Coronary Bifurcation Intervention: What Role Do Bifurcation Angles Play?

Carina: A major determinant in the pathophysiology and treatment of coronary bifurcation lesions

Over the last decade, several in vivo and computational investigations have significantly advanced our understanding of the pathophysiology of coronary bifurcations, contributing to the enhancement of their percutaneous revascularization. The carina of the coronary bifurcations plays a substantial role in generating their main hemodynamic features, including distinctive flow patterns with secondary flows and specific shear stress patterns. These factors play a pivotal role in determining the susceptibility, development, and progression of atherosclerosis. The underlying pathophysiological mechanisms of atherosclerosis in coronary bifurcations are complex and multifactorial. Understanding these mechanisms is fundamental to comprehending lesions at the bifurcation level and informing future treatment strategies. This review aims to present the currently available data regarding the pathophysiological and prognostic role of the carina in coronary bifurcations, offering an interpretation of these findings from the perspective of interventional cardiologists, providing valuable insights for their clinical practice.

A New Scoring System Predicting Side-Branch Occlusion in Patients Undergoing Left Main Bifurcation Intervention: The LM V-RESOLVE Score

BACKGROUND

The risk of side-branch (SB) occlusion is pivotal for decision making of stenting strategies during unprotected left main (LM) bifurcation percutaneous coronary intervention (PCI). Accordingly, this study aimed to develop a scoring system for predicting SB occlusion during unprotected LM bifurcation PCI.

METHODS

A total of 855 consecutive patients undergoing unprotected LM bifurcation PCI with provisional strategy at Fuwai Hospital from January 2014 to December 2016 were recruited. A prediction model was selected by means of all-subsets logistic regression, and a multivariable risk score (Left Main Visual Estimation for Risk Prediction of Side Branch Occlusion in Coronary Bifurcation Intervention [LM V-RESOLVE]) was then established with incremental weights attributed to each component variable based on its estimate coefficients. SB occlusion was defined as any decrease in Thrombolysis in Myocardial Infarction (TIMI) flow grade or absence of flow in SB after main vessel (MV) stenting.

RESULTS

SB occlusion occurred in 19 LM bifurcation lesions (2.22%). In multivariable model, 3 variables, including MV/SB diameter ratio, MV plaque ipsilateral to SB, and baseline diameter stenosis of SB, were independent predictors for SB occlusion (model C-statistic 0.829, 95% confidence interval [CI] 0.735-0.923, with good calibration). The risk score had a C-statistics of 0.830 (95% CI 0.738-0.923) with good calibration. Satisfactory discriminative ability of the risk score was also preserved in external validation (C-statistic 0.794, 95% CI 0.691-0.896).

CONCLUSIONS

The LM bifurcation-specific novel scoring system, LM V-RESOLVE, based on 3 simple baseline angiographic findings, could help to rapidly discriminate lesions at risk of SB occlusion during LM bifurcation PCI.

Influence of Wavy Arteries and Veins on Hemodynamic Characteristics: A Numerical Study

The present work is focused on the study of hemodynamic characteristics for tortuous arteries/veins. Tortuosity in arteries/veins is defined by introducing waviness in the wall of the tube. Analysis is further extended for bifurcated veins with and without wavy walls. Waviness is defined by two geometric parameters; pitch and depth of the wave. Four different combinations of pitch and depth are studied and compared with a plain straight wall. The present study is carried out numerically by using a computational fluid dynamics tool. Hemodynamics for a steady flow of blood is investigated through pressure, velocity, and wall shear stress distribution. Waviness in the wall of arteries/veins creates a recirculation zone at the crest and trough of the wall. Occurrence of the recirculation zone leads to reduction in velocity which in turn reduces wall shear stress. Variation in the magnitude of the velocity and corresponding wall shear stress at the crest and trough of the wavy wall depends on the pitch and depth of the artery/veins (tube).

Percutaneous coronary intervention of bifurcation lesions

Bifurcation coronary artery disease is common as the development of atherosclerosis is facilitated by altered endothelial shear stress. Multiple anatomical and physiological factors need to be considered when treating bifurcation lesions. To achieve optimal results, various stenting techniques have been developed, each with benefits and limitations. In this state-of-the-art review we describe technically important characteristics of bifurcation lesions and summarise the evidence supporting contemporary bifurcation techniques.

Efficacy of plaque debulking for bifurcated or ostial lesions by directional coronary atherectomy prior to second-generation drug eluting stenting

OBJECTIVES

We sought to evaluate the efficacy of plaque debulking by directional coronary atherectomy (DCA) prior to second-generation drug-eluting stent (DES) implantation for bifurcated coronary lesions.

BACKGROUND

Percutaneous coronary intervention (PCI) for bifurcated lesions still remains complex and challenging in terms of restenosis or stent thrombosis regardless of whether simple or complex stenting is used.

METHODS

Patients with bifurcated lesions were enrolled in this prospective multicenter registry. Pre-second-generation DES plaque debulking with a novel DCA catheter (ATHEROCUT®, Nipro Co., Osaka, Japan) was conducted. All patients were scheduled to perform a follow up angiography (9-12 month coronary angiography or coronary computed tomography). The primary end point was target vessel failure (TVF) at follow up. Secondary end points were procedure-related events and major adverse cardiac events at 1 year.

RESULTS

A total of 77 patients with bifurcated lesions were enrolled. PCI with DCA was performed successfully in all cases without any major procedure-related event and only one case required complex stenting. The TVF rate at 9-12 month follow up was 3.9% (3 of 77) and those were all associated with revascularization of the target vessel. Restenosis was only observed at the ostium of the main-branch in three cases. No death, coronary artery bypass grafting, or myocardial infarction were reported for any patients within the first year.

CONCLUSION

DCA before second-generation DES implantation can possibly avoid complex stenting and provide a good mid-term outcome in patients with bifurcated lesions.

Efficacy of drug-coated balloon angioplasty after directional coronary atherectomy for coronary bifurcation lesions (DCA/DCB registry)

OBJECTIVES

To evaluate the efficacy and safety of additional drug-coated balloon (DCB) angioplasty after directional coronary atherectomy (DCA) for coronary bifurcation lesions.

BACKGROUND

The optimal therapy for bifurcation lesions has not been established, even in the drug-eluting stent era. DCA possibly prevents plaque and carina shift in bifurcation lesions by plaque debulking; however, the efficacy of combined DCA and DCB (DCA/DCB) for bifurcation lesions remains unclear.

METHODS

This multicenter registry retrospectively recruited patients with bifurcation lesions who underwent DCA/DCB and follow-up angiogram at 6-15 months. The primary endpoint was the 12-month target vessel failure (TVF) rate. The secondary endpoints were procedure-related major complications, major cardiovascular events at 12 months, restenosis at 12 months, target lesion revascularization (TLR) at 12 months, and target vessel revascularization (TVR) at 12 months.

RESULTS

We enrolled 129 patients from 16 Japanese centers. One hundred and four lesions (80.6%) were located around the left main trunk bifurcations. No side branch compromise was found intraoperatively. Restenosis was observed in three patients (2.3%) at 12 months. TLR occurred in four patients (3.1%): 3 (2.3%) in the main vessel and 1 (0.8%) in the ostium of the side branch at 12 months. TVF incidence at 12 months was slightly higher in 14 patients (10.9%), and only two patients (1.6%) had symptomatic TVR. One patient (0.8%) had non-target vessel-related myocardial infarction.

CONCLUSIONS

Our data suggested that DCA/DCB provided good clinical outcomes and minimal side branch damage and could be an optimal non-stent percutaneous coronary intervention strategy for bifurcation lesions.

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.

In vitro validation of coronary CT angiography for the evaluation of complex lesions

AIMS

The aim of this study was to assess in vitro the diagnostic accuracy of computed tomography angiography (CTA) for the evaluation of complex coronary lesions.

METHODS AND RESULTS

Five Plexiglas phantoms with three bifurcation lesions each were designed to mimic the anatomic variations and fractal phenomena of the coronary tree. In addition, luminal stenoses were scaled up with increases of 10% from 40% to 80%, corresponding to luminal areas ranging from 3.0 mm2 to 0.22 mm2. Third-generation dual-source computed tomography was used. Automated quantitative CTA analysis was performed according to the bifurcation segment model. The primary objective was to determine the diagnostic accuracy of quantitative CTA in assessing bifurcation lesions with the phantoms as a reference. The accuracy of CTA for the assessment of minimal luminal diameter was -0.07 mm (limits of agreement -0.75 to 0.61), for reference vessel diameter 0.19 mm (limits of agreement -0.25 to 0.63) and diameter stenosis 8.2% (limits of agreement -13.2 to 29.5) with no difference regarding the location within the bifurcation (i.e., proximal and distal main vessel and side branch). In stenosis with minimal luminal diameter ≥1 mm, CTA overestimated the lesion severity (bias 0.19 mm, limits of agreement -0.09 to 0.47), whereas in lesions with severe stenosis and minimal luminal diameter ≤1 mm, CTA underestimated the lesion severity (bias -0.48 mm, limits of agreement -0.55 to -0.41). CTA was able to identify the contrast-filled lumen in all degrees of lesion severity.

CONCLUSIONS

In vitro, CTA is accurate for the evaluation of bifurcation lesions. CTA was able to distinguish contrast-filled lumen even in severe obstructive lesions. These findings require further validation in the clinical setting.

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.