A New Miniature Catheter with Side-Holes for Percutaneous Transradial or Transbrachial Coronary Angiography

The percutaneous arm approach through the radial or brachial artery is becoming more popular throughout the world for left heart catheterization and coronary angiography as a safe alternative to the standard cut-down brachial arteriotomy and the percutaneous axillary and femoral artery techniques.1–3 This technique has advantages, such as a lower incidence of access-site complications and decreased patient discomfort due to earlier ambulation after the procedure, particularly when small-diameter catheters are employed.2,3 High-quality coronary angiography requires the injection of radiographic contrast material at an adequate rate and volume to transiently replace the blood contained in the involved vessel with the slight but continuous reflux into the aortic root.4 Too vigorous an injection can cause complications such as coronary dissection.4 When smaller-diameter catheters are employed, high-flow jets of contrast material may increase the incidence of such complications.4 To avoid this type of complication, we designed and developed new small-diameter [4 French (Fr)] catheters with side-holes (Trail, Fukuda Denshi Co. Ltd., Tokyo, Japan). We demonstrated that the pressure produced against the vascular wall by the jets of contrast material exiting from the end-hole was substantially decreased in catheters with side-holes as compared to catheters without side-holes. In a preliminary clinical study, this new miniature catheter was feasible and effective for percutaneous transradial coronary angiography. Methods Under conditions similar to a clinical coronary angiography situation, we attempted to examine the pressure produced by jets of contrast material both in catheters with and without side-holes. While the contrast material is injected into the coronary arteries, the tip or end-hole of the catheter is often pushed and damped against the vascular wall with the force produced by the catheter’s elasticity. The jets exiting from the end-hole can produce pressure against the vascular wall, which may cause vascular injury such as dissection. Therefore, we measured the pressure produced by jets under the constant force with which the catheter was pushed against the vascular wall. Furthermore, we examined how the injection rates of contrast material affected the relationship between the force and the pressure. Design of new catheters with side-holes. In JL-type catheters, the first side-hole (0.6 mm in diameter) was created at 3 mm from the tip of the catheter, and a second hole of the same size was created 2 mm from the first. Both holes were located on the outer side of the catheter’s curvature (Figures 1A–1C). In JR-type catheters, two side-holes (0.6 mm in diameter) were created at 3 mm from the tip and were located on the opposite, lateral sides of the curvature (Figures 1D-1F). Measurement of force of catheter tip produced by elasticity. We first measured the force of the tip of a conventional end-hole JL-type, 4 Fr catheter produced by its elasticity when the catheter was fixed at an angle of 120° (Figure 2). We repeated the measurement in 5 different catheters in a water bath of 37°C, and the mean value was 10.0 gf. Measurements of pressure produced by jets. At forces ranging between 0 and 15 gf under a constant injection rate (2.0 ml/s), and at injection rates ranging between 2.0 and 3.5 ml/s under constant force (10 gf), we measured the pressure produced by jets of contrast material in 4 Fr catheters (1.38 mm outer diameter and 1.00 mm inner diameter) with and without side-holes. We analyzed how the presence of the two side-holes affected the pressure and how their location modified the pressure. The straight (without curvature in either JL- or JR-types) catheter was vertically held on the plate with constant force (Figure 3), and the end-hole of the catheter was horizontally faced toward the cylinder which was attached to the pressure sensor (AP-13, Keyence Corporation, Osaka, Japan). The internal diameter of the cylinder was the same as a 4 Fr catheter. The length of a spring (Young’s modulus = 4.18 gf/mm) was changed so that the force with which the tip of the catheter was pushed against the cylinder was 0.0, 5.0, 10.0 or 15.0 gf, and the force was maintained constant at each level during the injection of contrast material (Force Gauge; VFG-2000, Shinko Electronics, Odawara, Japan). The contrast material (Imagenil 350, Yoshitomi Pharmacy Co. Ltd., Tokyo, Japan; viscosity = 8.1 mPa.s at 37°C) was injected at rates ranging between 2.0 and 3.5 ml/ms by means of an autoinjector (M-800C, Nemoto Kyourindou Co. Ltd., Tokyo, Japan). These measurements were performed in a water bath of 37°C to simulate the relationship between the force and the pressure in the coronary artery. Results The presence of side-holes substantially decreased the pressure at forces ranging between 0.0 and 15.0 gf when measured at a constant injection rate of 2.0 ml/s by an autoinjector (Figure 4A). There was no significant difference in the pressure between the JL- and JR-type catheters, although the location of the side-holes differed between the 2 types of catheter. These data indicate that the location does not affect the pressure produced by the jets of contrast material. The pressure measured at a constant force (10.0 gf) was decreased by the presence of side-holes at all injection rates, but the location of the side-holes did not affect the injection rate-pressure relationship (Figure 4B). In a preliminary study, we employed the new catheter with side-holes for coronary angiography by a percutaneous transradial approach in 107 patients. Contrast material (volume = 7 ml; injection rate = 2.5 ml/s) was distributed into the left anterior descending coronary artery through the end-hole and into the left circumflex artery through the side-holes (Figure 5), although the tip of the catheter was damped against the vascular wall. Furthermore, the left main coronary artery was also clearly imaged by the slight but continuous reflux of the contrast material into the aortic root. Thus, we obtained left coronary angiograms using the new catheters with side-holes. Vascular complications such as dissection were not observed in these 107 patients. As shown in Figure 6, the right coronary arteries were clearly imaged even in a case in which the tip of the catheter was damped at right angles against the vascular wall (volume = 5 ml, injection rate = 2.5 ml/s). Figure 7A shows an angiogram obtained in a patient with a large left coronary artery. The artery was imaged with 7 ml of contrast material at an injection rate of 2.5 ml/s. Also, a large dominant right coronary artery was clearly imaged after 5 ml of contrast material was injected at a rate of 2.5 ml/s (Figure 7B). Discussion Smaller diameter (4 or 5 Fr) catheters are often employed for percutaneous transradial,1 transbrachial2,3 or transulnar5 coronary angiography. In these cases, high-flow jets of contrast material exiting from an end-hole toward the coronary arterial wall may increase the incidence of complications such as dissection.4 Using conventional 4 Fr catheters, we performed percutaneous transradial coronary angiography in 2,573 patients from January 1997 through December 1997. For this period, we experienced 3 cases of dissection of the left coronary artery and 1 case of dissection of the right coronary artery. As a solution to the problem of high-flow jets in general angiography, Daniel et al.6 proposed that the jets can be modulated by altering the catheter design, that is, the size and configuration of the end-hole and side-holes. In this study, we designed and developed new, small-diameter catheters with side-holes for coronary angiography. Both in JL- and JR-type catheters, we created 2 side-holes that were 0.6 mm in diameter. The 2 side-holes were located on the outer side of the curvature in the JL-type catheter, and on both lateral sides of the curvature in the JR-type catheter. The presence of 2 side-holes substantially decreased the pressure produced by jets in both types of catheters, and their location did not affect the pressure. At present, it is not clear how high-flow jets cause vascular complications during angiography. Single or multiple factors such as the velocity and thickness of the jets, the angle of the jets to the vascular wall, the distance between the vascular wall and end-hole, and the force or pressure produced by the jets against the vascular wall would contribute to the occurrence of complications. To examine the effect of side-holes on the jets of contrast material, Daniel et al.6 measured flow rates through the end-hole and side-holes of 5 Fr catheters under simulated physiologic arterial pressure. In this study, we measured the pressure produced by jets exiting from the end-hole of 4 Fr catheters in a water bath as a function of the force with which the catheters were held and as a function of the injection rate, and analyzed the effects of side-holes on the jets. Baim and Grossman4 reported that the volume and injection rate of contrast material necessary to obtain high-quality images averaged 7 ml at 2.1 ml/s in the left and 4.8 ml at 1.7 ml/s in the right coronary artery. Therefore, we examined the effect of side-holes on the pressure produced by jets at injection rates ranging between 2.0 and 3.5 ml/s. Also, we measured the force produced by the elasticity of the catheters (10.0 gf), and then obtained the relationship between forces ranging between 0.0 and 15.0 gf and the pressure produced by the jets. When the tip or end-hole of a catheter is pushed and damped against the coronary arterial wall, the pressure produced by jets exiting from the side-holes may cause arterial complications. In this study, we did not measure the relationship between the force and the pressure produced by the jets exiting from the side-holes. In the clinical situation, the pressure would probably be low, since a catheter in the coronary artery can easily move in a direction transverse to the catheter. In a clinical preliminary study, we usually obtained images with 7 ml of contrast material at a rate of 2.5 ml/s in the left coronary artery and with 5 ml at 2.5 ml/s in the right coronary artery. These volumes and rates are comparable to those usually used for coronary angiography.4 In the future, we should systematically assess how the presence of side-holes affects the quality of images of the right and left coronary artery in a large number of patients. There seem to be several disadvantages and advantages in the new catheters with side-holes. The first side-hole was located 3 mm from the tip, and the second one was located 2 mm from the first hole in JL-type catheters; both side-holes were located at 3 mm from the tip in JR-type catheters. The new JL-type catheters particularly have to be relatively deeply inserted into the coronary ostium in order to allow the side-holes to inject contrast material into the coronary artery. In patients with severe ostial stenosis, we therefore have to be careful because the sign of pressure damping is absent. In the JL type catheter, contrast material was evenly injected into the left anterior descending artery through the end-hole and into the left circumflex artery through the side-holes which were faced toward the artery. Even in the case of a short left main coronary artery, we could obtain a high-quality coronary angiogram because the velocity of the jets was decreased by the presence of side-holes. In addition, the contrast material exiting from the side-holes enabled good visualization of the coronary ostia and proximal coronary branches. The distribution of contrast material through the end-hole and side-holes decreased the incidence of dislodgement of the catheter from the coronary ostia which might otherwise be caused by the increased velocity of contrast material.7 In fact, the incidence was decreased from 10.0% (conventional catheters without side-holes) to 0.9% (new catheters with side-holes) in the left and from 17.5% to 3.7% in the right coronary angiography. Further studies are needed to clarify the advantages and disadvantages of the new miniature catheters with side-holes as compared to conventional catheters without side-holes. In summary, we designed and developed new miniature catheters with side-holes, and the catheters appeared to be feasible and effective for percutaneous transradial coronary angiography.

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