Mother-in-Child Assisted Tracking (MiCAT): A Mechanical Technique to Overcome Severe Radial Artery Spasm

Abstract

Background. Severe radial artery spasm (RAS) and tortuosity may hinder guide catheter advancement and manipulation, requiring the arterial access site to be changed. We describe the safety and the effectiveness of a technique designed to facilitate guide catheter advancement when faced with severe RAS. Methods and Results. We present our single-center experience using a novel mother-in-child assisted tracking (MiCAT) technique used to overcome severe RAS and facilitate guide catheter advancement to the aortic root. The MiCAT system consists of a 125 cm 4-Fr multipurpose (MP) diagnostic catheter inserted inside and protruding beyond a guiding catheter. The entire system can be advanced as one over a .035˝ guidewire into the aortic root. Procedural success was defined as achievement of the intended procedure without switching to an alternative access site with no vascular complications. The MiCAT system was utilized in 22 (0.59%) out of 3392 patients who underwent angiography between October 2019 and January 2021, with severe RAS hindering advancement of a 6-Fr guiding catheter despite conventional pharmacological therapy. MiCAT was successfully achieved via the left (55%) and right (45%) radial access routes using different 6-Fr guiding catheters. Procedural success was 100% and no vascular access or arterial complications were observed. Conclusions. In our early experience, the MiCAT technique was a safe and effective strategy to facilitate guide catheter advancement.

Keywords: multipurpose-assisted tracking, radial artery, radial artery spasm, radial coronary angiography

Transradial access (TRA) is the preferred and recommended access site for diagnostic angiography and percutaneous coronary intervention (PCI).¹ Compared to transfemoral access, TRA is safer and is associated with fewer bleeding and vascular complications in both elective and emergency procedures, including primary PCI for ST-segment elevation myocardial infarctions.^2-4 Additionally, TRA is associated with improved patient comfort and earlier mobilization and subsequent hospital discharge.^5-7

However, the significantly smaller diameter of the radial artery, as well as the greater prevalence of significant tortuosity, can pose specific technical challenges. Anatomical variations affecting the radial, subclavian, and brachiocephalic trunk are prevalent and can further add to the technical challenge of TRA.⁸ Furthermore, operators may encounter radial artery spasm (RAS), which can lead to difficulties in advancing and maneuvering a catheter into the aortic root. The incidence of RAS varies between 3% to 34% and it is defined as a temporary sudden narrowing of the radial artery lumen.⁹ RAS is associated with increased rates of vascular complications, requirement for alternative access, procedural failure, and patient discomfort.^10,11

Different pharmacological agents can be used to overcome the constraints posed by severe RAS.¹² However, the use of vasodilators can be limited in patients with hypotension or impaired left ventricular function, particularly in cases of acute coronary syndromes (ACS) complicated by cardiogenic shock.^12,13 To date, even in this subset of patients, radial access is associated with favorable outcomes, therefore the aim is to try to complete the procedure radially.¹¹ Subsequently, mechanical techniques, such as balloon-assisted tracking (BAT) or use of a long (25-cm) ­radial hydrophilic-coated sheath, have been employed in order to overcome the challenge posed by severe RAS without the need for further vasoactive pharmacotherapy.^14,15

We describe a case series of mother-in-child assisted tracking (MiCAT) technique in patients with severe RAS in order to facilitate guide catheter advancement and manipulation.

Methods

Patient population. All patients who underwent diagnostic or PCI procedures between October 2019 to January 2021 at our single center were recorded prospectively. Demographic, clinical, and procedural data were obtained for all patients in whom the MiCAT technique was employed to overcome severe refractory RAS. Figure 1 shows an outline of the study design.

Procedure. In all patients, local anesthesia was applied by subcutaneous injection of 0.5 ml lidocaine 2% after assessment of the radial artery pulse. TRA was secured using a short (10-cm) 6-Fr hydrophilic sheath (Radifocus, Introducer II, Terumo). A preventive spasmolytic cocktail composed of 200 mcg nitrates was administered routinely after sheath placement. Diagnostic coronary angiography was performed with the choice and number of catheters left to the operator’s discretion. If RAS occurred, a cocktail of 200 mcg nitrates and 2 mg midazolam I.V. was administered. The decision to administer any additional pharmacotherapy, including verapamil, was left to the operator’s choice. If a catheter  could not be advanced to the aortic root due to severe refractory RAS, we employed the MiCAT technique.

Mother-in-child assisted tracking (MiCAT) technique. A 125 cm, 4-Fr multipurpose diagnostic catheter (MP, Boston Scientific) is inserted inside a 6-Fr guiding catheter in a mother-in-child manner with the distal tip of the 4-Fr MP protruding past the distal tip of the guiding catheter (Figure 2). The system is then advanced as one over a 180 cm .035˝ guidewire into the aortic root. Once the aortic root is reached, the MP catheter can be retracted back into the guiding catheter to maintain stability for coronary cannulation or removed completely.

Postprocedure care. At the end of the procedure, the arterial 6-Fr hydrophilic sheath was immediately removed and the hemostasis achieved using a compression device (TR Band, Terumo) for 3 to 4 hours. Following hemostasis, the radial pulse and access site was regularly monitored until discharge.

Data collection and clinical outcomes. Demographic, clinical, and procedural data were prospectively collected for all patients in whom the MiCAT technique was utilized. Procedural success was defined as the achievement of the intended procedure without switching to an alternative access site. Radial arteriography findings, access site complications, including bleeding, hematoma, or radial artery perforations were collected.

Ethical approval. Ethical approval was waived by the Institutional Review Board of the Maria Cecilia Hospital.

Statistical analysis. Continuous variables are expressed as mean ± standard deviation or median (interquartile range [IQR]) and compared with a t test or Mann-Whitney test as appropriate. Categorical variables are presented as counts and percentages and compared with the chi-square test. A 2-sided P-value <.05 was considered statistically significant. Statistical analyses were performed using SPSS, version 25.0 (IBM).

Results

A total of 3747 patients underwent coronary angiography between October 2019 and January 2021. Of these, 3392 (90.5%) procedures were performed via TRA and 355 (9.5%) were performed via transfemoral approach. In 21 (0.56%) cases, an additional femoral access was obtained in order to position an intra-aortic balloon pump and 15 (0.40%) cases were complex procedures in which a second radial access was established. In 2 (0.05%), procedures radial access was converted to femoral access due to operator’s preference.

MiCAT cohort. Amongst 3747 patients who underwent diagnostic coronary angiography, the MiCAT procedure was successfully used in 22 (0.59%) patients, in whom severe RAS hindered guiding catheter advancement.  Baseline clinical characteristics of these patients are shown in Table 1. Twelve (55%) patients were female, the median age was 70 years [IQR 58, 82], and BMI was 26.7 [IQR 23.43, 30.37]. Risk factors such as arterial hypertension, dyslipidemia, diabetes, and smoke habits were observed in 86%, 86%, 18%, and 9% respectively. Ten (45%) patients were admitted with a diagnosis of acute coronary syndrome, whereas 12 (55%) patients underwent an elective procedure.

MiCAT procedure and outcomes. Procedural characteristics and outcomes are shown in Table 2. We utilized 6-Fr left and right radial arterial access in 12 (55%) and 10 (45%) patients, respectively. Severe RAS hindering guide catheter advancement was encountered following the use of either 2, 3, or 4 catheters in 2 (9%), 15 (68%), and 5 (23%) patients, respectively. The MiCAT technique was successfully performed using a 6 Fr extra back up (EBU, Medtronic) 3.5 (73%), Voda left  (Boston Scientific) 3 (9%), Judkins right (JR, Medtronic) 4 (9%), Judkins left (JL, Boston Scientific) 3.5 (4.5%), and Amplatzer left (Boston Scientific) 1 (4.5%) guiding catheters. Sixteen (73%) patients underwent PCI, while 4 (18%) patients underwent intracoronary assessment (fractional flow reserve, intravascular ultrasound) and 2 (9%) patients underwent only diagnostic angiography.

The procedural success rate was 100%, with all procedures completed from the intended TRA site.

There was no bleeding or vascular access site complication observed during the procedure or the index hospitalization.

Case Examples

Example 1: Severe spasm and tortuosity of RA. A 71-year-old male with stable angina underwent invasive angiography, which revealed a critical right coronary artery (RCA) lesion. Following diagnostic angiography with 5-Fr JR4 and JL3.5 catheters, he developed severe RAS which hindered advancement of a 6-Fr JR4 guiding catheter at the level of the brachial artery. Contrast injection revealed severe diffuse RAS associated with tortuosity (Figure 3A). Further nitrates and midazolam were administered, however, the RAS persisted. A 4-Fr multipurpose catheter was inserted inside the 6-Fr JR guiding catheter and the system advanced over the .035˝ wire to negotiate the severe spasm and tortuosity (Figure 3B). PCI of the RCA was completed successfully.

Example 2: Severe diffuse and resistant RA spasm. A 68-year-old female was admitted for elective PCI to the left anterior descending (LAD) coronary artery. A 6-Fr EBU 3.5 guiding catheter was selected upfront but could not be advanced beyond the elbow.

Contrast angiography revealed severe and diffuse RA spasm (Figure 4). A spasmolytic cocktail was administered without success. A standard .035˝ guidewire was advanced to the aortic root and a 4-Fr MP was inserted in the 6-Fr EBU guide catheter. The entire system was advanced using the MiCAT technique without any resistance, enabling successful completion of the LAD PCI via the intended TRA site.

Discussion

We report our initial experience of using the MiCAT technique when severe RAS hindered advancement of a guiding catheter into the aortic root. The MiCAT technique uses a long 4 Fr multipurpose catheter inside of a 6 Fr guiding catheter. This technique was effective in all patients. No vascular or bleeding complications were noted.

Overcoming the challenge of RAS. Despite the development of lower-profile catheters, use of hydrophilic coatings, and higher operator expertise, TRA failure still occurs in 1.5% of cases.⁵ In certain cases, this occurs due to RAS, which leads to difficulties in catheter manipulation and advancement. To tackle this challenge, numerous studies have evaluated the effectiveness of different pharmacological agents.¹⁰

Many drugs, including nitroprusside, verapamil, magnesium sulphate, nitroglycerin, nicorandil, diltiazem, isosorbide, and combinations of these have been evaluated. To date, a combination of verapamil and nitroglycerin appears to be the most effective.¹²

Despite their effectiveness, the use of vasodilators is not always feasible particularly in patients with hypotension or cardiogenic shock.

Subsequently, mechanical techniques have been reported that can surmount this problem. In certain cases, a smaller guiding catheter can be considered if it is feasible. An alternative mechanical technique is the use of balloon-assisted tracking, wherein an inflated PTCA balloon is advanced along a .014" coronary guidewire until it just protrudes through the distal end of the guiding catheter. The entire system is then advanced, with the relatively atraumatic end of the balloon negotiating the spasm and tortuous arterial segments.¹⁴ Other options include the dilatation of the radial artery via the pressure mediated injection of saline solution through the radial sheath or the use of pigtail catheter to avoid the razor blade effect.^15,16 Recently, novel devices such as sheathless GC systems have been introduced and proved to be a valid tool, but they are not currently available in all catheterization laboratories.¹⁷

Advantages of MiCAT technique. In our preliminary study, we demonstrate that the MiCAT technique was successful in all patients in whom it was employed, without developing any vascular complications. Several advantages of this technique should be noted. First of all, the system is advanced over a .035˝ guidewire without the need for guidewire exchange. Secondly, the 4-Fr multipurpose catheter creates a smooth mechanical tapering effect, which minimizes the risk of vessel trauma and the razor-effect. Thirdly, this technique can be employed with a wide range of 6-Fr guiding catheters (Judkins left 3.5, Judkins right 4, extra back up 3.5, Amplatzer 1, Voda left). Fourthly, such a mechanical technique mitigates the need for additional vasodilatory or sedative medications which may be counter-productive in certain patients. Finally, in comparison with the balloon-assisted tracking technique, our MICAT technique does not require the additional use of a .014" wire and angioplasty balloon.

Therefore, we present the algorithm to face severe RAS at our center (Figure 5).

Study limitations. This study has several limitations. First, the technique was utilized in a limited number of patients in our single center. Therefore, to further evaluate the safety and efficacy of this technique, larger studies in different patient populations are required. Second, the MiCAT technique was used to advance a 6-Fr guiding catheter in all patients, therefore we cannot comment on its effectiveness for larger lumen guiding catheters. Third, a maximal spasmolytic cocktail, including verapamil, was not administered in all the patients. Finally, alternative mechanical techniques such as placement of a long hydrophilic-coated radial sheath, balloon-assisted tracking, or sheathless GC system were not employed.

Conclusion

In our early experience, the MiCAT technique is an effective strategy to facilitate guide catheter advancement when faced with severe RAS and tortuosity. It can be employed with a wide range of 6-Fr guiding catheters without the need for guidewire exchange. It appears to be safe, as no vascular access or arterial complications were observed.

Affiliations and Disclosures

*Joint first authors.

From ¹GVM Care & Research, Maria Cecilia Hospital, Cotignola, Italy; ²Azienda Ospedaliero-Universitaria di Ferrara, Cona (FE), Italy; and ³IRCCS Humanitas Research Hospital, Rozzano, Milano, Italy.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Daemen reports institutional research support from Astra Zeneca, Abbott Vascular, Boston Scientific, ACIST Medical, Medtronic, Pie Medical, ReCor Medical, and PulseCath. Dr van Mieghem reports research grant support from Edwards, Medtronic, Abbott, Boston Scientific, Pulse Cath, ACIST Medical, and Essential Medical. Dr Neleman reports institutional research grant support from Acist Medical. Dr Masdjedi reports institutional grant support from ACIST Medical. The remaining authors report no conflicts of interest regarding the content herein.

Manuscript accepted January 15, 2022.

Address for correspondence: Alessandra Scoccia, MD, Interventional Cardiology Unit, GVM Care & Research Maria Cecilia Hospital, Via Corriera, 1, 48033 Cotignola, Ravenna, Italy. Email: scoccia.alessandra@gmail.com

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