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Ann Thorac Surg 2001;72:1552-1556
© 2001 The Society of Thoracic Surgeons
a Department of Cardiovascular Diseases, Catholic University School of Medicine, Santiago, Chile
b Clinica Alemana, Santiago, Chile
Accepted for publication June 28, 2001.
* Address reprint requests to Dr Moran, Department of Cardiovascular Diseases, Catholic University School of Medicine, Marcoleta 367, Santiago, Chile
e-mail: smoran{at}med.puc.cl
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Abstract |
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Methods. One hundred fifteen patients were studied who had myocardial revascularization with the radial artery plus internal mammary and vein grafts with 3.5 ± 1.1 grafts per patient. Sixty-three patients received diltiazem and 52 patients did not. Base line and follow-up angiographies were analyzed 1 year postoperatively in 50 of these patients with a quantitative computerized method.
Results. One hundred fourteen patients survived and were followed for 30.1 ± 12.6 months. Patency for mammary grafts was 100%, for radial grafts it was 80%, and for saphenous vein grafts it was 68%. Patent radial artery grafts had significantly greater degree of stenosis in the native vessels than occluded grafts (73% ± 14% vs 40% ± 24%), (p = 0.0007; confidence interval = 95%). Radial artery patency increased to 92% when arteries with 70% or more stenosis were considered. No differences were observed for clinical and angiographic end points in the patients that received diltiazem compared with the rest who had not.
Conclusions. The degree of stenosis in the native coronary artery significantly influences the patency rate of radial artery grafts, independent of diltiazem.
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Introduction |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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Our experience with RA started in 1993 in patients without saphenous veins as indication for its use. Excellent clinical and angiographic results in these cases prompted us to start a prospective study in order to evaluate the need for calcium-channel blockers and discern the most appropriate patient characteristics to obtain better angiographic results. Data on angiographic predictors of arterial graft patency, particularly RA grafts, are scarce.
We report the clinical results of 115 consecutive patients in whom the RA was utilized for myocardial revascularization in conjunction with one or two internal mammary arteries (IMAs) and saphenous vein grafts (SVGs), and the angiographic results of 50 patients who consented to one-year postoperative follow-up angiographies.
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Patients and methods |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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The surgical technique used for obtaining the RA graft was similar to that described by Acar and colleagues [1], with emphasis on minimal trauma and avoidance of intraluminal probes and catheters. The RA was externally irrigated with papaverine solution to release spasm while obtained concomitantly with other conduits, such as the IMAs or saphenous vein. Immediate closure of the forearm wound (before heparinization) together with a firm crepe bandage was used to lessen the chance of infection and hematoma. All patients were operated on with the aid of cardiopulmonary bypass under moderate hypothermia (28°C) and antegrade or retrograde cold crystalloid cardioplegia. The site of the proximal anastomosis was the ascending aorta in 74 patients, the head of a saphenous vein graft in the ascending aorta in 39 patients, or the left internal mammary artery as end-to-side anastomosis in 5 patients.
To evaluate the use of calcium-channel blockers, patients were randomly divided in two groups: 63 received diltiazem (group 1) and 52 did not (group 2). There were no statistical differences in patient characteristics between them. Diltiazem was given 1 µg x kg-1 x min-1 intravenously in the operating room as soon as harvesting started and was continued in the intensive care unit until the patient was able to take it orally (180 mg/d). These patients then continued the diltiazem in addition to aspirin (100 mg/d) for 1 year. Clinical end points were: the presence of visible RA spasm during the operation, episodes characterized by acute heart failure progressing to cardiac arrest associated with ischemic electrocardiogram changes postoperatively, perioperative myocardial infarction (new Q waves in the electrocardiogram), and recurrence of angina of any type.
The Institutional Review Board approved the postoperative study. All patients were offered an angiographic reevaluation of the coronary grafts 1 year after the operation. Indication for study was the patient’s acceptance only. Angiographies were performed on an ambulatory basis with 6-French catheters inserted through the other radial artery. A complete study of the coronary arteries and of all the implanted grafts and a left ventriculography was attempted in all patients. Attention was given to exact correspondence of different projections between preoperative and postoperative angiograms so that careful analysis of the degree of stenosis and the size of the recipient coronary artery could be performed.
All measurements on angiographic images were performed with a quantitative computerized angiography method utilizing a digital scanner (Microtek II; Microtek, San Francisco, CA) and an ad hoc National Institutes of Health program [10]. To calculate the degree of coronary stenosis, the normal segment of the artery proximal to the lesion was used as a reference and the difference with the minimum luminal diameter of the stenotic lesion was considered the percent of stenosis. The mean value of five measurements was considered the degree of stenosis for this study. Graft evaluation was classified as: (1) perfect patency, (2) patency with localized stenosis, (3) string sign or severe and extensive narrowing of the whole body of the graft, and (4) occlusion.
Clinical follow-ups were performed at regular intervals at the outpatient clinic or by referring doctors for out-of-town patients. No patients were lost to follow-up.
Statistical analysis
All results are expressed as means ± standard deviation and differences were considered significant when the p value was less than 0.05. Risk factors, patency rates and other parametric data were examined with contingency tables, Fisher’s exact test, or 
2 test as appropriate. Independent predictors of graft patency were estimated by multiple logistic regressions. For the comparison between the two groups, the analyses were made by the unpaired Student’s t test and 2 test. Multivariate regression analysis was performed to investigate the influence of the degree of native coronary stenosis, proximal and distal anastomosis site, and demographic and EF data on RA patency.
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Results |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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In the 115 patients in whom the ulnar blood flow was found adequate for RA harvesting, no unsuitable grafts were observed during operation. With respect to forearm status, there were no ischemic complications seen in any patients. No functional disturbances related to the RA harvesting were reported during follow-up. One patient had a wound infection of the forearm incision that healed rapidly with treatment.
Clinical follow-up was complete on all surviving patients. Mean follow-up was 30.1 ± 12.6 months (range, 12 to 51 months). Patients had follow-ups at 1 month and 3 months postoperatively and every 6 months thereafter. Hypertension, diabetes, or other medical conditions determined more frequent visits.
Most patients (96.5%) were free of angina during follow-up and there was no need for reoperation. Angina developed in 4 patients postoperatively. In 2 patients repeat coronary cine angiography showed graft occlusion and a patent but stenosed native coronary artery. Percutaneous transluminal coronary angioplasty was performed electively in these 2 patients.
No difference in clinical status was found between patients who received diltiazem (group 1) and those who did not (group 2). Specifically, there was no difference in the incidence of ischemic or other cardiac events suggesting graft occlusion or spasm of the RA graft in particular.
Fifty patients gave informed consent to undergo angiography 12.3 ± 4 months after the operation (range, 6 to 24 months; median, 13 months); 29 of these patients were in group1, and 21 of these patients were in group 2. One hundred seventy two grafts were studied, 56 IMAs, 51 RAs and 65 SVGs. In two patients the left IMA was not accessible through the right RA, and the patients refused a femoral puncture, and one SVG was not catheterized. All IMA grafts were patent although four had the string sign. Thirty-five RA grafts were widely patent, six had the string sign, and 10 were occluded. Forty-four SVGs were patent and 21 were occluded; there were no string signs in the vein grafts. Grafts with diffuse severe narrowing (string sign) were not responsive to in situ vasodilator injection. No statistical significant differences in angiographic patency were observed between patients receiving diltiazem and those who did not. Details of angiographic results are summarized in Table 4.
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Patent RA grafts had a significantly greater degree of native coronary artery stenosis than occluded grafts (73% ± 14% vs 40% ± 24%), (p = 0.0007; confidence interval = 95%). In 9 out of 10 occlusions there was a less than 70% lesion in the native recipient coronary artery. The string sign was present in four IMA grafts (7%) out of the 56 IMA grafts studied, and in two of them, the grafts were anastomosed to coronaries with less than 70% stenosis. The rest of the grafts were perfectly patent and had excellent flow. Radial artery grafts presenting the string sign had significantly less severe native coronary lesions than perfectly patent RA grafts (51% ± 19% vs 73% ± 14%), (p < 0.02). Neither the sites of the proximal or distal anastomosis nor the EF had a significant influence on RA graft patency. The EF in patients with patent RA grafts was normal in 70% (25 of 35), mildly impaired in 19% (6 of 35), and moderately impaired in 12% (4 of 35). Whereas, the EF in patients with occluded grafts was normal in 70% (7 of 10), mildly impaired in 10% (1 of 10), and moderately impaired in 20% (2 of 10). No differences in patency were found in patients with diabetes, hypertension, or hyperlipidemia. Univariate and multivariate analysis demonstrated that the degree of coronary artery stenosis was a strong predictor of RA patency (p = 0.00001; odds ratio = 1.08).
The occlusion rate of the saphenous vein graft anastomosis showed no correlation with the degree of stenosis of the bypassed lesion. Nevertheless, it must be taken into consideration that our policy was to utilize the SVG for secondary coronary arteries. In 15 patients with 21 occluded grafts, five were diagonals and 10 were small circumflex arteries (< 2 mm in diameter).
Overall patencies were 100% for left IMAs, 100% for right IMAs, 80% for RAs, and 68% for saphenous vein grafts at 1 year postoperatively. However, if only RA grafts to coronary arteries with stenosis 
70% are considered, their patency increased to 92%.
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Comment |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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Arterial graft spasm early after the operation can be a devastating event [2, 11], but in no instances was this complication seen in our experience. Other important clinical events such as myocardial infarction, recurrence of angina, or the need for repeat revascularization were very infrequent, and these did not differ between groups 1 and 2. This agrees with observations from other series in which patients that did not receive diltiazem or who discontinued diltiazem had no adverse effects [3, 4, 6].
Calafiore and colleagues [2] and Possati and colleagues [6] have advocated that RA grafts should be used when bypassing lesions with 70% or more based on their clinical experience. Angiographic evidence from our study, using a reproducible and objective method, gives a quantitative support to this advice. In our series, the degree of native coronary stenosis was a strong predictor of RA patency. When the degree of stenosis in the native coronary artery is 70% or more, the RA graft patency approaches that of the IMA at 1 year postoperatively. On the other hand, we also confirmed that the string sign is almost an exclusive finding in arterial grafts, phenomena that is significantly associated with bypassed stenosis of 70% or less, whereas SVGs are either completely patent or occluded [9, 12].
We also found that there were no differences between patients who received diltiazem and those who did not. Given the thickness of the RA muscular layer, spasm has been observed in response to mechanical stimuli that is twice as frequent as that observed for the IMAs [1, 13]. However, in the present series only 1 patient with asymptomatic vasospasm was seen in an RA graft studied 15 months postoperatively. Therefore the use of diltiazem seems unnecessary, and given the fact that it is poorly tolerated by some patients, particularly those with poor left ventricular function, this evidence may be relevant.
Our results show that patency in arterial grafts correlates with the degree of coronary stenosis and may be explained by the fact that these grafts adapt themselves to the amount of flow through them. They tend to diminish in size if low flow is present and they grow when demand increases [14, 15]. This effect could be related to the phenomenon of shear stress on nitric oxide production with its correspondent protective effect on endothelium and vascular smooth muscle [16].
Saphenous vein graft patency in our study was similar to that of other series in which it was used for secondary small coronary branches with less prognostic impact [17]. Although it has been shown to have excellent patency when anastomosed to major coronary arteries, its known tendency to occlusion after 10 years has led us to modify its indications [18]. On the other hand, it can be used when bypassing arteries with less than 70% stenosis, because there seems to be no correlation between the degree of stenosis of the recipient artery and the saphenous vein graft patency in our data as well as from other groups [19]. Another approach to this problem could be to avoid operations in nonsignificant coronary lesions, and if they increase to provoke ischemia during late follow-up, a less invasive therapy such as percutaneous transluminal coronary angioplasty could then be used.
Careful handling and good patient selection make the RA a very good conduit for coronary revascularization. With these recommendations and known potentiality for long-term patency [20], excellent clinical results and freedom from coronary events can be anticipated.
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Acknowledgments |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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This study was supported by a research grant from Clinica Alemana, Santiago, Chile.
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