that may be the culmination of device, patient, lesion and procedural factors. The strategy of provisional SB stenting is widely accepted for suitable bifurcation lesions, and is accompanied by low rates of ST. However, it is not applicable to all patients, and in these clinical scenarios (approx. 10%), there is no consensus on the best option for elective stenting with two stents regarding the incidence of ST. Excessive metal scaffolding, such as in the classical crush technique, should be avoided. Further accumulation of long-term data from larger clinical registries and randomised studies will be needed to elucidate the best technique regarding the avoidance of ST in bifurcation treatment. Dedicated bifurcation stents tailored for each type of lesion could resolve this issue, especially the excess of metal protruding in the vessel lumen or crushed onto the wall. However, they need to be tested in upcoming and ongoing trials. Stent thrombosis (ST) is the sudden occlusion of a stented coronary artery due to thrombus formation. Despite major improvements of antiplatelet therapy, thrombotic events remain the primary cause of death after percutaneous coronary interventions (PCI). The clinical consequences of ST are frequently catastrophic and include death in 20% to 48% or major myocardial infarction (MI) in 60% to 70% of the cases. In the drug-eluting stent era, ST and especially very late ST remains a concern of coronary intervention. Bifurcation lesions and bifurcation stenting have been reported to be the risk factors for ST. ST is a complex process that may be a culmination of device, patient, lesion, and procedural factors. The exact cause of the higher risk of ST in bifurcation lesions is unknown although pathologic studies have suggested that the arterial branch points are predisposed to development of atherosclerotic plaque, thrombus, and inflammation because they are foci of low shear stress.

Atheroma and coronary bifurcations: before and after stenting

First generation drug-eluting stents (DES) have significantly improved the treatment options for patients with symptomatic coronary artery disease by decreasing rates of restenosis after percutaneous coronary revascularisation procedures. However, early enthusiasm was tempered by reports of late stent thrombosis, primarily in "off-label" use. In particular, the treatment of atherosclerotic plaques at coronary bifurcations has been challenging for interventional cardiologists regardless of the stent choice due to the underlying nature of the atherosclerotic disease and the use of multiple stents. In this article we illustrate the location and severity of plaque and investigate the healing following both bare metal stents (BMS) and drug-eluting stents (DES) at bifurcations using post-mortem specimens. The presented data will demonstrate that neointimal growth following stent implantation correlate to flow conditions, as there is less underlying atherosclerotic disease at high shear regions and subsequently less neointimal growth is observed in these regions versus low shear regions. The occurrence of late stent thrombosis in DES is also shown to be associated with greater presence of uncovered stent struts at the high shear region, which is likely due to local flow mechanics.

3-D quantitative vascular shape analysis for arterial bifurcations via dynamic tube fitting

Reliable and reproducible estimation of vessel centerlines and reference surfaces is an important step for the assessment of luminal lesions. Conventional methods are commonly developed for quantitative analysis of the "straight" vessel segments and have limitations in defining the precise location of the centerline and the reference lumen surface for both the main vessel and the side branches in the vicinity of bifurcations. To address this, we propose the estimation of the centerline and the reference surface through the registration of an elliptical cross-sectional tube to the desired constituent vessel in each major bifurcation of the arterial tree. The proposed method works directly on the mesh domain, thus alleviating the need for image upsampling, usually required in conventional volume domain approaches. We demonstrate the efficiency and accuracy of the method on both synthetic images and coronary CT angiograms. Experimental results show that the new method is capable of estimating vessel centerlines and reference surfaces with a high degree of agreement to those obtained through manual delineation. The centerline errors are reduced by an average of 62.3% in the regions of the bifurcations, when compared to the results of the initial solution obtained through the use of mesh contraction method.

Bifurcations: focal points of particle adhesion in microvascular networks

OBJECTIVE

Particle adhesion in vivo is dependent on the microcirculation environment, which features unique anatomical (bifurcations, tortuosity, cross-sectional changes) and physiological (complex hemodynamics) characteristics. The mechanisms behind these complex phenomena are not well understood. In this study, we used a recently developed in vitro model of microvascular networks, called SMN, for characterizing particle adhesion patterns in the microcirculation.

METHODS

SMNs were fabricated using soft-lithography processes followed by particle adhesion studies using avidin and biotin-conjugated microspheres. Particle adhesion patterns were subsequently analyzed using CFD-based modeling.

RESULTS

Experimental and modeling studies highlighted the complex and heterogeneous fluid flow patterns encountered by particles in microvascular networks resulting in significantly higher propensity of adhesion (>1.5×) near bifurcations compared with the branches of the microvascular networks.

CONCLUSION

Bifurcations are the focal points of particle adhesion in microvascular networks. Changing flow patterns and morphology near bifurcations are the primary factors controlling the preferential adhesion of functionalized particles in microvascular networks. SMNs provide an in vitro framework for understanding particle adhesion.

New strategies in the treatment of coronary bifurcations

Despite major improvements in stent technology (i.e., drug-eluting stents, DES), treatment of coronary bifurcations is an ever occurring problem of the interventional cardiology. While stenting the main branch with provisional side branch stenting seems to be the prevailing approach, in the era of DES various two-stent techniques emerged (crush) or were re-introduced (V or simultaneous kissing stents, crush, T, culottes, etc.) to allow stenting in the side branch when needed. New techniques in imaging like optical coherence tomography help in better understanding bifurcation anatomy and, thus, have the potential to help us better treat this challenging subset of lesions. In addition, new dedicated bifurcation stents have been proposed in an attempt to overcome limitations associated with current approaches, and they showed promising results in early studies; however, the safety and the efficacy of these devices remain to be seen in the ongoing and upcoming trials. This review focuses on the current approaches and the development of new techniques employed for the treatment of bifurcation disease.