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"Side Balloon Stenting": A Novel Technique for Bifurcation Lesions
November 2001
Coronary angioplasty procedures involving bifurcations are still challenges with no easy solutions. Kissing wire and balloon techniques,1-2 directional and rotational atherectomy3-8 and excimer laser angioplasty9 have not resulted in satisfactory short- or long-term outcomes,10–12 and have a rate of complications that are still too elevated.13–16
The utilization of coronary stents, in order to obtain a better bifurcation coverage and a lesser recoil at the ostium site, is another reliable approach, but well-known risks are side branch occlusion,17-18 the inability to cross the stent struts with the wire or the balloon to dilate the ostium of the collateral vessel, or to recross the struts in the main branch in the case of a “culotte” technique19-20 and, finally, balloon entrapment in the struts and stent loss. Technical improvements in stent design and delivery systems allow new approaches providing excellent scaffolding of the entire bifurcation.21-24
We describe a new technique to treat coronary bifurcations by stenting the main vessel alone, or both the main and side branches if necessary. The aim of this technique, called “side balloon stenting”, is to treat the bifurcation lesions with the kissing balloon technique, using one or more stents without removing the guidewires, which remain in place during stent delivery, thus avoiding side branch recrossing problems. In addition, implanting the stent using the kissing balloon technique would prevent the “snow-plow” phenomenon (plaque shifting) in the side branch. Another important aspect, in terms of procedural safety, is the difficulty of displacing and losing the stent from the delivery system during the various placement maneuvers or while withdrawing the system; this because the presence of the side balloon prevents the stent slipping on the balloons (Table 2).
Technique description. The stent is manually crimped on two balloons (the delivery system). One of these balloons, the “side balloon”, is passed through the stent’s struts at a distance from the distal end of the stent, which varies according to the lesion’s morphology (Figure 1). The choice of a stent mesh should be made on the basis of best plaque coverage; in other words, the operator will pass the side branch balloon through a more proximal strut if the bulk of the plaque is located mostly distal to the bifurcation (“more stent” after the bifurcation to cover the lesion); a more distal cell is preferable if the plaque is longitudinally distributed and mostly proximal to the bifurcation (Figure 2).
Theoretically, there are no limits to the length of the stent, but obviously, anything longer than 18–20 mm will pose trackability problems. You can use bare or premounted stents. Choosing the second ones, the stent is dilated at low pressure until full expansion is achieved; the stylet, usually present in the monorail tract of some of the balloons, is then inserted in the chosen cell of the stent; “the side balloon” is advanced along this stylet, in order to avoid crushing the internal lumen. Alternatively, one could use the proximal extremity of the intracoronary guidewire. Finally, the stent is manually crimped on both balloons aiming at creating the smallest possible profile (Figure 3).
Regarding the choice of stent diameter, one should bear in mind that the parent vessel tapers significantly distally to a side branch larger than 2.0 mm, and so no more than a 1:1 vessel (proximal to the lesion)/stent diameter ratio should be chosen preferentially. The side balloon should have a diameter proportional to that of the vessel (no more than a 1:1 vessel size to balloon size ratio) and the length should be equal or slightly shorter than that of the other balloon in the delivery system. When the angle between side and main branch is more than 70°, access to the side branch is usually more difficult (both for entering the side branch with the wire, as well as to advance the side-balloon system). To avoid guidewire crossing, we recommend that the most difficult branch (usually the side branch) should be wired first.
A large, lumen guiding catheter must be selected with a proper tip curve to allow insertion of two balloons, optimal ostium engagement, vessel visualization and back-up support (7–8 French size; Extra Backup, Voda or Amplatz curve). Extra supportive guidewires in at least one branch (or better in both) are a good choice as well as advancing them without excessive rotation to avoid wire twisting. It is also necessary to predilate all stenosed branches; this can be done with a slightly undersized semi-compliant balloon, which can be later used as a “side balloon” in the side balloon stent delivery system (Figures 4 and 5).
The system is now ready to be advanced into the coronary vessel across the lesion(s). In most instances, this maneuver is easily accomplished and the balloons will enter the two vessel bifurcations separately according to the pre-selected choice (stent in the main or straighter vessel and the balloon’s free portion in the side branch or vice versa) (Figure 4B). In any case, it will be useful to push gently but firmly (percussion-type) while holding the guides steady, to insure the complete advancement and to guarantee that, when separating the balloons, there will be a perfect apposition of the delivery system’s carina to the vessel bifurcation. The angiographic control must be done in two views to be sure that the bare part of the side-balloon is as advanced as much as possible, in order to assure an optimal alignment of the stent mesh with the side branch ostium.
When the system is properly positioned, the side-balloon should be inflated first at low pressure (3–4 atm) (Figure 4C). This maneuver will prevent or minimize the snow-plow phenomenon, which often causes side branch occlusion or suboptimal results; moreover, it will allow the best alignment of the stent’s strut with the ostium of the vessel and will hold the system in place. At least 50% of the final diameter should be achieved before inflating the second balloon to its nominal pressure. After this, both balloons can be fully inflated to achieve proper stent and struts expansion (Figure 4D). If necessary, a second stent may be implanted through the first using the same technique.
In order to achieve the best results with this technique, it is essential to observe some procedural rules regarding the choice of the guiding catheter, guidewires, balloons and stents; in this way, it is possible to prevent or resolve problems encountered during the procedure. In terms of the type of stents, the ones with a coil or ring structure are not adequate because, once dilated, it is very hard to recrimp them manually. In contrast, the slotted stents turned out to be adequate since they provided greater radial support even at the level of the mesh dilated against the side branch. The last generation stents [BX Velocity (Cordis Corporation, Miami Lakes, Florida); BeStent (Medtronic AVE, Inc. Santa Rosa, California); ACS Multi-link RX (Santa Clara, California)] have given the best results. In all, there were 34 stents utilized: 26 BX Velocity (Cordis Corporation), 4 ACS Multi-link, 1 ACS Tristar, 2 BeStent (Medtronic, Inc.) and 1 NIR Primo 7 Cells (Boston Scientific/Scimed, Maple Grove, Minnesota).
Limitations. The most common difficulty encountered is the twisting of guidewires, which, in two instances, resulted in technique failure. It is possible to resolve this problem by withdrawing one of the guidewires (preferably the one on which the side-balloon is advancing) inside the balloon, thus freeing the junction and then going back into the side branch or crossing over the lesion without recrossing the other guidewire. This maneuver can be done with the delivery system positioned inside the catheter or directly in the coronary vessel just above the lesion, as long as the hemodynamic conditions and the patient’s symptoms allow it. In this last instance, there is a greater probability of success.
Conclusion. Coronary angioplasty procedures involving bifurcations remain a challenge, despite refinements in PTCA technology. Side balloon stenting, as proposed in this paper, appears to be a feasible and safe novel technique in treating coronary bifurcation lesions.
In particular, it is the correct execution, awareness of its limitations, utilization of the appropriate devices and a short but necessary learning period, that make it certainly more advantageous than the traditional approaches (Table 2). A larger cohort of patients and long-term clinical and angiographic follow-ups are needed to validate this novel approach to a difficult problem.
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