Pseudo-Candy Wrapper: Bifocal Radial Artery Graft Spasm
Following Stent Implantation

ABSTRACT: We encountered a case of intractable radial artery graft spasm after stent implantation which was partially responsive to nominal nitroglycerin therapy. We report this case with intravascular ultrasound imaging at the radial artery spasm site. J INVAS CARDIOL 2004;16:201–203 Key words: coronary bypass surgery, angioplasty, intravascular ultrasound Left internal mammary artery (LIMA) grafts to the left anterior descending coronary artery (LAD) during coronary artery bypass surgery (CABG) have greater patency rates than saphenous vein grafts and reduce long-term cardiac morbidity and mortality rates.¹ In view of the poor long-term results with saphenous grafts, alternate arterial conduits have been used such as the gastroepiploic, epigastric and free radial arteries.² Although prone to spasm, the radial artery (RA) is more commonly being used as a bypass graft conduit due to improved harvesting techniques together with the use of calcium channel blockers or other vasodilators.³ With this expanded use of the RA, the need to treat RA stenoses with angioplasty has increased.⁴ We encountered a case of intractable RA spasm after stent implantation which was unresponsive to a nominal dose of nitroglycerin therapy in the RA graft. We report this case with intravascular ultrasound (IVUS) imaging at the RA spasm site. Case Report. A 76-year-old man presented with Canadian Class II angina in August 1999. His coronary risk factors included hyperlipidemia, diabetes (oral drug therapy) and remote tobacco use. Coronary angiography revealed a severe luminal narrowing (80% diameter stenosis) in the proximal segment of his right coronary artery (RCA) and a moderate luminal narrowing (50% diameter stenosis) in the middle segment of the LAD. Left ventricular angiography demonstrated an ejection fraction of 60% and normal contraction of all myocardial segments. In September 1999, he underwent his first stent procedure (NIR stent, 3.5 mm x 13 mm, Boston Scientific SciMed, Maple Grove, Minn.) for the RCA lesion. One month later, the patient had another stent placed (DUET stent, 3.0 mm x 15 mm, Guidant Corporation, Santa Clara, Calif.) for the restenotic lesion located just distal to the NIR stent. In November 1999, the patient had his third stent placed (NIR stent, 3.0 mm x 16 mm, Boston Scientific SciMed) for the lesion in the LAD. By March 2000, the patient was admitted for severe in-stent restenosis of the RCA and CABG was performed. During CABG, a LIMA was placed to the LAD and first diagonal branch, and a radial artery graft was used to bypass the RCA. Seven months later, he developed recurrent symptoms of angina. Angiography revealed a severe luminal narrowing (80% diameter stenosis) in the ostium (proximal segment) of the radial artery graft and a patent LIMA graft. His native circumflex system remained patent. The patient was administered 0.2 mg of nitroglycerin into the RA graft, which resulted in no change of the luminal narrowing. Angioplasty was then performed. After 10,000 units of heparin was administered, the graft was engaged with an 8 F MPA-1 catheter with side holes. An ACS BMW wire was positioned distal to the lesion, a 2.5 x 13 mm balloon (Maxxum, Boston Scientific SciMed) was advanced, and 2 inflations were performed up to 8 atmospheres. A 15 mm long stent on a 3.0 mm balloon (S670 AVE) was implanted at 12 atmospheres (Figure 1A). Angiography revealed new tandem narrowings distal to the stent (Figure 1B). The patient was asymptomatic and no ST-T changes were noted on the electrocardiogram. To confirm appropriate stent deployment, a 2.9 F sheath-based IVUS catheter incorporating a 40 MHz transducer (Atlantis, Boston Scientific SciMed) was used. IVUS examination revealed discrete luminal narrowings distal to the stent without apparent thrombus or edge tears (Figure 2). Spasm was suspected based on the IVUS findings. The patient was then given 0.5 mg of nitroglycerin into the RA graft which resulted in partial reversal of the spasm. Further administration of verapamil (0.6 mg) into the RA graft resulted in complete relief of the spasm (Figure 1C). Discussion. Recently, the use of the RA as a coronary artery bypass conduit has enjoyed a revival² based on the belief that it will help improve long-term results of coronary operations. The favorable results have led to more frequent use of the RA with a resultant increase in RA angioplasty.⁴ Early reports have emphasized the great propensity of the RA to spasm.⁵ However, this propensity has been greatly reduced using both topically and systemically different categories of vasodilators including calcium channel blockers.^2,6,7 Clinically, although all arterial grafts may develop vasospasm, it develops more frequently in the RA2 and gastroepiploic artery8 than in the IMA and inferior epigastric artery.⁹ Although all arterial grafts react to vasoconstrictors such as endothelin (ET), thromboxane A2, prostaglandin F2, norepinephrine, phenylephrine, 5-hydroxytryptamine, histamine, acetylcholine and angiotensin II, some arteries have a stronger reaction to vasoconstrictors than others.^10,11 When the RA and the IMA were compared, the response to norepinephrine and 5-hydroxytryptamine, angiotensin, and ET-1 was higher in the RA.^12,13 The basal and stimulated releases of NO and endothelium-derived hyperpolarizing factor-mediated hyperpolarization in the IMA are significantly greater than those in the RA.¹⁴ The IMA is an a 1-adrenoceptor-dominant artery with little a 2- or b-function.¹⁵ In contrast, the RA has both a 1- and a 2-function, although its b-function is also weak.¹⁶ There are several differences in contractility and incidence of spasm between arterial and venous grafts. Acetylcholine, thrombin and adenosine diphosphate evoked potent endothelium-dependent relaxation in the IMA, but weak response in the saphenous vein, although endothelium-independent relaxation in response to sodium nitroprusside was similar in arteries and veins.¹⁷ Serotonin induced markedly greater contractions in saphenous veins than in artery grafts.¹⁸ In vivo IMA grafts also had more endothelium-derived nitric oxide release in response to acetylcholine than did saphenous vein grafts after coronary bypass grafting.¹⁹ NO-dependent relaxation of the RA is greater than that in the saphenous vein.²⁰ Dissection,²¹ coronary spasm,²² localized thrombosis,²³ mechanical coronary shortening and vessel wall invagination due to accordion effect,²⁴ and “pseudo-transection”²⁵ are sources of iatrogenic obstruction during angioplasty. Since this RA case was not a tortuous vessel and a stiff guidewire was not used, dissection, spasm and localized thrombosis were suspected. Based on IVUS findings and in regard to the potential for RA spasm, spasm was the main suspect. Luminal narrowings persisted despite the infusion of large doses of nitroglycerin (0.5 mg) into the RA graft over 10 minutes. Fortunately, administration of verapamil (0.6 mg) into the RA graft resulted in complete relief of the spasm. Considering the lesser responsiveness to intracoronary nitroglycerin, the original lesion might have been spasm. One case report described a patient who developed severe vasospasm of a RA graft during PTCA, partially responsive to nitroglycerin,²⁶ while another case report described coronary artery spasm unresponsive to intracoronary nitroglycerin during PTCA that later responded to intracoronary verapamil.²⁷ We believe this is the first report of RA spasm, previously partially responsive to intracoronary nitroglycerin during PTCA, that later responded to verapamil. During coronary interventions, angiography cannot provide complete information about vessel/lesion morphology leading to reduced vessel diameters.^28,29 When used adjunctively with PTCA, IVUS serves as an important diagnostic tool with the unique ability to visualize the coronary wall in vivo.^30,31 IVUS allows the ruling out of severe atherosclerosis, dissections and also provides important diagnostic clues for making the correct diagnosis.^28,29 In conclusion, patients with RA graft disease requiring angioplasty should receive sufficient doses of vasodilators as well as calcium channel antagonists before, during and after the procedure to minimize the incidence of spasm. Moreover, the use of IVUS during cases such as this can help to further diagnose and manage complications.