Asian Cardiovasc Thorac Ann 2002;10:20-24
© 2002 Asia Publishing EXchange Pte Ltd
Routine Use of the Radial Artery for Coronary Artery Revascularization
Zile Singh Meharwal, MCh,
Naresh Trehan, MD
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Department of Cardiovascular Surgery Escorts Heart Institute and Research Centre New Delhi, India
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Zile Singh Meharwal, MCh Tel: 91 11 682 5000 Fax: 91 11 682 5013 email: meharwal{at}hotmail.com Department of Cardiovascular Surgery, Escorts Heart Institute and Research Centre, Okhla Road, New Delhi 110025, India.
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ABSTRACT
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Between January 1997 and December 2000, a total of 4,000 patients underwent myocardial revascularization using the radial artery as one of the conduits. The mean age of the patients was 54 ± 7 years, and 92.8% of them were male. Of these patients, 31% had a left ventricular ejection fraction below 40% and 22.8% underwent urgent operation. A total of 4,225 distal anastomoses were performed using the radial artery. The average number of grafts was 3.3 ± 0.5. The hospital mortality rate was 0.8%. Low cardiac output, inotropic support, perioperative myocardial infarction, reoperation for bleeding, atrial fibrillation, and sternal infection occurred in 1.8%, 2.8%, 1.2%, 1.2%, 16.8%, and 1.2% of the patients, respectively. None of the patients had major ischemia of the hand. The incidence of local hand wound complications was 0.7% (wound infection, 0.4%; wound dehiscence without infection, 0.1%; and hematoma, 0.2%). The average length of stay in the intensive care unit was 20 ± 7 hours and in the hospital was 6 ± 2 days. Postoperative angiography, performed in 106 patients at a mean interval of 18 months, showed that 92.4% of radial artery, 96.2% of internal mammary artery, and 76.2% of saphenous vein grafts were patent.
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INTRODUCTION
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The long-term patency of vein grafts has been poor, and these conduits have been shown on angiography or reoperation to undergo atheromatous changes.1 The left internal mammary artery (LIMA), on the other hand, has produced good clinical results and excellent patency.2 It is, therefore, the first conduit of choice for the left anterior descending artery. The right internal mammary artery, either as pedicled or free graft, has also provided good long-term results.3 The other arterial conduits that are being used to achieve total or extensive arterial revascu-larization include the right gastroepiploic artery,4 inferior epigastric artery,5 and radial artery (RA). RA grafting, introduced in the 1970s6 but abandoned because of poor results, has been revived, and the results are encouraging. We started using the RA in 1996 and have been increasing its use progressively. We are now routinely using it as one of the conduits for myocardial revascularization. We analyzed our data to determine the midterm clinical and angiographic results of RA grafting.
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PATIENTS AND METHODS
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Patients who received the RA as one of the conduits during myocardial revascularization between January 1997 and December 2000 were included in the study, while patients who underwent associated procedures, such as valve repair or replacement or carotid endarterectomy, were excluded. Data were prospectively entered into a database and retrospectively analyzed.
The modified Allen's test was performed preoperatively in the ward. The patient was asked to clench the fist tightly for 10 seconds to exsanguinate the skin of the palm. With the fist still clenched, the radial and ulnar arteries at the wrist were occluded. The patient was then instructed to open the hand without hyperextending the wrist or fingers. The ulnar artery was then released and the capillary return time to the palm noted. The test was considered negative (normal) if there was capillary return within 6 seconds of releasing the ulnar artery.
In the operating theater, the collateral circulation of the hand was assessed by pulse oximetry. The saturation probe was applied to the index finger, and saturation of the finger and the amplitude of the curve were noted. The radial and ulnar arteries were then occluded in turn, and saturation and curve amplitude were again noted. If the amplitude was low or saturation did not return to normal within 10 seconds of compressing the RA, harvesting of the RA was abandoned. The nondominant hand was used for this purpose.
The arm from which the RA was harvested was placed on an armboard attached to the operating table. The arm was extended to about 70 to 80 degrees to avoid injury to the brachial plexus. Both the arm and the chest were draped together.
The distal end of the RA was exposed first by making a small incision above the radial styloid process. The size and quality of the artery were examined and any calcification noted. If the artery was considered suitable for use, the incision was extended towards the elbow up to about 1 cm medial and distal to the biceps tendon. The tissues, including the deep fascia, were divided up to the RA by low-voltage diathermy. Special care was taken to avoid injury to the lateral cutaneous nerve of the forearm, especially near the wrist where it crosses the RA from the lateral to the medial side.
The RA, which lies deep in the brachioradial muscle in loose areolar tissue, was harvested along with its vein and the surrounding tissue. The branches of the RA were clipped with hemoclips on 2 sides and separated with scissors. The artery was divided proximally and distally after heparinization. The proximal end was then cannulated using a small metal cannula, and the artery was flushed with blood mixed with papaverine and nitroglycerine. Any unclipped branches were clipped at this stage. The artery was kept in heparinized blood until it was used.
Intravenous diltiazem was used intraoperatively and postoperatively in patients whose blood pressure allowed its use. Aspirin was started orally in all patients after extubation. Oral diltiazem was used for 3 months postoperatively.
The patients were followed up in the outpatient clinic at intervals of 1 month, 3 months, 6 months, and then 1 year. They were examined for local wound complications, and their functional status assessed according to the New York Heart Association's classification. The patients who did not report for follow-up were either contacted by telephone or sent questionnaires. Their functional status, use of drugs, any hospitalization, and any intervention were recorded.
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RESULTS
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A total of 4,000 patients received the RA as one of the conduits for coronary artery bypass grafting during the study period. Their preoperative characteristics and associated comorbidities are shown in Table 1
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Most of the patients were operated on-pump, while 682 patients (17%) were operated on the beating heart. We started off-pump coronary bypass surgery in 1995 and have been doing so increasingly. Currently, about 70% of coronary bypass procedures are performed off-pump at our institute. The LIMA was used in 96.5% of patients (Table 2). The average number of grafts per patient was 3.3 ± 0.5. A total of 4,225 distal anastomoses were performed using the RA, most commonly to one of the obtuse marginal arteries (Table 3). In 33 patients where the LIMA could not be used because of poor flow or poor quality, the RA was anastomosed to the left anterior descending artery. Proximally, we anastomosed the RA to the aorta in 94.2% of cases, and to either the LIMA or the saphenous vein as a Y graft in the rest (Table 2).
The overall mortality was 0.8% (32 patients). Twenty patients (0.5%) died of low cardiac output, 16 of whom had a left ventricular ejection fraction below 30%. Other causes of death were septicemia in 6 (0.2%), multiorgan failure in 4 (0.1%), and mesenteric ischemia and stroke in 1 patient (0.02%) each. Postoperative complications are shown in Table 4. The incidence of perioperative myocardial infarction was 1.2%, and 2.6% of patients required intraaortic balloon pumping postoperatively. Twelve patients (0.3%) went into acute renal failure postoperatively, 8 (0.2%) of whom required dialysis.
Twenty-nine patients (0.7%) had local hand wound complications (Table 5), 16 of whom (0.4%) had wound infection of the forearm that required antibiotics and 5 (0.1%) had wound dehiscence without infection that required resuturing. Localized hematoma developed in 8 patients (0.2%), which was evacuated. Numbness and paresthesias were temporary in most cases. None of the patients had major ischemia of the hand.
The patients were followed up from 3 months to 4 years with a mean follow-up of 22 months. Follow-up was completed in 3,520 patients (88.0%). Clinically, 3,132 patients (89.0%) were in New York Heart Association functional class I or II, 317 (9.0%) in class III, and 71 (2.0%) in class IV. Twelve patients (0.3%) developed late forearm infection; all responded to antibiotics and local wound dressings. In the majority of the patients, numbness and paresthesias improved within 3 months. Postoperative angiography was performed in 106 patients at a mean interval of 18 months. Of 106 RA grafts, 98 (92.4%) were patent (either perfect or with minor irregularities). In the same patients, 100 (96.2%) out of 104 internal mammary artery grafts studied were patent, while 96 (76.2%) out of 126 vein grafts studied were patent.
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DISCUSSION
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The patency rate of arterial conduits is higher than that of venous conduits because of their biological characteristics that result in slower and lesser development of arteriosclerosis.1 The excellent results associated with grafts of the left2 and right4,5 internal mammary arteries led to a search for other arterial conduits that produce good long-term results after coronary bypass surgery.
Since the revival of RA grafting, its deployment in myocardial revascularization has increased. Many studies have shown good early and midterm results.7,8 We have been using the RA routinely since 1996, and it is our second conduit of choice in patients less than 65 years of age (the RA of older patients is not routinely used because generally it is more heavily calcified). In nondiabetic young patients, we tend to use the bilateral internal mammary arteries, in which case the RA becomes our third choice. We perform the modified Allen's test preoperatively and pulse oximetry intraoperatively in all our patients, and none of them have had any major ischemic complications of the hand, although Fox and colleagues9 reported a case of acute upper limb ischemia after RA grafting.
The RA is a surgeon-friendly conduit in terms of size, length, and handling characteristics. It can be easily harvested, and it can reach almost any artery on the surface of the heart for anastomosis. We prefer to use the RA for the left coronary system, but if the right coronary system has a large area of myocardial supply, we also use it for the right coronary artery or the posterior descending artery. The length of the RA is normally sufficient to reach any coronary vessel except in females of small stature. The lumen diameter of the RA corresponds well to most recipient coronary vessels, and its thick muscular wall is appropriate for both aortic and coronary anastomoses.10
We have encountered calcification in the RA in a small number of patients. If the calcification is mild, the artery is still used, but not if the calcification is heavy. During the study period, we encountered heavy calcification in 6 patients only.
Proximally, the RA can be anastomosed to either the aorta or one of the other conduits (LIMA or saphenous vein). We usually anastomose the RA proximally to the aorta, although some surgeons prefer to graft it to the LIMA in a T or Y fashion.11 Royse and coworkers12 observed lower patency for pedicled RA (grafted to the internal mammary artery) than aortocoronary RA, but the difference was not statistically significant. Amano and colleagues13 did not find any significant difference in patency rates of the RA between composite Y grafts and free grafts. We anastomose the RA to the LIMA or the saphenous vein only when the aorta is of poor quality. Whether the aorta or the internal mammary artery is a better site for proximal anastomosis for RA grafts has yet to be established.
Various techniques of RA harvesting have been described, including ultrasonically activated scalpel14 and endoscopic harvesting. We harvest the artery using low-voltage diathermy and applying clips on both sides of its branches. Ronan's group15 found that ultrasonic dissection of the RA was associated with decreased RA spasm and good hemostasis without adding to harvest time.
The incidence of mortality and morbidity in our study is comparable to other studies.16 We have not encountered a higher incidence of morbidity by the routine use of the RA. This has been the experience of other surgeons too.17 If total arterial revascularization can be performed, it avoids the morbidity associated with leg incision and promotes early postoperative mobility.18 The incidence of hand complications in our study was low, although 29.9% of our patients were diabetic, of whom 7.5% were insulin-dependent. Only 2.6% of our patients required intraaortic balloon pumping, although 12.6% of our patients had a left ventricular ejection fraction below 30%. On follow-up, most patients had normal functional utilization of the hand, and symptoms of paresthesia and numbness disappeared within 3 months in most of them.
There has been concern regarding the vasospastic tendency of the RA,7,19 and various antispastic agents have been recommended to prevent vasospasm, including calcium channel blockers. We use diltiazem postoperatively if the patient's blood pressure permits it, and oral diltiazem is prescribed for 3 months postoperatively. The occurrence of RA spasm in our experience is rare and is probably related to poor dissection and poor handling of the artery. We encountered intraoperative spasm on 4 occasions only, which responded to local papaverine.
Follow-up angiography performed in 106 patients who were symptomatic or had a positive exercise test showed comparable patency of RA conduits and LIMA grafts, much better than that of saphenous vein grafts. Although our results were obtained from symptomatic patients only, Royse's group12 did not find any difference in the patency rates of symptomatic and asymptomatic patients. Good midterm patency rates of the RA have also been demonstrated in other studies.11,20
The patency of RA and other conduits can be affected by a number of factors, including the degree of coronary stenosis, the coronary territory where the conduit is used, distal runoff of the coronary artery, and whether single or sequential anastomoses were performed. We prefer not to use the RA in coronary arteries with less than 70% stenosis because this may result in flow competition between the RA and the native coronary artery. Royse and colleagues12 found that grafting coronary arteries with lower stenosis was the most important factor in the development of the string sign. Flow competition can also develop among composite (LIMA–RA Y) grafts. If the coronary artery where the RA is used has poor distal runoff, the flow in the RA may decrease in comparison with that in the LIMA, leading to the string sign or no flow.
We tend to use the RA more often for the circumflex territory with significant stenosis. We did not find a significant difference in the patency rates of the RA in the circumflex and right coronary systems, although Royse's group12 found that RA patency was lower in the right coronary territory than in the left anterior descending and circumflex coronary artery territories. As for vein grafts, the fact that we used them for relatively less important coronary arteries might be partly responsible for their poorer patency.
Routine grafting of the RA is safe and is associated with good early and midterm results after coronary bypass surgery. Meticulous dissection and proper handling are important for achieving good results.
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ABSTRACT
INTRODUCTION
