Use of a Novel Catheter, the MOT-C, for Selective Angiography of the Internal Mammary Artery From Ipsilateral Radial Access

Abstract

Objective. We describe a novel catheter, the MOT-C (Merit Medical Systems), for selective diagnostic angiography of the internal mammary artery from radial access. Methods. We analyzed the pattern of radial versus femoral access for bypass angiography at our institution between 2012 and 2020. We also examined the difference in contrast volume and fluoroscopy time between radial and femoral access and between MOT-C and traditional internal mammary artery (IMA) catheter for bypass angiography. Results. Since the introduction of MOT-C catheter to our laboratory in 2016, there has been a 1.5-fold increase in the use of radial access for bypass angiography. No significant difference in contrast volume or fluoroscopy time was noted between radial and femoral access for bypass angiography. The MOT-C catheter was successfully used in 46% of all cases and 77% of all radial cases between 2016 and 2020 to selectively engage the IMA. When compared with the traditional IMA catheter, no statistically significant difference was noted in contrast volume or fluoroscopy time with the use of MOT-C for bypass angiography, although there was a trend toward lower contrast use. Furthermore, no catheter-related complications occurred. Conclusions. The MOT-C facilitates improved engagement of IMA grafts with minimal manipulation and allows for high-quality diagnostic angiograms with a potential decrease in contrast volume compared with the more traditionally used IMA catheter.

J INVASIVE CARDIOL 2022;34(5):E408-E411. Epub 2022 April 8.

Key words: angiography, IMA grafts, radial access

The radial approach has gained increasing acceptance for ­selective angiography of coronary bypass grafts. Recent studies have shown that there is no significant difference in procedural time and fluoroscopy dose between radial and femoral approach for coronary bypass graft angiography.^1-3 However, angiographic catheters used for radial access are typically the same catheters used for femoral access, and graft engagement can be challenging, requiring conversion to femoral access. In the case of the internal mammary artery (IMA), the angle of the origin of the vessel from the subclavian artery can preclude selective engagement with the traditional internal mammary artery (IMA) catheter from ipsilateral radial access. We describe the use of a novel catheter, the MOT-C (Merit Medical Systems), for routine selective diagnostic angiography of the IMA from radial access.

Description of MOT-C catheter. The MOT-C catheter was designed by interventional radiologist Amir Motarjeme for thrombolytic therapy of the iliac arteries.⁴ The catheter is manufactured by Merit Medical and is available as a 4- or 5-Fr, 100-cm diagnostic catheter with an 0.040˝ inner lumen diameter and is available for routine clinical use. The catheter tip shape resembles a Rösch inferior mesenteric (RIM) catheter, but is available in a length that facilitates radial access angiography of the IMA (Figure 1A). The soft curve of the tip of the catheter approximates the angle of take-off of the IMA from the subclavian artery better than the traditionally used IMA catheter (Figure 2 and Supplemental Video).

Methods

A retrospective analysis of anonymized data from all patients who underwent bypass angiography at the VA Connecticut Healthcare System between 2012 and 2020 was performed. We analyzed the rate of radial vs femoral access for bypass angiography during this time period and compared contrast volume and fluoroscopy time between the 2 access sites using the Student’s t test. We also compared the contrast volume and fluoroscopy time between patients who underwent bypass angiography with MOT-C catheter and traditional IMA catheter.

Catheterization technique. The catheter is advanced over an 0.035˝ guidewire from radial or ulnar access into the ipsilateral subclavian artery just proximal to the IMA origin. The wire is removed and the catheter is gently withdrawn with its tip directed inferiorly toward the IMA, where it atraumatically engages the ostium of the vessel with excellent selectivity (Figure 2A). If the catheter is out of plane with the ostium of the IMA, gentle clockwise or counterclockwise rotation can be used to engage vessels with anterior or posterior take-offs. After selective angiography is performed, the catheter can be withdrawn into the subclavian and removed over a guidewire.

Results

Initial experience. Between May 2012 and May 2020, we performed bypass graft angiography in 506 patients in the VA Connecticut Healthcare System. Throughout the study period, radial access was employed in 182 cases (36%) and femoral access was used in 324 cases (64%). There was no significant difference in fluoroscopy time used for bypass angiography between patients who underwent radial and femoral access (14.89 ± 9.95 minutes vs 13.67 ± 8.55 minutes, respectively; P=.43). Furthermore, there was no significant difference in contrast volume used for bypass angiography between patients who underwent radial and femoral access (107.04 ± 68.56 mL vs 116.59 ±  53.65 mL, respectively; P=.17) (Table 1).

The MOT-C catheter was introduced to our laboratory in 2016. Since then, the rate of radial or ulnar access for bypass graft angiography at our laboratory increased significantly. Between May 2016 and May 2020, radial or ulnar access was used in 54% and femoral access was used in 46% of cases. This was a steep increase when compared with the rate of radial access over the preceding period of May 2012 to April 2016, when it was only 22% (Figure 3). Furthermore, there was no difference in the rate of conversion from radial to femoral access between the 2 periods. During the entire study period, 12 cases were converted from radial to femoral access and 11 cases were converted from femoral to radial access.

For the study period from 2016 to 2020, a total of 218 bypass angiograms were performed. The MOT-C catheter was used in 45% of all cases and 77% of radial cases to selectively engage the IMA (Figure 4). The right IMA was engaged in 3 of the 81 cases and bilateral IMAs were engaged in 1 case via right radial approach. There was no significant difference in the mean fluoroscopy time between patients who underwent angiography with MOT-C and IMA catheters (Table 2) and there was a trend toward less contrast use with the MOT-C catheter compared with the IMA catheter (94 mL vs 114 mL, respectively; P=.08). There were no documented adverse events, including IMA or subclavian artery dissection, related to diagnostic angiography.

Discussion

Radial access for coronary angiography is associated with improved clinical outcomes as compared with the femoral approach due to lower bleeding and major vascular complication rates.⁵ The radial approach is now considered by many operators to be the default strategy in the invasive assessment of patients presenting with acute coronary syndrome.⁶ However, the rate of radial access for coronary bypass angiography remains low even in high radial volume centers. In trials comparing radial and femoral access for bypass graft angiography, patients who had prior coronary bypass grafting were either excluded or significantly underrepresented.⁷

Anatomically, catheters entering the ascending aorta from the left subclavian artery or the descending aorta follow a similar trajectory, allowing for the use of the same preshaped catheters for radial or femoral coronary and bypass graft angiography. For selective angiography of the IMA, operators have historically used an IMA catheter, Judkins right, or VB1 catheter. However, for IMA vessels with acute angle take-offs or tortuous subclavian arteries, standard femoral access catheters may not adequately engage the ostium of the IMA from ipsilateral radial access requiring transition to femoral access or resulting in inadequate angiographic visualization. Radial-specific catheters such as the Yukimo (Goodman) have been developed for IMA engagement, but these are not widely available in the United States. The MOT-C has become a valuable tool for diagnostic angiography of the IMA at our facility due to the favorable shape for selective, atraumatic engagement. Notably, the catheter has been used by numerous trainees in our laboratory with varying levels of experience. Anecdotally, IMA engagement has been significantly easier with the MOT-C as compared with the IMA catheter. The introduction of the MOT-C catheter has been a significant factor in the transition to radial access as the default approach for bypass angiography in our lab. Since the introduction of MOT-C catheter to our lab in 2016, we noted a 1.5-fold increase in the rate of transradial approach for coronary bypass angiography and this rate increases every year.

To date, there has been only 1 randomized controlled trial comparing radial and femoral approaches in bypass angiography.⁸ This trial, RADIAL-CABG, found that radial access for diagnostic bypass angiography was associated with increased contrast volume, increased fluoroscopy and procedure times, increased radiation exposure, and a high cross-over rate, but on the other hand, higher patient satisfaction.⁹ However, other observational studies have found that the radial approach is associated with similar procedural time, fluoroscopy time, success rate, and contrast volume, and significantly lower rate of access-site complications as compared with the femoral approach.⁸ As we identify and utilize radial-specific catheters and develop increasing operator experience, it is possible that radial access may reduce adverse events related to diagnostic angiography. This also highlights the need for more randomized controlled trials assessing the safety and efficacy of these 2 approaches for bypass angiography and intervention in the current era.

Over the past 10 years, among patients who present for coronary angiography, the rate of patients with prior CABG has increased 2-fold.⁷ These patients represent a subset with higher procedural complexity due to complex coronary and peripheral vascular disease, wide range of graft configuration, and high-risk target lesions for PCI. Therefore, access site should be carefully selected and matched with post-CABG anatomy. For patients with unilateral IMA graft, ipsilateral radial access can be considered as the primary access given potential advantages related to patient satisfaction and reduced risk of access-site complications.

Conclusion

The MOT-C facilitates improved engagement of IMA grafts with minimal manipulation and allows for high-quality diagnostic angiograms via radial access. The introduction of this catheter coincided with a significant increase in the rate of transradial access for coronary bypass angiography in our lab.

Affiliations and Disclosures

From ¹Yale New Haven Hospital; New Haven, Connecticut; ²Yale School of Medicine, New Haven, Connecticut; and ³Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut.

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 accepted July 8, 2021.

Address for correspondence: Samit Shah, MD, PhD, 950 Campbell Avenue, West Haven, CT 06516. Email: samit.shah@yale.edu, samit.shah2@va.gov

References

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