The 4-in-5 Mother-Child Technique: 5 Fr Transradial Coronary Intervention for Complex Lesions Using a 4 Fr Child Catheter

Abstract: Small 5 Fr guiding catheters are now used in percutaneous coronary intervention (PCI). However, when treating severely calcified and/or tortuous complex coronary lesions, the back-up support of a 5 Fr guiding catheter is often insufficient. We previously developed a 4 Fr child catheter (Kiwami ST-01; Terumo Corporation) and proposed a 4 Fr double-coaxial technique (“mother-child” configuration) to facilitate stent implantation in treating complex coronary lesions. In this manuscript, we report 2 cases of 5 Fr transradial coronary intervention in which stent delivery failed with conventional techniques. In these 2 cases, our 4 Fr double-coaxial technique was employed, and stents were successfully delivered to the target lesions. To the best of our knowledge, this is the first report demonstrating the potential of the 4-in-5 technique during 5 Fr PCI.

J INVASIVE CARDIOL 2013;25(8):406-408

Key words: new techniques, coronary interventions, stenting

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Recent advancements in the technology of manufacturing angioplasty devices have enabled the use of small guiding catheters, such as 4 Fr and 5 Fr sizes. Due to their small diameters, however, these guiding catheters have limitations with regard to back-up support. As a result, stent delivery sometimes fails when treating severely calcified lesions and/or tortuous vessels using small guiding catheters. In such conditions, several techniques, including deep engagement of the guiding catheter and the use of a buddy wire, have been employed. However, operators are often forced to use larger guiding catheters.

We previously reported that the use of a 4 Fr guiding catheter (the “child” catheter) with a 6 Fr guiding catheter (the “mother” catheter) would facilitate stent implantation during treatment of severely calcified or tortuous lesions.¹ In this case report, we employed a 4 Fr child catheter (Kiwami ST-01; Terumo Corporation) with a 5 Fr mother catheter (Figure 1), and successfully treated lesions for which back-up support of a 5 Fr guiding catheter was insufficient and conventional techniques failed to deliver stents. To the best of our knowledge, this is the first report demonstrating the potential of this 4-in-5 technique.

Case 1

The first case was a 75-year-old woman complaining of chest pain on exertion. Previously, she had undergone endovascular aneurysm repair (EVAR) for thoracoabdominal aortic aneurysm. Diagnostic angiography revealed severe narrowing (Figure 2A, open arrow) in the distal right coronary artery (RCA). Percutaneous coronary intervention (PCI) was performed via the right radial artery. Since she had a narrow radial artery, a 5 Fr guiding catheter was chosen. Following engagement of a 5 Fr, Heartrail II, BL 3.5 guiding catheter (Terumo Corporation) into the RCA, the lesion was crossed with a Runthrough Hypercoat guidewire (Terumo Corporation) and dilated with a 2.5 x 15 mm Sprinter Legend balloon (Medtronic). Although a 3.0 x 15 mm Endeavor Sprint stent (Medtronic) was advanced, it failed to cross the mid-RCA even after balloon dilatation (Figure 2B). Therefore, a 4 Fr child catheter (Figure 2C, arrow) was advanced using an anchor-balloon technique, after which the Endeavor Sprint stent was successfully delivered to the distal RCA through the child catheter. After deployment of the stent, the child catheter was pulled back to the mid-RCA (Figure 2D, arrow) and an additional Endeavor Sprint stent (3.0 x 24 mm) was delivered (Figure 2E). Postdilatation of both stents was performed with a 3.0 x 10 mm NC Quantum Apex balloon (Boston Scientific) at 24 atm. Intravascular ultrasound (IVUS) and angiography confirmed sufficient expansion of each stent (Figure 2F). 

Case 2

The second case was a 61-year-old man who presented with effort angina. Diagnostic coronary angiography revealed moderate narrowing (Figure 3A, open arrow) in the proximal left anterior descending artery (LAD). After engagement of a 5 Fr BL 3.5 guiding catheter into the left coronary artery, a Runthrough Hypercoat guidewire was advanced. After predilatation of the lesion with a 2.5 x 15 mm Trek balloon (Abbott Vascular), a 3.5 x 24 mm Endeavor Sprint stent was advanced. However, the stent failed to pass the proximal bend of the LAD (Figure 3B). A 4 Fr Kiwami ST-01 was inserted into the 5 Fr guiding catheter and advanced close to the lesion using an anchor-balloon technique. With the 4 Fr child catheter (Figure 3C, arrow), the stent could easily pass the proximal bend and was deployed. Angiography confirmed optimal dilatation of the target lesion (Figure 3D). 

Discussion

The use of a small guiding catheter may reduce puncture-site injury and procedural complications such as bleeding and pseudoaneurysm.² In addition, the small inner diameter may also decrease the volume of contrast media required. However, as the diameter decreases, the back-up support decreases as well. This can result in failure of stent delivery. 

To overcome insufficient back-up support of guiding catheters, several techniques have been proposed.³ These techniques include active/passive guiding-catheter support, wire support, the anchor balloon technique, the Tornus device (Asahi Intecc), and the Proxis catheter (St Jude Medical). Among these techniques, active/passive guiding catheter support and wire support are currently applicable for 5 Fr PCI.⁴

In the cases reported herein, stent delivery failed despite mild bending and stenosis, probably due to insufficient back-up support of the 5 Fr guiding catheter. We therefore employed a 4-in-5 technique and successfully delivered the stents. We recently demonstrated that the support of a guiding system nearly doubles when a 4 Fr child catheter is advanced through a 5 Fr mother guiding catheter in vitro.¹ With this technique, the maximum support power of the guiding system becomes almost equal to that of a 6 Fr guiding catheter. In addition, a deeply inserted child catheter acts like a stent delivery sheath. It is important to note that deep insertion of a 4 Fr child catheter does not usually compromise coronary flow because of the small size profile (outer diameter of 1.43 mm or 0.056˝).

The 4 Fr child catheter is currently available from 3 different manufacturers: the Kiwami catheter from Terumo Corporation, the Cokatte catheter from Asahi Intecc, and the i-Works catheter from Medikit. These 3 child catheters have similar specifications (length, 120 cm; inner diameter, 1.27 mm or 0.050˝), and their flexibility and trackability are optimized for deep insertion into the coronary artery. The only difference in these 3 catheters is the outer diameter. The outer diameter of the Cokatte catheter is 1.50 mm, whereas the Kiwami and i-Works catheters have outer diameters of 1.43 mm. Therefore, only the latter 2 catheters can be used as the child catheter with a 5 Fr mother guiding catheter. An inner diameter of >1.49 mm (0.059˝) is required for the mother guiding catheter to accommodate a 4 Fr child catheter. Among currently available 5 Fr guiding catheters, only the Heartrail II catheter from Terumo Corporation meets this requirement.

Potential complications exist with the use of the 4-in-5 system, and include stent dislodgment, myocardial infarction, target vessel dissection, wire perforation, and distal embolization.¹ Thus far, we have not experienced any of these complications. It should be noted, however, that during the initial learning curve of the 4-in-6 system (not the 4-in-5 system), we experienced stent dislodgment in 4% of cases.¹ 

Finally, as is the case in 4 Fr PCI, the small diameter of the 4 Fr child catheter limits the use of intravascular ultrasound and some of the coronary stents.⁴ For example, 3.5 mm or larger Nobori stents (Terumo Corporation) and S stents (St Jude Medical) are not compatible with the 4 Fr child catheter. In addition, there would be a strong friction when advancing 3.5 mm or larger Xience Prime stents (Abbott Vascular) and Multi-Link 8 stents (Abbott Vascular) through the 4 Fr catheter. It is also important to note that certain techniques, such as kissing-balloon inflation and use of a buddy wire, are not allowed with the 4-in-5 mother-child system.

References

1. Takeshita S, Shishido K, Sugitatsu K, et al. In vitro and human studies of a 4F double-coaxial technique (“mother-child” configuration) to facilitate stent implantation in resistant coronary vessels. Circ Cardiovasc Interv. 2011;4(2):155-161.
2. Faqih B, Beaudry Y. Pseudoaneurysm: a late complication of the transradial approach after coronary angiography. J Invasive Cardiol. 2000;12(4):216-217.
3. Di Mario C, Ramasami N. Techniques to enhance guide catheter support. Catheter Cardiovasc Interv. 2008;72(4):505-512.
4. Takeshita S, Shiono T, Takagi A, Ito T, Saito S. Percutaneous coronary intervention using a novel 4-French coronary accessor. Catheter Cardiovasc Interv. 2008;72(2):222-227.