Abstract
Background
Loss of side-branch vessels is a serious complication following stent implantation in parent vessels of bifurcation lesions. The purpose of this study was to introduce and test a new stent design for the protection of side-branch vessels in the management of bifurcation lesions.
Methods and materials
This stent has multiple radio-opaque markers in its central portion, whose presence is useful in avoiding stent-strut placement across the side-branch orifice and in correctly directing the insertion of a second guide wire through the struts into the side branch to minimize jailing of side branches during stent deployment in the parent vessel. In vitro tests of the acrylic resin bifurcation phantom model were performed under fluoroscopic guidance in the catheterization laboratory with 10 stents with multiple radio-opaque markers and 10 stents without. Kissing balloon angioplasty was performed across the side branch after stent implantation in the parent vessel in both groups. Side-branch jailing by the stent (presence of any stent struts crossing the side-branch orifice) was determined visually and compared between the two groups.
Results
The jailed side branch with the stent struts was observed in one of 10 new stents and in five of 10 conventional stents without them.
Conclusions
The in vitro tests demonstrated the superiority of a new stent design for the reduction of side-branch jailing in bifurcation lesions.
Percutaneous coronary intervention for coronary bifurcation lesions is considered technically challenging and has historically been associated with lower procedural success rates and worse clinical outcomes than for nonbifurcation lesions . Several studies recommend a one-stent rather than a two-stent technique for the management of bifurcation lesions even in the era of drug-eluting stents . When the one-stent technique is used, there are risks of occlusion or significant narrowing of side-branch vessel immediately after stent implantation in the parent vessel for bifurcation lesions. Several mechanisms including plaque shift, carina shift, or side-branch jailing by stent struts may contribute to occlusion or significant narrowing of the side-branch vessel . When currently available stents with tubular design are deployed in the parent vessel across side branches, whether or not side-branch jailing occurs cannot be adequately predicted. If side-branch jailing could be avoided by a special stent design, it may decrease the occurrence of side-branch occlusion. For this reason, a special stent to avoid jailed side branches was designed and its immediate applicability was tested in this study.
1
Methods
1.1
Stent design
The status of optimal stent-strut placement on the side-branch orifice could not be determined because of the poor radio-opacity of each stent strut in commercially available stent designs. Several outcomes are expected from the complete absence to severe side-branch jailing by the stent struts crossing the side-branch orifice. However, presence of some landmarks within the stent structure that discriminate each strut may allow specific stent positioning to avoid jailed side branches. Radio-opaque markers are useful in guiding stent placement with minimal stent struts crossing the side-branch orifice before stent deployment and in directing the insertion of a second guide wire through the stent struts into the side branch to avoid side-branch jailing after stent implantation in the parent vessel. A diagram of a new stent which has multiple radio-opaque markers is shown in Fig. 1 (HJ Stent). These radio-opaque markers are located on the central one-third of commercially available stents. Three radio-opaque markers located on the connecting bridges or specific segment of the stent struts are positioned in the same vertical line at circumferential intervals of 120°. The other three markers are located in the adjacent connecting bridges. Three rather than one or two radio-opaque markers in the same vertical line are more helpful to overcome directional rotation for accurate targeting of radio-opaque markers to avoid jailing of side branches by stent struts. With two rows of radio-opaque markers, one row with radio-opaque markers is accurately placed in the proximal part of the parent vessel and the other row with radio-opaque markers is adequately placed in the distal part of the parent vessel during and after kissing balloon angioplasty. They are also helpful to avoid jailing of side branches by stent struts. Stent struts were made of Co-Cr alloy (L605) with surface processing through electropolishing methods. Strut thickness was 80–90 μm and maximal strut orifice area was 12.5 mm 2 when a 3.0-mm stent was deployed. Radio-opaque markers were made of platinum.
1.2
In vitro testing
In vitro tests were performed under fluoroscopic guidance in an acrylic resin phantom model with a 45° angle between the parent and side-branch vessel in the catheterization laboratory . The bifurcation phantom model was connected with a 7F guiding catheter. A 0.014-in. guide wire was introduced into the parent vessel and a stent was deployed across the side-branch vessel under fluoroscopic guidance. A second guide wire was inserted through the stent struts into the side-branch vessel. Finally, kissing balloon angioplasty was performed. These tests were performed with 10 new stents and 10 conventional stents without radio-opaque markers. Side-branch jailing was defined as the presence of any stent struts crossing the side-branch orifice as determined visually. The incidence of side-branch jailing was compared between the two groups.
2
Results
When a new stent was deployed in the bifurcation phantom model, we attempted to place the stent in a way that avoids side-branch jailing by stent struts using radio-opaque markers for positioning before stent implantation in the parent vessel ( Fig. 2 A ). After stent implantation, the presence of radio-opaque markers around the side-branch orifice was helpful in correctly guiding the insertion of a second guide wire that passes through the stent struts into the side branch and in minimizing the occurrence of side-branch jailing ( Fig. 2 B). The result after final kissing balloon angioplasty is shown in Fig. 2 C.
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