Eur J Cardiothorac Surg 2003;23:432-434
© 2003 Elsevier Science NL
Reversal of radial artery ‘string sign’ at 6 months follow-up
Maurizio Merlo,
Amedeo Terzi*,
Maurizio Tespili,
Paolo Ferrazzi
Departments of Cardiovascular Surgery and Cardiology, Ospedali Riuniti di Bergamo, Bergamo, Italy
Received 16 September 2002;
received in revised form 29 October 2002;
accepted 11 November 2002.
* Corresponding author. U.O. Cardiochirurgia, Ospedali Riuniti di Bergamo, Largo Barozzi 1, Bergamo 24100, Italy. Tel.: +39-035-269322; fax: +39-035-266662
e-mail: terzia{at}cyberg.it
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Abstract
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The clinical importance of radial artery string sign is still debated. We present a case of reversal of radial artery string sign in 6 months with concomitant involution of competitive flow arising from an important collateral coronary circulation to an occluded right coronary artery. The hypothesis that the string sign is an extreme form of autoregulation of the radial artery is confirmed, and the flow reserve of this conduit is emphasized.
Key Words: Radial artery • String sign • Reversal
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1. Introduction
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The use of the radial artery (RA) as an alternative conduit for coronary bypass grafting has recently been extended. Many groups propose RA as the graft of second choice for myocardial revascularization after the left mammary artery (LIMA) [1,2]. The early and midterm angiographic patency rate, similar to that obtained with LIMA [3,4], encourages the use of RA, especially in pursuing a strategy of total arterial revascularization. However, RA is a muscular conduit and it is prone to vasospasm.
We present a case in which a virtually non-functional RA graft (i.e. string sign) at early postoperative angiographic study showed an impressive increase in diameter and flow after 6 months (in a setting of complete involution of collateral circulation).
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2. Case report
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A 61-year-old man with a history of exertional angina was referred for elective coronary revascularization. Exercise testing exhibited induced ST-segment depression in leads V3–6. Preoperative angiography showed 75% left main coronary stenosis with a significant proximal lesion of the left anterior descending (LAD) artery involving the origin of first diagonal branch, and 80% proximal left circumflex artery narrowing. The right coronary artery (RC) was proximally occluded, but through collateral circulation an important antegrade flow occurred into the bed distal to the obstruction. The strategy of the operation was as follow: a Y composite graft included end to side anastomosis of free right mammary artery (RIMA) on an in situ LIMA. The LIMA was grafted to the LAD and the RIMA to the first diagonal and first marginal branches. The posterior descending artery (PDA) was grafted with RA directly from the aorta.
The postoperative course was uneventful, on medical treatment with Ca2+ channel blocker, and the patient was discharged after angiographic control. After 15 days exercise testing and echocardiography did not document inducible ischemia.
The patient volunteered for a postoperative angiogram research study which included two angiograms at 1 week and 6 months postoperatively, with the aim of assessing the efficacy of total arterial revascularization that had been recently introduced in our center.
The first postoperative angiography (Fig. 1)
showed proximal RC occlusion with grade 2 (according to Thrombolysis In Myocardial Infarction (TIMI) [5]) flow sustained by omo coronary (vasa-vasorum) collateral circulation. The RA graft, selected by using a 6 french Amplatz (CordisTM) catheter, appeared diffusely of small caliber (string sign) with very slow ‘run off’ of contrast dye. After nitroglycerin intracoronary infusion no substantial modifications either of the size or of the antegrade flow were observed. The Y composite graft was working perfectly with TIMI 3 flow antegrade on both vessels. After 6 months the patient was in good clinical condition, asymptomatic and on oral medical treatment with diltiazem (180 mg/day) and aspirin (100 mg/day). The second postoperative angiography (Fig. 2)
was done at this time, and showed total occlusion in the proximal portion of the RC with absence of antegrade flow. The RA graft, selected by a 6 french Judkins catheter (CordisTM), appeared of optimal caliber (about two fold the catheter size) with TIMI 3 anterograde flow, perfectly filling the RC to the proximal occlusion site with normal run off into a good sized (PDA) and postero-lateral branch. The Y composite graft on LAD and the first diagonal and marginal branch maintained good angiographic postoperative results.
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Fig. 1. (A) Coronary angiography on the 7th postoperative day showing right coronary occlusion (arrowhead) with antegrade flow sustained by omo coronary collateral vessel (white arrow). (B) Same angiography showing string sign (white arrow) in aorta-coronary RA to PDA (arrowhead).
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Fig. 2. (A) Coronary angiogram obtained 6 months after surgery showing complete involution of the omo coronary collateral circulation to the RC. (B) Subsequent frame showing the RA graft (white arrow) perfectly filling the right artery to the proximal occlusion site with good run off into a good sized PDA and postero-lateral branch.
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It is worth mentioning that the patient was enrolled in another study protocol and underwent a new angiography 1 year after the last one, and this third postoperative coronary angiogram appeared indistinguishable from the second.
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3. Comment
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Use of RA for coronary artery bypass grafting was first introduced by Carpentier et al. in 1971 [6], but was subsequently abandoned until its revival following the observations of late patency reported by Acar et al. [7]. Since then there has been a vast increase in the use of this conduit in coronary surgery. The advantages of using RA include the favorable handling characteristics, the extended length of this conduit, and avoidance of the morbidity associated either with bilateral IMA harvesting [8] or saphenous vein procurement in patients with legs deemed high risk for complications (peripheral vascular disease, obesity, diabetes). However, RA is a highly reactive conduit, and graft malfunction due to graft spasm has been reported and raises some concern about its use. The patient described in this report may help in shedding some more light on the significance and implications of the string sign of RA. We already know from previous reports the importance of the grade of stenosis of the native coronary artery in the rate of the string sign [9]. It is suspected that what could be determinant is the grade of competitive flow in relation to the vascular bed supplied by the graft. In this way the coronary target locations play a role in RA patency: the risk of anastomotic failure is increased for circumflex and right coronary distribution [3]. What is peculiar in this case is the nature of the competitive flow affecting the RA and the rapid involution of this flow in favor of the grafted conduit. The RC was occluded, but initially an important collateral circulation probably maintained a translesion coronary flow which competed with the RA graft in the early postoperative period, when the conduit is more reactive. Subsequently the RA, after increasing in diameter three times, supplied a large distribution territory whose existence had not been suspected before, and the collateral circulation to the RC artery disappeared. The potential role of antispastic drugs (the patient was on oral diltiazem from the 2nd postoperative day) is difficult to assess. Nonetheless no modifications occurred in RA following the intracoronary infusion of nitroglycerin, which has been reported as a superior conduit vasodilator and more effective in preventing graft spasm than diltiazem [10].
We could speculate that RA is susceptible to the compliance of the vascular bed, herein confirming what was already suspected from data concerning the effect of the coronary stenosis location on graft patency. The diffuse narrowing of the RA appeared to be an extreme form of autoregulation as hypothesized by others. At the same time the spontaneous closure of collateral circulation with the concomitant dramatic increase in the dimension of RA in a 6 months time span would indicate the potential flow reserve associated with the use of this conduit in coronary revascularization.
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References
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Abstract
1. Introduction
