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Ann Thorac Surg 1995;59:1456-1463
© 1995 The Society of Thoracic Surgeons

Does It Make Sense to Use Two Internal Thoracic Arteries?

Department of Cardio-thoracic Surgery, Catharina Hospital, Eindhoven, the Netherlands

Accepted for publication February 17, 1995.

	Abstract

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
Retrospectively, the first 143 patients who were operated on with bilateral internal thoracic arteries (BITA group) were matched with 143 patients operated on with only one left internal thoracic artery anastomosed on the left anterior descending artery and additional vein grafts (LITA group) and followed up for a maximum of 8 years. At 5 years follow-up there were no significant differences in event-free survival between the groups. After 8 years, the overall survival was 96% and 92% (not significant [NS]), cardiac survival 99% and 97% (NS), angina-free cardiac survival 51% and 35% (NS), infarction-free cardiac survival 95% and 78% (NS), reintervention-free cardiac survival 87% and 88% (NS), and all cardiac event-free survival 49% and 31% (NS) for the BITA and LITA groups, respectively. The incidence of late pulmonary, wound, and other complications was comparable. Cox proportional hazards analysis showed that a higher left ventricular end-diastolic pressure and female sex were predictors of recurrent angina and late cardiac events. During this intermediate-term follow-up, the use of one or two internal thoracic arteries was of no value in predicting angina-free or cardiac event-free survival.

	Introduction

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
It has been proved that the use of the left internal thoracic artery (LITA) anastomosed to the left anterior descending artery (LAD) results in a better cardiac event-free and reoperation-free survival than the use of the saphenous vein as conduit to the LAD [1–4]. Few studies show that the use of both internal thoracic arteries (BITA) results in a better cardiac event-free survival than the use of the LITA only [4–7]. For patients aged 60 years or younger this incremental improvement might be more pronounced [6; Cosgrove DM, personal communication]. To achieve such an improvement in cardiac event-free and reoperation-free survival, one should question at what price this can be reached in terms of hospital mortality and morbidity and at what postoperative interval the expected improvement occurs. Recently we proved that the two internal thoracic arteries (ITA) can be used with similar hospital mortality and morbidity as with the use of only the LITA [8]. With this study, we want to answer the questions if the expected improvement in cardiac event-free survival occurred already within an intermediate term follow-up and if the use of one or two ITAs has an independent predictive value in predicting late cardiac events in comparison with other preoperative and operative variables.

	Material and Methods

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
Although more than 1,000 bilateral ITA operations have been performed in our center, we only studied retrospectively the first 143 hospital survivors with bilateral ITAs (BITA group) operated on between October 1985 and December 1988, and matched these survivors with 143 hospital survivors with only one LITA anastomosed on the LAD and additional vein grafts to other coronary arteries (LITA group). The patients were matched to the following criteria: time of operation (next consecutive patient), age, sex, and extent of coronary artery disease. Patients underwent BITA operation depending on preference of the surgeon. All patients were operated on with pedicled ITAs as single or sequential grafts.

In the LITA group, the left ITA was anastomosed toAu: OK? the LAD, its branches, or both. In the BITA group, the left ITA was anastomosed toAu: OK? the LAD or its branches in 60.4% and to the circumflex coronary artery or its branches in 39.6% of the patients. In BITA patients the right ITA was anastomosed toAu: OK? the LAD system in 37.7%, to the circumflex system in 30.4%, and to the right coronary artery and/or its branches in 31.9% of the patients. For the details of our operative techniques we refer to an earlier publication from our group [8]. Patients with free ITAs, gastroepiploic arteries, reoperations, or combined procedures were excluded from the study, as well as patients operated for an acute myocardial infarction. Completeness of revascularization was determined by computer analysis of the total number of distal anastomoses divided by the number of all coronary vessels that were narrowed by more than 50%. Recurrent angina was defined as angina class 2 or more during follow-up. Objective ischemia at follow-up was defined as a positive electrocardiogram (ECG) stress test. If a thallium stress test was also done, the result of this test overruled the ECG stress test. An ECG stress test or a thallium stress test was performed by preference of the referring cardiologist on an elective basis, for symptoms, or a combination of these two.

Data Collection and Statistical Methods
All data were compiled in a computerized databank and analyzed with the Number Cruncher Statistical System (Hintze, Kaysville, UT) (Appendix 1). Statistical analysis of categorical variables was performed on cross-tables using the Pearson ² test. Continuous variables were analyzed with the two-sample t test if the variances of the groups were equal; otherwise the Mann-Whitney U test was used. Survival curves were estimated with the Kaplan-Meier method [9]. Differences of survival rates between the two treatment groups were analyzed by the log rank test. Because of the small number of patients at 8 years follow-up, a comparison also was made of the cumulative survival probability after a 5-year period. For event-free survival analysis, events were defined as all late cardiac deaths, new myocardial infarctions, recurrent angina, and coronary reinterventions (coronary artery bypass graft or percutaneous transluminal coronary angioplasty [PTCA]). For analysis of the cardiac death-free, angina-free, reinfarction-free, coronary reintervention-free, and event-free survival, only death attributable to a cardiac cause was considered as mortality. For analysis of predictors for the angina-free and event-free survival the Cox proportional hazards regression model [10] was used, using all data in patients with a follow-up of at least 6 months. To determine the best subset of predictors, a selection of variables was made by McHenry's algorithm [11] from 22 preoperative and peroperative variables, to which the type of ITA procedure was added (Appendix 2). Regression analysis was then performed with backward elimination and was continued until all nonsignificant predictors were removed. In Table 7 the relative risks are calculated from the beta estimates, with 95% confidence limits using the standard errors of the beta estimates. In all statistical tests a two-sided p value of less than 0.05 was considered to be significant.

	Results

Top Footnotes Abstract Introduction Material and Methods Results Comment References

View larger version (20K): [in this window] [in a new window]   Fig 1. . Overall survival estimates for left internal thoracic artery (lita) and bilateral internal thoracic arteries (bita) patient groups. (NS = not significant.)

View larger version (20K): [in this window] [in a new window]   Fig 2. . Cardiac survival estimates for left internal thoracic artery (lita) and bilateral internal thoracic arteries (bita) patient groups. (NS = not significant.)

View larger version (21K): [in this window] [in a new window]   Fig 3. . Angina-free cardiac survival estimates for left internal thoracic artery (lita) and bilateral internal thoracic arteries (bita) patient groups. (NS = not significant.)

View larger version (20K): [in this window] [in a new window]   Fig 4. . Infarct-free cardiac survival estimates for left internal thoracic artery (lita) and bilateral internal thoracic arteries (bita) patient groups. (NS = not significant.)

View larger version (20K): [in this window] [in a new window]   Fig 5. . Reintervention-free cardiac survival estimates for left internal thoracic artery (lita) and bilateral internal thoracic arteries (bita) patient groups. (NS = not significant.)

View larger version (21K): [in this window] [in a new window]   Fig 6. . Event-free cardiac survival estimates for left internal thoracic artery (lita) and bilateral internal thoracic arteries (bita) patient groups. (NS = not significant.)

	Comment

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
The long-term survival and relief of angina and infarction after a coronary bypass operation are related to the preoperative status of the patient, progression of coronary artery sclerosis, and patency of the conduits used [12]. The patency of an internal thoracic artery graft 5 to 12 years after the operation is superior to that of saphenous vein grafts, being 97% versus 46%, respectively [13]. In retrospective [1–4] and prospective [14] studies it has been shown that the use of the LITA, instead of the saphenous vein, anastomosed to the LAD results in a significantly better cardiac event-free survival. There are only a few studies that compare the late results after the use of one versus two ITAs [4–7]. Cameron and colleagues [4]Au: Cameron is first author in Ref. 4 (38 BITA patients) and Cosgrove and colleagues [6; personal communication] (327 BITA patients) did not apply their statistics on the comparison of two versus one ITA, but to the triple comparison with a no ITA group as well. Only Fiore [5] and Naunheim [7] and their colleagues compared 100 BITA patients with a similar group of LITA patients, as in our study. One should be cautious to compare our study with these other studies. Not only are there differences in study design and patient populations, but there are also differences in the time frame of the operations, in the duration of follow-up, in operative techniques, in percentage of incomplete revascularization, and in myocardial preservation techniques used. Cameron and associates [4] did not perform sequential grafts with their ITAs and operated on a fibrillating heart. Fiore [5] and Naunheim [7] and their co-workers performed only single ITA anastomoses, placing the left ITA always on the LAD and the right ITA always on the right coronary artery. We demonstrated that the overall survival for hospital survivors after 92 months was comparable for the BITA (96%) and LITA groups (92%) (NS). Naunheim and colleagues [7] failed to show a significant benefit in survival (including the hospital mortality), over a 15-year period of patients in which they used two versus one ITA. Cosgrove and colleagues [6; personal communication], excluding the hospital mortality, could not demonstrate a significantly better 8-year survival for two ITAs in patients older than 60 years of age. Only in patients younger than 60 years of age did they demonstrate a significantly better survival after BITA operation. The number of late deaths in our study was too small to allow for an analysis of predictors for these incidents. Sergeant and associates [15] could not demonstrate in a multivariate analysis any additional benefit on late survival with the additional use of the right ITA. But this could be due to the fact that they used exclusively the right ITA on the diagonal branch, adding not much to the effect of the LITA on the LAD.

We could not demonstrate any significant difference in late cardiac mortality between the studied groups, being 1% in the BITA and 3% in the LITA group. Several investigators [1, 15] have shown that the use of the LITA to bypass a LAD lesion is an important predictor of cardiac survival. It is likely that in an 8-year period the additional use of the right ITAAu: OK? on another vessel does not affect cardiac survival.

We found no significant difference in angina-free cardiac survival after 92 months in our BITA (51%) and LITA (35%) patients. Cameron and colleagues [4] found 68% of their BITA patients and 52% of their LITA patients free of recurrent angina after a follow-up of 13 years. Fiore and associates [5] showed a significantly better recurrent angina-free survival for BITA (36%) than for LITA (27%) patients after a follow-up of 15 years. Although the use of one ITA does not appear to have much effect on recurrent angina [12], it is likely that the use of a second ITA does. In our multivariate analysis, we found female sex and a higher left ventricular function as predictors for recurrent angina. Also Sergeant and associates [16] showed in their Cox hazards analysis that these same variables, among others, were risk factors for angina after the operation.

The incidence of late myocardial infarctions in our study was low and not different between the studied groups. Fiore and colleagues [5] found no difference in myocardial infarction after one or two ITAs in the first 10 years of follow-up, but at 15 years 75% of the BITA and 59% of the LITA patients were infarction free. Therefore, it is likely that during the first 8 to 10 years there is no difference in recurrent infarction between one or two ITAs, but that after that time the curves diverge.

After 92 months, 87% of the BITA and 88% of our LITA patients did not need a coronary artery reintervention. All reinterventions in our patients were for PTCA. Cameron [4] and Fiore [5] and their associates did show that the incidence of reoperation was the lowest for BITA patients at 15 years' follow-up.

After 8 years, we demonstrated a cardiac event-free survival for BITA patients of 49% and for LITA patients of 31% (NS). Because of the small number of patients remaining on study at 8 years, the 49% versus 31% comparison should not yet be interpreted as being suggestive of a trend. Cameron and colleagues [4] found a cardiac event-free survival of 48% with BITA and 27% with LITA patients after 14 years of follow-up. During the first 8 years, Fiore and colleagues [5] also could not demonstrate a difference in ischemic events between LITA and BITA patients. However, after 8 years, the curves diverged. Thirty-two percent of the BITA patients and 18% of the LITA patients were ischemic events-free at a follow-up of 15 years, which was significantly different. We found that left ventricular pressure and female sex were predictors for late cardiac events, and not the fact that one or two ITAs were used. Cosgrove and colleagues [6; personal communication] found age, the use of one ITA, a history of heart failure, and diabetes were such predictors. In patients younger than 60 years of age, they also found left ventricular function and sex as predictors.

In summary, we demonstrated earlier that a BITA operation can be done with comparable hospital mortality and morbidity as an LITA operation [8]. With this study, we also showed that, at intermediate-term follow-up, the event-free survival of a BITA operation is comparable to that of using only the LITA. Although the use of one or two ITAs has no predictive value for the angina-free and event-free survival during the first 8 years after operation, such a patient should not be denied the use of both ITAs if this patient is to be expected to survive beyond these 8 to 10 years postoperatively, especially if such a patient is younger than 60 years of age, although such difference for the age groups has to be confirmed.

Appendix 1.

Appendix 2.

	Footnotes

Top Footnotes Abstract Introduction Material and Methods Results Comment References

	References

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 

1. Loop FD, Lytle BW, Cosgrove DM, et al. Influence of the internal-mammary-artery on 10-year survival and other cardiac events. N Engl J Med 1986;314:1–6.[Abstract]
2. Okies JE, Page US, Bigelow JC, et al. The left internal mammary artery: the graft of choice. Circulation 1984;70(Suppl 1):213–21.
3. Killen DA, Arnold M, McConahay DR, et al. Fifteen-year results of coronary artery bypass for isolated left anterior descending coronary artery disease. Ann Thorac Surg 1989;47:595–9.[Abstract]
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5. Fiore AC, Naunheim KS, Dean P, et al. Results of internal thoracic artery grafting over 15 years: single versus double grafts. Ann Thorac Surg 1990;49:202–9.[Abstract]
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13. Lytle BW, Loop FD, Cosgrove DM, et al. Long-term (5–12 years) serial studies of internal mammary artery and saphenous vein coronary bypass grafts. J Thorac Cardiovasc Surg 1985;89:248–58.[Abstract]
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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 Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Berreklouw, E. Articles by Bredée, J. J. Search for Related Content PubMed PubMed Citation Articles by Berreklouw, E. Articles by Bredée, J. J.