Residence time in complex left main bifurcation disease after stenting

BACKGROUND

Data regarding the mean resident time (RT) after left main (LM) bifurcation stenting are scant. In the present study we performed a patient-specific computational fluid dynamic (CFD) analysis to investigate the different post-stenting mean RT values in LM patients treated with single-or double stenting techniques.

METHODS

Patients were identified after reviewing the local Optical Coherence Tomography (OCT) scans database. Overall, 27 patients (mean age 65.5 ± 12.4, 21 males) [10 patients treated with provisional cross-over stenting, 7 with the double kissing crush (DK crush) and 10 with the nano-inverted T (NIT) technique, respectively] with isolated and significant LM bifurcation disease were analyzed.

RESULTS

After LM bifurcation stenting, the NIT showed a higher averages WSS values at all bifurcation sites compared to DK crush and provisional cross-over stenting. Moreover, the mean RT resulted lower after NIT compared to provisional or DK crush. During the diastolic phase, the average RT of the entire LM bifurcation was 0.46 s, 0.38 s and 0.33 s after using the provisional stenting, DK crush and NIT, respectively. Moreover, the average RT in the LM bifurcation decreased by 17.1 % using the DK crush and by 28.2 % using the NIT compared to the Provisional.

CONCLUSION

The present OCT-derived CFD analysis revealed that, in patients with complex bifurcation LM disease, the provisional approach resulted in lower WSS values, while double stenting techniques, especially the NIT technique, resulted in a marked reduction of average RT compared to the provisional approach.

CONDENSED ABSTRACT

In the present study we performed a patient-specific Optical coherence tomography (OCT)-based computational fluid dynamic (CFD) analysis to investigate the different post-stenting mean RT values in 27 patients treated with provisional cross-over stenting, DK crush and Nano-inverted-T (NIT) stenting. The NIT showed a higher averages WSS values at all bifurcation sites compared to DK crush and Provisional. The mean RT resulted lower in NIT compared to Provisional or DK crush. During the entire diastolic phase, the average RT of the entire LM bifurcation was 0.46 s, 0.38 s and 0.33 s after using the provisional stenting, DK crush and NIT, respectively. Moreover, the average RT in the entire LM bifurcation decreased by 17.1 % using the DK crush and by 28.2 % using the NIT compared to the Provisional.

The impact of the bifurcation angle for the Nano-Crush two-stent coronary bifurcation technique on long-term outcomes in a real-world clinical population

AIM

This study aims to assess the direct impact of bifurcation angle (BA) on immediate procedural outcomes and patient prognosis post-Nano-Crush stenting for coronary bifurcation lesions.

METHODS

A retrospective analysis was conducted for all consecutive patients treated with the Nano-Crush technique across two high-volume interventional centers from January 2020 to October 2022.

PRIMARY ENDPOINT

comparison of target lesion failure rate in two cohorts based on bifurcation angle (<70° vs. ≥70°), with secondary endpoints including side branch ostium coverage, rate of successful final kissing balloon inflation (FKBI), need for conversion to another technique, and procedure length.

RESULTS

Baseline demographics included 71 patients in the BA<70° group and 49 in the BA≥70° group, with well-balanced characteristics. Angiographic characteristics revealed similar trends, including anatomic and morphological lesion characteristics (referencing Syntax score, Medina classification, and presence of calcifications). Both groups predominantly had complex coronary disease, with a baseline mean Syntax score of 24.18 ± 8.19 in the BA<70° group and 23.91 ± 7.29 in the BA≥70° group, respectively. A dedicated debulking device for lesion preparation was used in 25.35 % of patients in the first group and in 28.57 % of patients in the second group. The primary endpoint occurred in 5.63 % of patients in the BA<70° group and in 4.08 % of patients in the BA≥70° group (P = 0.7014) after ≥ 2 years of clinical follow-up. Angiographic success was achieved in 100 % of both groups, with procedural time averaging 74.99 ± 25.55 min in the BA≥70° and 76.94 ± 27.81 min in the BA<70° (P = 0.6922). The rate of successful final kissing balloon inflation was 98.59 % in the BA<70° group and 95.91 % in the BA≥70° group (P = 0.3566). The mean contrast volume was 189.54 ± 73.74 ml in BA<70° and 168.9 ± 62.77 ml in BA≥70° (P = 0.1126). Clinical follow-ups at 30 days and 2 years revealed similar outcomes and complications for each group, as summarized in Table 3.

CONCLUSIONS

Our results demonstrate that the bifurcation angle does not significantly impact long-term clinical outcomes or procedural parameters, such as side branch ostium coverage, conversion to a modified DK Crush technique, FKBI success rate, and procedure length. These findings suggest that the Nano-Crush technique can be a viable option for bifurcation lesions, irrespective of the bifurcation angle, achieving optimal side branch ostium coverage while preventing excessive protrusion into the main vessel.

The CABRIOLET registry

BACKGROUND

Re-POT (proximal optimization technique (POT)) is a simple provisional sequential technique for percutaneous coronary bifurcation revascularization with better arterial geometry respect compared to classical techniques. Re-POT has demonstrated excellent mechanical and short-term clinical results. The multicenter CABRIOLET registry (NCT03550196) evaluate the long-term clinical benefit of the re-POT sequence in non-selected patients.

METHODS

All consecutive patients presenting a coronary bifurcation lesion for which provisional stenting was indicated were included in 5 european centers. Re-POT strategy was systematically attempted. The primary endpoint was target lesion failure (TLF), comprising cardiac death, myocardial infarction, stent thrombosis and target lesion revascularization (TLR) at 12 months' follow-up. The secondary endpoints were the individual components of the primary endpoint, all-cause death, target vessel failure (TVF) and target vessel revascularization (TVR). Complex bifurcation was defined as Medina 0.1.1 or 1.1.1.

RESULTS

A total of 500 patients aged 67.7 ± 11.7 years, 78.4% male, were included from 2015 to 2019, 174 of whom (34.8%) were considered having complex bifurcation lesions. Bifurcations involved the left main in 35.2% of cases. The full re-POT sequence was systematically performed in all cases. At 1 year, TLF was 2.0% (1.7% in complex vs. 2.1% in non-complex bifurcation; p = NS), and TLR was 1.6%, (1.1% vs. 1.8% respectively; p = NS). TVF and TVR rates were 3.2% and 2.8%. On multivariate analysis, only multivessel disease was predictive of TLF at 1 year (OR = 1.66 (1.09-2.53), p = 0.02).

CONCLUSIONS

In this large prospective all-comer registry, provisional stenting with re-POT technique appeared safe and effective at 1 year, without anatomical bifurcation restriction.

Clinical outcomes of a dedicated bifurcation stent system

INTRODUCTION

Percutaneous coronary intervention (PCI) of bifurcation lesions is technically challenging and associated with higher rates of complications such as stent thrombosis or in-stent restenosis. In this paper, we present the clinical outcomes of BiOSS LIM C (Balton, Poland), a dedicated bifurcation stent.

METHODS

In this retrospective single-center study we analyzed the outcome of patients with bifurcation coronary artery disease treated with the BiOSS LIM C stent system. The primary endpoint was the cumulative rate of major adverse cardiac events (MACE) including cardiac death, myocardial infarction (MI) and target lesion revascularisation (TLR) at the longest available follow-up.

RESULTS

The study population consisted of 25 patients (mean age 73.6 ± 9.7 years, 25 % females). In 80 % of the cases (n = 20) BiOSS LIM C stent was implanted in the left main coronary artery. Intravascular imaging was used in 70 % of the cases and an additional regular drug-eluting stent (DES) was deployed in the side branch in 24 % of the cases. The device success rate was 100 % and we observed no in-hospital adverse events. At a median follow-up of 15 ± 6 months, the MACE rate was 56 %, cardiac death was 4 %, and clinically driven TLR was 55 %. One patient died in the LM subgroup, 5 months after the index PCI, due to NSTEMI complicated by cardiogenic shock. Two patients died due to non-cardiac causes.

CONCLUSIONS

In this consecutive series of patients treated with BiOSS LIM C in major coronary bifurcation lesions, mostly in the left main stem, the mid-term clinical outcomes demonstrated a high incidence of major adverse events, mainly caused by TLR, despite an adequate implantation technique.

The COBRA II (COmplex Bifurcation lesions: RAndomized comparison of a fully bioresorbable modified-T stenting strategy versus bifurcation reconstruction with a dedicated self-expanding stent in combination with bioresorbable scaffolds) study: Final 5-year follow-up

BACKGROUND

In order to advocate further research in bioresorbable scaffold (BVS) technology we report the final 5-year outcomes of the COBRA II study, the only randomized controlled trial (RCT) performed to investigate the safety, feasibility, and performance of Absorb BVS (Abbott Vascular) in true coronary bifurcations.

METHODS

COBRA II was a prospective single-center RCT. Fifteen patients with true coronary bifurcation lesions were randomized to bifurcation treatment with self-expanding biolimus-eluting Axxess bifurcation device (Biosensors International) combined with additional bioresorbable everolimus-eluting Absorb BVS in the bifurcation branches on (Axxess group) or to 2-stent mod-T stenting technique with Absorb BVS (mod-T group). Optical coherence tomography was performed post-procedure and at 30-months. The primary endpoint was change in minimal luminal area (MLA) on OCT from baseline to 30-months.

RESULTS

Fifteen patients with coronary bifurcation lesions were randomized to the Axxess group (n = 8) or Modified-T group (n = 7). At 30 months, MLAs were significantly smaller than post-procedure in the majority of bifurcation segments treated with BVS due to neointima formation, while MLAs in the proximal Axxess segment remained stable (primary endpoint). Five-year clinical follow-up was available for all patients. Only 1 major adverse cardiac event occurred; a patient underwent target lesion revascularization at 30 months in the Axxess group. There were no cases of cardiac death, spontaneous MI, or stent/scaffold thrombosis.

CONCLUSIONS

In this small RCT bifurcation study, BVS luminal dimensions were significantly smaller at 30 months, with acute strut discontinuities and late Intraluminal dismantling frequently observed, although acceptable clinical outcomes were noted at 5 years.

Impact of coronary bifurcation angle on stent malapposition in a randomized comparison between proximal optimization technique followed by side branch dilatation and kissing balloon inflation

Background

The impact of coronary bifurcation angle (BA) on incomplete stent apposition (ISA) after crossover stenting followed by side branch (SB) intervention has not been established.

Methods

A total of 100 crossover stentings randomly treated with proximal optimization technique followed by short balloon dilation in the SB (POT-SBD group, 48 patients) and final kissing balloon technique (KBT group, 52 patients) were analyzed in the PROPOT trial. Major ISA with maximum distance > 400 μm and its location was determined using optical coherence tomography before SB intervention and at the final procedure. The BA was defined as the angle between the distal main vessel and SB. Optimal POT was determined when the difference in stent volume index between the proximal and distal bifurcation was greater than the median value (0.86 mm3/mm) before SB intervention.

Result

Major ISA was more frequently observed in the POT-SBD than in the KBT group (35% versus 17%, p < 0.05). In the POT-SBD group, worsening ISA after SBD was prominent at the distal bifurcation. The BA was an independent predictor of major ISA (odds ratio 1.04, 95% confidence interval 1.00-1.07, p < 0.05) with a cut-off value of 59.5° (p < 0.05). However, the cases treated with optimal POT in the short BA (<60°) indicated the lowest incidence of major ISA. In the KBT group, BA had no significant impact.

Conclusion

A wide BA has a potential risk for the occurrence of major ISA after POT followed by SBD in coronary bifurcation stenting.

Results from the real-world multicenter registry

OBJECTIVE

There is a lack of data regarding the long-term clinical efficacy of the kissing balloon inflation (KBI) after provisional stenting of coronary bifurcation lesions. The aim of this study was to analyze the impact of KBI on long-term clinical outcomes in patients undergoing provisional stenting for the coronary bifurcation lesions in a large real-world population.

METHODS

A total of 873 patients who underwent percutaneous coronary interventions (PCI) with provisional stenting and had clinical follow up were analyzed. Patients treated with 2-stent strategy were excluded. To reduce the effect of potential confounding factors in this observational study, propensity score matching was conducted.

RESULTS

KBI was performed in 325 patients (37.2%). The median follow-up duration was 37.3 months. Patients treated with KBI more often had a previous PCI (48.6% vs. 42.5% SMD = 0.123). Patients in non-kissing group had more complex coronary disease with higher prevalence of calcification (14.8% vs. 21.4% SMD = 0.172), thrombosis (2.8% vs. 5.8% SMD = 0.152) and longer side branch lesions (8.3% vs. 11.7% SMD = 0.113). There were no significant differences in the major adverse cardiac events including death, myocardial infarction, target lesion revascularization after KBI versus no KBI (15.4% vs. 15.7%, p = 0.28), in total cohort or in matched patients (17.1% vs. 15.8%, adjusted HR 1.01, 95% CI: 0.65-1.65, p = 0.95). The lack of effect of KBI on clinical outcomes was consistent across various subgroups including left main disease.

CONCLUSION

In this multicenter real-world registry, KBI did not improve long-term clinical outcomes in patients with coronary bifurcation lesions treated with provisional stenting technique.

Drug-coated balloon in the treatment of coronary bifurcation lesions: A hope or hype?

When compared to non-bifurcation lesions, percutaneous coronary intervention in coronary bifurcation lesions is technically demanding and has historically been limited by lower procedural success rates and inferior clinical results. Following the development of drug-eluting stents, dramatically better results have been demonstrated. In most of the bifurcation lesions, the provisional technique of implanting a single stent in the main branch (MB) remains the default approach. However, some cases require more complex two-stent techniques which carry the risk of side branch (SB) restenosis. The concept of leaving no permanent implant behind is appealing because of the complexity of bifurcation anatomy with significant size mismatch between proximal and distal MB which may drive rates of in-stent restenosis and the potential impact of MB stenting affecting SB coronary flow dynamics. With the perspective of leaving lower metallic burden, a drug-coated balloon (DCB) has been utilized to treat bifurcations in both the MB and SB. The author gives an overview of the existing state of knowledge and prospects for the future for using DCB to treat bifurcation lesions.

Polymer-free biolimus-eluting stents or polymer-based zotarolimus-eluting stents for coronary bifurcation lesions

BACKGROUND

A polymer-free biolimus-eluting stent (PF-BES) and a zotarolimus-eluting stent (ZES) recently showed similar clinical profiles and appear to be competing options in specific clinical settings of patients undergoing percutaneous coronary intervention (PCI). Whether they perform similarly also in complex procedural settings as coronary bifurcation lesions remains unaddressed.

METHODS

All consecutive patients undergoing coronary bifurcation PCI with PF-BES or the new iteration of the ZES from three large multicenter real-world registries were included. The primary outcome was major adverse cardiovascular events (MACE), a composite of all-cause death, myocardial infarction (MI), target lesion revascularization (TLR) and stent thrombosis (ST). Multiple analyses to adjust for baseline differences were carried out including propensity-score matching, propensity-score stratification and inverse-probability-weighting. Outcomes are reported according to Cox proportional hazard models censored at 400-day follow-up.

RESULTS

1169 patients treated with PF-BES (n = 440) or ZES (n = 729) on the main branch of a coronary bifurcation lesion were included (mean age 69 ± 11 years, 75.4% male, 53.8% acute coronary syndrome at presentation, 26.6% left main bifurcation, median dual antiplatelet therapy duration 12 [range 12-12] months). MACE, all-cause death, TLR and ST tended towards non-statistically higher rates with the PF-BES as compared to the ZES. Higher MI and target vessel revascularization occurrence was observed with PF-BES.

CONCLUSIONS

In this large contemporary cohort of patients undergoing coronary bifurcation PCI, the occurrence of MACE was non-statistically different with the use of PF-BES and ZES devices. However, differences favoring the ZES device that may entail clinical relevance were observed. Further studies are needed to confirm these findings and explore whether they remain valid when a short dual antiplatelet therapy is adopted.

Efficacy of coronary imaging on bifurcation intervention

During the coronary bifurcation intervention procedure, imaging including intravascular ultrasound and optical coherence tomography is essential to provide precise anatomy of the lesion and morphological information. This consensus document between the Korean Bifurcation Club and the Japanese Bifurcation Club summarizes practical guidelines and current evidences on lesion assessment, device selection, procedural guidance, and the optimization of bifurcation intervention by the imaging.

A case of very late stent thrombosis on the protruded struts at the left main coronary bifurcation

A previous autopsy study has revealed that malapposed or protruded struts in the coronary bifurcation were a risk factor for very late stent thrombosis (VLST); however, a live clinical case has not yet been reported due to difficulty in observation at the VLST site. In this case, a 56-year-old male patient underwent a zotarolimus-eluting stent implantation in the proximal left anterior descending artery for acute myocardial infarction 3 years previously and had been treated with dual antiplatelet therapy. The patient experienced chest pain and suddenly collapsed due to acute coronary syndrome caused by a huge thrombus in the left main coronary bifurcation. After insertion of the intra-aortic balloon pump, kissing balloon inflation improved coronary flow and hemodynamics. Two weeks later, a 3-dimensional optical frequency domain imaging (3-D OFDI) revealed uncovered protruded struts on the ostium of the left circumflex artery (LCX). We removed the protruded struts using a double lumen catheter, for which the second wire was advanced to more distal cell along with the first wire located in the same LCX branch. 3-D OFDI clearly demonstrated that uncovered protruded struts at the LCX ostium were the cause of VLST and navigated optimal wiring with a double lumen catheter. Learning objective: Existence of protruded struts at the coronary bifurcated branch ostium is a risk factor for very late stent thrombosis. Three-dimensional optical frequency domain imaging clearly demonstrates the protruded strut configuration at the side branch of ostium and facilitates optimal guide wire re-crossing for kissing balloon inflation. Usage of double lumen catheter increases the possibility of optimal side branch wiring.

Szabo 2-stent technique for coronary bifurcation lesions: procedural and short-term outcomes

BACKGROUND

Provisional 1-stent technique is currently regarded as the default approach for the majority of bifurcation lesions. Nonetheless, 2-stent techniques may be required for complex bifurcations with high compromise risk or fatal consequences of side branch (SB) occlusion. Limitations exist in current approaches, as stents gap, multiple metal layers and stent malapposition caused by imprecise placement with fluoroscopic guide and intrinsic technical defects. This study was designed to investigate the effectiveness of the novel Szabo 2-stent technique for coronary bifurcation lesions.

METHODS

In the Szabo 2-stent technique, one stent is precisely implanted at the SB ostium with Szabo technique resulting in a single strut protruding into the main vessel (MV). After MV rewiring and SB guidewire withdrawal, another stent is implanted in MV followed by proximal optimization technique, SB rewiring, and final kissing inflation (FKI).

RESULTS

The technique tested successfully in silicone tubes (n = 9) with: procedure duration, 31.2 ± 6.8 min; MV and SB rewiring time, 26.8 ± 11.2 s and 33.3 ± 15 s; easy FKI; and 2.3 ± 0.5 balloons/procedure. Bifurcation lesions (n = 22) were treated with angiographic success in MV and SB, respectively: increased minimal lumen diameter (0.63 ± 0.32 mm to 3.20 ± 0.35 mm; 0.49 ± 0.37 mm to 2.67 ± 0.25 mm); low residual stenosis (12.4 ± 2.4%; 12.4 ± 2.3%); and intravascular ultrasound confirmed (n = 19) full coverage; minimal overlap and malapposition; minimal lumen area (2.4 ± 1.2 mm²; 2.1 ± 1.0 mm²); plaque burden (78.1 ± 11.3%; 71.6 ± 15.5%); and minimal stent area (9.1 ± 1.6 mm²; 6.1 ± 1.3 mm²). Periprocedural cardiac troponin increased in 1 asymptomatic patient without electrocardiographic change. There was no target lesion failure (cardiac death, myocardial infarction, target lesion revascularization) at 6-month follow-up.

CONCLUSIONS

The Szabo 2-stent technique for bifurcation lesions provided acceptable safety and efficacy at short-term follow-up.

Comparison of bioresorbable vs durable polymer drug-eluting stents in unprotected left main (from the RAIN-CARDIOGROUP VII Study)

BACKGROUND

There are limited data regarding the impact of bioresorbable polymer drug eluting stent (BP-DES) compared to durable polymer drug eluting stent (DP-DES) in patients treated with percutaneous coronary intervention using ultrathin stents in left main or bifurcations.

METHODS

In the RAIN registry (ClinicalTrials NCT03544294, june 2018 retrospectively registered) patients with a ULM or bifurcation stenosis treated with PCI using ultrathin stents (struts thinner than 81 μm) were enrolled. The primary endpoint was the rate of target lesion revascularization (TLR); major adverse cardiovascular events (MACE, a composite of all-cause death, myocardial infarction, TLR and stent thrombosis) and its components, along with target vessel revascularization (TVR) were the secondary ones. A propensity score with matching analysis to compare patients treated with BP-DES versus DP-DES was also assessed.

RESULTS

From 3001 enrolled patients, after propensity score analysis 1400 patients (700 for each group) were selected. Among them, 352 had ULM disease and 1048 had non-LM bifurcations. At 16 months (12-22), rates of TLR (3.7% vs 2.9%, p = 0.22) and MACE were similar (12.3% vs. 11.6%, p = 0.74) as well as for the other endpoints. Sensitivity analysis of outcomes after a two-stents strategy, showed better outcome in term of MACE (20.4% vs 10%, p = 0.03) and TVR (12% vs 4.6%, p = 0.05) and a trend towards lower TLR in patients treated with BP-DES.

CONCLUSION

In patients with bifurcations or ULM treated with ultrathin stents BP-DES seems to perform similarly to DP-DES: the trends toward improved clinical outcomes in patients treated with the BP-DES might potentially be of value for speculating the stent choice in selected high-risk subgroups of patients at increased risk of ischemic events.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03544294. Retrospectively registered June 1, 2018.

Noncalcified plaque burden quantified from coronary computed tomography angiography improves prediction of side branch occlusion after main vessel stenting in bifurcation lesions: results from the CT-PRECISION registry

OBJECTIVES

To assess the incremental value of quantitative plaque features measured from computed tomography angiography (CTA) for predicting side branch (SB) occlusion in coronary bifurcation intervention.

METHODS

We included 340 patients with 377 bifurcation lesions in the post hoc analysis of the CT-PRECISION registry. Each bifurcation was divided into three segments: the proximal main vessel (MV), the distal MV, and the SB. Segments with evidence of coronary plaque were analyzed using semi-automated software allowing for quantitative analysis of coronary plaque morphology and stenosis. Coronary plaque measurements included calcified and noncalcified plaque volumes, and corresponding burdens (respective plaque volumes × 100%/vessel volume), remodeling index, and stenosis.

RESULTS

SB occlusion occurred in 28 of 377 bifurcation lesions (7.5%). The presence of visually identified plaque in the SB segment, but not in the proximal and distal MV segments, was the only qualitative parameter that predicted SB occlusion with an area under the curve (AUC) of 0.792. Among quantitative plaque parameters calculated for the SB segment, the addition of noncalcified plaque burden (AUC 0.840, p = 0.003) and low-density plaque burden (AUC 0.836, p = 0.012) yielded significant improvements in predicting SB occlusion. Using receiver operating characteristic curve analysis, optimal cut-offs for noncalcified plaque burden and low-density plaque burden were > 33.6% (86% sensitivity and 78% specificity) and > 0.9% (89% sensitivity and 73% specificity), respectively.

CONCLUSIONS

CTA-derived noncalcified plaque burden, when added to the visually identified SB plaque, significantly improves the prediction of SB occlusion in coronary bifurcation intervention.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03709836 registered on October 17, 2018.

A Systematic Review of Jailed Balloon Technique for Coronary Bifurcation Lesion: Conventional-Jailed Balloon Technique vs Modified-Jailed Balloon Technique

BACKGROUND

In this systematic review, we aim to evaluate the latest evidence on the efficacy and safety of conventional jailed balloon technique and modified jailed balloon technique for bifurcation lesion, and also whether the former or latter is more effective for preventing side branch occlusion during main branch stenting in bifurcation lesions.

METHODS

We performed comprehensive search on studies assessing the efficacy and safety of conventional jailed balloon and modified jailed balloon technique for bifurcation lesion from several electronic databases.

RESULTS

There were 908 patients from six studies comprising of 615 in conventional jailed balloon technique group and 293 in modified jailed balloon technique group. Side branch loss was lower in modified jailed balloon technique group, however, the proportion of lesions with TIMI flow <3 in the final percutaneous coronary intervention result was somewhat higher in the modified jailed balloon technique group. The efficacy issue regarding side branch dissection was reported as high as 3.4%, especially at proximal stent edge in conventional jailed balloon technique group, but not quantitatively described in the modified jailed balloon technique group. Zero percent major adverse cardiovascular events at 9-12 months follow up was demonstrated in modified jailed balloon technique group, and 1-5% in the conventional jailed balloon group at a longer observation period up to 2.7 years.

CONCLUSION

Our study showed that modified jailed balloon technique is potentially better compared to conventional jailed balloon in terms of side branch loss, dissection, and major adverse cardiovascular events. Further controlled studies are warranted for definite conclusion.

Accuracy of RESOLVE score derived from coronary computed tomography versus visual angiography to predict side branch occlusion in percutaneous bifurcation intervention

INTRODUCTION

Visually estimated angiographic V-RESOLVE score was developed as a simple and accurate prediction tool for side branch (SB) occlusion in patients undergoing coronary bifurcation intervention. Data on the use of coronary computed tomography angiography (coronary CTA) for guiding percutaneous coronary intervention in bifurcation lesions is scarce.

OBJECTIVES

We aimed to validate the ability of quantitative CTA-derived RESOLVE score for predicting SB occlusion in coronary bifurcation intervention and to compare its predictive value with that of the angiography-based V-RESOLVE score.

METHODS

We included 363 patients with 400 bifurcation lesions. Angiographic V-RESOLVE score and CTA-derived RESOLVE score were calculated utilizing the weights from the QCA-based RESOLVE score. The scoring systems were divided into quartiles, and classified as the non-high-risk group and the high-risk group. Accuracy was assessed using areas under the receiver-operator characteristic curve (AUC). SB occlusion was defined as any decrease in Thrombolysis in Myocardial Infarction flow grade (including the absence of flow) in the SB after main vessel stenting.

RESULTS

In total, 28 SB occlusions (7%) occurred. CTA-derived RESOLVE and V-RESOLVE scores achieved comparable predictive accuracy (0.709 vs. 0.752, respectively, p = 0.531) for predicting SB occlusion, and the analysis of AUC for each constituent element of the scores did not show any significant difference between CTA and visual angiography. The total net reclassification index was -18.6% (p = 0.194), and there were no significant differences in the rates of SB occlusion in the non-high-risk group (4.9% vs. 3.8%, p = 0.510) and the high-risk group (13.8% vs. 18.6%, p = 0.384) between CTA-derived RESOLVE and V-RESOLVE scores.

CONCLUSIONS

The quantitative CTA-derived RESOLVE score is an accurate and reliable alternative to the visually estimated angiographic V-RESOLVE score for prediction of SB occlusion in coronary bifurcation intervention.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT03709836.

Efficacy of the proximal optimization technique on crossover stenting in coronary bifurcation lesions in the 3D-OCT bifurcation registry. Int J Cardiovasc Imaging. 2019;35:981-990. [PMID: 30887408 DOI: 10.1007/s10554-019-01581-1]

AIM

We sought to investigate the efficacy of the proximal optimization technique (POT) on crossover stenting followed by side branch (SB) dilation under optical coherence tomography guidance in a multicenter registry study.

METHODS AND RESULTS

A total of 135 bifurcation lesions in 134 patients were divided into POT (n = 52) and non-POT groups (n = 83). The POT was performed before SB dilatation (pre-POT; n = 26), finally (final-POT; n = 12), at both timing (re-POT; n = 13), and uncertain (n = 1). There were no significant intergroup differences in the success rate of guide wire re-crossing (GWR) into the optimal cell (72% vs. 65%), incidence of the link-free type in the configuration of the SB jailed struts (51% vs. 49%), or incomplete strut apposition at the bifurcation (13 ± 11% vs. 10 ± 9%). However, insufficient stent expansion close to the carina in the proximal main vessel (MV) due to inappropriate POT was likely to induce greater incomplete strut apposition (ISA) around the bifurcation. Only re-POT provided more symmetric proximal MV expansion, while pre- and final-POT did not.

CONCLUSION

The POT did not provide the expected beneficial effects, such as reduction of ISA or more optimal GWR, under the OCT guidance. Wide stent expansion in the proximal MV induced by the POT increased the likelihood of achieving optimal GWR, whereas symmetric stent expansion was provided by re-POT.

Mid-term outcomes after percutaneous interventions in coronary bifurcations

BACKGROUND

The optimal treatment of patients undergoing percutaneous coronary interventions (PCI) for lesions located at coronary bifurcations is still debated.

METHODS

Data on 5036 consecutive patients who underwent PCI on coronary bifurcation at 17 major coronary intervention centers between January 2012 and December 2014 were collected.

RESULTS

Follow-up at a median 18 months (IQR 11-28) was available for 4506 patients (89%). Major Adverse Cardiac Events (MACE) occurred in 395 patients (8.8%): cardiac death in 152 (3.4%), myocardial infarction, excluding periprocedural, in 156 (3.5%) and stent thrombosis in 110 cases (2.4%). At multivariable Cox regression, left ventricular ejection fraction ≤30% (P < 0.001), bail-out stenting (beyond a planned strategy of either single or double stenting) (P < 0.001), admission for an acute coronary syndrome (P < 0.001), age >66 years (P < 0.001), multivessel disease (P < 0.001) and diabetes (P < 0.001) were independently associated with MACE. Sensitivity analysis identified premature discontinuation of dual antiplatelet therapy (DAPT) (P < 0.001) and side branch (SB) lesion length ≥9 mm (P < 0.05) as additional independent predictors of MACE.

CONCLUSIONS

Beyond traditional risk factors, multivessel disease, the length of the SB lesion, "bail-out" stenting and premature DAPT discontinuation are independent predictors of mid-term MACE after PCI of coronary bifurcations. This highlights the importance of a carefully planned PCI strategy and adequate therapy adherence to improve the clinical outcomes in these patients.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT01967615.

Thin and crush: The new mantra in left main stenting?

Complex bifurcations have been suggested to be better approached by a planned double stent technique; however, recent randomized trials have shown better outcomes of provisional compared to planned two-stent strategy, in terms of both short-term efficacy and safety. In left main (LM) bifurcations, double kissing (DK)-Crush has demonstrated its superiority over Culotte and provisional-T in terms of restenosis and stent thrombosis, gaining respect as one of the most performant techniques for bifurcations stenting. On the other hand, the Nano-Crush technique has recently become part of the repertoire of double stenting techniques, providing evidence that the use of ultrathin strut stents and very minimal crush would be beneficial for both the physiological and rheological properties of the complex bifurcations, even in LM scenario, leading to a lower rate of thrombosis and restenosis at both side branch and true carina. Finally, the newest generation of ultrathin strut stents are gaining a reputation for its safe and effective use in LM treatment thanks to improved design with increased expansion rate capable of LM treatment up to 5-6 mm diameter. The modern crush techniques, such as DK-Crush and Nano-Crush, are providing excellent results on mid and long-term follow up, suggesting that minimal crushing obtained using ultra-thin stents is a good way to obtain surgical-like outcomes in the treatment of complex LM bifurcation disease.

Benefits of final proximal optimization technique (POT) in provisional stenting

AIMS

Initial proximal optimization technique (POT) in provisional stenting improves global malapposition, side-branch (SB) obstruction (SBO) and conservation of arterial circularity. The specific mechanical effects of a final POT sequence concluding the main provisional stenting techniques, on the other hand, are unknown.

METHODS AND RESULTS

Synergy™ stents were implanted on fractal coronary bifurcation bench models using the main provisional stenting techniques (n = 5 per group): kissing-balloon inflation (KBI), snuggle, and rePOT (initial POT + SB inflation + final POT). Final results were quantified on 2D and 3D OCT before and after final POT. Whichever the technique, final POT significantly decreased global malapposition (from 7.6 ± 5.3% to 2.2 ± 2.5%, p < 0.05) and proximal elliptic deformation (from 1.15 ± 0.07 to 1.09 ± 0.04, p < 0.05), without impact on SBO (from 11.5 ± 9.6% to 12.9 ± 10.6%, NS). However, final POT failed to completely correct the elliptic deformation induced by balloon juxtaposition during the KBI and snuggle techniques, with final elliptic ratios of 1.11 ± 0.03 and 1.11 ± 0.04 respectively, significantly higher than with the complete rePOT sequence: 1.05 ± 0.02 (p < 0.05).

CONCLUSIONS

Like initial POT, final POT is recommended whatever the provisional stenting technique used. However, final POT fails to completely correct all proximal elliptic deformation associated with "kissing-like" techniques, in contrast to results with the rePOT sequence.

A randomized trial comparing two stent sizing strategies in coronary bifurcation treatment with bioresorbable vascular scaffolds - The Absorb Bifurcation Coronary (ABC) trial

BACKGROUND

Limited information is available on the use of Bioresorbable Vascular Scaffold (BVS) in bifurcations involving significant side branches. When treating bifurcation disease with metal stents, the recommendation is to choose a stent diameter based on the distal main vessel diameter. Whether this sizing strategy is applicable to BVS is currently unknown.

METHODS

We randomised 37 patients undergoing elective PCI for 'false' bifurcation disease (Medina 0,1,0; 1,0,0; 1,1,0) to receive BVS based either on proximal or distal reference diameters. Optical Frequency Domain Imaging (OFDI) measurements were performed pre BVS insertion to obtain proximal and distal reference diameters and post implantation. BVS size was chosen according to the proximal or distal reference diameter as per randomisation. Implantation was performed using the PSP technique tailored to bifurcation stenting. OFDI was repeated post implantation to confirm satisfactory expansion and apposition.

RESULTS

Baseline demographics between the two groups were similar. Patients were aged 62.8 ± 3.3 years; 76% were male. Mean side branch diameter was 2.24 ± 0.13 mm. TIMI III flow in the main vessel was achieved in all cases. Side branch occlusion occurred in 1 case (2.7%). In the distal-sizing arm, there was a greater incidence of significant malapposition (>300 μm) at the proximal end of the scaffold on OCT (2.3% versus 0.8%, p 0.023). The incidence of distal edge dissections was numerically greater in the proximal-sizing group but this was not statistically significant (31.3% vs 11.8%, p 0.17).

CONCLUSION

Both proximal and distal sizing strategies have similar procedural complication rates when using the ABSORB BVS to treat coronary bifurcations. However a proximal sizing strategy is associated with less malapposition and may be preferable.

Treatment of Bifurcation Lesions: Has DK Crush"ed" the Competition?

PURPOSE

This paper reviews the double-kiss crush (DK crush) technique in coronary artery bifurcation lesions. The technical aspects of the procedure and the clinical data supporting its use are summarized.

RECENT FINDINGS

Randomized studies support the adoption of DK technique in complex bifurcation lesions for both left main and non-left-main lesions. For true bifurcation lesions, DK crush may become the default technique for lesions in which the side-branch disease is complex and long. Optimal technique is essential for obtaining the clinical outcomes noted in the DKCRUSH randomized studies.

A review in enormity of OCT and its enduring understanding of vulnerable plaque in coronary bifurcation lesion

Optical coherence tomography (OCT) has emerged as one of the most promising tools to assist the optimization of percutaneous coronary intervention (PCI). Its ability to provide unique information on the plaque at high risk for rupture, plaque composition, the thickness of the fibrous cap, the presence of macrophage and thrombi has not only assisted simple PCI but also in many complex bifurcation lesions PCI. OCT has helped to provide valuable anatomic information to optimize stent implantation and adapt PCI strategy in individual patients. This review article summarizes the current role of OCT as an imaging technology and prediction of vulnerable plaque, its site and composition at the coronary bifurcation lesions for supporting the clinical decision.

Bifurcation Culprit Lesions in ST-segment Elevation Myocardial Infarction: Procedural Success and 5-year Outcome Compared With Nonbifurcation Lesions

INTRODUCTION AND OBJECTIVES

We assessed short- and long-term outcomes of primary angioplasty in ST-segment elevation myocardial infarction by comparing bifurcation culprit lesions (BCL) with non-BCL.

METHODS

Observational study with a propensity score matched control group. Among 2746 consecutive ST-segment elevation myocardial infarction patients, we found 274 (10%) patients with BCL. The primary outcome was a composite endpoint including all-cause death, myocardial infarction, coronary artery bypass grafting or target vessel revascularization, assessed at 30-days and 5-years.

RESULTS

Baseline characteristics showed no differences after propensity matching (1:1). In the BCL group, the most frequent strategy was provisional stenting of the main branch (84%). Compared with the non-BCL group, the procedures were technically more complex in the BCL group in terms of need for balloon dilatation (71% BCL vs 59% non-BCL; P = .003), longer procedural time (70 ± 29minutes BCL vs 62.8 ± 28.9minutes non-BCL; P = .004) and contrast use (256.2 ± 87.9mL BCL vs 221.1 ± 82.3mL non-BCL; P < .001). Main branch angiographic success was similar (93.4% BCL vs 93.8% non-BCL; P = .86). Thirty-day all-cause mortality was similar between groups: 4.7% BCL vs 5.1% non-BCL; P = .84. At the 5-year follow-up, there were no differences in all-cause death (12% BCL vs 13% non-BCL; P = .95) or the combined event (22% BCL vs 21% non-BCL; P = .43).

CONCLUSIONS

Primary angioplasty of a BCL was technically more complex; however, main branch angiographic success was similar, and there were no differences in long-term prognosis compared with non-BCL patients.

New insight to estimate under-expansion after stent implantation on bifurcation lesions using optical coherence tomography

Optical coherence tomography (OCT) allows full volumetric segmentation of the lumen. However, for the estimation of stent under-expansion we still rely on the conventional method (CM) of single cross-sectional narrowing compared with reference vessel, likely masking true lesion significance, especially for bifurcations and tapered vessels. We, therefore, suggest a novel concept of volumetric metrics that take into account vessel tapering and major side branches and is capable of obtaining ideal lumen area for every frame of the stent by OCT. Forty-four patients with bifurcation lesions were enrolled. In volumetric metrics, expansion index was calculated as [(actual lumen area/ideal lumen area) × 100] in all frames. While minimum expansion index (MEI) was often located in the proximal segment to the major side branch, minimum stent area (MSA) by CM was frequently located in the distal segment (p < 0.001). Furthermore, the frequency of the under-expansion was significantly greater in newly metrics compared with CM [21 (47.7%) and 11 (25.0%), p = 0.045]. New metrics changed the presence of the under-expansion in 40.9% (18/44) of patients and the locations of MEI and MSA were different in 72.7% (32/44) of cases. Volumetric assessment enables to more accurately assess stent under-expansion.

Healthy and diseased coronary bifurcation geometries influence near-wall and intravascular flow: A computational exploration of the hemodynamic risk

Local hemodynamics has been identified as one main determinant in the onset and progression of atherosclerotic lesions at coronary bifurcations. Starting from the observation that atherosensitive hemodynamic conditions in arterial bifurcation are majorly determined by the underlying anatomy, the aim of the present study is to investigate how peculiar coronary bifurcation anatomical features influence near-wall and intravascular flow patterns. Different bifurcation angles and cardiac curvatures were varied in population-based, idealized models of both stenosed and unstenosed bifurcations, representing the left anterior descending (LAD) coronary artery with its diagonal branch. Local hemodynamics was analyzed in terms of helical flow and exposure to low/oscillatory shear stress by performing computational fluid dynamics simulations. Results show that bifurcation angle impacts lowly hemodynamics in both stenosed and unstenosed cases. Instead, curvature radius influences the generation and transport of helical flow structures, with smaller cardiac curvature radius associated to higher helicity intensity. Stenosed bifurcation models exhibit helicity intensity values one order of magnitude higher than the corresponding unstenosed cases. Cardiac curvature radius moderately affects near-wall hemodynamics of the stenosed cases, with smaller curvature radius leading to higher exposure to low shear stress and lower exposure to oscillatory shear stress. In conclusion, the proposed controlled benchmark allows investigating the effect of various geometrical features on local hemodynamics at the LAD/diagonal bifurcation, highlighting that cardiac curvature influences near wall and intravascular hemodynamics, while bifurcation angle has a minor effect.

Coronary fractional flow reserve measurements of a stenosed side branch: a computational study investigating the influence of the bifurcation angle

Background

Coronary hemodynamics and physiology specific for bifurcation lesions was not well understood. To investigate the influence of the bifurcation angle on the intracoronary hemodynamics of side branch (SB) lesions computational fluid dynamics simulations were performed.

Methods

A parametric model representing a left anterior descending—first diagonal coronary bifurcation lesion was created according to the literature. Diameters obeyed fractal branching laws. Proximal and distal main branch (DMB) stenoses were both set at 60 %. We varied the distal bifurcation angles (40°, 55°, and 70°), the flow splits to the DMB and SB (55 %:45 %, 65 %:35 %, and 75 %:25 %), and the SB stenoses (40, 60, and 80 %), resulting in 27 simulations. Fractional flow reserve, defined as the ratio between the mean distal stenosis and mean aortic pressure during maximal hyperemia, was calculated for the DMB and SB (FFR_SB) for all simulations.

Results

The largest differences in FFR_SB comparing the largest and smallest bifurcation angles were 0.02 (in cases with 40 % SB stenosis, irrespective of the assumed flow split) and 0.05 (in cases with 60 % SB stenosis, flow split 55 %:45 %). When the SB stenosis was 80 %, the difference in FFR_SB between the largest and smallest bifurcation angle was 0.33 (flow split 55 %:45 %). By describing the ΔP_SB−Q_SB relationship using a quadratic curve for cases with 80 % SB stenosis, we found that the curve was steeper (i.e. higher flow resistance) when bifurcation angle increases (ΔP = 0.451*Q + 0.010*Q² and ΔP = 0.687*Q + 0.017*Q² for 40° and 70° bifurcation angle, respectively). Our analyses revealed complex hemodynamics in all cases with evident counter-rotating helical flow structures. Larger bifurcation angles resulted in more pronounced helical flow structures (i.e. higher helicity intensity), when 60 or 80 % SB stenoses were present. A good correlation (R² = 0.80) between the SB pressure drop and helicity intensity was also found.

Conclusions

Our analyses showed that, in bifurcation lesions with 60 % MB stenosis and 80 % SB stenosis, SB pressure drop is higher for larger bifurcation angles suggesting higher flow resistance (i.e. curves describing the ΔP_SB−Q_SB relationship being steeper). When the SB stenosis is mild (40 %) or moderate (60 %), SB resistance is minimally influenced by the bifurcation angle, with differences not being clinically meaningful. Our findings also highlighted the complex interplay between anatomy, pressure drops, and blood flow helicity in bifurcations.

Hemodynamics of Stent Implantation Procedures in Coronary Bifurcations: An In Vitro Study

Stent implantation in coronary bifurcations presents unique challenges and currently there is no universally accepted stent deployment approach. Despite clinical and computational studies, the effect of each stent implantation method on the coronary artery hemodynamics is not well understood. In this study the hemodynamics of stented coronary bifurcations under pulsatile flow conditions were investigated experimentally. Three implantation methods, provisional side branch (PSB), culotte (CUL), and crush (CRU), were investigated using time-resolved particle image velocimetry to measure the velocity fields. Subsequently, hemodynamic parameters including wall shear stress, oscillatory shear index (OSI), and relative residence time (RRT) were calculated. The pressure field through the vessel was non-invasively quantified and pressure wave speeds were computed. The effects of each stented case were evaluated and compared against an un-stented case. CRU provided the lowest compliance mismatch, but demonstrated detrimental stent interactions. PSB, the clinically preferred method, and CUL maintained many normal flow conditions. However, PSB provided about a 300% increase in both OSI and RRT. CUL yielded a 10 and 85% increase in OSI and RRT, respectively. The results of this study support the concept that different bifurcation stenting techniques result in hemodynamic environments that deviate from that of un-stented bifurcations, to varying degrees.

Complex coronary bifurcation revascularization by means of very minimal crushing and ultrathin biodegradable polymer DES: Feasibility and 1-year outcomes of the "Nano-crush" technique

AIM

To assess feasibility and 1-year outcomes of ultrathin biodegradable polymer double stenting using a very minimal crushing (nano-crush technique) in a series of patients with large (≥2.5mm) complex coronary bifurcation.

METHODS

From January 2015 to June 2016, patients referred for large (≥2.5mm) complex coronary bifurcation percutaneous coronary interventions (PCI) were enrolled to receive Orsiro (Biotronik Inc., Bulack, Switzerland) double stenting using a very minimal crush technique (nano-crush). Per our institutional protocol, follow-up was conducted by physical examination at 1, 6, 12month and yearly whereas angiographic control was eventually scheduled at 6-8months on the basis of symptoms recurrence or/and positive induced ischemia tests.

RESULTS

Fifty-two patients (15 females mean age 77.2±6.2years) were enrolled. Mean angles between main branch and side branch were 63.6±21.3°. The mean diameter and length of implanted stents were 3.8±0.4mm and 27.1±8.7mm in main branch and 2.8±0.3mm and 22.1±.7.1mm in side branch. Immediate success was 100%. Clinical follow-up was available for 100% of patients: at a mean follow-up of 12.0±2.6months, no patient death, or acute myocardial infarction or target vessel revascularization were observed. Angiographic follow-up was available in 25/52 patients (48%) at a mean time from the procedure of 7.2±0.5months and showed no significant angiographic restenosis.

CONCLUSIONS

The revascularization of complex large (≥2.5mm) coronary bifurcation disease using the nano-crush technique and the ultrathin polymer biodegradable stent appeared feasible in our small study with promising 1year outcomes.

Comparison of failure rates of crossing side branch with pressure vs. coronary guidewire: a meta-analysis

OBJECTIVES

The aim of this study was to compare the failure rates of crossing side branch (SB) with pressure guidewire vs. coronary guidewire after main vessel (MV) stenting in coronary bifurcation lesions (CBL).

BACKGROUND

Percutaneous coronary intervention of CBL is technically difficult. The European Bifurcation Club recommends performing either fractional flow reserve (FFR) estimation of the SB or final kissing balloon inflation (FKBI) after the MV stenting when a significant SB ostial stenosis is present. Even though FFR is recommended in CBL, there is concern about SB crossing with pressure guidewire among interventionists.

MATERIALS AND METHODS

We undertook a comprehensive literature search to identify all relevant studies reporting the failure rates of SB crossing after MV stenting with either pressure or coronary guidewire. A random effects model was used to compare the failure rates between the two approaches.

RESULTS

Our search identified six studies that reported failure rates of SB crossing with a pressure guidewire (n = 648) and 11 studies that reported failure rates of SB crossing with a coronary guide-wire (n = 2601). Estimated pooled failure rate was 3·9% (95% CI: 1·5% to 9·6%) for inability to cross SB with pressure guidewire. Estimated pooled failure rate of SB crossing with coronary guidewire was 3·1% (95% CI: 1·5% to 6·2%). There was no significant difference between the failure rates in the two groups (P = 0·70).

CONCLUSION

The failure rates of SB crossing after MV stenting are low with both pressure and coronary guidewire procedures, with no significant difference between the two approaches.

Impact of final kissing balloon inflation on vessel healing following drug-eluting stent implantation: Insight from the optical coherence tomography sub-study of the J-REVERSE trial

BACKGROUND

We sought to clarify the impact of final kissing inflation (FKI) after single stenting of bifurcation lesions on vessel healing.

METHODS

From the J-REVERSE registry enrolling 303 bifurcation lesions treated with provisional single stenting using sirolimus- (SES) or everolimus-eluting stent (EES), 65 lesions treated with (n=30) and without (n=35) FKI underwent 9-month follow-up optical coherence tomography. Average stent eccentricity index (SEI: minimum/maximum stent diameter) and neointimal unevenness score (NUS: maximum/average neointimal thickness of the same cross-section) for the proximal, bifurcation, and distal segments were compared between FKI and non-FKI groups.

RESULTS

At the proximal segment, the FKI group demonstrated significantly larger average stent area with greater asymmetric stent expansion, and average lumen area remained significantly larger at 9-month follow-up despite a tendency toward greater neointimal proliferation. Jailed strut and thrombus incidence were also significantly lower at the side branch orifice, and NUS was significantly smaller at the bifurcation and proximal segments in the FKI group.

CONCLUSIONS

Nine months after SES and EES treatment of bifurcation lesions, FKI reduced proximal-segment luminal narrowing. Considering its homogeneous neointimal distribution and fewer jailed struts, FKI may be beneficial for treating bifurcation lesions.

Numerical investigation of blood flow in a deformable coronary bifurcation and non-planar branch

INTRODUCTION

Among cardiovascular diseases, arterials stenosis is recognized more commonly than the others. Hemodynamic characteristics of blood play a key role in the incidence of stenosis. This paper numerically investigates the pulsatile blood flow in a coronary bifurcation with a non-planar branch. To create a more realistic analysis, the wall is assumed to be compliant. Furthermore, the flow is considered to be three-dimensional, incompressible, and laminar.

METHODS

The effects of non-Newtonian blood, compliant walls and different angles of bifurcation on hemodynamic characteristics of flow were evaluated. Shear thinning of blood was simulated with the Carreau-Yasuda model. The current research was mainly focused on the flow characteristics in bifurcations since atherosclerosis occurs mostly in bifurcations. Moreover, as the areas with low shear stresses are prone to stenosis, these areas were identified.

RESULTS

Our findings indicated that the compliant model of the wall, bifurcation's angle, and other physical properties of flow have an impact on hemodynamics of blood flow. Lower wall shear stress was observed in the compliant wall than that in the rigid wall. The outer wall of bifurcation in all models had lower wall shear stress. In bifurcations with larger angles, wall shear stress was higher in outer walls, and lower in inner walls.

CONCLUSION

The non-Newtonian blood vessels and different angles of bifurcation on hemodynamic characteristics of flow evaluation confirmed a lower wall shear stress in the compliant wall than that in the rigid wall, while the wall shear stress was higher in outer walls but lower in inner walls in the bifurcation regions with larger angles.