The Transradial Approach for Bifurcation Lesions


Cath. size

Devices

Techniques

Radial compatibilitya (%)

5F

Ballons ≤5 mm

No kissing balloon

100
 
Microcatheter
   
Stents ≤4.5 mm
   
IVUS
   
Rota 1.25 mm
  
6F

All coronary balloons

Kissing balloons (compliant or NC)

86.9
 
All coronary stents

Two microcatheters
  
Cutting/scoring balloon

Microcatheter and monorail B.
  
Rota ≤1.75 mm

Anchoring balloon
  
Most protection devices
   
Tornus
  
7F

Angioguard

Kissing stent

76.9
 
Rota 2 mm

Microcatheter and IVUS
 
8F

Rota >2 mm
 
64.7


aY Louvard, Population of 150 french people with echographic diameter measurement of radial artery



The support provided by a 6 or 5 F guiding-catheter at the level of the coronary ostium can be improved by active support maneuvers like deep intubation on a wire. A 5 F catheter with no specific shape, longer than the guiding-catheter can be inserted co-axially in the coronary artery (5 in 6, mother and child) [38]. Monorail catheter extensions can be used for the same purpose (Guideliner [39], Guidezilla Boston Sc). With their inner diameter equivalent to 5 F guiding-catheters, these catheters can facilitate stent delivery distally, but they cannot be used in the treatment of coronary bifurcations (no kissing balloon, but balloon or stent plus a wire is possible).



16.3 Angioplasty of Coronary Bifurcations


Coronary trees are pseudo-fractal objects with assymetric bifurcation self replication up to the level of myocardial penetration. Each bifurcation is an anatomo-functional entity whose 3 diameters are ruled by Murray’s law [40, 41] modified by Huo-Kassab [42] and simplified by Finet [43].

In each of the three segments of a bifurcation there is a linear relation between the diameter, the length of the distal segment, flow, and the vascularized myocardial mass. Any anatomical variation may result in a functional change.

Coronary bifurcation sites are prone to the development of atheroma [44, 45]. Proximal to the bifurcation, blood flow is laminar with a transversal diastolic flow profile and maximal velocity in the mid-segment. Flow is less rapid along the vessel walls where a high level of friction exerts a protective effect against the atheroma. In coronary bifurcations, flow is rapid and wall shear stress is high at the level of the flow divider whereas flow is turbulent, recirculating with low wall shear stess on the walls of the main vesel (proximal and distal) and the side branch opposite the flow divider. This accounts for the fact that the flow divider is initially free of atheroma.


16.4 Definition, Classifications, Designation, Measurements and Imaging of Coronary Bifurcation Lesions


The European Bifurcation Club (EBC) adopted a simple and open definition: a coronary bifurcation lesion is a coronary artery narrowing occurring adjacent to and/or involving the origin of a significant side branch. A significant side branch is a branch that you do not want to lose in the context of a specific patient.

Medina’s classification [46] (Fig. 16.1) proposed in 2006 and adopted by the EBC is simple and well suited to research purposes and provides a thorough description of lesion characteristics. In order to describe a bifurcation lesion accurately, it is necessary to designate the side branch (SB) from the two distal vessels. Coronary bifurcations can be described using Medina’s classification (e.g., LM, Circ, LAD where LAD is considered as the SB) [47].

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Fig. 16.1
Medina classification

A classification of the various bifurcation treatment strategies [48] (Fig. 16.2) was established by the EBC based on the positioning of the first stent (MADS). The techniques used are defined according to final stent positioning. This classification does not include balloon maneuvers such as kissing, or the Proximal Optimization Technique (POT) used to give a cross-over stent selected according to the distal diameter of the main vessel its proximal diameter corresponding to the proximal diameter of the vessel.

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Figs. 16.2
(a) MADS classification based on the final position and the order of deploiement of stent(s) in a bifurcation. Bifurcation techniques are classified by stategy defined by the position of the first stent. All the techniques described have been published or reported. In the (a) figure are the “straight” techniques, in (b) are the “inverted” techniques, distal main vessel (normally the biggest, longest …) is exchanged with the side branch. Not all the wires and balloons maneuvers are described

As described previously, coronary arteries do not have a linear reference diameter from the ostium to the distal segment but the diameter between two bifurcations is constant with a stepped reference function (Figs. 16.3 and 16.4). Conventional QCA software produce erroneous data on reference diameters (interpolated reference) especially in the vicinity of bifurcations and when the analysis is performed from the proximal segment of the vessel towards the SB [48]. There are currently at least two software programs dedicated to bifurcation lesion analysis [49, 50]. For some operators, angiographic data in bifurcations do not provide adequate information about the vessel wall and the extent of atheromatous plaque. However, although the benefit of endocoronary echography has been recently highlighted in a meta-analysis [51], potential improvements in the results of coronary bifurcation stenting under systematic IVUS guidance or CT scan have not yet been demonstrated in large randomized trials. Optical Coherence Tomography (OCT) could prove a useful tool for procedure guidance as this technique allows very rapid 3D reconstruction of the artery and the implanted stent [52].

A327643_1_En_16_Fig3_HTML.jpg


Fig. 16.3
Description of a dedicated bifurcation software. The reference diameter of the proximal main to distal main vessel (left) or proximal main vessel to side branch (right) is no more linearly decreasing like in former QCA software (dotted red line) but stepped at the level of the bifurcation (reconstruction). The diameter is deducted from the automatically detected vessel contour. The standard QCA software decreases the stenosis rate proximal to the bifurcation and strongly increases it distally specially when the design is done from proximal main vessel to side branch


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Fig. 16.4
Stepped of the provisional strategy. After wiring the two branches, a stent choosen from the diameter of the distal main vessel is implanted across the SB, then a big balloon according to the diameter of the proximal main vessel is deployed in the proximal part of the stent (distal marker in front of the carena), then the wires are safely exchanged, the main vessel wire prepared with a long shape is entering the side branch through the most distal stent cell and the SB wire is de-jailed and push in the main distal vessel (loop). Then a kissing balloon inflation can be performed with short and non-compliant balloons adapted to the two distal diameters. Finally a decision is taken about the need for stenting the side branch


16.5 One or two Stents in a Bifurcation?


This issue has generated a large number of publications involving bare metal stents and drug-eluting stents [53]. Of the seven randomized trials conducted with DES, six have shown that systematic double stenting does not provide any benefit [5456].

A Chinese study (DK-Crush) on complex lesions (true bifurcation lesions with significant stenosis in both branches) showed a 1-year difference in terms of repeat revascularization in favor of the double stenting strategy following, however, systematic coronary angiography at 8 months (known to provoke a higher rate of reintervention) [57, 58].

Provisional SB stenting is currently the gold standard strategy for the treatment of bifurcation disease not involving the left main and when access to the SB is possible [59].

The results of several registries suggest that a similar approach to treatment of distal left main lesions could be considered [60, 61].


16.6 How to Implement the Provisional Stenting Strategy


Figure 16.5 shows the different steps of this strategy. The first step consists in deploying a stent directly or following predilatation, in the main artery through the side branch into which a wire has been previously inserted. The stent size should be selected according to the distal diameter of the main branch in order to avoid carena shift towards the side branch and occlusion of the side branch. Predilatation of a diseased SB has long been the subject of debate, as it carries a risk of dissection potentially requiring a change of strategy. Following stent deployment, the proximal segment is inevitably malapposed in the proximal main vessel, which may require guide wire exchange outside the stent, and neutralize the biological effect of the DES whilst increasing the risk of thrombosis. In order to address this issue, it is necessary to implement the proximal optimization technique (POT) before any guide wire exchange. This technique consists in the complete deployment of the proximal stent segment using a balloon matching the proximal diameter of the vessel. The balloon must be short in order to prevent the occurrence of geographic miss. Any additional treatment of the SB depends on the results of subsequent angiographic examination, namely, the presence of symptoms, EKG changes, occurrence of dissection, or a suboptimal result in relation to the size of the vessel. Angiographic assessement of the result is always difficult due to the fact that the lumen of the SB ostium which is normally round, becomes oval or is reduced to a slit and is always visualized in the worst possible angiographic view. FFR [62, 63] measurement or OCT show that the SB lesion is not significant in most instances. In such cases, Kissing balloon inflation is carried out with balloon diameters matching the size of the two distal branches using a non-compliant balloon in the SB in order to avoid excessive dilatation [64]. The Kissing technique can be replaced by successive inflation of two balloons in order to avoid stent distortion due to inflation in the SB only. This strategy allows the deployment of a second stent in the SB when necessary, by using either the T stenting or the TAP technique (T and Protrusion) according to the partial protrusion of the main branch stent into the SB [65]. This can be clearly visualized using the stent enhancement technique [66].

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Fig. 16.5
Relative simplicity of the DK-Crush technique


16.7 Bifurcation Stenting Through Transradial Approach: Case Exemples


Most bifurcation techniques can be performed through transradial approach, including techniques beginning with side branch stenting. Some techniques are more comfortable with 7 F guiding catheters which can be used transradially (specially with a sheathless) like classical crush or TAP where a balloon is present in the main branch during stenting of the side branch. Classical crush is now clearly replaced by balloon crush technique or even better DK-crush technique. The only one technique that cannot be performed in 6 F is the SKS, simultaneous kissing stent, where two stents are delivered simultaneously with creation of a neo carena. This strategy has not been compared with other strategies in a randomized trial. We will illustrate the provisional stenting strategy in non-left main and left main bifurcation lesions with single or double stenting.


Conclusion

Radial artery is now a widely accepted approach for coronary interventional cardiology. It is known to reduce the risk of vascular complications, increased patient comfort and the best support for outpatient diagnostic or interventions. This approach has been adapted since 20 years to most patients, clinical settings, lesions and techniques with a potential of life saving in ST elevated acute coronary syndroms.

Coronary bifurcation stenosis stenting has been during the last 15 years the field of intense clinical research and strong controversies. The actual consensus is to try to minimize the number of implanted stents. The best way to reach this goal is to use the provisional SB stenting strategy beginning by a crossover mainvessel stenting across the side branch. Most studies and meta-analysis show that systematic SB stenting first has no advantage over provisional strategy and may be responsible of a higher rate of stent thrombosis. In some situations (difficult SB access…) DK-crush technique or Culotte technique can provide effective and safe treatment (Fig. 16.6).

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Fig. 16.6
Complexity of the Culotte technique (here the straight one, the inverted one being even more complex because of the diameter discrepancy between proximal and distal vessel)

Radial approach in 6 F allow the use of most bifurcation techniques (excepted SKS). In case of small radial artery a sheathless guiding catheter can be used.


References



1.

Radner S. Thoracal aortography by catheterization from the radial artery; preliminary report of a new technique. Acta Radiol. 1948;29(2):178–80.CrossRefPubMed


2.

Seldinger SI. Catheter replacement of the needle in percutaneous arteriography; a new technique. Acta Radiol. 1953;39(5):368–76.CrossRefPubMed

Sep 30, 2017 | Posted by in CARDIOLOGY | Comments Off on The Transradial Approach for Bifurcation Lesions

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