Sharp Dissection versus Electrocautery for Radial Artery Harvesting

Abstract

Radial arteries have been increasingly used during the last decade as conduits for coronary artery revascularization. Although various harvesting techniques have been described, there has been little comparative study of arterial damage and patency.

A radial artery graft was used in 44 consecutive patients, who were randomly divided into 2 groups. In the 1st group, the radial artery was harvested by sharp dissection and in the 2nd, by electrocautery. These groups were compared with regard to radial artery free flow, harvest time, number of clips used, complications, and endothelial damage.

Radial artery free flow before and after intraluminal administration of papaverine was significantly greater in the electrocautery group (84.3 ± 50.7 mL/min and 109.7 ± 68.5 mL/min) than in the sharp-dissection group (52.9 ± 18.3 mL/min and 69.6 ± 28.2 mL/ min) (P =0.003). Harvesting time by electrocautery was significantly shorter (25.4 ± 4.3 min vs 34.4 ± 5.9 min) (P =0.0001). Electrocautery consumed an average of 9.76 clips, versus 22.45 clips consumed by sharp dissection. The 2 groups were not different regarding postoperative complications, except for 3 cases of temporary paresthesia of the thumb in the electrocautery group; histopathologic examination found no endothelial damage.

We conclude that radial artery harvesting by electrocautery is faster and more economical than harvesting by sharp dissection and is associated with better intraoperative flow and good preservation of endothelial integrity.

Using the radial artery (RA) as an arterial conduit was first proposed by Carpentier and colleagues in 1973;¹ but shortly thereafter, some surveys showed high occlusion rates,^2,3 which at last led to the abandonment of RA use. In the 1990s, studies showing long-term patency of RA grafts—of about a decade—revived the use of RA grafts,⁴ so that nowadays the RA is increasingly used as the 2nd conduit of choice, after the internal mammary artery,⁵ especially in cases of total arterial revascularization.

The radial artery and other limb arteries are classified as type III, according to He's functional classification system,⁶ and are constructed predominantly of muscle cells (in the middle layer of their walls), which makes them vulnerable to vasospasm as a result of mechanical or thermal stimuli.^6,7 Furthermore, these arteries show a higher contractility in response to vasoconstrictors.⁸ Early graft failures and occlusions were attributed to this vasospasm mechanism and to the endothelial damage caused by trauma during harvesting, which leads to a higher propensity for platelet aggregation and thrombosis.⁹

To prevent these events, the so-called minimally traumatic harvesting technique^10,11 was developed to minimize touching and manipulating the vessel. In addition, various antispasmodic drug protocols were introduced to prevent vasospasm; these protocols included the use of vasodilator drugs such as verapamil, nitroglycerin, nitroprusside, milrinone, and papaverine, given singly or in combination.^12–15 Acar and colleagues¹⁴ suggested the systemic use of diltiazem and the topical or intraluminal use of papaverine;⁴ furthermore, others¹³ showed that 10 minutes of exposure to intraluminal papaverine would result in near-maximal RA dilation.

At our center, we started using RA for coronary artery bypass grafting (CABG) in 1999. Initially, we harvested the arteries by sharp dissection, which was very time-consuming and expensive, because it used too many hemostatic clips. Harvesting by electrocautery was thought to be free of these problems, but we were concerned about the possibility of early graft occlusion due to thermal damage.

We designed and conducted this randomized prospective clinical trial to determine the better harvesting technique in terms of RA blood flow, harvesting time, number of hemostatic clips used, integrity of RA endothelium, and postoperative complications.

Patients and Methods

Study Groups

Over a 10-month period from May 2000 through February 2001, 44 consecutive patients who were candidates for CABG were enrolled in the study. The patients' preoperative clinical details are summarized in Table I. The study was approved by our Medical Ethics Committee, and informed written consent was obtained from each participant.

Table I. Patients' Characteristics, Including Preoperative Risk Factors

To determine the sufficiency of ulnar circulation to the hand, an Allen's test was performed on the nondominant hand of all patients. Arterial flow to the palm was occluded by applying external pressure on both the ulnar and the radial arteries just above the wrist, and the patient was asked to rapidly clench and relax his hand a few times while avoiding hyperextension at the wrist. The test was regarded as positive and the patient was excluded from the study if capillary refilling took longer than 5 seconds after release of the ulnar artery.

If the test results were negative, a modified Allen's test was done to confirm the result. During the same procedure, oxygen saturation of the thumb was measured by means of a pulse oximeter. If the saturation returned to normal level (98%–100%) in less than 5 seconds, the patient would enter the study. Those patients with a positive Allen's or modified Allen's test were excluded from the study.

The patients were randomly assigned to 2 groups, to undergo surgery according to one or the other of the 2 techniques.

Surgical Techniques

No needles or angiography catheters were introduced into the nondominant hand that was to be operated upon; also, the intra-arterial cannula for monitoring the arterial blood pressure during operation was inserted into the other hand.

In the execution of each method, a sharp incision was made—simultaneous with the sternotomy procedure—on the skin of the volar forearm, extending from a point lateral to the biceps tendon and 2 cm distal to the cubital crease, following curvilinearly the rounded belly of the brachioradialis muscle down to a point about 1 to 2 cm above the wrist crease at the radial artery pulse.

Using electrocautery, we divided the subcutaneous tissue and the fascia between the brachioradialis and flexor carpi radialis muscles, taking care to keep the lateral antebrachial cutaneous nerve in the lateral part of the division. Retracting the brachioradialis muscle reveals the full course of the RA in the forearm. Anatomical variations to the RA are very rare; occasionally, the distal segment lies superficial to the fascia, which does not alter the mentioned technique.

Sharp Dissection.

From this point on, in the 1st technique—with emphasis on minimal touch of the artery by instruments—we sharply dissected with scissors the RA pedicle, including satellite veins, from the surrounding tissues; and we divided the arterial and venous branches with scissors, between 2 small hemostatic clips.

Electrocautery.

The 2nd technique was similar, except for the use of diathermic dissection by means of low-voltage electrocautery. Only greater arterial branches were occluded with 1 metal clip near the RA and divided by diathermy, while smaller branches were divided by diathermy alone. With this technique, we tried to keep diathermy at a minimum.

In both techniques, the pedicled main trunk of the RA, with satellite veins, was mobilized. After clamping the distal stump of the RA, we performed sharp distal division and measured the free flow of the RA by collecting blood for 15 seconds in a syringe. Then we administered papaverine hydrochloride intraluminally through a 22-gauge cannula and clamped the distal end of the harvested vessel. With its proximal end still connected, the harvested RA remained in situ—covered with gauze soaked in warm isotonic saline solution—until the coronary artery anastomosis could be accomplished. Before dividing the proximal RA for coronary artery anastomosis, we again measured RA free flow by removing the distal clamp. This was followed by sharp proximal division and suture ligature of the distal and proximal stumps.

At both stages of flow measurement, we simultaneously recorded the patient's arterial blood pressure. Cardiopulmonary bypass was conducted at 30 to 32°C (moderate hypothermia) for all of the patients. After completion of CABG, we examined the harvest site again for proper hemostasis and closed the incision in 2 layers, in the usual manner.

Data Collection

For each patient, we recorded—in addition to the preoperative clinical profile (Table I)—the harvesting technique and the duration of the harvesting procedure, from skin incision to distal division of the RA. In addition, the number of hemostatic clips used for each patient was recorded.

Radial artery free flow and concomitant blood pressure were measured immediately after distal division of the RA (in situ free flow before papaverine) and immediately before proximal division of the RA (in situ free flow after papaverine).

Follow-up was performed on every patient during the early postoperative period (up to 1 month), as we looked for complications such as ischemia, bleeding, paresthesia, neuralgia, and wound infection.

Histopathologic Evaluation

A tissue sample of 1 to 2 cm in length was collected from the distal end of the conduit, after distal division of the RA. Instantly after collection, the samples were immersed in Bouin's fixative solution for 12 to 24 hours at room temperature. Then the specimens were washed in phosphate buffers, dehydrated with increasing concentrations of alcohol, and embedded in paraffin. Cross-sections of 5 m in thickness were cut and stained with hematoxylin-eosin and elastin (van Gieson) stains. Also, the specimens were subjected to immunohistochemical reaction with anti-factor VIII, then stained before assessment under an optical microscope by a histopathologist, who was blinded and who used a semiquantitative scoring method that he himself had developed.

Samples were assigned a score of 0 to 3, depending on the severity of damage to the integrity of the endothelium, according to which “0” is normal endothelium, “1” mild damage, “2” moderate damage, and “3” severe damage and endothelial necrosis.

The unavailability of a transmission electron microscope—the most precise instrument for examining specimens for evidence of endothelial damage—was the greatest limitation of our study.

Statistical Analysis

Data were analyzed using the SAS-8 (Statistical Analysis System, SAS Institute Inc.; Cary, NC) software package for Windows. Values were expressed as mean ± SD, and P values less than 0.05 were considered statistically significant.

Logarithmic transformation was performed to normalize the data in accordance with the Shapiro-Wilk test for normality. Multivariate analysis by 2-way ANOVA testing was performed to seek any significant differences between free flows of the 2 groups in terms of age, sex, and arterial blood pressure. Comparing harvest time and free flows before and after papaverine administration in the 2 techniques was done using an independent t-test. The Mann-Whitney nonparametric test was used to analyze the expenses of the 2 techniques, in regard to the number of hemostatic clips used.

Results

Analyses of the data are presented in Table II.

Table II. Comparison of Operative Data Concerning the 2 Harvesting Techniques

Radial artery free flow, both before and after papaverine administration, was significantly greater when the electrocautery technique was used. Analyses revealed no significant differences between free flows of the 2 groups in terms of age, sex, and arterial blood pressure.

Harvesting time was significantly longer for the sharp-dissection technique; that technique also required a greater number of hemostatic clips.

Apart from a small subintimal hematoma (the overlying endothelium had been spared) that our pathologist encountered in 1 specimen harvested by the sharp-dissection technique, the survey of RA samples showed no significant endothelial damage in any member of the 2 groups: all the specimens were scored “0” in accordance with the semiquantitative scoring system for endothelial damage.

Temporary paresthesia of the thumb was encountered in 3 members of the electrocautery group, but that cleared completely during the 1-month follow-up period. There were no other complications, such as ischemia, hematoma, compartment syndrome, neuralgia, bleeding from the RA grafts, and infection in the hand or forearm.

Discussion

As we pointed out above, the radial artery graft is more prone to vasospasm than are other arterial grafts,⁸ possibly due to its abundant muscle cells.^6,7 Despite this disadvantage, the use of the RA has been widely accepted by many surgeons because of characteristics like sufficient length, ease of concurrent harvest during other grafting procedures, thick walls, and lumens wide enough to suit many grafting applications.¹⁶

To overcome the disadvantages of the RA, investigators have suggested various routines that make use of vasodilators or of minimal touch during harvesting. Yet studies that compare the outcomes of these techniques—sharp dissection, electrocautery dissection, ultrasonic scalpel dissection, and endoscopic harvesting—are few. In comparing the first 2, we found electrocautery to be faster and, because it uses a remarkably smaller number of clips, more economical. When performed meticulously to minimize thermal damage, electrocautery harvesting also causes less spasm and provides greater RA free blood flow.

Histopathologic examination of the specimens by means of optical microscopy did not reveal any difference between the 2 techniques, nor did postoperative complications, except for some thermal injury to sensory nerves in the electrocautery group. This appeared to be reversible, and avoidable by careful dissection.

We believe that, in the experienced hands of a careful surgeon, harvesting by electrocautery is an easy, fast, and economical technique that yields better patency. This method has become routine in our practice, because we do not have access to superior methods, such as ultrasonic scalpel dissection and endoscopic harvesting.^17–19