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MMCTS
(January 9, 2006). doi:10.1510/mmcts.2004.000752 Copyright © 2006 European Association for Cardio-thoracic Surgery Procedure Radial artery graftingDepartment of Cardiac Surgery, Catholic University, Largo A. Gemelli 1, 00168 Rome, Italy * Corresponding author: * Tel.: +39-06-3015 4639; fax: +39-06-3055 535. E-mail: mgaudino{at}tiscali
After its recent reintroduction in coronary surgery the radial artery is gaining wide acceptance as complementary arterial conduits for surgical myocardial revascularization. The main technical aspects of radial artery harvesting, the biological and vasoactive characteristics of radial artery grafts as well as the mid- to long-term angiographic results and the role of the antispatic therapy are reviewed.
Key Words: Coronary disease • Radial artery • Surgery
The radial artery (RA) is a thick-walled muscular artery (Photo 1).
RA removal and forearm vasculature Traditionally the clinical Allen test has been adopted for non-invasive assessment of the palmar circulation and of the adequacy of blood supply to the hand from the ulnar artery (UA). Anyway, this test has long been recognized longer to be largely unreliable with respect to purposes related to RA harvest; even if improved by static Doppler assessment of flow in the UA (modified Allen test), it still carries a 73% false-positive rate and a remarkably high false-negative rate, with a positive predictive value of 0.47 and a negative predictive value of 0.99 [1]. Among the first investigators describing innovative and standardized methods aimed at identifying patients at risk of unexpected complications to the hand, Pola and coworkers [2] proposed the routine adoption of (a) anatomic evaluation of the major arteries of the forearm by means of static Doppler ultrasonography and (b) functional assessment of collateral ulnar compensation during RA compression using dynamic Doppler testing. Intuitively, the first allows identification of atherosclerotic plaques, which place the residual arteries after surgery at risk of embolism and, according to these authors, contraindicates removal of RA. A detailed description of this method is presented in Video 1.
More recently, the measurement of direct digit pressure before and during RA compression has been proposed as an alternative method. Even intravascular ultrasound has been advocated in an effort of ameliorating preoperative predictivity and chances to identify conditions favouring the development of ischemic complications. After RA removal forearm blood supply becomes totally dependent from the UA; this compensation is expressed by the significant increase in flow of the UA of the operated site that becomes evident from the early postoperative period and remains unchanged at 5 and 10 years follow-up [3]. At rest UA collateral flow is sufficient to meet the hand metabolic demand; however, in condition of sustained muscular effort, the UA cannot provide the same amount of flow reserve than the intact forearm circulation and instrumental evidence of subclinical ischemia of the operated hand has been described [3]. Even more interesting is the recent observation of significantly increased intima-media thickness (IMT) values in the UA of the operated arm [4]; this difference, already evident at 5 years from surgery increases in the successive years and becomes significant at 10 years follow-up. As IMT is an accepted marker of early atherosclerosis it is assumable that the chronic flow increase to which the UA is exposed after RA removal can lead in the long-term to an increased risk of development of atherosclerotic disease; this hypothesis is supported by the alarming incidence of overt atherosclerosis reported in the UAs of the operated side (Photo 2) and requires further extensive investigation.
Harvesting technique The traditional open technique is shown in Videos 2,3,4,5,6. More recently, an endoscopic technique has been proposed and compared in several clinical trials with the open harvest.
Several authors have reported excellent early angiographic patency of RA grafts. The first study reporting early and mid-term results (1 and 5 years angiographic follow-up) in the same patients cohort underscored that a) one-year patency rate exceeds 87%, including a 4% rate of stringed RA and that b) at five years there was a surprising reduction in the percentage of irregular, stringed and occluded RA grafts. The decrease in the number of irregular grafts reached statistical significance (P=0.03) [5]. Similarly, Acar and coworkers reported the five-year angiographic results of their patients series [6], with a satisfactory 83% patency rate of RA in this population versus 91% patency of left internal thoracic grafts; freedom from angina was 86%. Long-term follow-up data confirmed the tendency of RA patency rates to increase with the time due to the progressive decrease of the spastic attitude of the artery: overall patency and perfect patency rates of 91.6% and 88% have been reported [7]. Moreover, RA graft analysis by intravascular ultrasound ruled out phenomena of intimal hyperplasia and signs of accelerated atherosclerosis typical of venous grafts (Photos 3 and 4) and endovascular challenge by means of selective infusion of serotonin hydrochloride revealed preserved endothelium-dependent and endothelium-independent RA vasodilatory reserve.
Some investigators suggested a possible influence of the site of the target vessel on RA graft patency and described how patency rate is impaired when the RA is anastomosed to a posterolateral or posterior descending branch [8]. However, successive investigations did not confirm these findings [7]. On the basis of our current knowledge, the most important factor affecting the RA patency rate is the degree of stenosis of target coronary vessel (see Video 3). Acar already noted that failure preferably occurs when the artery is grafted on native coronary vessels with subcritical stenosis, and successive studies confirmed this finding (Graph 1). This effect is much more evident when the RA is proximally anastomosed to an internal thoracic artery in Y-graft configuration [9].
Of note, proximal RA grafts (i.e. conduits obtained from the more proximal half of the artery) have a less pronounced muscular component in the media and have been shown to achieve better perfect patency rates and lower tendency to spasm than distal RA segments [10].
Vasoactive profile, morpho-functional remodeling and administration of calcium-channel blockers Traditionally, administration of calcium channel blocker has been considered mandatory in patients with RA grafts. However, recent investigations denied any effect of these drugs on RA angiographic results and clinical/scintigraphic outcome both in the early and long term [13,14]. Moreover, the treatment with oral diltiazem does not seem to influence the early vasoreactive profile of the RA graft. On the basis of the current knowledge, the indication to postoperative administration of calcium channel blockers in patients with RA grafts seems actually unsubstantiated and the necessity of a chronic anti-spastic therapy and the drug to be used remain to be determined.
The RA is an excellent conduit and can probably be considered the second arterial graft of choice. In general, RA grafts which do not fail within the immediate postoperative years are very unlikely to undergo late failure and remain patent a decade after surgery. Long-term patency rates are therefore comparable to those of the internal thoracic artery. The feared spastic attitude of the graft tends to decrease within time and has almost completely disappeared at mid- and long-term follow-up. The refinement of harvesting procedures and the careful patients selection by non-invasive evaluation of the forearm circulation minimized the risk of acute ischemic forearm complications. However, care should probably be used in deciding RA harvesting in patients involved in manual activities. Finally, research is still ongoing concerning the optimal antispastic therapy and the chronic consequences of RA removal on forearm vasculature.
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Surgical technique
