Double Mammary Technique:
for Myocardial Revascularization?
Germán A. Girela, Fernando M. Barbosa, José M. Quiroga,
Pedro Luis Urdiales, Pablo A. Garcia, Gonzalo H. Gutierrez, Juan C. Baro, Francisco A. Mansilla,
Mario Grasso, Demetrio Thalasselis
Instituto Cardiovascular del Sur, Fundación Médica de Río Negro y Neuquén.
Paso de los Libres 712. Barrio Manzanar, Cipolletti, Río Negro.
The authors declare not having a conflict of interest.
Objective: The aim of this study is to evaluatethe feasibility of usingtheright internalmammary artery, withthe left internalmammary artery as majorgraftsincoronary artery bypass.
Material and Methods: SinceJanuary 2011 we performed120consecutive myocardial revascularization procedures usingthe doublemammary technique associated with radialarteryandsaphenous vein, as needed: GroupI-DOMA. The results were comparedwith an equal numberofconsecutivesurgeries, previouslymade, usingthe left mammary artery, radial artery, andsaphenous vein: Group II-MASI. Emergency patients, combinedsurgeryandreoperations were excluded.
Results: The averageage in theDOMAgroupwas60.78 yearsand60.80 yearsforthe MASIgroup. The averagenumber ofbypass, for Group Iwas2.91 and2.94for Group II(p 0,98). Risk factors influence andco-morbidities were evaluated in both groups.Themortalityin group I (DOMA) was2.50% and3.84% in group II(p 0.265). The prevalence ofperioperativestrokewas1.98% in Group I (DOMA), and 4.8% in Group II(p 0.261). Complete revascularizationwas achieved in89.72% in GroupI and88.67% in Group II(p 0.87). Thedreadedcomplicationwith the DOMA technique, mediastinitis, was present in2.97% for GroupIand2.88% for GroupII-MASI (p 0.97).
Conclusions: The use of the double mammary technique for myocardial revascularization in this study population was technically simple and reproducible. The follow-up of these patients is necessary to assess the longevity of the permeability of the bypasses and corroborate the benefits of long-term use.
|Key words: Bilateral internal thoracic artery. Myocardial revascularization. Operative technique.
Rev Fed Arg Cardiol. 2013; 42(2): 135-140
The left internal mammary artery is the duct of choice in myocardial revascularization surgery (MRS), showing permeability in the long term, free from coronary events in the follow-up [1,2,3]. Other ducts, the internal saphenous vein (ISV) and radial artery (RA) are used equally frequently, in lesion of multiple vessels, although without the benefits of the mammary artery. The use of both mammary arteries is widely known [4,5,6,7], but meanwhile, this technique is resisted and underused by different surgical teams , due to aprobable fear to the sternal wound infection associated to diabetic and obese patients, chronic obstructive pulmonary disease (COPD), advanced age, or maybe by technical difficulties and a greater surgical time that may be required, so it has not been adopted as the ideal revascularization technique [7,9].
The objective of our surgical group was to assess whether the revascularization technique with the use of the double internal mammary artery (DIMA) presents similar risks as the use of the single internal mammary artery (SIMA) and whether this technique is technically feasible and reproducible, to evaluate secondly, the potential benefit in the long run of this technique [10,11,12].
MATERIAL AND METHODS
Since January 1, 2011, we made 120 MRS consecutively, using the double internal mammary artery (DIMA) technique, associated to radial artery and internal saphenous vein, according to need: Group I-DIMA. These procedures were compared with an equal number of consecutive surgeries, previously made, in which the internal mammary artery, RA and ISV were used; Group II-SIMA: Single internal mammary artery.
The patients in emergency, candidates to mixed surgeries (cardiac surgery associated to valve or carotid intervention) or to reoperation were excluded.
The concept of incomplete revascularization is controversial. In this paper, we consider as such, not performing a coronary artery bypass, at least to one epicardial coronary vessel, with angiographic criteria for revascularization [10,13,14].
We interpret as revascularizable vessel, those that had a lesion affecting >50% of their caliber, as also those with complete occlusions and visible distal bed by collateral circulation.
We interpret as mediastinitis, the presence of pus in the mediastinum space between both pleurae and the sternum.
The use of the double internal mammary artery (DIMA) technique in MRS may be conducted by 2 techniques in “Y” and “in situ”. In both cases, we dissected both internal mammary arteries in a skeletonized way [15,16], isolated, leaving the satellite veins untouched. In the Y technique, termino-lateral anastomosis is made between both mammary arteries; the left one is sutured in situ to the anterior descending artery and the right mammary artery is anastomosed to the marginal branches of the circumflex artery and whenever possible, to the posterior descending artery of the right coronary artery .
In the in situ technique, the right internal mammary artery is directly anastomosed to the vessel to be revascularized. It is used when the right coronary artery presents a proximal lesion or is occluded, and the circumflex artery does not have revascularizable lesions.
Whichever the technique used, in Y or in situ, the permeability in both cases, in the long term, is similar according to different authors [3,16,18].
The left internal saphenous vein or the radial artery are often used as a supplement to the technique in Y of the double internal mammary artery. In general, the saphenous vein is chosen when the right coronary artery is dominant or the diameter of it is significant enough to prevent the occlusion of the radial artery or the right mammary artery by flow competence . In the case of finding a thinner distal bed, or complete occlusion of the right coronary artery, the radial artery is preferred to the radial artery as a supplement to the bypass of both mammary arteries.
MRS without extracorporeal circulation was the technique of choice of our surgical group, although as participants in the international multicenter CORONARY study , intervention with extracorporeal circulation (ECC) was also carried out in 8.9% of group I (DIMA) and 12.5% of group II (SIMA) when randomized in this manner. The procedures with or without ECC were made with the usual technique.
There were 12 samples taken from all the patients included in the DIMA group (10%) to perform an anatomopathological study of both arteries, right and left mammary arteries, not tagged, so that the report is as objective as possible, to verify if there is evidence of histological differences or not between both arteries.
For the description of the sample, single variable descriptive analysis was used, as mean, standard deviation, and range. The percentages corresponding to the categories of the qualitative variables were estimated, and compared with chi-squared tests (χ2) of independence to determine the association between variables, considering a level of significance below 5%; besides odd ratios were analyzed in the possible cases. Box-plot and dispersion diagrams were applied to describe the behavior of the quantitative variables.
The average age in the DIMA group was 60.78 years old, while in the SIMA group was 60.80 years old (p 0.67), with greater prevalence of the male gender of 82.17% in group I and 79.80% in group II (p 0.55). To evaluate in a fair measure how comparable were both groups, the risk factors and co-morbidities present were recorded in the analyzed groups (smoking, hypertension, diabetes, obesity, dyslipidemias, family history, ejection fraction, previous AMI, vascular disease, stroke and COPD), which are summarized in Table 1.
Table 1. Co-morbidities present in the population studied
AMI: Acute myocardial infarction; COPD: Chronic obstructive pulmonary disease; PVD: Peripheral vascular disease; LVEF: Left ventricular ejection fraction.
The most frequent reason for the consultation in both groups was the presence of unstable angina, then AMI and chronic angor, with a rate of presentation of 54.45% and 67.30% (p 0.55), 18.81% and 15.38% (p 0.62), 12.87% and 5.76% (p 0.09) for groups I and II respectively.
The pre-operative lab did not show significant differences between both groups.
The average number of coronary artery bypasses for Groups I and II was 2.91 and 2.94 respectively (p 0.98). The bypasses made in both groups are summarized in Figures 1 and 2.
|Figure 1 y 2. RMAB: Right mammary artery bypass; ADLMAB: Anterior descending left mammary artery bypass.
The anatomopathological study of the samples taken in both mammary arteries (10% of the total), did not show histological differentiations between the left and right mammary arteries.
The severe impairment of the ventricular function (ejection fraction ≤35%) was present in both groups, in 14% in group I and in 9% in group II (p 0.23).
In the OR, 66.34% of the patients in group I were extubated and 75% in group II (p 0.17).
Complete revascularization could be made in 89.72% (Group I) and in 88.67(Group II) (p 0.87).
Post-operative complications are shown in Table 2.
Table 2. Post-operative evolution
ECC: Extracorporeal circulation; SIRS: Systemic inflammatory response syndrome.
The so feared complication of mediastinitis was present in 2.97% of the patients in Group I (DIMA) and in 2.88% of Group II (SIMA) (p 0.97) with mortality of 2.50% in group I and 3.84% in group II (p 0.265).
Group II (SIMA) presented infection at the surgical site of the saphenectomy in 6.13% of the cases, which caused a re-admittance of the patients to the OR to make a toilet of the affected area. The DIMA group did not present infection in the surgical site.
The average time of post-operative stay in the Coronary Unit was 2.61 days in the DIMA Group and 3.0 days in the SIMA Group (p 0.0243). The total number of hospitalization days, since the surgery until the institutional discharge, was 5.61 for the DIMA Group and 6.31 for the SIMA Group (p 0.0147, OR 0.31, CI 95% of 0.12-08).
An appropriate myocardial revascularization prevents necrosis and/or myocardial ischemia with the relief of their symptoms. There are two ways to revascularize the myocardium, coronary angioplasty (PTCA) and myocardial revascularization surgery (MRS). PTCA with the important challenge of defeating the restenosis rate and the need of performing new procedures, is less invasive with a significant rate of successes, while MRS is a more aggressive procedure with very good results in the long term. Different ducts may be used, the left and right mammary artery, internal saphenous vein and radial artery . It has been proven that the permeability of coronary bypasses exceeds by far the one obtained by PTCA, and that the patients that receive a mammary bypass to the anterior descending artery have a greater survival and less amount of coronary events in the follow-up in the long term .
In MRS, different authors showed that the use of both internal mammary arteries  yields better results than those revascularized only with the left mammary artery [23,24,25,26,27,28]. Although the DIMA technique is already very well known, it is not accepted by all the surgical groups; as an example of this we have the work by Tabatas et al , who using the database of the Society of Thoracic Surgeon, showed that over 541,368 MRS performed in the period from 2002 to 2005, only in 4% the double internal mammary artery (DIMA) was used.
Diabetes is an independent predictor of greater mortality by cardiovascular disease [26,29]. Its presence entails a greater progression of the disease, occlusion of coronary bypasses and greater mortality after MRS [30,31,32]. The BARI study  showed in a 7-year follow-up, better results in revascularized diabetic patients with a mammary coronary bypass in regard to the venous bypasses with a greater survival free from cardiovascular events.
The use of DIMA is more discussed in insulin-dependent diabetic patients .
From the patients revascularized by our surgical group with double mammary internal artery (DIMA), 46.53% were diabetic, from whom 21.27% required insulin; in the SIMA group, 36.53% were diabetic and from them, 27.1% required insulin.
There were no significant differences in the presence of mediastinitis between both groups, mainly with the skeletonized dissection technique on both internal mammary arteries in isolation, leaving the satellite veins untouched. With this technique, sternal irrigation was not affected, as it does happen when the mammary arteries are dissected in a pediculated way (dissecting the satellite veins jointly), preserving the vascularization of the sternum, with less chances of suffering infection or dehiscence [15,34,35,36,37,39].
The use of the double mammary artery technique puts the cardiovascular surgeon in front of one of his/her greatest challenges, wondering about the use of such grafts in diabeticand obese patients, or those with history of COPD, by the danger of a mediastinitis, without a clear evidence that would justify not using these grafts in patients in high risk. Our experience did not show a significant difference in the presentation of this entity between both groups. Using the double mammary artery technique entails a deterioration in the irrigation of the sternum, which meant an increase in the incidence of mediastinitis, a fact that did not happen in our cases, as it did not happen in the wide bibliography consulted either [11,35,36,37,38]. We support that using the skeletonized double mammary artery protects the sternal vascularization over the pediculated dissection, so according to our results, using these grafts is advised in a skeletonized fashion, even in diabetic and obese patients, or those with history of COPD [11,38,39].
The rate of mediastinitis for the DIMA group was 2.97% and 2.88% for the SIMA group (p 0.97). There was no greater rate of mediastinal infection in diabetic patients, including those that required insulin in both groups, a fact that supports that diabetes in its different clinical forms is not a contradiction for the use of the double mammary artery technique, in agreement with other authors that show similar results with the application of DIMA in diabetic patients .
It is worth mentioning that the only statistically significant value in favor of the DIMA group was the time of hospitalization, 5.61 for the DIMA group and 6.31 for the SIMA group (p 0.0147; OR 0.31; CI 95% of 0.12-0.8), without finding a clear explanation for this finding.
The similar histological findings in the examined non-tagged samples, manifest that both mammary arteries, right and left, are identical, so they should be considered optimal ducts to revascularize more than one coronary vessel and not choosing another duct as an alternative (saphenous vein or radial artery) [17,40].
The use of the DIMA technique, currently underused as a duct for myocardial revascularization, is technically feasible, simple, reproducible even in patients considered in high risk (diabetic and obese patients, those with COPD) in whom the immediate results were satisfactory, with a low rate of complications, comparable to those of the SIMA technique. The long term follow-up is necessary to evaluate the permeability of the bypasses and verify if the immediate benefits are maintained over time.
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Publication: June 2013