Efficacy of Lacrosse NSE Using the “Leopard-Crawl” Technique on Severely Calcified Lesions

Abstract: Calcified lesions often encounter difficulties associated with stent delivery and underexpansion. Lesion preparation of calcified lesions prior to stent implantation is important to facilitate stent delivery and provide concentric stent expansion. The Lacrosse NSE, a balloon catheter with 3 nylon elements, provides an efficacious scoring effect when used for predilatation of calcified lesions. Although bench testing on a calcified model verified that Lacrosse NSEand other scoring catheters provide a greater scoring effect compared to conventional plain old balloon angioplasty, delivery to target lesion location using standard delivery techniques for severely calcified lesions is typically more problematic. One method for overcoming the obstacles faced by difficult delivery is use of the “leopard-crawl” technique. This technique uses a low inflation pressure to create a wedge into the calcification and then subsequently advances the catheter during balloon deflation to facilitate catheter delivery across the stenosis. This technique is well suited for the Lacrosse NSEdue to the unique catheter design. We hereby report on the initial clinical use of the leopard-crawl technique for facilitating catheter delivery in cases of severely calcified lesions in which standard delivery was unsuccessful, while creating an efficacious scoring effect into the calcified lesion that reflects the results of bench testing.

J INVASIVE CARDIOL 2013;25(10):555-564

Key words: calcified lesion, leopard-crawl technique, intravascular ultrasonic imaging, CT angiography

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The scope of cases treated with PCI has increased with further advances in medical devices and techniques. However, treatment of calcified lesions by PCI remains problematic,^1-3 with difficulties associated with stent delivery, underexpansion, and asymmetric expansion resulting in worse patient prognosis. Therefore, it is considered that predilatation to create multiple scoring effects into the lesion prior to stenting leads to better stent expansion.^4,5 

Recently, the novel Lacrosse NSE catheter(Goodman Co, Ltd) has become commercially available. The catheter contains three triangular nylon elements (width, 0.014˝; height, 0.015˝) that are free floating on the outside of the balloon surface, and attached proximal and distal to a 13 mm balloon length. Dilatation using a Lacrosse NSE creates a scoring effect into calcified tissue through a focused transmission of force through the elements. An investigation was performed into the   dilative effect of various types of commercially available scoring balloons on fully circumferential calcified models.

Unfortunately, current designs of scoring balloons result in reduced functionality in regard to delivery in comparison to conventional balloons, and difficulties associated with delivery and lesion crossability of scoring catheters occur in a clinical setting.⁶ The Lacrosse NSE elements are attached distal to the balloon location, and for instances whereby the catheter is unable to cross lesion location, a “leopard-crawl” technique can assist in facilitating device delivery. The efficacy of the leopard-crawl technique in crossing calcified lesions in a clinical setting is also further addressed.

Methods

Testing method for identifying scoring effect. Twelve cylindrical tubes (inner diameter, 3.0 mm; thickness, 0.7 mm; approximate length, 7.1 mm) comprised of New Diastone Yellow (dental stone; Morita Co, Ltd) (Figure 1) and covered by silicone tubing (thickness, 1.0 mm) were used to represent a calcified lesion (Figure 2) (calcified models were provided by Goodman Co, Ltd). Three catheters of each of the following devices were dilated within the calcified models: 3.5 x 10 mm Powered Lacrosse non-compliant balloon (Goodman Co, Ltd); 3.5 x 13 mm Lacrosse NSE scoring balloon; 3.5 x 10 mm Flextome cutting balloon; and 3.5 x 10 mm Scoreflex (Orbus Neich Medical). Inflation pressure, total number of cracks, and dimensions (longitudinal length) were recorded (Figure 3). 

Results

A cracking effect was observed for the various scoring balloons during inflation from nominal burst pressure (NBP) to rated burst pressure (RBP), with multiple cracks observed for two of the scoring devices. For the scoring balloons, both Lacrosse NSE and the Flextome cutting balloon incurred cracking in at least 2 locations and throughout the entire calcified model for all units. The Scoreflex balloon incurred cracking in 1 location throughout 1 calcified model, with partial cracking observed in others (Figure 3).

In comparison, a cracking effect was observed for only 1 non-compliant balloon when inflated beyond RBP, with the remaining calcified models not incurring any visible cracking effect at the maximum 30 atm inflation pressure.

Optical coherence tomography (OCT) imaging was performed on all calcified models, with measurements relating to the number and length of cracking recorded. Cracking of less than 2 mm in length was observed on the inner luminal wall for a calcified model inflated by a non-compliant balloon (with no cracking observed from the outside) (Figure 4). 

In comparison to the non-compliant balloon, the expansion function of both the Lacrosse NSE and Flextome cutting balloon catheters determined a reproducible, efficacious cracking effect. The Scoreflex device produced only a single cracking effect throughout the length of the calcified model, failing to create multiple cracking effects considered necessary to ensure optimal stent expansion (Table 1). 

The triangular shape of the Lacrosse NSE elements provides for a greater transmission of force at the apex of the element into the target lesion during balloon expansion (Figure 5) compared to the shape of other scoring device elements. 

The Leopard-Crawl Technique

Device requirements. For cases whereby the Lacrosse NSE catheter is unable to cross the culprit lesion, a low inflation pressure provides for indentation of the calcification, which allows the catheter to be advanced further into the target lesion during balloon deflation. Repeating this process facilitates catheter delivery across the target lesion (Figure 6). This is considered an effective technique given the preconditions of: (1) a low profile of the distal catheter that allows the tip to be advanced to the lesion location; and (2) a good re-wrap functionality of the balloon or tapering to provide multiple inflations at the calcified location.

Construction of the Lacrosse NSE

The Lacrosse NSE consists of three elements attached distal to the balloon segment. Given that the elements extend beyond the balloon (approximately 9 mm from marker to location of connection), provided the catheter can be delivered proximally to the target lesion location, an inflation of the balloon facilitates a cracking effect from the very distal portion of the elements (Figure 7). The Lacrosse NSE elements extend beyond the balloon, allowing for rewrapping of the balloon given the distance between balloon shoulder and distal segment. When undertaking the leopard-crawl technique, the Lacrosse NSE profile is derived from the structure of the elements and not the deflated balloon, thus providing a lower profile post inflation. 

Following Lacrosse NSE deflation, the connection of elements located distal to the balloon folds similar to the folding mechanism of an umbrella, with the distal profile derived from the size of the folded element. The elements refold parallel to the body of the catheter, ensuring that the Lacrosse NSE distal portion maintains a low profile. In comparison, other scoring balloons have either: (1) fewer elements, making multiple scoring effects difficult; or (2) a blade contained within the balloon segment affecting the rewrap functionality.

A larger balloon profile post inflation affects the ability to perform the leopard-crawl technique (Figure 8). 

Case Reports

Case 1. An 81-year-old male presented to our facility complaining of shortness of breath with exertion. Coronary computed tomography (CT) angiography (Figure 9) and coronary angiography (Figure 10A) determined a severely calcified, long diffuse lesion of the left anterior descending (LAD) coronary artery. Using a right femoral approach, a 7 Fr Vista XC Brite Tip 4.0 guiding catheter (Cordis Corporation) was used to engage the left coronary artery (LCA) with a Sion guidewire (Asahi Intecc) crossed through the LAD. Intravascular ultrasound (IVUS) imaging determined fully circumferential calcification from the mid-LAD (Figure 11C). A 2.5 x 13 mm Lacrosse NSE was selected for predilatation, but was unable to cross the calcified location. The NSE was inflated at 4 atm and advanced further into the lesion location during deflation (Figure 10B). The process was repeated (Figures 10C and 10D), resulting in the NSE catheter successfully crossing the lesion site, and subsequent dilatation of the lesion was performed at 14 atm. Following predilatation, IVUS imaging showed two locations of plaque disruption within the fully circumferential calcified lesion (Figure 11). A 3.0 x 24 mm Nobori stent (Terumo Corporation) was implanted at 12 atm in the mid-LAD, with a 3.5 x 24 mm Endeavor Sprint (Medtronic Vascular) implanted at 14 atm in the proximal location. A 3.75 mm NC Sapphire (Orbus Neich Medical) was used for postdilatation and IVUS was performed to confirm a good final result (Figure 2).

Case 2. A 68-year-old male patient presented with effort angina. Coronary CT angiography (Figure 13) and coronary angiography (Figure 14A) determined a severely calcified, long diffuse lesion in the right coronary artery (RCA). Using a right femoral approach, a 7 Fr Mach1 Amplatz left short-tip Curve Styles guiding catheter (Boston Scientific) was engaged into the RCA and a Sion guidewire crossed through the lesion. IVUS imaging determined severe calcification from the proximal RCA. A 3.0 mm Lacrosse NSE was selected for predilatation, but was unable to cross the lesion location. A 6 atm inflation was performed and the catheter was able to be advanced during deflation (Figure 14B). This process was repeated until the catheter fully crossed the lesion (Figure 14C). A 14 atm inflation was performed and successful expansion of the lesion was achieved. Both IVUS (Figure 15C) and optical coherence tomography (Figure 15D) confirmed a cracking effect in 2 locations. A 3.5 x 28 mm Xience Prime LL (Abbott Vascular) was implanted at 14 atm in the mid-RCA and a 3.5 x 15 mm Endeavor Sprint was implanted in the proximal RCA at 16 atm (Figure 15A). IVUS confirmed a good result, completing the procedure (Figure 16).

Case 3. An 85-year-old male presented to our institution due to shortness of breath with exertion. Coronary CT angiography (Figure 17A) and coronary angiography (Figure 17B) determined a severely calcified, long diffuse lesion of the RCA. Using a right radial approach, a 6 Fr Heartrail II Ikari Right 1.0 guiding catheter (Terumo Corporation) was engaged to the RCA and a Sion guidewire was crossed through the lesion. Both the IVUS catheter and a 2.25 mm Lacrosse NSE were unable to cross the lesion. Due to inadequate guiding catheter support, a Runthrough NS Extra Floppy guidewire (Terumo Corporation) was used to undertake a double-wire support technique (Figure 17C). Again, the IVUS catheter was unsuccessful in crossing the lesion and the leopard-crawl technique was performed using the Lacrosse NSE. Repeating a 6 atm inflation followed by advancing the catheter during deflation resulted in successfully crossing the lesion (Figures 17D and 18A). The Lacrosse NSE was inflated from distal to proximal at 12-14 atm. IVUS confirmed a 2 mm fully circumferential section of calcified plaque at the minimal luminal diameter, with multiple cracks of the calcified plaque observed (Figure 18D). Two Endeavor Sprint stents (3.5 x 15 mm and 3.5 x 24 mm) were implanted from mid to proximal RCA at 12 atm. Postdilatation with a 3.75 mm NC Voyager (Abbott Vascular) was performed at 22 atm (Figure 8C) with IVUS confirming good stent expansion and apposition (Figure 19). 

Discussion

The advent of the drug-eluting stent (DES) has led to a reduction in restenosis, which is considered the Achilles’ heel of percutaneous coronary intervention. However, treating severely calcified lesions remains problematic.^1-3 For severely calcified lesions, not only is stent delivery often difficult, stent underexpansion and eccentric stent expansion occur,⁷ which result in higher restenosis rates⁸ and are considered a contributing factor of stent thrombosis.² Moussa et al reported that delivery of a DES is comparatively more difficult than a bare-metal stent (BMS),⁹ and while lumen asymmetry at time of stent deployment does not impact neointimal hyperplasia,¹⁰ other reports indicate that an increase in luminal asymmetry results in a worsening of coronary flow and worse clinical outcomes.^11-14

Creating a scoring effect in calcified lesions during predilatation is considered advantageous for stent implantation. Bench testing of a calcified model with the Lacrosse NSE showed multiple cracking effects throughout the entire length of the model, which provided adequate stent expansion. However, delivery of a Lacrosse NSE to the lesion location in a clinical setting is more difficult than a conventional balloon. Using a step-by-step dilatation approach as outlined by the leopard-crawl technique, which is highlighted in the above-mentioned case reports, increases the deliverability of the Lacrosse NSE catheter in severely calcified lesions and provides another treatment option for calcified lesions. 

Ability to create cracking effect in calcified lesions. The Lacrosse NSE elements, which are triangular in shape, are ideal for creating a cracking effect for calcified lesions given that the force provided by the apex is greater than that of other elements (Figure 5). The height of the elements (0.0155˝) in the Lacrosse NSE is greater than in other scoring balloons, providing an effective working height for creating a scoring effect. 

Calcified lesions are often observed in tortuous vasculature. The design of the Scoreflex catheter is subject to a potential “slacking” phenomenon, and is also unable to create multiple scoring effects. The Flextome cutting balloon lacks flexibility, with an increased risk for causing vessel rupture given the higher stress burden on the inner curvature during straightening of the vessel caused by inflation of a tortuous section of vasculature.^15,16 The Lacrosse NSE easily conforms to tortuous vasculature, with a comparatively lower burden on the inner curvature side.

Leopard-crawl technique using the Lacrosse NSE. When creating multiple cracking effects in a calcified lesion, the selection of an appropriate Lacrosse NSE size is determined by the lumen at the location of calcification, ensuring that high-pressure inflation of the elements in healthy vasculature is avoided. 

Generally, the Lacrosse NSE can be safely and effectively used for calcified lesions through
selection of a catheter size that limits expansion to a smaller size than the adventitia or media. Confirmation of vessel diameter and luminal size of the calcified lesion using multidetector CT or IVUS imaging prior to percutaneous coronary intervention is preferable; however, when multidetector CT is not undertaken, size selection based on 25%-50% less than the vessel diameter at calcified location determined by coronary angiography is considered a safe alternative.

Lesion characteristics determined by coronary CT angiography or IVUS (if the catheter can be successfully crossed) are used for reference. Coronary CT can confirm the distribution of calcification, and determine wire bias, balloon selection, and sizing. Typically, when utilizing the leopard-crawl technique, the balloon is naturally directed toward the outer curvature; when the outer curvature contains minimal calcification, a smaller balloon size is selected or inflation is performed at low pressure. After the Lacrosse NSE has been delivered to the distal location, retrieving the catheter will result in the balloon naturally passing closest to the inner curvature. High inflation pressure is then applied as the catheter is dilated from distal to proximal, depending on the distribution of calcification on the inner curvature and thickness of calcified plaque. Initial confirmation of calcification distribution and vessel lumen diameter and shape helps reduce risk of perforation given that the elements come into contact with other plaque material.

The lumen area of the calcified location is used to determine balloon sizing for a fully circumferential calcified lesion. However, given 180-270° of calcification, a low plaque component without calcification (minimal difference between lumen and vessel wall) would require a quarter size down, and given a larger degree of plaque material (greater plaque thickness), a quarter size up is considered more appropriate.

Balloon inflation pressure should commence from a low inflation and increase slowly (4 atm to 6 atm to 8 atm). A rapid, high-pressure inflation may result in cracking of the healthy vessel component, and it is important to consider the potential risk of vessel rupture.

Careful consideration of both sizing of the Lacrosse NSE and the inflation pressure applied (ie, the type of expansion achieved during inflation and observation of plaque shift from either inner or outer curvature) is important. 

Advancing the device during balloon deflation following a low inflation pressure can result in successfully crossing the target lesion. Removal of any slack in the guidewire and improvement in guide catheter positioning can also be effective in delivering the catheter when advancing during deflation. If initial IVUS imaging can be performed, it provides information relating to catheter positioning. Furthermore, catheter positioning can be determined from the position of the calcification observed under angiography without IVUS imaging, and using low inflation pressure the catheter can slowly and safely be advanced. As the elements extend beyond the balloon segment, there is potential to cause expansion beyond the length of the balloon. However, the leopard-crawl technique utilizes a small balloon size at low inflation pressure, minimizing the risk of causing injury beyond the target lesion. After successfully delivering the Lacrosse NSE to the distal site, dilatation using higher pressure can be performed to treat the target lesion.

When the segment of vasculature immediately distal to the target site involves a tortuous vessel, there is potential for the element to contact one side of the vessel wall and cause a dissection beyond the lesion site, requiring the use of a longer stent than initially planned.

Balloon inflation at a healthy site of the vessel will result in the balloon shifting to a concentric position prior to the elements coming into contact with the vessel wall, minimizing trauma to the wall caused by the elements.

The leopard-crawl technique will not succeed when the catheter tip is unable to advance to the target lesion. In this circumstance, either a double-wire technique or use of a low-profile semicompliant balloon may facilitate use of the leopard-crawl technique and create a scoring effect into the target lesion calcification.

The Lacrosse NSE was selected for 72 consecutive lesions (stable angina; 48 males; 180-360° calcified lesions determined by coronary CT; n = 39 LADs, 11 LCXs, and 22 RCAs) that due to severe calcification were determined difficult to cross and dilated by standard plain old balloon angioplasty. Of all cases requiring use of the leopard-crawl technique, delivery failure occurred in 3 cases. Two cases involved lesions in the LCX, with severe tortuosity of the proximal vessel (left anterior oblique caudal view showing >90° angulation of the LCX). Given that delivery of a conventional balloon would also be problematic, catheter delivery was performed with a double-wire technique, but was unsuccessful in delivering the catheter. A short, conventional balloon was used for anchor ballooning while a mother-in-child technique was able to deliver the Lacrosse NSE to the lesion location. In particular with LCX cases involving severely tortuous vessels, typically, delivery of a conventional balloon, stent, or Lacrosse NSE is difficult without the guidewire stretching out the vasculature, requiring the development of new techniques or improvement to length of currently available balloons. The remaining case involved a long, severe calcification of the LAD. The vessel contained a short section of s-shaped vasculature with calcification, which prevented the catheter tip from advancing through the lesion location. All cases involved tortuous vasculature that negatively influenced delivery, and it is considered that the development of a short-tip Lacrosse NSE could be advantageous in such situations.  

Conclusion

The bench model validated the dilative effect of the Lacrosse NSE, and the leopard-crawl technique has proven to be an effective strategy to deliver the Lacrosse NSE catheter. The design of the Lacrosse NSE complements this type of delivery technique, and is able to effectively create a cracking effect into calcified lesions following successful catheter delivery. 

Acknowledgment. Calcified models used in bench testing and ANSYS analysis of elements were provided by Goodman Co, Ltd.

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From the Department of Cardiology, Yokohama Shintoshi Neurosurgical Hospital, Yokohama, Japan.

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 March 28, 2013, provisional acceptance given April 22 2013, final version accepted May 28, 2013. 

Address for correspondence: Kazuhiro Ashida, MD, PhD, 433 Edacho, Aoba-ku, Yokohama-shi, Kanagawa, Japan. Email: kazuhiro.ashida@gmail.com