Bifurcation Quantitative Coronary Angiography Research Articles

The need for dedicated bifurcation quantitative coronary angiography (QCA) software algorithms to evaluate bifurcation lesions.

Single-vessel quantitative coronary angiography (QCA) software is inaccurate when used in bifurcation lesions due to the specific anatomical characteristics of bifurcations, including the natural step-down in diameters after every bifurcation. Dedicated bifurcation QCA software has been developed to overcome the limitations of single-vessel QCA in bifurcations. A phantom validation study has shown the superior accuracy of these bifurcation QCA algorithms compared to the single-vessel QCA software. These QCA software algorithms are currently highly recommended to assess bifurcation lesions.

Inter-core lab variability in analyzing quantitative coronary angiography for bifurcation lesions: a post-hoc analysis of a randomized trial.

This study sought to evaluate inter-core lab variability in quantitative coronary angiography (QCA) analysis of bifurcation lesions. QCA of bifurcation lesions is challenging. To date there are no data available on the inter-core lab variability of bifurcation QCA analysis. The randomized Tryton IDE (Tryton Pivotal IDE Coronary Bifurcation Trial) compared the Tryton Side Branch Stent (Tryton Medical, Durham, North Carolina) with balloon angioplasty as side branch treatment. QCA was performed in an angiographic subcohort (n = 326) at 9-month follow-up. Inter-core lab variability of QCA analysis between the Cardiovascular Research Foundation and the Cardialysis core labs was evaluated before and after alignment of the used QCA methodology using angiographic data derived from this angiographic follow-up cohort. In the original analysis, before alignment of QCA methodology, the mean difference between the core labs (bias) was large for all QCA parameters with wide 95% limits of agreement (1.96 × SD of the bias), indicating marked variability. The bias of the key angiographic endpoint of the Tryton trial, in-segment percentage diameter stenosis (%DS) of the side branch, was 5.5% (95% limits of agreement: -26.7% to 37.8%). After reanalysis, the bias of the in-segment %DS of the side branch reduced to 1.8% (95% limits of agreement: -16.7% to 20.4%). Importantly, after alignment of the 2 core labs, there was no longer a difference between both treatment groups (%DS of the side branch: treatment group A vs. group B: 34.4 ± 19.4% vs. 32.4 ± 16.1%, p = 0.340). Originally, a marked inter-core lab variability of bifurcation QCA analysis was found. After alignment of methodology, inter-core lab variability decreased considerably and impacted angiographic trial results. This latter finding emphasizes the importance of using the same methodology among different core labs worldwide. (Tryton Pivotal Prospective, Single Blind, Randomized Controlled Study to Evaluate the Safety & Effectiveness of the Tryton Side Branch Stent Used With DES in Treatment of de Novo Bifurcation Lesions in the Main Branch & Side Branch in Native Coronaries [TRYTON]; NCT01258972).

Comparison of two and three dimensional quantitative coronary angiography to intravascular ultrasound in the assessment of left main coronary artery bifurcation lesions

Background Angiographic evaluation of left main coronary artery (LMCA) bifurcation lesions is often limited. two dimensional (2D) quantitative coronary angiography (QCA) with segmental analysis provides accuracy for quantification of the degree of stenosis in the main vessel and side branch ostium but can be affected by foreshortening and variable magnification. The accuracy of three dimensional (3D) QCA has recently developed to overcome 2D QCA limitations, however, accuracy and precision of 3D bifurcation QCA measurements in LMCA bifurcation lesions has not been established. Methods We investigated whether such 3D and 2D bifurcation QCA measurements differ in their accuracy in assessing significant LMCA bifurcation lesions defined by intravascular ultrasound (IVUS) as a minimum luminal area (MLA) <6 mm2 of LMCA and MLA <4 mm2 of proximal left anterior descending (LAD) and/or proximal left circumflex (LCX) Results LMCA bifurcation lesions were assessed in 44 patients undergoing elective percutaneous coronary intervention. From 2D QCA measurements, MLA correlated moderately with threshold intravascular ultrasound MLA for LMCA (r=0.81, P <0.000 1), LAD (r=0.54, P=0.000 1) and LCX (r=0.58, P <0.000 1). Severity of lesion as MLA by derived 3D QCA, correlated moderately with threshold intravascular ultrasound MLA for LMCA (r=0.84, P <0.000 1), LAD (r=0.53, P=0.000 2); LCX (r=0.66, P <0.000 1). Overall, the C statistics tended to be slightly higher for 3D QCA and 2D QCA measurements in LMCA segment compared with proximal LAD and LCX segments, and there were no significant predictive power of percent diameter stenosis and percent area stenosis on 3D QCA for LCX IVUS MLA <4 mm2 (percent diameter stenosis: area under curve 0.55, cutoff 23%, sensitivity 88%, specificity 37%, P=0.618 6; percent arer stenosis: area under curve 0.56, cutoff 41%, sensitivity 83%, specificity 38%, P=0.518 4, respectively). Conclusions The accuracy of 3D bifurcation QCA in detecting significant LMCA bifurcation lesions is limited, especially the proximal LCX ostium. When IVUS is not available or contraindicated, 3D QCA may assist in the evaluation of intermediate LMCA lesions with MLA.

Advanced three-dimensional quantitative coronary angiographic assessment of bifurcation lesions: methodology and phantom validation

Validation of new three-dimensional (3-D) bifurcation quantitative coronary angiography (QCA) software. Cardiovascular Angiography Analysis System (CAAS 5v10) allows 3-D angiographic reconstructions based on two or more 2-D projection images. Measurements for minimal lumen diameter (MLD), reference vessel diameter (RVD), percent diameter stenosis (DS) and bifurcation angle (BA) were validated against precision manufactured phantom bifurcations. Length measurements were validated against angiographic measurement catheters inserted into a plexiglas bifurcation phantom. In 3-D reconstructions based on two 2-D images, acquired at variable rotation and angulation, accuracy and precision (mean difference ± SD) of the 11-segment model for MLD, RVD and DS were 0.013±0.131 mm, -0.052±0.039 mm and -1.08±5.13%, respectively; inter-observer variability was 0.141 mm, 0.058 mm and 5.42%, respectively. Adding the antero-posterior (optimal) projection to these basic reconstructions resulted in reduced variability (0.101 mm, 0.041 mm and 3.93% for MLD, RVD and DS, p<0.01 for all) and showed a trend towards improved precision (0.109 mm, 0.031 mm and 4.26%, respectively, p>0.05 for all). In basic reconstructions, accuracy and precision for BA was -1.3±5.0°, whereas inter-observer variability was 7.5°; respective measures for length were 0.15±0.26 mm and 0.54 mm. Adding the antero-posterior projection resulted in decreased precision (0.47 mm, p<0.01) and increased variability (1.03 mm, p<0.01) for length measurements; precision (5.4°) and variability (7.9°) for BA did not change significantly (p>0.30). Advances in the methodology of 3-D reconstruction and quantitative analysis for bifurcation lesions translated into highly accurate, precise and reproducible measures of diameter, length and BA.

Advances in two-dimensional quantitative coronary angiographic assessment of bifurcation lesions: improved small lumen diameter detection and automatic reference vessel diameter derivation

To validate a new two dimensional (2-D) bifurcation quantitative coronary angiography (QCA) software. In the latest edition of the Cardiovascular Angiography Analysis System (CAAS 5.9; Pie Medical Imaging, Maastricht, The Netherlands) video-densitometric information is dynamically integrated into the edge-detection algorithm of 11- and 6-segment models to reduce overestimation of small diameters. Furthermore, automatic reference obstruction analysis was optimised. Values of the minimal lumen diameter (MLD), reference vessel diameter (RVD), percent diameter stenosis (DS) and bifurcation angle (BA) for the different bifurcation segment models were validated against precision manufactured plexiglass phantoms. In anteroposterior views, accuracy and precision (mean difference±SD) of 11- and 6-segment models for MLD were 0.013±0.082 mm vs. 0.003±0.100 mm, for RVD -0.030±0.047 mm vs. -0.029±0.045 mm and for DS -0.48±3.66% vs. -0.11±3.97%. In smaller vessel segments (true MLD <0.7 mm), MLD overestimation was reduced. Inter-observer variability for MLD, RVD and DS for either model was ≤0.052 mm, ≤0.043 mm and ≤2.24%, respectively. Agreement between models for MLD, RVD and DS was ±0.076 mm, ±0.021 mm and ±2.53%, respectively. Accuracy and precision for BA were -2.6±3.5°, and variability was ≤1.2°. Accuracy and precision for diameter-derived parameters were slightly decreased in projections with 30° rotation; BA precision dropped to 6.2°. MLD quantification is improved for true MLD <0.7 mm, resulting in highly accurate and precise diameter measurements over the entire range of phantom diameters. Automatic reference obstruction analysis provides highly accurate, precise and reproducible RVD and DS measurements.

Novel bifurcation phantoms for validation of quantitative coronary angiography algorithms

Validation is lacking for two- and three-dimensional (2D and 3D) bifurcation quantitative coronary angiography (QCA) algorithms. Six plexiglas phantoms were designed, each of them mimicking a coronary vessel with three successive bifurcations lesions, wherein at least one vessel segment had a percent diameter stenosis (DS) of ≥60%. The five most frequently occurring Medina classes (1,1,1), (1,1,0), (0,1,0), (0,1,1), and (1,0,0) were used in the design. Diameters of the daughter vessels in every bifurcation were dictated by the scaling law of Finet. Lesions were cosinus-shaped in longitudinal view and circular-shaped in cross-sectional view. At the level of the carina, lesions were becoming eccentric, favoring "plaque" at the outer bifurcation walls. Adjacent bifurcation lesions were kept distant by nontapering, stenosis-free segments of ≥10 mm length. The direction of the side branch relative to the main vessel was based on relevant literature. The phantoms were precision manufactured using computer-aided design and machining techniques. Because of the high drilling accuracy (within 10 μm), the 3D luminal surface description of the phantom could be used to determine the true lumen dimensions and bifurcation angle (BA) values of the final geometry. Our series of bifurcation phantoms comprised 33 narrowed and 21 stenosis-free vessel segments with a mean true minimal lumen diameter (MLD) value of 0.98 ± 0.40 mm (range, 0.53-1.96 mm) and 2.29 ± 0.74 mm (range, 1.40-4.00 mm), respectively. Overall, the mean true values for MLD, reference diameter, and DS were 1.49 ± 0.85 mm, 2.70 ± 0.71 mm, and 40.9% ± 34.2%. The mean true values for the proximal and the distal BA were 123.6° ± 19.0° and 69.6° ± 19.9°, respectively. Six plexiglas phantoms containing a total of 18 bifurcations lesions with variable anatomy and Medina class were designed and precision manufactured to facilitate the validation of bifurcation QCA algorithms.

Two‐dimensional quantitative coronary angiographic models for bifurcation segmental analysis

Quantitative coronary angiography (QCA) analysis for bifurcation lesions needs to be standardized. In vitro validation of two models for bifurcation QCA segmental analysis. In the latest edition of the Cardiovascular angiography analysis system (CAAS 5v8, Pie Medical Imaging, Maastricht, The Netherlands) a 6-segment model for two-dimensional coronary bifurcation analysis was implemented next to the currently available 11-segment model. Both models were validated against 6 precision manufactured plexiglas phantoms, each of them mimicking a vessel with three successive bifurcation lesions with variable anatomy and Medina class. The phantoms were filled with 100% contrast agent and imaged with a biplane gantry. Images acquired in antero-posterior (AP) direction by either C-arm and at 30° right and left anterior oblique angulation were analyzed by two independent analysts, blinded to the actual dimensions. Manual correction of the contours was not allowed. Measurements for minimal lumen diameter (MLD), reference vessel diameter (RVD), percent diameter stenosis (DS) and bifurcation angle (BA) were compared with the true phantom dimensions. In AP views the accuracy and precision (mean difference ± SD) of 11- and 6-segment model for MLD, RVD, and DS were 0.065 ± 0.128 mm vs. 0.058 ± 0.142 mm, -0.021 ± 0.032 mm vs. -0.022 ± 0.030 mm, and -2.45% ± 5.07% vs. -2.28% ± 5.29%, respectively. Phantom MLD values ≤ 0.7 mm were systematically overestimated; if excluded, MLD accuracy and precision became 0.015 ± 0.106 mm and 0.004 ± 0.125 mm for the 11- and 6-segment model, respectively. Accuracy and precision for BA were -2.2° ± 3.3°. Interobserver variability for MLD, RVD, DS, and BA for either model was ≤ 0.049 mm, ≤ 0.056 mm, ≤ 2.77%, and 1.6°, respectively. Agreement between models for MLD, RVD, and DS was ± 0.079 mm, ± 0.011 mm, and ± 2.07%. Accuracy and precision for diameter-derived parameters were slightly decreased in angulated projections; precision for BA measurements dropped to 6.1°. The results of both models are highly reproducible and for phantom MLD values >0.7 mm in excellent agreement with the true dimensions.

Bifurcation lesion morphology and intravascular ultrasound assessment

This repot reviews the angiographic and intravascular (IVUS) assessment of coronary bifurcation lesions. Overall, bifurcation lesion anatomy and morphology is critical for technical decision making, and a key factor for successful bifurcation PCI. Optimal viewing is essential for proper angiographic assessment, especially for evaluation of the degree of SB involvement. Current classifications based on the presence or absence of significant angiographic stenosis within the three segments of the bifurcation anatomy may not provide sufficient anatomic and morphologic information to guide technical decision making. Dedicated 2D bifurcation quantitative coronary angiography with segmental analysis of the bifurcation provides greater accuracy for quantification of the degree of stenosis in the PV and especially the SB ostium. IVUS assessment at preprocedure provides valuable information regarding vessel size, and plaque morphology and distribution (particularly in relation to the SB ostium) that may help select treatment strategy. At postprocedure, IVUS imaging evaluates stent apposition within the stented segment(s) and the appropriateness of stent expansion particularly at the SB ostium, what may impact long-term outcomes.

Essentials of quantitative angiography for bifurcation lesions

Introduction Visual estimation of vessel diameter and lesion length supported by balloon predilation (known length and diameter) has been a common strategy, when final stent implantation is anticipated. Quantitative coronary angiography (QCA) being highly accurate and reproducible can refine the visual estimate and provide several important parameters which have been accepted as surrogate endpoints in many clinical studies on new PCI technologies. However, stand-alone percent diameter/area stenosis measurements derived from conventional (single-vessel) twodimensional (2-D) QCA analysis fail to predict the functional significance of coronary vessel obstruction. This holds even more for the analysis of bifurcation lesions, where the discrepancy in vessel size proximal and distal to the carina (step-down phenomenon) results in stenosis being overestimated in the distal branches and underestimated in the proximal main vessel (PMV). Dedicated 2-D bifurcation software algorithms have been developed recently in order to make up for the shortcomings of 2-D singlevessel QCA by reporting angiographic parameters separately for the PMV and each of the distal branches. The proximal and the distal branches of a single bifurcation often do not lie on a single plane; thus vessel overlap and foreshortening together with the lesion eccentricity may compromise the results of 2-D angiographic analysis. In the last 10 years evidence has accumulated that three dimensional (3-D) angiographic reconstruction is accurate, precise and reproducible. Reduced time requirements for a single 3-D reconstruction facilitates realtime analysis; single-vessel as well as bifurcation lesions can be reconstructed and analysed via dedicated QCA algorithms. In this short review we will attempt to emphasise the relative merits of bifurcation QCA compared to visual assessment, report on the options currently available for 2-D and 3-D bifurcation QCA analysis and outline the challenges yet to be addressed.