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Ann Thorac Surg 1999;67:1631-1636
© 1999 The Society of Thoracic Surgeons
a Departments of Cardiothoracic and Vascular Surgery, Cardiothoracic Centre, All India Institute of Medical Sciences, New Delhi, India
b Departments of Cardiology and Cardiac Anesthesia, Cardiothoracic Centre, All India Institute of Medical Sciences, New Delhi, India
Accepted for publication December 8, 1998.
Address reprint requests to Dr Bhan, Department of Cardiothoracic and Vascular Surgery, Cardiothoracic Centre, All India Institute of Medical Sciences, Ansari Nagar, New Delhi - 110029, India
| Abstract |
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Methods. A no touch, atraumatic harvesting technique coupled with gentle hydrostatic and pharmacological dilatation of the radial artery graft was employed. Radial artery was used to revascularize coronary vessels with >80% proximal stenosis. Postoperatively, the patients were administered a low dose nifedipine that was continued for 6 months thereafter. The patients were followed up clinically after discharge from the hospital and angiographic evaluation of the grafted radial artery by selective injection was done at a mean interval of 16.2 ± 5.1 months (324 months) postoperatively.
Results. There was no perioperative or late myocardial infarction or mortality. No significant complications related to the harvesting of radial artery were encountered. Angiographically, the radial artery grafts were found to be patent in 96.8% of patients (60/62). Mild distal anastomotic narrowing was seen in angiogram of one patient with good filling of the target vessel. Another patient showed diffuse spasm of radial artery graft. The patency of the pedicled left internal mammary grafts was also 98.2% (56/57). All the patients were asymptomatic.
Conclusions. Radial artery seems to be an excellent alternate arterial conduit for myocardial revascularization with early and midterm patency rates equivalent to that of pedicled internal mammary artery, and it should be used more often for myocardial revascularization as an adjunct to pedicled internal mammary artery graft.
| Introduction |
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We present our experience with the use of radial artery as a conduit for CABG at the All India Institute of Medical Sciences, New Delhi.
| Patients and methods |
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Radial artery harvesting protocol
The radial artery was harvested using an atraumatic, no touch technique as described by Fremes and colleagues [6]. All of the radial arteries were harvested and implanted by one surgeon (AB) and thereby a uniformity in the operative technique was possible.
Technique
A preoperative pulse oximetry was performed on the thumb of the side on which the radial artery was harvested [8]. The numerical values and the magnitude of trace of the pulse oximetry were noted. Radial and ulnar arteries were occluded, in turn, by applying external pressure and the changes in trace of the pulse oximetry were noted. If there was significant fall in the magnitude of pulse wave during the radial artery compression, the radial artery was not harvested. The skin incision was made just medial to brachioradialis muscle bulk and extended down toward the radial styloid process depending on the length of graft needed. The brachioradialis muscle was lifted off and the entire length of the radial artery was exposed. An attempt was made to include the widest pedicle of the radial artery including the surrounding fat and the two satellite veins. At no time was the radial artery held directly. All of the lateral branches were clipped and the length of radial artery required was selected. Before finally harvesting the artery, the main pedicle of the artery was clipped and the pulse felt beyond the clip. This gave an idea of the adequacy of ulnar flow and the palmar arch. In no instance did we have to abandon because of absence of pulse in the distal segment. After harvesting the artery, both the cut ends were transfixed. Special precautions were taken to preserve the integrity of the superficial radial nerve, by staying away from it. Adequate hemostasis was ensured and the muscle edges approximated by a running suture. The subcutaneous tissue was also approximated by running suture and skin edges brought together by interrupted sutures of nylon. No drain was used. The closure of the arm was done before heparinizing the patient. A compression bandage was given for 24 hours to prevent the formation of any hematoma.
Preparation of radial artery
The radial artery was prepared for grafting prior to the institution of cardiopulmonary bypass as were the other arterial grafts. The artery was gently dilated with a papaverine + verapramil solution (60 mg papaverine + 5 mg verapamil diluted in 10 ml Ringer Lactate) using a 1 mm cannula (Medronic DLP, Grand Rapids, MI, USA) taking care not to over distend the artery. Following this both the ends of the radial artery were tailored for grafting. While preparing the ends for anastomosis it was ensured that the surface having the maximum branches was facing away from epicardium. We also clipped both the satellite veins towards the distal and proximal anastomoses, as at times, these veins produce lot of nuisance bleeding. We preferred to use the distal end of radial artery (towards radial styloid) for distal anastomosis and the proximal end because of its better caliber, for the proximal anastomosis to aorta.
Myocardial revascularizations with radial artery
The vein grafts were placed before the arterial grafts. The order of placement of arterial grafts was radial to right gastroepiploic to left internal mammary. The suitability of a coronary artery for receiving the radial artery graft required fulfillment of following criteria: Critical proximal stenois (
80%) and adequate size target vessel.
Presence of significant left main disease was considered as a contraindication initially but encouraged by the initial angiograms, of late we have been using the radial artery in this subset of patients as well.
Post-operative dilation of the radial artery conduit was accomplished by administration of intravenous Nitroglycerine and sublingual nifedipine (5 mg every 8 hours). Nitroglycerine was tapered off after 24 hours while nifedipine was continued orally (5 mg every 8 hours) after extubation. Nifedipine was continued for next 6 months with strict monitoring of blood pressure. Presently we do not use nitroglycerine for radial artery dilatation.
Perioperative evaluation
Perioperative evidence of myocardial ischemia was monitored by serial electrocardiograms. Serial estimations of serum creatinine phosphokinase and its MB fraction were done. The patients were monitored for postoperative bleeding and any evidence of low output syndrome.
Following discharge from the hospital, the patients were called for follow up at 1 month, 3 months, 6 months, 1 year and then every year subsequently. Cineangiography to assess the morphology of the radial artery graft at midterm follow-up was done at a mean interval of 16.2 ± 5.1 months (324 months) postoperatively.
| Results |
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Three patients were reoperated for excessive bleeding. One patient had complete heart block postoperatively which recovered spontaneously after 48 hours. This patient had a diffusely diseased right coronary artery that was not grafted. Another patient who was a known diabetic and hypertensive, had postoperative drug induced renal failure and required prolonged peritoneal dialysis. She recovered to normal renal parameters.
Patients were ventilated over a period of 8 to 42 hours (mean 16.4 ± 6.8 SD). Ten patients required ionotropic support. The mean intensive care unit stay and mean hospital stay were 2.3 days and 7.4 days, respectively.
Ischemic complications of the hand were not encountered. Seven patients did complain of mild numbness in the area bordering the forearm incision. One patient, apprehensive of pain developed flexion deformity of the finger, which responded very well to physiotherapy. There was one instance of significant infection of the harvesting site. The local cultures were positive for Staphylococcus aureus and required vancomycin therapy for 8 days.
The subsequent clinical follow up was 100% and ranged from 728 months (mean 18.7 ± 6.2 SD). All the patients were in NYHA (New York Heart Association) class I. There was no late mortality or any cardiac events. Cineangiography was done 324 months (mean 16.2 ± 5.1 SD) postoperatively. The radial artery conduit was patent in 60 patients (96.8%) (Fig 2 and Fig 3 ). There was no narrowing at the proximal anastomotic site in any of the patients. Mild narrowing at the distal anastomotic site was seen in one patient but the target vessel was filling adequately (Fig 4 ). This patient had the radial artery revascularization of the obtuse marginal artery. One patient showed diffuse spasm of the radial artery graft (Fig 5 ). He had not been on a calcium channel blocker. He was started on regular nifedipine and continued to be asymptomatic on subsequent clinical follow up. The left internal mammary artery grafts were patent in 98.2% patients (56/57). Localized narrowing of the graft at the anastomotic site was visualized in one patient. Right gastroepiploic artery and right internal mammary artery were patent in patients where these were used.
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| Comment |
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Radial Artery as a conduit for coronary artery bypass grafting has many inherent advantages. It can be harvested concurrently with other arterial and vein grafts. Its length (1525 cm) is usually adequate for anastomosis with even the most distal obtuse marginal vessels. Moreover its wider lumen and thicker wall allow for direct anastomosis with the aorta proximally and make the distal anastomosis with the coronary vessel somewhat less demanding technically. A recent study has demonstrated that the vasa vasorum of the radial artery do not penetrate its media, thereby implying that they have little if any role in arterial nourishment [11]. This property would make the radial artery an ideal conduit for use as a free graft. The radial artery can be anastomosed proximally with a saphenous vein graft or another arterial graft like internal mammary artery in case of inadequate length. This can also be done if one radial artery is divided for use as two conduits [5]. Some surgeons have demonstrated superior patency of the free arterial grafts if they are anastomosed proximally to pedicled arterial grafts rather than directly to aorta [12]. However, in all our studied patients (except one) the proximal anastomosis was done with the aorta with gratifying results.
We have relied upon Allens test exclusively to determine the adequacy of palmar collateral flow. Only in 1 patient, with a negative Allens test, the radial artery was exposed and not harvested. On temporary occlusion of radial artery there was fall in oxygen saturation and the decrease in magnitude of the trace as detected by the oximeter probe placed on the thumb of the same hand [8]. Perhaps the preoperative use of more objective methods like upper limb Doppler or digital plethysmography can help in averting such a situation.
Radial artery is predisposed to spasm, as it is a thick walled muscular artery with large number of leiomyocytes in its media. Moreover it is very sensitive to mechanical stimuli. The harvesting techniques used in the 1970s and the use of metallic probes for the radial artery dilatation [1] were most probably the cause of its early postoperative spasm and resultant graft failure. We remove the radial artery enbloc along with its pedicle. During dissection we do not handle the radial artery at all. We use the tissue of pedicle for holding and retraction. Some surgeons loop the radial artery and use it for retraction during the process of harvesting. It is our belief that this practice may lead to vessel spasm and should be avoided.
Meticulous hemostasis and closure of the forearm wound should follow the harvesting immediately so as to avoid hematoma formation and infective complications.
Intraoperatively, we use a papaverine and verapamil combination for pharmacological dilatation of the radial artery as described by Fremes and associates [6]. We have not used diltiazem as advocated by Acar and colleagues [5]. Our postoperative protocol for sustaining dilatation of the radial artery differs from others. Nifedipine has been the mainstay for postoperative dilatation of the radial artery in our patients. We did use intravenous nitroglycerine initially, but since we obtained similar results subsequently without its administration, we have discontinued it use unless required otherwise. Based on this experience, we believe that the key to prevention of spasm of the radial artery graft primarily lies in its meticulous, no touch harvesting, and gentle pharmacological dilatation of the artery. The use of calcium channel blockers as recommended by Fremes and associates[6] may have an important role to play. In one patient, who was not on vasodilators postoperatively, the angiogram did show evidence of spasm of the artery.
Acar and colleagues found 100% patency for radial artery graft (56/56) in the early postoperative period (<2 weeks), but the patency fell to 93.5% (29/31) when they repeated angiography after a mean follow up of 9.2 months [5]. Calafiore and colleagues also reported 94.1% (16/17) angiographic patency of radial artery graft at a mean interval of 9.5 months after surgery [12]. Our results of 96.8% radial artery graft patency at a mean interval of 16.2 months postoperatively compare favorably with the above mentioned reports. The patency rate in the present series is more consistent as the early/intermediate reported patency of the radial artery is based on the results of a consecutive series of patients all of whom have undergone follow-up angiography. Only the pedicled internal mammary artery graft matches these results with the use of the radial artery, which is the conduit of choice for myocardial revascularization.
The issue regarding the spasm of the radial artery has largely been tackled. Six out of the 56 patients (7.9%) studied angiographically by Acar displayed segmental spasm of the radial artery graft. On repeat angiography 612 months later, only 4 patients had residual spasm [5]. No radial artery graft spasm was found in the series reported by Calafiore [12]. One patient in our series (1/62) had segmental spasm of the radial artery graft (1.6%). Since he had not been taking any calcium channel blockers, he was started on nifedipine, but he refused further angiographic evaluation. Distal anastomotic narrowing was present in one of our patient (1.6%) done early on in our experience. Acar [5] and Calafiore [12] and their colleagues did not report any distal anastomotic narrowing in their patients. The pedicled internal mammary artery is not immune to spasm. A combined incidence of graft spasm and distal anastomotic narrowing of 8% (24/320) was reported by Fitzgibbon and coworkers [13]. Sarabu [14] and Blanche [15] and their associates have also reported instances of postoperative internal mammary artery graft spasm leading to hemodynamic instability.
Hence, the good results achieved currently with the use of radial artery for myocardial revascularization has prompted us to use the radial artery more often as an adjunct to the pedicled internal mammary artery graft. However, since intimal hyperplasia has also been implicated as one of the factors for late radial artery graft failure, long term angiographic follow-up is awaited.
With the data available from the literature, and based on our own experience, the mid term results of free radial artery graft seem to be comparable to the pedicled internal mammary artery graft and we feel that this conduit should be used more often for myocardial revascularization. However, the long-term results have to be available before the two conduits can be given a comparable status.
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