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Ann Thorac Surg 2000;70:1378-1383
© 2000 The Society of Thoracic Surgeons

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Original articles: cardiovascular

Myocardial revascularization with radial and mammary arteries: initial and mid-term results

^a Department of Cardiovascular Surgery, Favaloro Foundation, Buenos Aires, Argentina
^b Department of Medicine, Institute of Cardiology and Cardiovascular Surgery, Favaloro Foundation, Buenos Aires, Argentina

Address reprints requests to Dr Weinschelbaum, Larrea 1007 "10 ° C" Z.C: C1117ABE, Buenos Aires, Argentina
e-mail: ew{at}datamarkets.com.ar

	Abstract

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
Background. The radial artery is being used with increasing frequency instead of the saphenous vein in coronary artery bypass grafts. We analyzed the in-hospital and midterm results in patients undergoing coronary artery bypass surgery in whom a combination of arterial grafts was used, including radial artery and one or both internal mammary arteries.

Methods. Between 1995 and 1998, 1,023 patients underwent coronary artery bypass surgery using arterial conduits. The left internal mammary artery and the right internal mammary artery were employed in combination with the radial artery.

Results. An average of 3.2 grafts per patient were done. The left internal mammary artery and radial artery were used in 100% of patients, the right internal mammary artery in 21.7%, and a venous graft in 31%. The operative mortality rate was 2.5%. On repeat angiography performed in 62 patients before their discharge, the arterial conduits were patent in 98.4%. Mean follow-up was 25.0 ± 9.6 months (1 to 48 months). The probability of survival was 92.8%

Conclusions. Revascularization using mammary and radial artery grafts is safe. Complications are not higher than those observed with saphenous vein grafting. It was possible to use arterial conduits in all the patients, even in those with impaired left ventricular function.

	Introduction

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
Despite the significant advance observed in cardiology and cardiovascular surgery over the past decades, coronary artery disease continues to be the main cause of death in developed countries [1].

In recent years, the use of myocardial revascularization surgery for coronary artery disease has grown, employing autologous saphenous vein grafts (SVG) alone or in combination with diverse arterial conduits (ACs), mainly the internal mammary artery (IMA) and, more recently, the radial, epigastric, and gastroepiploic arteries [2–6].

Surgical success depends, among other factors, on the quality of the native vascular beds receiving the revascularization and, obviously, upon the midterm patency of the grafts. In this regard, it has been unquestionably demonstrated that IMA shows a high midterm patency rate, comparatively higher than that of SVG, resulting in a lower incidence of events and better survival [7–12]. The development of a peculiar form of arteriosclerosis in this vein encouraged the investigators to pay attention to other type of grafts, particularly arterial ones (other than the IMAs), to improve the mid term outcome of myocardial revascularization [13]. Interestingly, the radial artery (RA) was first used as an alternative conduit for coronary artery bypass grafting (CABG) in the early 1970s by Carpentier and colleagues [14]. However, given the poor results obtained during that early experience, its use was abandoned. Twenty years later, Acar and colleagues resuscitated interest in the use of this artery when they reported very good midterm results [15]. Probably, the main reasons for this success were first, the use of calcium antagonists to treat or prevent RA spasm; second, modifications of the harvesting technique; and third, avoiding endothelial damage through a more careful manipulation during anastomosis. Since then, other groups have reported and encouraged RA use due to the very good results obtained [6–8].

The main objective of the present study was to prospectively analyze the in-hospital and midterm results observed in consecutive patients undergoing CABG in whom a combination of AC were used. We utilized the left internal mammary artery (LIMA) as an in situ graft, and/or the right internal mammary artery (RIMA) as a free or in situ graft, and the RA connected to the LIMA, mainly through a T or Y anastomosis or, less frequently, directly emerging from the ascending aorta.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
We prospectively analyzed the in-hospital and midterm results of myocardial revascularization surgery using ACs in 1,023 consecutive patients operated upon between May 1995 and May 1998. Patients with single vessel lesions, associated surgical procedures, chronic renal failure, hemodialysis, or a combination of those factors were excluded from the study, as were patients with type I diabetes. The mean age of the study population was 59.8 years (range, 33 to 86 years); 139 (13.5%) were older than 70 years. The study population included 908 (88.7%) men and 115 (11.3%) women.

In all patients, we employed a conventional surgical technique previously published by one of the authors [8].The mean time of extracorporeal circulation was 97.8 ± 34.2 minutes and that of aortic cross clamp was 80.79 ± 28.98 minutes.

For premedication, patients received lorazepam 2.5 mg orally 6 hours before surgery and 1 mg sublingually 1 hour before surgery. Anesthesia was induced with sufentanil citrate 250 µg/kg or pancuronium 8 to 10 mg, and maintained with propofol 5.7 mg · kg^-1 · min^-1 and 100% O₂. In all cases, the surgical approach was a midsternotomy.

Preparation of the conduits
The dissection technique of the IMAs, both for free and in situ grafting, was conventional [16].

The RA was dissected through a skin incision starting 2 cm distal to the elbow and ending 3 cm proximal to the wrist. All collaterals were occluded using hemostatic clips. The length thus obtained ranged from 18 to 20 cm. In all cases, a triple evaluation of the irrigation of the hand was made. The first evaluation took place the day before surgery by means of a modified Allen’s test [17]. The use of the RA was discarded when the test was positive and in order to maximize safety, it was also ruled out when the result of the test was doubtful. The second evaluation was made by the anesthetist in the operating room, and the third was made with the RA exposed. Before sectioning, recurrent circulation through the palmar arches was tested. Although compressed at its proximal end with two fingers of one hand, the artery was emptied in distal direction over approximately 20 cm with two fingers of the other hand. Then the distal compression was removed, and the circulatory sufficiency of the palmar arch was assessed by observing retrograde arterial repletion. Any time this retrograde repletion was abnormal or considered inadequate, use of the RA was discarded. The RA was harvested only from the nondominant forearm. Excess removal of surrounding tissue was avoided.

Anastomosis of the conduits
The LIMA was used as an "in situ" graft, generally to revascularize the left anterior descending artery (LAD) territory, in combination with the RIMA, the RA, or both, preferentially directed to the territories of the circumflex artery, the right coronary artery, and the diagonal branch of the LAD. All arterial anastomoses were performed using a continuous suture with 8-0 polypropylene (Prolene, Ethicon, Somerville, NJ). When the RA was connected to the IMA, the technique described by Tector and colleagues was used [18]. Figure 1 is an example of the procedures employed.

View larger version (109K): [in this window] [in a new window]   Fig 1. Total arterial revascularization with the left anterior internal mammary artery (LIMA) and double sequential radial artery (RA) graft. Contrast is injected through the LIMA only. Another segment of the RA revascularizes the distal posterior descending artery of the right coronary artery (RCA). The proximal anastomosis was made in a chronically occluded stump of the RCA. (A) Left anterior oblique view of the LIMA graft to the left anterior descending artery and RA graft to the diagonal (DG) and circumflex (CX).(B) Left anterior oblique view of a coronary-coronary bypass in the RCA using the RA. The arrows indicate the sites of the anastomoses.

Angiographic restudy
Consent was obtained from the first 62 patients to undergo coronary angiography with conventional Judkins technique [19] to assess patency and angiographic characteristics of the grafts.

Follow-up was conducted either by clinic visit or by telephone interview every year. When patients could not be contacted, information was obtained from a family physician. Eight patients (0.8%) were lost to follow-up. The mean follow-up time was 25.0 ± 9.6 months (range, 1 to 48 months).

Statistical analysis
The software S-plus (S-plus Data Analysis Products Division. MathSoft, Seattle, WA) was used for statistical analysis. The estimates of the survival curves were computed using the Kaplan-Meier method and standard errors with the Greenwood formula. We used the modified Peto method to compute the confidence intervals, a method known to be useful when there are few observed events.

For multivariate analysis, we included the variables considered as possible risk factors listed in Table 1 for arterial revascularization only. Stepwise logistic regression analysis was applied to identify independent risk factors for in-hospital mortality. Then, excluding in-hospital deaths, Cox proportional hazard regression analysis was used to identify the risk factors for late mortality and development of angina class III to IV. We considered a risk factor as statistically significant when p 0.05.

	Results

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

In total, 4,728 anastomoses (4.6 per patient) were performed, and 3,383 grafts (3.3 per patient) were inserted. A single IMA was used in 801 patients (78.3%), and two mammary arteries were used in 225 (22%). The LIMA was used in 1,023 patients (100%) and the RIMA in 225 (22%). Table 2 shows the single and sequential anastomoses performed with the LIMA and the territories revascularized with the RIMA.

No neurologic or ischemic complications were observed in the arm from which the RA was harvested. In 156 patients (15.2%) transitory dysesthesias occurred in the operated arm. In 15% of the patients, the use of the RA was discarded due to inadequate retrograde circulation. Those patients were excluded from this report.

Angiography restudy
One graft was occluded (1.6%) and 1 (1.6%) showed a less than 50% narrowing of the lumen. One patient (1.6%) had challenged flow between the RA and mammary graft, with excellent distal filling. In 3 patients (4.8%) we observed a steal phenomenon of the RA to the distal third of the IMA with no clinical or functional relevance. Radial artery spasm occurred in 3 patients (4.8% of those who underwent angiographic study). All mammary grafts were patent.

Follow-up
Twenty-six patients died during follow-up. The cause of death was cardiac in 16, noncardiac in 7, and unknown in 3. Including in-hospital mortality, Kaplan Meier survival estimates at 3 years was 92.8% (95% confidence interval, 90.5 to 95.1) (Figure 2). Multivariate analysis showed that ejection fraction less than 20 (hazard ratio, 2.9, p, 0.01) and older age (hazard ratio, 1.05, p, 0.03) were the statistically significant predictors of late mortality. Nine hundred sixty-three patients were alive. During follow-up a repeat angiogram was necessary in 15 patients (1.5%) because of signs or symptoms or both of ischemia at a mean of 13.5 months postoperatively. The mean age of these subjects was 60.5 years (range, 37 to 73 years). They had a total of 15 LIMA grafts, 14 (93.3%) of which were patent, including all 6 RIMA grafts. Of the RA grafts, 9 (60%) were patent and 6 were occluded; of the saphenous grafts, 1 was patent and 2 were occluded.

View larger version (13K): [in this window] [in a new window]   Fig 2. Estimated survival including hospital deaths and 95% confidence interval for all patients.

View larger version (13K): [in this window] [in a new window]   Fig 3. Estimated survival free from angina and 95% confidence interval.

	Comment

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

Because of the high midterm patency rates achieved with single and double IMA grafts, it is reasonable to assume that the use of this artery in combination with other ACs would further improve the results of CABG. Therefore, the use of arterial grafts in patients with coronary artery disease undergoing CABG expanded progressively over the course of our study [20].

The need for the use of other ACs arises from the impossibility of achieving complete revascularization with only the IMAs in multiple vessel disease.

The midterm advantages of the in situ IMA graft were in fact the reasons that directed its use almost exclusively to the most important myocardial territory, generally that supplied by the LAD [7–9, 11]. Other ACs were thus employed for areas supplied by the right coronary artery and the circumflex artery.

The present study shows that the use of mammary anastomoses in combination with the RA does not increase surgical mortality, which was similar to that reported by others [22]. The role of the RA is placed after the established LIMA pedicle graft and even after the RIMA pedicle or free graft.

The combined use of both IMAs and the RA allowed us to perform an average of 3.2 grafts per patient, which, in turn, permitted complete myocardial revascularization. Moreover, achievement of complete revascularization with only ACs was possible in 69% of the patients.

It has been claimed that the use of the RA and, in general terms, of ACs, may result in low myocardial flow because of the technical difficulties associated with multiple mammary-radial and radial-coronary anastomoses, and because of the vasospastic tendency of the RA [6, 23]. It has also been claimed that it should not be used in patients with poor left ventricular function, preexisting heart failure, or both. Our study showed that the incidence of perioperative acute myocardial infarction was very low (3.1%), that only 8.5% of the patients developed cardiac failure postoperatively, and that the need for postoperative aortic counterpulsation was 3.7% despite the fact that 14.8% of the population exhibited severely depressed preoperative left ventricular function.

It has been suggested that a prolonged extracorporeal circulation time is a poor prognosis predictor [22] and that the use of ACs is associated with longer duration of cardiopulmonary bypass. This was not the case of the present study, in which the time of extracorporeal circulation was similar to that of conventional CABG using LIMA combined with SVG.

It should be noted that, given the significant thickness of the RA muscular layer, spasm is prone to develop in response to mechanical stimuli [6, 15, 23]. This vasoconstrictive response is twice that of the IMA, presumably because of it’s the thick muscular media [24]. However, in the present series, vasospasm was seldom angiographically documented.

The use of calcium channel blockers has been presumed to be very effective in treating spasm. However, Manasse and colleagues [25] demonstrated that calcium antagonists offer no protection against serotonin-induced vasoconstriction of the RA. This may explain the lack of differences in outcome between patients treated continuously with calcium blockers and those who discontinued calcium blockers early (20% in our series) because of adverse effects, such as hypotension, bradycardia, or heart failure.

A change in harvesting technique along with pharmacological prevention of spasm by the use of calcium antagonists and better and more-delicate manipulation of the graft avoiding any instrument inside the lumen are thought to be the primarily reasons for the improved early results.

Particularly relevant is the fact that the use of the RA did not provoke any functional consequences in the arm from which it was harvested. In only a few patients of this series, the use of the RA had to be discarded because of a positive Allen test. It should be noted that the tests employed to assess sufficiency of retrograde circulation through the palmar arch gave reliable results, since no ischemic complications were observed either in the early postoperative period or in the midterm.

Although there is no absolute contraindication for reoperation, caution is needed when assessing the distal portion of the graft, which sometimes suffers lumen loss secondary to hyperplasia produced by cannulation and puncture during the initial procedure. This may affect the length of the graft and must be taken into consideration when planning the operative strategy.

Calcification of the RA is another point of caution. The artery is rarely occluded, but the observation of calcified plaques may suggest the presence of Monckeberg’s arteriosclerosis [13], in which case the use of the artery should be discouraged. This was seen in 5% of our experience, and it is more frequent in diabetic patients.

Caution must be taken when revascularizing coronary arteries with 50% to 70% stenosis. This situation has been associated with graft occlusion; in such patients, a SVG might have better late results.

The hypoperfusion syndrome is well known to occur with IMA grafts and it can also occur with the radial grafts. This is a multifactorial phenomenon seen in all ACs, and it is related to arterial spasm from a variety of causes, among which are competitive flow, poor run off, technical defects during harvesting, and saline slush in the pericardium. When the syndrome is recognized, a supplemental SVG to the same artery must be urgently performed, in the present study, however, we never saw this syndrome.

Additional advantages of the RA with respect to other conduits are its easy access, and availability; in addition, its relatively great length allows multiple anastomoses, as shown in this article.

We have frequently used the T-shaped anastomosis with LIMA and we have also performed side-to-side anastomoses to revascularize several lateral branches at the same time. The operative technique was described previously by one of the authors [8]. More follow-up information will be needed on this technique

Finally, although angina is usually considered a relatively soft end point, we consider that in asymptomatic patients, a high proportion show a clear-cut improvement in quality of life and a significant absence of recurrent ischemia. In addition, the low mortality rate, the excellent survival curve, and the almost absent need for new revascularization procedures in midterm encourage the use of RA in combination with the IMAs for myocardial revascularization.

We conclude that it is possible to achieve multiple revascularization by combining the RA with one or both IMAs for the following reasons: Myocardial revascularization procedures using a combination of mammary and RA grafts are safe. In-hospital and midterm morbidity and mortality are not higher than those observed with SVG. It is possible to achieve myocardial revascularization with ACs, even in patients with multiple lesions and impaired left ventricular function, and ACs can be used in elderly patients. However, longer follow-up times are needed to draw firm conclusions.

	Acknowledgments

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
We thank Dr Marta García Ben for statistical assistance, Dr Gerardo Edgar Bozovich, from the Emergency Department, and Dr Alberto Crottogini, from the Basic Sciences Research Institute (Favaloro Foundation), for helping in the preparation of the manuscript.

	References

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Ernesto E. Weinschelbaum Víctor M. Caramutti Mariano R. Favaloro Roberto R. Favaloro Eduardo A. Dulbecco Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Weinschelbaum, E. E. Articles by Gabe, E. D. Search for Related Content PubMed PubMed Citation Articles by Weinschelbaum, E. E. Articles by Gabe, E. D.