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Ann Thorac Surg 1996;61:1708-1712
© 1996 The Society of Thoracic Surgeons

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Original Article: Cardiovascular

Right Internal Thoracic Artery Through the Transverse Sinus in Myocardial Revascularization

Hospital Beneficência Portuguesa de São Paulo, São Paulo, Brazil

Accepted for publication December 30, 1995.

	Abstract

Top Footnotes Abstract Introduction Patients and Methods Results Comment References

 
Background. This study presents the late patency rate of the right internal thoracic artery (ITA) used in situ through the pericardium transverse sinus to the circumflex artery and its branches.

Methods. From April 1983 to December 1994, 2,642 patients were submitted to myocardial revascularization; 201 of them had bilateral ITAs. The right ITA through the transverse sinus was grafted to obtuse marginal artery in 170 patients (84.5%) and the left ITA was grafted to the anterior descending artery in 188 patients (93.5%). Angiographic studies were performed in 80 patients, 44 patients in the immediate postoperative period and 36 patients in the late follow-up (mean, 51.6 months).

Results. The right ITA was patent in 75 patients (93.7%) and the left ITA was patent in 77 (96.2%). At the late postoperative period, the right ITA was patent in 33 patients (91.6%) and the left ITA was patent in 34 (94.4%).

Conclusions. The right ITA placed through the pericardium transverse sinus has a good long-term patency rate, similar to that observed with the left ITA and superior to that of saphenous vein grafts for myocardial revascularization.

	Introduction

Top Footnotes Abstract Introduction Patients and Methods Results Comment References

 
See also page 1712.

The internal thoracic artery (ITA) is considered the ideal graft for myocardial revascularization. Several authors reported elevated early and late patency of the left ITA, especially when used to the left anterior descending artery; this method leads to a lower incidence of cardiac events and necessity of reoperation and to better long-term survival when compared with the use of saphenous vein grafts alone [1–5].

Although some authors reported no increased surgical risk and good long-term survival with bilateral ITA grafts [6–9], there are few comparative studies between the use of two versus one ITA [10, 11], and the real benefit of the use of bilateral ITA grafts in myocardial revascularization remains controversial [12].

The topographic anatomy of the left ITA is favorable to be used in situ and grafted to the left anterior descending artery. On the other hand, the right ITA has been used for several coronary branches through different methods. In 1984, Puig and associates [13] demonstrated that the right ITA can be used in myocardial revascularization in situ through the transverse sinus to the circumflex artery and its branches. This study presents our late results with this technique.

	Patients and Methods

Top Footnotes Abstract Introduction Patients and Methods Results Comment References

 
Patient Population
From April 1983 to December 1994, 2,642 patients were submitted to myocardial revascularization. In 201 of these patients, the right ITA was placed through the transverse sinus and grafted to the circumflex artery and its branches, and the left ITA was grafted to the left anterior descending artery. These 201 patients provide the basis for this study.

Bilateral ITA grafts with the right ITA through the transverse sinus were used in patients with normal ventricular function, mild to moderate ventricular dysfunction, and triple- or double-vessel disease with the proximal lesion in the circumflex artery and its branches. Severe obesity, chronic obstructive pulmonary disease, and age more than 70 years were contraindications to this procedure. This series also excluded emergency cases, reoperations, and patients who had concomitant valve procedures, carotid endarterectomy, or aneurysmectomy.

Preoperative Clinical Characteristics
There were 155 men (77.1%) and 46 women (22.8%), their ages ranging from 35 to 68 years with a mean of 48.9 years. Coronary risk factors included hypertension (diastolic pressure greater than 90 mm Hg) in 102 patients (50.7%), diabetes in 17 patients (8.4%), smoking in 128 patients (63.6%), and prior myocardial infarction in 43 patients (21.3%). The patient's preoperative symptoms for angina were defined by the New York Heart Association classification [14]. Immediately before the operation, 50 patients (27%) were in class I, 14 (6.9%) in class II, 114 (56.7%) in class III, and 23 (11.4%) in class IV.

Preoperative Angiographic Findings
Preoperative angiographic study showed triple-vessel disease (greater than 50% stenosis in all branches) in 139 patients (69.1%) and double-vessel disease in the remaining 62 patients (30.8%). Fifteen of these patients (8%) had left main coronary artery stenosis. Left ventricular function was assessed on basis of segmental impairment using the standard ventricular score of the National Heart and Blood Institute [15] and was judged to be normal in 127 patients (63.1%), mild impairment in 59 patients (29.3%), and moderate impairment in 15 patients (7.4%).

Surgical Procedure
The right and left ITAs were harvested with adjacent tissue. The intercostal and mediastinal branches were ligated. Dissection was performed from the origin of the ITA at the subclavian artery to about 2 cm before their bifurcation near the diaphragm. After distal sectioning, the internal diameters of the ITA were measured with a 1.5-mm probe to ensure that the arteries were of adequate size. In all instances, the probe penetrated easily.

The right ITA was passed through a wide pericardial incision anterolateral to the superior vena cava and behind the aorta, through the transverse sinus. The mobilization of the pedicle with adjacent tissues, vein, and fascia can help positioning via this route and avoid possible stretching of the right ITA. In this way, the circumflex artery and its branches, the diagonalis artery, and the first diagonal branch can be reached by it (Fig 1).

View larger version (149K): [in this window] [in a new window]   Fig 1. . Right internal thoracic artery placed through the transverse sinus and grafted to a circumflex artery and its branches.

After establishment of total extracorporeal circulation, the patient's temperature was cooled to 27°C, the aorta was clamped, and cold blood cardioplegia was infused into the aortic root at flow rate of 250 to 350 mL/min for 3 to 5 minutes and maintained by reinfusion every 20 minutes at a flow rate of 200 mL/min for 2 minutes. The distal and proximal vein graft anastomoses were sequentially constructed during aortic cross-clamping, allowing cardioplegic solution to be delivered through the previously constructed vein grafts to ensure its better distribution. The ITA grafts were always the last performed, and they were kept clamped during cardioplegia. The anastomoses of the ITA to the coronary arteries were performed with continuous 7-0 Prolene suture (Ethicon, Somerville, NJ).

Operative Data
A total of 537 coronary artery bypass grafts was performed, with an average of 2.9 grafts per patient. The right ITA was placed through the transverse sinus and grafted to the obtuse marginal artery in 168 patients (83.5%), diagonalis artery in 23 patients (11.4%), circumflex artery in 5 patients (2.5%), first diagonal artery in 3 patients (1.5%), and posterior ventricular branches of the circumflex artery in 2 patients (0.9%). The left ITA was grafted to left anterior descending artery in 188 patients (93.5%), diagonal artery in 5 patients (2.4%), and obtuse marginal artery in 2 patients (0.9%), and was sequentially grafted to the diagonal and left anterior descending arteries in 6 patients (2.9%). A total of 161 saphenous vein grafts were also performed, 100 (62.1%) of them grafted to the right coronary artery or to the posterior descending artery, 38 to the diagonal artery, and 23 to the circumflex artery and its branches.

Clinical Follow-up
Perioperative data were obtained from patients' hospital records. Follow-up information was collected directly with patient contact, from patients' personal physicians, or by telephone interview with the surviving patients or family members.

Angiographic Studies
Hemodynamic studies were proposed to all patients in the immediate postoperative period and at the late follow-up. They were performed if the patient accepted, independent of the presence of symptoms. In fact, most of the patients were asymptomatic when the hemodynamic studies were performed. Patients signed a special informed consent form approved by the Scientific Committee of the hospital.

Statistical Analysis
Data are presented as percentage ± 70% confidence limits. Patient survival and long-term patency rates were calculated by the actuarial method. The comparison between the actuarial curves was done using the log-rank method. Statistical significance was assumed when the p value was less than 0.05.

	Results

Top Footnotes Abstract Introduction Patients and Methods Results Comment References

 
Immediate Postoperative Period
Operative mortality was defined as death occurring at the hospital during the operation or at first postoperative month. Death occurring after discharge from the hospital but within 30 days of the surgical procedure was counted as operative mortality. In the present series, the operative mortality was 2.9% (6 patients). The causes were ventricular fibrillation in 3 patients (1.4%), digestive complications in 2 patients (0.9%), and stroke in 1 patient (0.4%).

Nineteen patients (9.4%) had cardiac perioperative morbidity, which was reoperation for bleeding in 4 patients (1.9%), respiratory failure in 8 patients (3.9%), digestive complication in 3 patients (1.4%), renal failure in 1 patient (0.4%), stroke in 1 patient (0.4%), and wound complications in 2 patients (0.9%).

Perioperative myocardial infarction was defined as new electrocardiographic Q waves combined with cardiac enzyme elevation creatine kinase MB fraction. It was documented in 5 patients (2.4%).

Long-Term Clinical Follow-up
The follow-up period ranged from 6 to 127 months (mean, 71 months). There were 8 late deaths (3.9%): 1 due to cardiac failure, 1 to stroke, 1 to renal failure, and 5 to unknown cause. Actuarial survival was 95.8% at 1 year of follow-up, 91.2% at 5 years and 88.3% at 10 years (Fig 2).

View larger version (16K): [in this window] [in a new window]   Fig 2. . Actuarial survival curve of patients submitted to myocardial revascularization with bilateral internal thoracic arteries and the right internal thoracic artery placed through the transverse sinus.

Graft Patency
Eighty patients (41%) were submitted to postoperative angiographic studies: 44 in the immediate postoperative period and 36 at the late follow-up, ranging from 3 to 120 months after the operation (mean, 51.6 months).

In the immediate postoperative period, 43 left ITAs (97.7%) and 42 right ITAs (95.4%) of the 44 bilateral ITA grafts that were studied were patent. Concomitantly, 30 (78.9%) of 38 studied saphenous vein grafts were also patent. Of the 36 bilateral ITA grafts studied in the late postoperative period, 34 left ITAs (94.4%) and 33 right ITA grafts (91.6%) were patent (Fig 3). Only 19 (67.8%) of the 28 saphenous vein grafts studied at that time were patent.

View larger version (178K): [in this window] [in a new window]   Fig 3. . Angiographic study performed 10 years after the operation showing good patency of a right internal thoracic artery placed through the transverse sinus and grafted to the obtuse marginal artery.

View larger version (21K): [in this window] [in a new window]   Fig 4. . Actuarial curves of late patency rate of the right internal thoracic artery (ITA) used through the transverse sinus to the circumflex artery and its branches, of left ITA used to the left anterior descending artery and its branches, and saphenous vein grafts (SVG) used to several coronary arteries.

	Comment

Top Footnotes Abstract Introduction Patients and Methods Results Comment References

Retrospective analysis and comparative studies have failed to demonstrate additional benefit in patients receiving bilateral ITAs over a single ITA graft [12, 16, 17]. In addition, the late patency rate and the best way to use the right ITA remain controversial.

The elevated late patency rate of the left ITA placed to left anterior descending artery has been highly emphasized [1, 18]. On the other hand, the right ITA presents a lower late patency rate when compared with the left ITA. Lytle and associates [4] reported an 82.5% late patency rate after a mean of 26 months of follow-up for the right ITA and 92% for the left ITA. Galbut and colleagues [19] reported an 87% late patency rate for the right ITA and 92% for the left ITA at a mean of 51 months.

Fiore and associates [10] analyzed the late patency rates using actuarial methods and reported that the cumulative patency rate at 13 years was 82% for the left ITA and 85% for the right ITA, with no significant difference between the two ITAs. In the present study, the actuarial late patency rates of the left and the right ITAs were 97.6% versus 92.1%, 93.8% versus 84.1%, and 93.8% versus 84.1% at 1, 5, and 10 years of follow-up, respectively.

Regarding the patency of ITA grafts to specific coronary arteries, the late patency rate of right ITAs ranged from 82.3% to 87% with no difference when used to graft the right coronary artery or the obtuse marginal artery [10, 19, 20]. Only Galbut and associates [11] presented a 69.2% late patency rate when the right ITA was used to the right coronary artery, but this occurred in elderly patients. Although the right ITA can be used in different coronary branches, we prefer to use it to graft the circumflex artery and its branches. In this way, using the left ITA to left anterior descending artery and right ITA to obtuse marginal artery, the left coronary artery will be revascularized with two arterial grafts and a great area of myocardium will be protected for more time.

In 1984, Puig and colleagues [13] reported the use of right ITA through the transverse sinus for the circumflex artery and its branches with proximal lesions. Regardless, some authors reported that the use of right ITA through the transverse sinus could compromise the blood flow due to the risk of overstretching and rotating the right ITA. Also, the difficulties in managing pedicle bleeding could limit the usefulness of this route [21, 22]. On the other hand, Galbut and associates [11, 19, 20] reported increased progressive use of the right ITA through the transverse sinus with good late patency rate and survival. In the present study, we did not have problems with blood flow in the right ITA used via this route, and the incidence of bleeding was no greater than that reported in the literature.

We believe that the association of left ITA to left anterior descending artery should not be changed. One of the goals of myocardial revascularization is to obtain similar results using other arterial grafts for other coronary branches; in this respect the right ITA via transverse sinus represents a good alternative for revascularization of the circumflex artery and its branches, better than saphenous vein graft.

In the present study, we reported the late results of this technique, which was developed in our service. The actuarial late patency rate of the right ITA was 84.1% at 5 and 10 years of follow-up, which was not significantly different from that of the left ITA in the same period.

In conclusion, myocardial revascularization with bilateral ITA grafts can be performed with low operative mortality and morbidity and with good long-term survival and graft patency. Our primary indication for use of both ITAs in situ for myocardial revascularization is for all patients with left main, double-, or triple-vessel disease, with proximal lesion in the circumflex artery or its branches, and with normal to moderate left ventricular dysfunction. The presence of diabetes, severe obesity, and age more than 70 years do not represent critical contraindications for bilateral ITA grafts, but these patients need judicious selection. The right ITA in situ through the transverse sinus presents excellent long-term patency rates, similar to those observed with the left ITA and superior to those of saphenous vein grafts.

	Footnotes

Top Footnotes Abstract Introduction Patients and Methods Results Comment References

 
Address reprint requests to Dr Puig, Hospital Beneficência Portuguesa, Rua Maestro Cardim, 769 - 2° Sub- Solo/Bloco 5, São Paulo, SP, Brazil 01323-001.

	References

Top Footnotes Abstract Introduction Patients and Methods Results Comment References

 

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This Article Abstract 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): Luís Roberto Gerola Luiz Boro Puig Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Gerola, L. R. Articles by Souza, A. H. S. Search for Related Content PubMed PubMed Citation Articles by Gerola, L. R. Articles by Souza, A. H. S. Related Collections Related Article