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3
Provisional Stenting Technique for Non–Left
Main Coronary Bifurcation Lesions:
Patient Selection and Technique
Remo Albiero and Emiliano Boldi
Cath Lab, Clinica San Rocco di Franciacorta, Ome (Brescia), Italy
INTRODUCTION
Bifurcation lesions are frequent in routine practice, accounting for up to 20% of all coronary
disease treated by percutaneous coronary intervention (1). Compared to the left main coronary
artery bifurcation, the size of the vessels in non–left main bifurcations is smaller and the angle
between them is narrower (2). On the basis of the results of six randomized controlled trials
(RCTs) (3–8) (Fig. 1), in true coronary bifurcations with a short side branch lesion length, a
stepwise provisional side branch stenting strategy with drug-eluting stents is consensually
considered the preferable technique compared to deliberate elective double stenting (9). It is
critically important to emphasize the statement “with a short side branch lesion length” since
all these trials included bifurcations with side branches that have short lesions of moderate
severity. Hence, these data cannot be presumed to apply to patients with coronary bifurcations
who are not well represented in these trials (i.e., those with large side branches that have severe
stenoses which are long or have unfavorable angulation).
For instance, patients in Figures 2 through 5 had true bifurcation lesions with features
that would be inappropriate for the provisional stenting approach, so elective double stenting
technique was performed.
This chapter focuses on proper patient selection for the provisional stenting approach as
well as on proper technique execution.
WHO QUALIFIES FOR THE PROVISIONAL STENTING TECHNIQUE?
Understanding the anatomical characteristics of coronary bifurcations is required to optimize
the results of the provisional side branch stenting strategy. Although the Medina classification
(10) of coronary bifurcation lesions has gained wide acceptance (11) becauseit is considered the
most simple to understand and remember (Fig. 6), this classification does not consider several
critical anatomic elements that are relevant to bifurcation intervention: (a) the angle between
the two branches; (b) the side branch lesion length; (c) the observed/expected diameter; (d) the
plaque distribution.
Angle Between the Branches
By angiography, bifurcations are classified according to the internal angle between the main
vessel and the side branch (in the working view), with a Y-shaped lesion having an angle
<70 degrees and a T-shaped lesion having an angle ≥70 degrees. The analysis of the natural
distribution of bifurcation angles by MDCT (multidetector computed tomography) (2) reveals
that left main bifurcations (LAD/LCx) are T-shaped with an average value of 80 degrees, while
non–left main bifurcations (LAD/Diagonal; LCx/OM, PDA/PL) are mostly Y-shaped with an
average angle of46 to 53 degrees. The provisional side branch stenting strategy ismore suitable
for Y-shaped bifurcations with an internal angle <60 degrees, therefore is more suitable for
non–left main bifurcations. Attempts to apply provisional stenting in true bifurcations with a
severely angulated SB origin can result in SB occlusion (Fig. 7).
Lesion Length
Side branch lesions, specifically those enrolled in the RCTs, are mostly angiographically short
(3,12)—on averageless than5 to6 mm(Table1). Procedural sidebranch occlusionis less common
PROVISIONAL STENTING TECHNIQUE FOR NON–LEFT MAIN CORONARY BIFURCATION LESIONS
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15
2 stents
R
V
10
T
r
Ro
L
T
5
%
1 stent + PTS
49
0
Colombo
Figure 1 Low rate of reintervention with drug-eluting stents in six randomized trials comparing provisional
T stenting versus elective double stenting in true bifurcation lesions with a short side branch lesion length (lesions
suitable for both treatments).
(3)
Ferenc
(6)
BBC ONE
(8)
Cactus
(7)
Pan
(4)
Nordic I
(5)
in short compared to long side branch stenoses (8.2vs. 35.0%;p =0.003) (13). Inbifurcations with
a side branch lesion length less than 3 to 5 mm, the provisional side branch stenting strategy
allows to obtain a good final result in both branches in the majority (>70–80%) of cases by
stenting only the main branch and using a final kissing balloon inflation to optimally scaffold
the side branch ostium. The provisional stenting approach is more suited to treat bifurcations
with side branches that have short lesions rather than long stenoses. For example, the patient
in Figure 3 underwent elective double stenting because the SB is large and has a severe long
lesion at the ostium.
Observed/Expected Diameter
As demonstrated by Finet et al.(14) in 173 angiographicallynormal coronary bifurcations, there
is an important mother/daughter-vessel mathematical relationship, first described by Murray
(“Murray’s law”)—in particular, the constant ratio R = Dm/(Dd1 + Dd2) between the mothervessel diameter and the sum of the daughter-vessel diameters is 0.678. By using this simple
(A)
(B)
Figure 2 Bifurcation that requires the elective implantation of a SB stent. (A) Baseline
angiogram of the LAD-D1 bifurcation; (B) final
result after drug-eluting stent (DES) implantation in the proximal and mid-LAD and one long
DES at the ostium-proximal segment of the diagonal branch using the modified T stenting technique, and followed by final “kissing balloon”
inflation.
50
ALBIERO AND BOLDI
(A)
(B)
Figure 3 Bifurcation that requires the elective implantation of a SB stent. (A) Baseline
angiogram of the LAD-D1 bifurcation; (B) final
result after drug-eluting stent (DES) implantation in the proximal LAD and one long DES at the
ostium-proximal segment of the diagonal branch
using the modified T stenting technique, and
followed by final “kissing balloon” inflation.
(A)
(B)
Figure 4 Bifurcation that requires the elective implantation of a SB stent. (A) Baseline
angiogram of the LAD-D1 bifurcation; (B) Final
result after drug-eluting stent (DES) implantation in the proximal–mid-LAD and one long DES
at the ostium-proximal segment of the diagonal
branch using the modified T stenting technique,
and followed by final “kissing balloon” inflation.
PROVISIONAL STENTING TECHNIQUE FOR NON–LEFT MAIN CORONARY BIFURCATION LESIONS
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(A)
(B)
Figure 5 Bifurcation that requires the elective implantation of a SB stent. (A) Baseline
angiogram of the LAD-D1 bifurcation; (B) final
result after drug-eluting stent (DES) implantation inthe proximal LAD and one long DES atthe
ostium-proximal segment of the diagonal branch
using the modified T stenting technique, and
followed by final “kissing balloon” inflation.
51
Figure 6 Original Medina classification.
52
Tab le 1 Side Branch Lesions are Usually Angiographically Short
TULIPE (12) Sirolimus (3)
Patients (n) 187 85
Reference (mm) 2.3 ± 0.5 2.1 ± 0.3
Lesion length (mm) 3.7 ± 3.3 5.3 ± 4.2
Stenosis SB (%) 52 ± 17 52 ± 19
ALBIERO AND BOLDI
(A)
(D)
Figure 7 Side branch occlusion after main branch stent implantation using the provisional stenting strategy.
(A) Baseline angiogram in the LAO caudal view of the LCx-OM1 bifurcation showing the difficult SB take-off with
an angle >70
predilation; (D) side branch predilation; (E) angiogram after predilation of both branches; (F) final angiogram after
main branch stenting showing side branch occlusion.
◦
;(B) baseline angiogram in the RAO caudal view of the LCx-OM1 bifurcation; (C) main branch
(B)
(E)
(C)
(F)
ratio, relating mother-vessel diameter (Dm) and the daughter-vessel diameters, by the formula
Dm =0.678 (Dd1 + Dd2), one daughter-vessel diameter can easily be calculated when the other
daughter-vessel diameter and the mother-vessel diameter are known. Moreover, this formula
can be very useful for evaluating the correct mother (proximal reference)-vessel diameter in a
bifurcation lesion when both daughter-vessel diameters are known.
Plaque Distribution
Atherosclerotic plaque in human coronary arteries is localized almost exclusively on the outer
wall of one or both daughter vessels at major bifurcations, where the flow is either slow or
disturbed with the formation of slow recirculation and secondary flows and where Wall Shear
Stress (WSS) islow. Pathologic studiesin coronary arteries showthat the atherosclerotic plaques
are located mainly along the inner side of the curved coronary arteries, close to the areas of low
shear stress. Regions exposed to the nonuniform low shear stresses develop early atherosclerotic lesions, whereas areas exposed to uniform high shear stresses are protected (15–22). Consequently, atherosclerotic plaque usually develops in both branches opposite the flow divider
(23–26), which is almost always free of disease, due to the atheroprotective effect of high shear
PROVISIONAL STENTING TECHNIQUE FOR NON–LEFT MAIN CORONARY BIFURCATION LESIONS
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5.5 mm
(B)
53
L
(A)
(C)
Figure 8 Carina is not involved by atherosclerosis. (A) Angiogram of the LCx-OM bifucation (Medina 1,1,0). (B)
IVUS shows that the carina is the largest segment of bifurcation: arrow indicates the largest diameter (5.5 mm)
between the outer wall of the main branch and the outer wall of the side branch ostium; (C) IVUS shows that the
carina is minimally involved by atherosclerotic plaque (P), which is localized on the outer wall of the main branch.
The two small arrows indicate the flow divider (carina).
Abbreviations
: P, plaque; L, lumen.
stresses (27–30). In an intravascular ultrasound (IVUS) study in left main bifurcations in 73
patients (31), angiography suggested that the flow divider (carina) was involved in 61%, while
IVUS showed that the carina was spared in all 73 patients. Our personal IVUS observations
(Figs. 8 and 9) confirm these findings. We have therefore modified the Medina classification on
the basis of these results, removing the plaques at the level of the carina (Fig. 10).
Understanding the pattern of plaque distribution in coronary bifurcations has led to
technique modification that increased the likelihood of success with provisional stenting.
PROVISIONAL SIDE BRANCH STENTING STRATEGY
Provisional stenting consistsof stenting themain branch first,followed, if necessary, by delivery
of asecond stent to the sidebranch through themain branch stent in aclassic T (32), TAP (T And
small Protrusion) (33), inverted Culotte (34,35), or Internal Crush configuration (36) (Fig. 11).
The advantageof this approach is thatthe use ofa second stentis only provisional.In the MADS
classification (treatment description techniques of coronary bifurcation lesions published in a
consensus paper from the first European Bifurcation Club meeting; Ref. 11), the acronymof this
technique is A (Main Across side first).
P
54
ALBIERO AND BOLDI
1.
2.
3.
P
P
4.
(A)
Figure 9 Carina is not involved by atherosclerosis. (A) True bifurcation lesion (Medina 1,1,1) in the mid-LAD
involving the ostium of diagonal branch; (B) IVUS performed before stenting shows that the flow divider (carina)
(images 4. and 5.) is not involved by the atherosclerotic plaque (P), which is localized (C) on the outer wall of one
or both daughter vessels, where wall shear stress (WSS) is low.
(B)
5.
6.
7.
P
(C)
1,1,1 1,1,0 1,0,1 0,1,1
1,0,0
Figure 10 Modified Medina classification based on IVUS and pathologic observations: atherosclerotic plaque in
bifurcations is distributed on the outer walls of the mother and daughter vessels, sparing the flow divider (carina).
The plaques at the level of the carina have been removed.
0,1,0
0,0,1
PROVISIONAL STENTING TECHNIQUE FOR NON–LEFT MAIN CORONARY BIFURCATION LESIONS
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55
1
2
3
45
1
2
3
4
6
7
7a
7b
7c 7d
Figure 11 Procedure for treatment of bifurcations using a provisional stenting strategy. 1. Wires are advanced
in both the distal main vessel and the side branch. 2. The main vessel is predilated if necessary.
the side branch is avoided when possible. 3. A stent is deployed in the main vessel, jailing the wire in the side
anch. 4. Once the main vessel result is seen to be satisfactory, the side branch is rewired: this maneuver is
br
performed using the main branch wire by pulling it back slowly from the main vessel (guidewires exchange) or
by using a third wire and pointing the tip toward the side branch ostium with the intention to cross into the side
branch through the distal strut closest to the flow divider. 5. The “jailed wire” is withdrawn from the side branch
and pushed distally in the main branch. 6. A kissing inflation is systematically performed in order to open the
stent struts to cover the ostium of the side branch, while preserving the result in the main vessel. 7.Ifatthis
point there is normal (Thrombolysis in Myocardial Infarction flow grade 3) flow in the side branch and <50%
residual angiographic stenosis, this marks the end of the procedure; if this is not achieved, a second stent is
deployed in the side branch. The side branch stent crosses the struts of the first stent and is deployed in a simple
T configuration (7a). To achieve complete ostial side branch lesion coverage, especially after a proximal cross
and kissing balloon, the second stent can be implanted slightly protruding into the main branch (T And Protrusion,
TAP) (7b) or with internal crush configuration (7c), or by using an inverted culotte technique (7d) followed in all
cases by a final kissing inflation to correct any possible main branch stent deformation.
Predilation of
Wiring Both Branches
Provisional SB stenting strategy begins with wiring of both branches (Fig. 11,1), selecting
guidewires with good torquability, steerability, and adequate support. The BMW 0.014 wire
(Abbott) is our first choice. Polymer-coated guidewires, such as the Choice PT, PT2, and PT
Graphics (Boston Scientific), can be used in the presence of tortuosity, calcifications, or difficult
access to side branch. However, we do not recommend to leave polymer-coated guidewires
“jailed” because of the possible risk of wire fracture during retrieval (a theoretical concern that
has not been corroborated), especially when the distal tip is severely bended. When polymercoated wiresare required to access the sidebranch, we recommend to use other polymer-coated
wires such as Whisper (Abbott) or Fielder (Asahi), or they can be exchanged for a BMW after
the first polymer-coated wire has modified the side branch angulation: in fact after wiring, a
T-shaped can become a Y-shaped bifurcation.
56
ALBIERO AND BOLDI
Predilation
The main vessel is then predilated if required (Figure 11,2).
Predilation of the side branch is
avoided when possibleand performedonly in the presence of severe ostial stenosis, unfavorable
extreme angulation of the side branch take off, severe calcification, or a long significant lesion
(>3–5 mm).
of the
Data from the TULIP (12) and the SURF registry (37) have shown that predilation
side branch is not a predictive factor for “strut rewiring” success and for side branch
angiographic success. <P>Predilation is also dependent on the planned strategy after main
branch stenting with regard to the performance of kissing balloon inflation.
r
When final kissing balloon inflation is planned, we recommend avoiding side branch predilation. The reason not to predilate the side branch with this strategy is that the plaque in
coronary bifurcations (see above) is localized almost exclusively on the outer wall of one or
both daughter vessels (23–26), with the flow divider (carina) almost always free of disease
(27–30). After main branch stenting, the carina (free of disease) is displaced/shifted toward
the side branch ostium facing the intact (not disrupted by predilation) plaque on the outer
wall of the side branch. Therefore, during the subsequent step (rewiring the side branch),
would be much easier for the operator to cross into the side branch through the stent
it
strut at the tip of the flow divider (distal cross) (Figs. 12 and 13). Rewiring the side branch
through this point of the bifurcation will guarantee optimal side branch ostium scaffolding
after subsequent kissing balloon inflation.
r
On the other hand,if final kissing balloon inflationis not planned, a stepwise strategy issuggested with the firststep beingthe systematicballoon angioplastyof theside branchfollowed
by stenting of the main vessel (38). The drawback of this latter strategy is that predilatation
of the sidebranch could create a dissection that could hamper guidewire recrossing through
the main branch stent strut and increase the risk of crossing a proximal strut (proximal
cross) (Fig. 14), which may lead to deformation of the main branch stent during subsequent
kissing balloon inflation and increasing the odds of needing provisional stent implantation
[Fig. 15(A)and 15(B)]. Inthis latter scenario,to optimally scaffold the side branchostium, the
provisional side branch stent typically protrudes into the main branch, creating a neo-carina
in the main vessel [Fig. 16(D)], with potentially increased risk of stent thrombosis.
(A) (B)
Figure 12 Stent implantation in a true bifurcation (Medina 1,1,1) without side branch predilation. (A) Atherosclerotic plaque is located on the outer wall of the mother and daughter vessels; (B) after main branch stenting the
flow divider (carina) is shifted (
carina shift, because the guidewire will cross the stent strut exactly at the tip of the flow divider (
short arrow
). Side branch predilation should be avoided to take advantage of the
long arrow
).
PROVISIONAL STENTING TECHNIQUE FOR NON–LEFT MAIN CORONARY BIFURCATION LESIONS
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57
(A)
(D)
(C)
(B)
Figure 13 Stent implantation in a true bifurcation (Medina 1,1,1) without side branch predilation. (A)Inthe
baseline angiogram,the atherosclerotic plaqueis depicted aslocated on theouter wall of themother and daughter
vessels; (B) after 3.0 × 23 mm stent implantation at 12 atm with a jailed wire in the side branch the flow divider
(carina) is shifted; (C) magnification of part B showing the carina shift (
kissing), the tip of the wire will cross through the stent into the side branch exactly at the tip of the flow divider
(carina, shifted); (D) kissing balloon inflation; (E) final optimal angiographic result after single stent implantation
and kissing balloon: the side branch ostium is optimally scaffolded by the struts of the main branch stent.
arrow
). During guidewire exchange (before
(E)
(A) (B) (C)
Figure 14 Stent implantation in a true bifurcation (Medina 1,1,1) with side branch predilation. (A) Atherosclerotic
plaque is located on the outer wall of the mother and daughter vessels; (B) side branch predilation dissects
the atherosclerotic plaque; (C) after main branch stenting and carina shift (
(induced by side branch predilation) to rewire the side branch through a proximal strut (
short arrow
), there is the possibility
arrow
; proximal cross).
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