Three-Dimensional Bifurcation Angle Analysis in Patients With Left Main
Disease: a Substudy of the SYNergy Between Percutaneous Coronary
Intervention With TAXus and Cardiac Surgery (SYNTAX) Trial
Chrysafios Girasis*, Yoshinobu Onuma*, Marie-Claude Morice† #, Antonio Colombo‡ #, David R. Holmes§ #, Ted E. Feldman║ #, Keith Dawkins¶ #, Patrick W
Serruys* #
Erasmus MC, Rotterdam, The Netherlands, #On behalf of the SYNTAX Investigators
Abstract
Methods
Background: Bifurcation angle (BA) is emerging as an independent predictor of outcome after PCI
of bifurcation lesions. Three-dimensional (3-D) quantitative coronary angiography (QCA)
eliminates the shortcomings of 2-D analysis, thus providing reliable data. We explore the variables
describing the BA of the Left Main (LM) and the impact of PCI on this angulation. Methods: This
is a substudy of the SYNergy between percutaneous coronary intervention with TAXus and cardiac
surgery (SYNTAX) trial. We reviewed the cineangiograms of the 354 patients with LM disease
who were randomized to PCI. Analysis was performed with 3-D QCA software (Cardiop-B, Paieon
Medical Inc, Israel). The proximal BA (between LM and LCx) and the distal BA (between LAD
and LCx) were computed in enddiastole and endsystole, both pre- and post-PCI; the variation of the
BA during the heart cycle was also determined. Results: Complete analysis with 3-D QCA was
feasible in 266 (75.1%) patients. Post-PCI there was a significant reduction in the width of the distal
angle. The proximal angle was not modified significantly (table 1). During systolic motion there
was an enlargement of the proximal angle and a reduction of the distal angle (p<0.001 for both).
The prognostic significance of these measurements will be presented at the time of the congress.
Conclusion: Left Main bifurcation angle analysis with 3-D QCA is feasible. PCI affects the distal
angle, whereas both proximal and distal angles are affected by the heart’s motion.
This is a substudy of the SYNTAX trial, which was a prospective, randomized, all-comers
clinical trial with the overall goal of assessing the optimum revascularization treatment for
patients with de novo three-vessel-disease (3VD) or LM disease (either isolated or in
combination with 1, 2, or 3VD). We reviewed the cineangiograms of the 354 patients with
LM disease who were randomized to PCI.
3-D reconstruction was performed off-line by two experienced operators (CG and YO), using
a validated program for 3-D QCA (CardiOp-B system version 2.1.0.151, Paieon Medical
Ltd, Park Afek, Israel). Two separate single-plane projections from a given angiographic
study, taken at the same heart phase, were chosen and uploaded into the software (Figure 1);
the selected projections should display the region of interest with no or minimal overlap and
foreshortening, and should be separated by at least 30°, otherwise a third projection was
employed for enhancing accuracy.
Table 1. Left Main Bifurcation Angles, pre- and post-PCI
Pre-PCI
Post-PCI
p-value*
Diast_proximal BA, °
105.9±21.7
107.9±21.4
0.064
Syst_proximal BA, °
114.0±19.6
114.5±18.6
0.621
SDV_proximal BA, °
8.2±13.2
6.7±12.3
0.118
Diast_distal BA, °
95.6±23.6
91.1±22.0
<0.001
Syst_distal BA, °
87.1±22.9
83.0±20.8
<0.001
SDV_distal BA, °
8,5±12.5
8.1±12.7
0.670
PCI=Percutaneous coronary intervention, BA=Bifurcation angle, SDV=Systolic-diastolic variation
*Paired t-test, two-sided, p significant <0.05
Background
The optimal treatment of left main (LM) disease remains contentious with much of the debate
focused on the treatment of its distal part. The importance of anatomical parameters such as the
bifurcation angle (BA) has not been fully appreciated. A number of studies identify the significance
of this angle in predicting the immediate or the long-term outcome, however most of these studies
rely on two-dimensional (2-D) analysis. The LM is particularly difficult to image because of
foreshortening and vessel overlap; 3-D quantitative coronary angiography (QCA) eliminates these
shortcomings of 2-D analysis and may be beneficial in this setting.
The purpose of this study was to test the feasibility of assessment of the LM bifurcation angle using
a 3-D QCA algorithm, describe the baseline angulation parameters and their systolic-diastolic
variation and evaluate the changes resulting from percutaneous coronary intervention (PCI).
Institutions: *Thoraxcenter, Erasmus Medical Center, Rotterdam, The Netherlands, †Institut Cardiovasculaire
Paris Sud, Massy, France, ‡San Raffaele Scientific Institute, Milan, Italy, §Mayo Clinic, Rochester, MN, USA,
║Evanston Hospital, Evanston, IL, USA, ¶ Boston Scientific Corporation, Natick, MA, USA
Figure 2. Bifurcation angle (BA) calculation. The
weighted vector (Tw) is calculated as the sum of
two vectors, each of them connecting the junction
point with distal points along the vessel centerline,
distant by 5mm (T1) and 10mm (T2) respectively.
Results
Complete 3-D QCA analysis was feasible in 266 (75.1%) out of the 354 patients. Distal and
proximal BA had mean pre-PCI enddiastolic values of 95.6±23.6° and 105.9±21.7° and
ranged from 44° to 165° and from 54° to 168° respectively; values were inversely correlated
(r= -0.75, p<0.001) and followed a normal distribution. In 229 cases (86.1%) the LM
bifurcation was T-shaped.
There was a statistically significant effect of systolic motion on both parameters, a mean
decrease of 8.5° (p<0.001) for the distal BA and a mean increase of 8.2° (p<0.001) for the
proximal BA. A similar effect was seen with post-procedural values.
The effects of PCI on BA are summarized in Table 1. In the entire cohort (n=266), PCI
conferred a significant mean decrease in the distal BA (ΔBA=4.5°, p<0.001) (Figure 3),
whereas the proximal BA increased by a mean of 2.0° (p=0.064). However, studying the Yshaped LM bifurcations (13.9%) separately, the opposite phenomenon was apparent; distal
BA increased post-PCI by a mean of 10.3° (p=0.001) and proximal BA decreased by 5.5°
(p=0.056). PCI had equivalent impact on the endsystolic BA values.
Beyond the 266 cases completely analyzed, another 88 could be analyzed either partly or not
at all (48 and 40 cases respectively). Less than complete analysis was attributable to 3 main
reasons: 1.Inadequate cineangiography and difficult anatomy in 42 cases (47.7%). 2. Failure
to record two separate angiographic projections in 23 cases (26.1%). 3. Twenty-three studies
(26.1%) could not be processed with the 3-D QCA software.
Figure 3. Histograms, with superimposed
normal curves, showing the Gaussian
distribution of enddiastolic distal angle
values, pre- and post-PCI. Post-PCI mean
values
are
significantly
decreased
(p<0.001). Values are shown in degrees.
Figure 1. Three-dimensional (3-D) bifurcation
angle (BA) analysis (CardiOp-B system, Paieon
Medical Ltd, Israel).
Two BA variables are presented in accordance with the European Bifurcation Club
consensus document. Proximal Angle A is defined as the angle between the proximal main
vessel (PMV) and the side branch (SB), whereas distal Angle B is delineated between the
distal main vessel (DMV) and the SB (Figure 1). By convention left anterior descending
(LAD) was designated as the DMV and left circumflex (LCX) as the SB. The angles were
calculated from the 3-D reconstructed vessel centerlines; individual values were computed
between the weighted vectors of direction of the respective vessel segments (Figure 2). BA
measurements were made without guidewires in place, which could modify the angle. The
LM bifurcation was designated as T-shaped or Y-shaped for distal BA values ≥70° or <70°
respectively.
Separate 3-D reconstructions were performed for the enddiastolic and endsystolic frames,
both before as well as after the procedure. Systolic-diastolic variation (SDV) of BA reflects
the variation of either proximal or distal BA throughout the heart cycle and equals the
difference of the respective enddiastolic and endsystolic values. Analysis was deemed
complete, only if all four of the 3-D images, that were required, were successfully
reconstructed; a case study was categorised as partial- or non-analyzable, when less than
four or no images at all, respectively, were obtained.
Conclusions
Three-dimensional bifurcation angle analysis for the Left Main, before and after PCI is
feasible; LM angulation parameters vary considerably. Heart motion exerts a reciprocal
effect on proximal and distal BA, the former being increased and the latter decreased during
systole. PCI modifies the distal BA; it increases the narrowest pre-PCI angles (Y-shaped
lesions), whereas it decreases wider than 90° angles. The clinical significance of these
findings will require further study.
Disclosures
Chrysafios Girasis, Patrick W. Serruys, Yoshinobu Onuma, David R. Holmes and Marie-Claude Morice
have no disclosures. Antonio Colombo is a minor share holder in Cappella Inc., producer of a dedicated
bifurcation stent for side branches. Ted E. Feldman has received grant support and consulting fees from
Abbott and Boston Scientific, and lecture fees from Boston Scientific. Keith D. Dawkins is employee of
Boston Scientific with BSC stock options.