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Ann Thorac Surg 1995;60:109-110
© 1995 The Society of Thoracic Surgeons
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Introduction |
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 Top Introduction |
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DR HENDRICK B. BARNER (St. Louis, MO):This excellent presentation by Dr Dietl represents the first North American experience with the radial artery since it was abandoned 20 years ago because of poor patency in the first year after grafting. However, the dismal experience of the 1970s has been abrogated by the 94% patency at 6 to 16 months as reported by Acar in Paris and by Calafiore in Chieti, Italy, as well as the unpublished experience of Richard Brodman of Montefiore Hospital in Manhattan, who has obtained 98% patency in 50 radial artery conduits studied 1 to 28 weeks postoperatively. Thus, a better understanding of the necessity to avoid surgical trauma to conduits generally and the recognized need for morphologic and functional preservation of the endothelium probably have been responsible for the improved patency of the current era.
Doctor Dietl, I would be interested in knowing your acceptable time limits for capillary refilling that were employed to interpret the preoperative Allen test. You indicate in the manuscript that 3 patients had a positive intraoperative Allen test and that dissection of the radial artery was abandoned. Does this mean that the preoperative Allen test did not exclude the use of the radial artery in these patients, or are you using the intraoperative Allen test to assess collateral circulation to the hand?
The manuscript reports ``gentle dilation of the radial artery with heparinized saline solution.'' ``Gentle'' can be interpreted broadly, and I would be concerned about the use of excessive pressure with extravasation of saline solution into the arterial wall as well as endothelial damage. Physiologic saline solution, unless buffered, has an acid pH and is known to be injurious to endothelium. Without angiographic control in your patients we do not know if these variables might have affected conduit patency adversely. We allow the patient's blood pressure to dilate the radial artery after filling it with blood containing papaverine.
We have encountered medial calcification in 3 of 155 radial arteries, one of which could not be used for this reason. Have you encountered this problem?
It is my belief that the radial artery has returned as an appropriate alternative arterial conduit and that its future may be more than that of an alternative.
DR JACK J. CURTIS (Columbia, MO): Doctor Dietl's well-articulated refrain joins an international chorus of renewed enthusiasm for use of the radial artery. The common perception is that if one only knows how to harvest the radial artery properly, it is a good conduit. The converse of that, of course, is if you do not harvest it properly, you will have big problems, as occurred in 65% of the radial artery grafts examined in the 1970s.
The intima of a radial artery is delicate; the intimal proliferation that is very common in radial arteries interposed as coronary artery bypass conduits is not so delicate. Doctor Dietl, do you have any histologic follow-up of any of your grafts? What are the present indications for use of the radial artery graft?
DR RICHARD F. BRODMAN (Bronx, New York): I have been using the radial artery as my conduit of choice after the left internal thoracic artery for the past 14 months in 120 patients. I, however, have been reluctant to rely solely on the modified Allen's test because it is somewhat subjective. We have used a number of more objective tests. Sixteen of these patients had unilaterally positive and 19 patients had bilaterally positive assessments that had showed extreme radial dominance. The radial arteries were not harvested from these extremities. When radial dominance is identified, removal of the radial artery may result in ischemia to the hand. I would like to know, apropos of Dr Barner's question, your protocol for the modified Allen's test and if you are using more objective tests to evaluate collateral flow.
The other issue has to do with the use of calcium-channel blockers. I too use the protocol that was described by Dr Acar and his associates but had to taper the intraoperative infusion not infrequently because of hypotension and bradycardia. We subsequently reduced by 50% the intraoperative dosing protocol recommended by Dr Acar. In a significant number of patients, administration of the diltiazem has been stopped postoperatively. At early postoperative angiography, there does not appear to be any difference in the appearance or patency of the radial artery grafts in the 20 patients who were not receiving calcium-channel blockers compared with the 25 patients who still were receiving calcium-channel blockers at the time of the angiography.
I would be interested in your comments.
DR ALAIN F. CARPENTIER (Paris, France): This important report confirms our own findings regarding the good results obtained to date with the radial artery used as an arterial conduit for coronary artery bypass grafting. It has not always been the case. Some of you may remember that after having proposed this technique in 1971, I advised 2 years later to discontinue its use because of a 30% incidence of what was thought to be graft obstruction. Yet 18 years later, a cardiologist sent me a coronary arteriograph from 1 of my very first patients in whom the postoperative coronary arteriograph showed an obstruction of the radial artery: the radial artery was large and well visualized, with no anomaly or atherosclerotic plaque. Three other patients operated on in this early phase also showed a good late patency of the radial artery. An arterial spasm during the injection of the dye at the first coronary arteriography most probably was the cause of what was thought to be an early obstruction of the graft. New vasodilators, namely calcium-channel blockers, available today stimulated us to revive the use of the radial artery in 1989. We use diltiazem during and after the operation for at least 6 months. Since then, together with Dr Acar, we have placed a radial artery in addition to pedicled or free internal mammary artery in 327 patients in our institution. Graft patency was assessed 1 month to 1 year postoperatively by coronary arteriography in 141 patients. It showed a 92% patency of the pedicled internal mammary artery, a 90% patency of the radial artery, and an 86% patency of the free internal mammary artery. Doctor Dietl and associates insisted on the precautions that should be taken to avoid ischemia of the hand. Using the same precautions, we have not observed any ischemia of the hand; the only disability seen in few instances was a transitory hypoesthesia of the ulnar region. Doctor Dietl, have you been using plethysmography, a test proposed by Dr Brodman to avoid ischemia?
DR DIETL: I thank all the discussants for their comments. Doctor Barner, in our experience, the accepted time limit for the Allen test is 6 seconds. However, we extend this limit up to 10 seconds in some patients who have normal Doppler studies of the upper extremity. But even if the Allen test is negative and the Doppler flows are normal, the decision to remove the radial artery is based on the intraoperative Allen test, which consists in palpating or simply visualizing a pulse in the radial artery distal to a vascular clamp temporarily applied. To answer your question on gentle dilation of the graft, all I do is flush any potential clots inside the graft with heparinized saline solution, without exerting any pressure, because I do not intend to ``dilate'' the graft. As far as medial wall calcification, we did observe it in only 1 patient in the distal segment, which was discarded, and the rest of the radial artery was used.
Doctor Curtis, regarding your question on histologic follow-up, we have not performed any such studies, because we have not yet had to replace any radial artery graft. In our present series, only 1 patient required a reoperation, which consisted in replacing an occluded vein graft with a right gastroepiploic artery pedicled graft. So far, only 5 patients in our series had recurrent angina, and the radial artery grafts were widely patent on angiography in all 5 of them.
Doctor Brodman, regarding your question on the assessment of collateralization, we rely almost exclusively in the intraoperative Allen test, already described. We have not used Doppler studies routinely; we request these studies only if the preoperative Allen test is positive. We think that the Allen test, if performed with a well-relaxed hand, is an excellent method of screening patients who may have radial artery dominance, which are just a few. So far, only 1 patient with an occluded ulnar artery (confirmed by Doppler echography) was denied radial artery harvesting. In 8 other patients who had a positive Allen test, we decided to go ahead and harvest the radial artery because the preoperative Doppler studies were normal. However, the radial artery was not removed in 3 of these patients because the ``intraoperative Allen test'' suggested poor collateralization. In summary, we do not rely on Doppler studies, which have been misleading in 3 patients. We believe that the intraoperative assessment is more dependable.
To answer your question on calcium-channel blockers, we also had several patients who were bradycardic or hypotensive, which may be caused or aggravated by the diltiazem drip. If these problems occur, we simply reduce the dose to one-half. We prefer to continue the drip of diltiazem at 3 to 5 mg/h, and add low-dose inotropic support if needed. We also use temporary atrial pacing wires to increase the heart rate if necessary. Finally, in patients with severe left ventricular dysfunction, we prefer to use amlodipine (5 to 10 mg/day) when the patient can tolerate oral medications.
Doctor Carpentier, I appreciate your comments very much. We have no experience with the plethysmography test, but I agree that it may be of great clinical value.
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