Radial artery spasm is frequently associated with transradial coronary access. Incidence varies around 10% and is caused by many factors. Spasm rarely leads to serious complications such as eversion atherectomy,¹ but is commonly associated with procedural failure and patient discomfort. Since transradial coronary access aims to be maximally patient-friendly, many strategies are developed to reduce spasm.

Definition of spasm. With “radial artery spasm” (RAS) one usually means the considerable amount of friction — along with the associated patient discomfort — encountered when manipulating the arterial sheath or guide catheter in a radial artery. This friction is caused by mismatch between the outer diameter of the sheath or guide and the inner diameter of the radial artery.

Of course this mismatch can be caused by true arterial spasm. But other causes can also play a role, such as fixed atherosclerotic lesions, vessel tortuosity, small radial artery diameter or erroneous entrance into small side branches. Causes other than spasm can be ruled out or demonstrated by proper patient examination and by performing a radial artery angiogram once resistance is encountered. In this review, “spasm” is defined as the resistance between the radial artery and the equipment used.

Current study. The study by John Coppola and investigators in this issue of the Journal showed that they were unable to demonstrate a clinical effect in terms of spasm reduction with the use of additional nitroprusside compared with nitroglycerin and a calcium channel blocker.² The endpoints, although clinically relevant, were rather subjective, such as the inability to freely manipulate the catheter, difficulty in removing the sheath and arm pain.

Measurement of radial artery spasm. In daily practice, RAS is manifested by resistance during manipulation of intra-arterial equipment and by a patient complaining of pain in the forearm. It is difficult to define these two manifestations as endpoints for studies of spasm since the endpoints are hard to quantify objectively. A quantitative measure of RAS will help in the evaluation and comparison of strategies to prevent or treat RAS. We have used an automatic pullback device (APD) for removal of arterial sheaths to establish a parameter to quantify RAS.

In 50 consecutive transradial procedures, the APD was used to measure the force required for sheath removal. The mean “maximal pullback force” (MPF) was 0.53 ± 0.52 kg (range 0.1 to 3.0 kg). In 48 (96%) cases, the MPF was reached within the first 5 seconds of pullback. All patients with clinical RAS (n = 4) had a MPF greater than 1.0 kg, while the remaining had a MPF less than 1.0 kg. All patients with severe pain during sheath removal (n = 3) had a MPF greater than 1.0 kg, while no patient with a MPF less than 1.0 kg experienced severe pain. Thus, the MPF can be used as a reliable quantitative endpoint for the assessment of RAS.³

Effect of an intra-arterial cocktail to prevent RAS. With this APD we were able to study the effect of administering an intra-arterial vasodilating cocktail on the reduction of the incidence and severity of radial artery spasm.4 One hundred patients undergoing coronary procedures via the radial artery were divided into two groups of 50 each. Patients in Group A received an intra-arterial cocktail (5 mg of verapamil plus 200 g nitroglycerine in 10 ml of normal saline), while patients in Group B did not receive any vasodilating drug. The pullback device was used for sheath removal at the end of the procedure. Seven (14%) patients in Group A experienced pain (i.e., pain score of III to V) during automatic sheath removal, compared to 17 (34%) in Group B (p = 0.019). The mean pain score was significantly lower in Group A than in Group B (1.7 ± 0.94 vs. 2.08 ± 1.07; p = 0.03). The maximal pullback force (MPF) was also significantly lower for Group A (0.53 ± 0.52 kg; range = 0.10–3.03 kg) as compared to Group B (0.76 ± 0.45 kg; range = 0.24–1.99 kg; p = 0.013). Only 4 (8%) patients in Group A had a MPF value greater than 1.0 kg, suggesting the presence of significant radial artery spasm, as opposed to 11 (22%) in Group B (p = 0.029). Thus administration of an intra-arterial vasodilating cocktail prior to sheath insertion reduces the occurrence and severity of radial artery spasm.

Additional effect of hydrophilic coating to the arterial sheath. A hydrophilic-coated sheath may additionally reduce the force required to remove a radial sheath. We assessed whether a hydrophilic coating reduces the required force and discomfort associated with removal of a radial sheath following transradial coronary intervention.⁵ Ninety patients undergoing percutaneous coronary intervention via the radial artery were randomly assigned to two groups receiving either coated or uncoated introducer sheaths. All patients received the cocktail as described above. Radifocus Introducer II (Terumo) 25 cm, 6 Fr radial sheaths and sheaths that were identical apart from the presence of the coating were used in all patients. The APD was used for sheath removal at the end of the procedure. Three patients (7%) in the coated group experienced discomfort during automatic sheath removal, compared to 12 patients (27%) in the uncoated group (p = 0.02). The MPF was significantly lower in the coated compared to the uncoated group (0.24 ± 0.31 vs. 0.44 ± 0.33 kg; p = 0.003). Similarly, the mean pullback force was significantly lower in the coated group (0.14 ± 0.23 vs. 0.32 ± 0.24 kg; p < 0.001). Only 1 patient (2%) in each group had a MPF greater than 1.0 kg, together with clinical evidence of radial artery spasm. Removal of the coated Terumo Radifocus sheath requires less force than an identical uncoated sheath. The coated sheath was also associated with less discomfort for the patient.

Current practice and incidence of spasm. Today we are using a combination of an intra-arterial cocktail described above with a short (10–15 cm) hydrophilic sheath, reducing the clinical incidence of spasm to 5% (including patients with small arteries).

Other cocktails have been suggested. Chen et al. could not demonstrate an additional effect on clinical spasm of verapamil added to nitroglycerin intra-arterially and proposes simple administration of nitroglycerin 100 µg together with heparin.⁶ Ruiz-Salmeron et al. randomized phentolamine and verapamil as active components of a spasmolytic cocktail.⁷ RAS is mediated by stimulation of alpha-adrenoreceptors, and alpha-blockers like phentolamine could be an effective spasmolytic agent. Although both agents resulted in an increase in the radial artery diameter, verapamil was a stronger spasmolytic agent. The beneficial effect of a hydrophilic sheath in spasm management has been demonstrated by several other groups as well.^8,9

Prevention and general management of patient discomfort caused by mismatch of radial artery and equipment size
Proper patient examination may reveal a small radial artery. The mismatch of radial artery and equipment diameters will be associated with problems for the operator and patient. If the radial artery is small on palpation consider to use the other radial artery, the ulnar artery or no arm procedure at all.

Patient preparation. If the radial approach is preferred, even in this situation prepare the patient carefully by explanation of the causes for possible discomfort, by extra sedation and by administration or spasmolytic agents. Prophylactic intravenous pain killers (e.g., fentanyl) might be of additional help if the development of spasm is anticipated (history, radial artery size). Perhaps the most effective anxiolytics are the narcoleptic medications.

Single puncture. A straightforward, accurate, single puncture will lower the risk of spasm. If the radial artery is touched but missed during the first attempt, spasm, as well as hematoma formation, can occur.

Material selection
Sheath
• Sheathed or unsheathed? Patients with small radial arteries might benefit from a 5 Fr approach or an unsheathed 6 Fr approach.
• Long or short? The advantage of a long sheath is the free movement of the guide in relation to the radial artery wall. Less mechanical stimulation of the wall will be associated with less spasm. However, if spasm develops it will be difficult to retrieve the sheath. We have stopped using them. A short or ultra-short (5 cm) sheath will be easier to retrieve.
• Coated or uncoated? Sheaths coated with lubricious material are easy to retrieve. They sometimes are “milked out” spontaneously. There is certainly a place for these sheaths in transradial coronary angioplasty.
• Side-holes or no side-holes? Multiple small side-holes in the sheath allow for local application of spasmolytics if spasm had occurred. Side-holed sheaths are currently available.

Guidewire
• Short or long? A long wire has the advantage of easier and thus less spasmogenic catheter exchanges with preserved distal access.
• Normal or hydrophilic? Hydrophilic wires cross tortuous segments more easily. Less wire manipulations will result in less spasm.
• Shaped or straight? A shaped wire allows for easier wire manipulation across tortuous segments and along side branches.
• 0.025 inch or 0.035 inch? The selection of the wire will depend on the puncture system used. A thinner wire might be of value in patients with small radial arteries.

Guiding Catheters
• 6 Fr or smaller? Small-sized guides are more suitable in patients with small radial arteries.
• Multipurpose or dedicated? A multipurpose catheter does not have to be changed for LCA/RCA cannulation. Less catheter manipulations will result in less spasm.

And last but not least: The incidence of spasm inversely relates to operator experience. The more experienced the operator, the less manipulations, the shorter and smoother the procedure and the more patient comfort…thus less spasm.