Stabilization of Coronary Stents Using the Floating-Wire Technique

Abstract: Aims. Excessive movement of coronary stents within the artery can make accurate stent placement difficult. This study assessed the use of the floating-wire technique to reduce stent motion to improve placement accuracy. Methods and Results. During percutaneous coronary intervention, if excessive stent movement prevented accurate stent placement, the floating-wire technique was performed to reduce stent motion within the coronary artery during both stent positioning and deployment. Postprocedural angiograms were analyzed by two independent operators to measure the motion length of the stent delivery system relative to the coronary artery before and after using the floating-wire technique. The floating-wire technique was considered necessary in 19 patients. No procedural complications occurred. The extent of motion was markedly reduced by using the floating-wire technique (4.04 ± 1.25 mm to 1.11 ± 0.81 mm; P<.001). Conclusions. The floating-wire technique is an effective and safe method to reduce stent movement and facilitate accurate stent deployment. This simple technique can be easily applied in any interventional cardiac catheterization laboratory without the need for additional training or equipment. 

J INVASIVE CARDIOL 2015;27(11):497-500

Key words: percutaneous coronary intervention, stent, floating-wire technique

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Accurate placement of intracoronary stents is necessary to treat discrete stenotic lesions of coronary arteries during percutaneous coronary intervention (PCI), particularly in the treatment  of ostial and bifurcation lesions. However, in some cases, the precise positioning of the stents is prevented by excessive movement of the stent within the artery due to myocardial contraction. Inaccurate stent placement may result in incomplete target-lesion coverage or may cover a previously uninvolved branch vessel. There are several methods to reduce the cardiac-cycle related movement of the stent delivery system, including deep guide-catheter engagement, partial balloon inflation of the stent delivery system,¹ and rapid right ventricular pacing.^2-4 However, it sometimes remains difficult to reduce this movement because of the higher amplitude of cardiac-cycle dependent motion. In the present study, we first assessed the safety and efficacy of the floating-wire technique to reduce stent motion during deployment and improve the accuracy of stent placement.

Methods

Study population. The patients in this study were selected from a series of 646 patients who underwent PCI from October 2013 to September 2014. Stent movement was considered excessive if it was >3 mm after deep engagement of the guide catheter into the coronary artery. Difficulty was encountered in precise positioning of the stent in 19 consecutive patients due to cardiac-cycle dependent extensive movement of the stent delivery system. We applied the floating-wire technique to achieve precise stent delivery in these 19 patients. This study was performed in compliance with the Declaration of Helsinki with regard to investigations in human subjects, and the study protocol was approved by the ethics committee of our hospital.

Study protocol. Coronary angiography and PCI were performed using the standard radial approach. All patients received intravenous administration of heparin prior to the procedure. After the stent delivery system was placed around the target lesion, the catheter was carefully withdrawn to disengage the tip. Next, the second wire was advanced into the aortic root, where it remained floating. The catheter was then advanced over the vessel wire, with constant forward pressure against the shaft of the floating wire to maintain alignment adjacent to the ostium (Figure 1). After final positioning, a coronary arteriogram was recorded and the stent was deployed. Following the procedure, digital angiograms were analyzed using commercially available quantitative coronary angiography (QCA) software (QAngio XA; Medis Medical Imaging Systems). Movement of the stent relative to an anatomical reference point in the diseased vessel (usually a side branch) was measured before and after application of the floating-wire technique. 

Statistical analysis. All data are given as mean ± standard deviation. All statistical analyses were performed using SPSS 14.0 software. The extent of motion of the stent delivery system before and after application of the floating-wire technique was compared using the Student’s paired t-test (two-group t-test). P<.05 indicated statistical significance.

Results 

Patient and lesion characteristics. The floating-wire technique to stabilize the coronary stent and facilitate accurate stent placement was carried out in 19 patients (19 lesions) in whom pulsatile movement hindered correct stent placement. Table 1 summarizes the patient and lesion characteristics. The mean age of the study patients was 55.4 ± 7.6 years. One patient presented with stable angina, 10 patients with unstable angina, and 8 patients with acute myocardial infarction. This technique was mainly applied in PCIs for the right coronary artery (84.2% of cases). The proximal segment was treated in 57.9% of cases, the medial segment in 26.3%, and the distal segment in 5.3%. Lesions were ostial in 10.5% of these cases. The mean vessel diameter was 3.32 ± 0.50 mm and mean lesion length was 23.21 ± 6.98 mm. The mean minimal luminal diameter prior to stent implantation was 0.41 ± 0.28 mm.

Safety and efficacy of the floating-wire technique. Implantation was considered successful in all cases and no procedural complications occurred. As shown in Table 2, the mean stent excursion for all patients before application of the floating-wire technique was 4.04 ± 1.25 mm; after application of the floating-wire technique, this was reduced to 1.11 ± 0.81 mm (P<.001). Mean movement ranged from 2.40-7.23 mm before application of the floating-wire technique and from 0.10-2.82 mm after application of the technique. The mean difference in stent movement before and after the floating-wire technique was 2.92 ± 1.30 mm. 

Representative case. A 63-year-old man presented with acute non-ST segment elevation myocardial infarction. Emergent coronary angiography showed thrombotic occlusion at the proximal portion of the right coronary artery (Figure 2A). PCI was performed with aspiration thrombectomy followed by coronary artery stenting via routine radial approach using a 6 Fr Judkins right 4.0 guiding catheter. However, the attempt to stent the discrete stenotic lesion with a 3.5 x 18 mm Firebird 2 stent (MicroPort Medical Company, Ltd) was met with difficulty due to excessive cardiac-cycle related movement of the stent delivery system, and the stent movement could result in incomplete target-lesion coverage (Figures 2B and 2C). The deep guide-catheter engagement failed to prevent the stent movement. The floating-wire technique was then performed to reduce the movement of the stent delivery system. The motion of the stent delivery system relative to the right coronary artery disappeared almost completely after the technique was performed (Figures 2D and 2E). The stent was implanted successfully after accurate positioning and postdilatation was performed with the help of the floating-wire technique. Final angiographic appearance was good, with no residual stenosis (Figure 2F).

Discussion

Our results suggest that the floating-wire technique is associated with a significant reduction in stent motion before stent deployment and facilitates accurate stent placement. In this small series, the floating-wire technique was not associated with any complications.

Imprecise stent positioning may result in incomplete target-lesion coverage or may cover healthy coronary segments. In some cases, poor stent positioning means that a second stent is needed to cover the entire target lesion. Some studies have indicated there is a higher risk of stent thrombosis and restenosis associated with longer stent length.^5,6 Therefore, stent displacement during angioplasty can lead to a suboptimal outcome and increase the complication rate.

Various techniques have been described to facilitate accurate stent placement. The most commonly used techniques include deep guide-catheter engagement, placement of a parallel guidewire,⁷ partial balloon inflation of the stent delivery system,¹ and rapid right ventricular pacing.^2-4 However, despite useful applications in select situations, each of the above procedures has its own limitations. Deep guide-catheter engagement may cause pressure damping or coronary vessel injury, and the catheter tip may extend into the segment requiring stent coverage. The partial inflation of a stent balloon at low pressure to create friction between the stent delivery system and the vessel wall can reduce the stent motion during cardiac cycle, but precise stent placement may still remain challenging due to uncertainty of the stent expansion. Moreover, partial stent deployment may increase the risk of stent loss or deformation within the coronary artery. Right ventricular pacing by catheters is not always without complications. It can cause ventricular perforation, cardiac tamponade,⁸ and vascular access-site complications. Other disadvantages of this technique are the longer procedure time and greater consumption of material resources. In addition, if there is a reasonably sized side branch proximal to the lesion, a second wire (anchor-wire technique) or a following balloon (anchor-balloon technique) can be inserted deeply into this branch to fix the stent position. However, the potential for vessel injury, such as dissection, may complicate the techniques.

In this study, we described a novel method of coronary stent immobilization by floating wire. In the procedure, after the floating wire was advanced into the aortic root, the catheter could be advanced over the vessel wire with constant forward pressure, which significantly increased the stability of the entire device system, and this may be the main mechanism for reducing the stent motion. There are many advantages of this technique, such as simplicity of operation, short learning curve, short procedure time, and low cost. Moreover, the floating wire can prevent deep engagement of the guide catheter, thus avoiding damage to the coronary artery ostium and limitations in coronary flow, and thereby may be especially suitable for cases of aorto-ostial stenosis. 

In the present study, this technique was mainly applied in PCI of the right coronary artery. The reasons may be as follows: (1) In right coronary artery PCI via the radial access route, the Judkins right catheter is the most frequently used guide catheter. However, this catheter cannot contact the contralateral aortic wall at all and its back-up force is much weaker when compared with the guiding catheter for the left coronary artery, so the stability of the entire device system is poor and the stent delivery system is more prone to movement. (2) When difficulty is encountered in stent positioning during left coronary artery PCI, some adjunctive techniques, such as the anchor-wire or anchor-balloon technique, can be used to reduce stent movement. However, the above adjunctive techniques are less suitable to be used in facilitating exact stent placement in the right coronary artery because there is no reasonable side branch. Thus, the floating-wire technique may be more suitable for use in right coronary artery PCI to reduce stent movement.

Conclusion

The floating-wire technique is an effective and safe method to reduce stent movement and facilitate precise stent positioning when this is prevented by extensive movement of the stent delivery system in association with the cardiac cycle.

References 

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3.     Okamura A, Ito H, Iwakura K, et al. Rapid ventricular pacing can reduce heart motion and facilitate stent deployment to the optimal position during coronary artery stenting: initial experience. EuroIntervention. 2007;3:239-242.

4.     O’Brien DG, Smith WH, Henderson RA. Stabilisation of coronary stents using rapid right ventricular pacing. EuroIntervention. 2007;3:235-238.

5.     de la Torre-Hernández JM, Alfonso F, Hernández F, et al. Drug-eluting stent thrombosis: results from the multicenter Spanish registry ESTROFA (Estudio ESpañol sobre TROmbosis de stents FArmacoactivos). J Am Coll Cardiol. 2008;51:986-990.

6.     Goldberg SL, Loussararian A, De Gregorio J, Di Mario C, Albiero R, Colombo A. Predictors of diffuse and aggressive intra-stent restenosis. J Am Coll Cardiol. 2001;37:1019-1025.

7.     Katoh O, Reifart N. New double wire technique to stent ostial lesions. Cathet Cardiovasc Diagn. 1997;40:400-402.

8.     Nashed G, French B, Gallagher D, et al. Right ventricular perforation with cardiac tamponade associated with use of a temporary pacing wire and abciximab during complex coronary angioplasty. Catheter Cardiovasc Interv. 1999;48:388-389.

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From the Cardiovascular Department, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang Province, People’s Republic of China.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted January 19, 2015, provisional acceptance given March 6, 2015, final version accepted March 18, 2015.

Address for correspondence: Yongtai Gong, MD, Cardiovascular Department, The First Affiliated Hospital of Harbin Medical University, No. 23 Youzheng Street, Nangang District, Harbin, Heilongjiang Province, 150001, PR China. Email: gongth@126.com