The Incremental Value of Three or More Arterial Grafts in CABG: The Effect of Native Vessel Disease

Abstract

Background.

We investigated whether extended arterial grafting with three or more arterial grafts in patients with a left internal thoracic artery to left anterior descending artery graft improves survival in coronary artery bypass graft surgery patients and whether its effects will depend on the extent of coronary artery disease; specifically three-vessel disease (3VD) versus two-vessel disease (2VD).

Methods.

Fifteen-year mortality was analyzed in 11,931 patients with multivessel disease and primary isolated left internal thoracic artery to left anterior descending artery coronary artery bypass graft surgery with 2 or more grafts. Patients were aged 64.3 ± 10.5 years; 3,484 (29.2%) were women; 2,532 (21.2%) had 2VD and 9,399 (78.8%) had 3VD. Patients were grouped into one single-artery group (n = 6,782, 56.9%; reference group), and two multiple artery groups: two arteries (n = 3,678, 30.8%) and three arteries (n = 1,471, 12.3%). Long-term survival was compared by Kaplan-Meier estimates. Risk-adjusted mortality hazard ratio (HR) with 95% confidence interval (CI) were derived by covariate adjusted Cox regression to quantify multiple artery effects versus one artery in the overall cohort and separately among patients with 2VD and 3VD.

Results.

Radial artery (94%) and right internal thoracic artery (6%) conduits were used for additional arterial grafts. For the entire multivessel cohort, increasing number of arterial grafts was associated with incrementally improved 15-year survival (two arteries HR 0.85, 95% CI: 0.78 to 0.92; three arteries HR 0.75, 95% CI: 0.65 to 0.85). The three arteries versus two arteries comparison was consistent, even if not significant (HR 0.89, 95% CI: 0.77 to 1.03). The benefits derived from additional arterial grafts were more pronounced in case of 3VD (two arteries HR 0.84 95% CI: 0.76 to 0.92; three arteries HR 0.73, 95% CI: 0.63 to 0.84), without survival benefit with 2VD.

Conclusions.

Our results support the use of extended arterial grafting to maximize long-term coronary artery bypass graft surgery patient survival, especially for 3VD patients.

Numerous studies confirm that preferential use of arterial grafts, either the right internal thoracic artery or radial artery (RA), over saphenous venous grafts in left internal thoracic artery (LITA) based coronary artery bypass graft surgery (CABG) is associated with improved long-term survival [1–9]. Despite these reports of improved long-term survival with such two-artery versus one-artery grafting strategies and practice guidelines supporting multiarterial grafting [10–12], 90% of CABG patients in the United States undergo a single-artery operation [13].

The potential incremental survival benefit of extended arterial grafting with three or more arterial conduits (three arteries) is less clear. Only a limited number of studies, with contradictory outcomes, are available [14–24], and their generalizability is limited due to small study cohorts. Moreover, a number of these studies focused on the rarely used gastroepiploic artery as the third arterial graft [14–17] in bilateral internal thoracic artery (BITA) grafting. When the more commonly used RA constituted the third arterial graft in BITA-CABG, conflicting survival results are reported [19–24], although a meta-analysis found a late survival benefit for three versus two arterial grafts. Nevertheless, extended arterial grafting is very rarely used in clinical practice; only 0.5% of patients within The Society of Thoracic Surgeons database undergo this grafting strategy [13]. Importantly, there are no data on the value of extended arterial grafting outside of BITA grafting, and the impact of the extent of native coronary vessel disease on the results of extended arterial grafting is unknown.

Given this knowledge gap and the increased risk of deep sternal wound infection associated with BITA grafting [25], we assessed the value of extended arterial grafting, principally with RA grafts, in LITA-based CABG. We hypothesize that this approach is associated with improved long-term survival compared with single-artery grafting. To extend the current focus on personalized medicine to CABG patients, we separately analyzed the impact of extended arterial grafting in patients with two-vessel disease and patients with three-vessel disease.

Patients and Methods

This is a retrospective analysis of databases collected prospectively at two Ohio centers (in accordance with The Society of Thoracic Surgeons Adult Cardiac Surgery Database definitions and criteria) and one New York center (in accordance with the New York State Department of Health Cardiac Surgery Reporting System). It was approved by the corresponding Institutional Review Boards. With no additional patient contact, informed consent was waived.

Patients and Study Groups

Our analysis included nonsalvage, primary, multivessel disease LITA to left anterior descending artery CABG (1994 to 2011) patients with at least two grafts. Patients with recent (less than 24 hours) myocardial infarction, preoperative renal failure, or those undergoing concomitant procedures were excluded except for those with concurrent coronary or carotid endarterectomy or atrial fibrillation ablation. Risk-adjusted survival was compared in patient cohorts based on the number of arterial grafts: one artery, two arteries, or three or more arteries. Comparisons were repeated separately within the two-vessel disease (2VD) and three-vessel disease (3VD) subcohorts. The number of grafts was equal to the number of distal anastomoses.

Surgery and Follow-Up

The surgical techniques have been previously reported [3, 4, 8]. The RA grafts were harvested both open and endoscopically and were deployed to the right and left coronary artery branches with high-grade stenoses.Mortality data were secured (last, November 2011) from the Social Security Death Index (http://ssdi.genealogy.rootsweb.com). The follow-up period ranged between 3 and 189 months.

Statistical Methods

Categorical variables were summarized as counts (percentage) and compared across subgroups using the χ² test. Continuous variables were reported as mean and standard deviation and compared based on normality of data with either the unpaired Student’s t test or Mann-Whitney rank sum test in case of two groups, or analysis of variance, or analysis of variance on ranks if three or more groups. Survival data were calculated using the Kaplan-Meier product limit method to estimate unadjusted survival and compared by log rank test. Quantifying the incremental effects of one, two, or three arterial grafts was achieved by deriving associated risk adjusted hazard ratio (HR) with 95% confidence interval (CI) using Cox regression analysis as follows: (1) in all patients irrespective of native vessel disease (three arterial grafting categories, with one artery as reference) with comprehensive risk adjustment including all variables in Table 1 in addition to completeness of revascularization index (number of completed grafts minus number of diseased coronary vessels) and vessel disease (covariate adjusted); and (2) covariate-adjusted pairwise (two arterial categories per analysis) hazard ratios overall and repeated for 2VD and 3VD strata. A two-sided p value of 0.05 was adopted to indicate significance in all cases. Analyses were done using IBM SPSS Statistics 21.0 software (IBM Corporation, Armonk, NY).

Table 1.

Patient Demographics, Risk Factors, and Operative Variables Compared for One-, Two-, and Three-Artery Grafting Strategy in Two-Vessel (n = 2,532) and Three-Vessel (n = 9,399) Disease Subcohorts

	Two-Vessel Disease						Three-Vessel Disease
	One Artery (n = 1,543)		Two Arteries (n = 756)		Three Arteries (n = 233)		One Artery (n = 5,239)		Two Arteries (n = 2,922)		Three Arteries (n = 1,238)
Categoric Variables	n	%	n	%	n	%	n	%	n	%	n	%
Female	587	38	189	25	52	22.3	1,768	33.7	675	23.1	217	17.5
Diabetes mellitus	497	32.2	249	32.9	66	28.3	2,024	38.6	1,090	37.3	451	36.4
Insulin-dependent diabetes	22	12.1	13	11.8	2	11.8	76	19.9	34	12.8	8	14.3
Hypertension	1,159	75.1	541	71.6	160	68.7	4,109	78.4	2,240	76.7	837	67.6
Peripheral vascular disease	205	13.3	75	9.9	12	5.2	847	16.2	297	10.2	115	9.3
Cerebrovascular disease	322	20.9	76	10.1	21	9	1,208	23.1	397	13.6	126	10.2
COPD	371	24	126	16.7	42	18	1,378	26.3	545	18.7	182	14.7
Congestive heart failure	173	11.2	44	5.8	9	3.9	810	15.5	254	8.7	80	6.5
Left main disease	468	30.3	217	28.7	82	35.2	1,440	27.5	678	23.2	326	26.3
All arterial	36	2.3	305	40.3	125	53.6	32	0.6	134	4.6	350	28.3
BMI category, kg/m2
<25	380	24.6	100	13.2	52	22.3	1,284	24.5	475	16.3	213	17.2
Overweight, 25–29.9	587	38	307	40.6	80	34.3	2,125	40.6	1,102	37.7	512	41.4
Obese 1, 30–34.9	370	24	202	26.7	60	25.8	1,251	23.9	806	27.6	302	24.4
Obese 2, 35–39.9	145	9.4	100	13.2	28	12	402	7.7	342	11.7	145	11.7
Obese 3, >40	61	4	47	6.2	13	5.6	177	3.4	197	6.7	66	5.3
Priority status
Elective	462	29.9	223	29.5	64	27.5	1,519	29.0	892	30.5	312	25.2
Urgent	950	61.6	486	64.3	160	68.7	3,351	64.0	1,889	64.6	875	70.7
Emergency	131	8.5	47	6.2	9	3.9	369	7	141	4.8	51	4.1
Continuous Variables	Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD
Age	65.7	10.5	59.4	10.2	59.3	9.5	67.9	9.7	60.9	9.7	59.5	9.9
Body surface area, m2	2.0	0.2	2.0	0.2	2.0	0.2	1.9	0.2	2.0	0.2	2.0	0.2
BMI	28.9	5.7	30.2	5.5	29.6	5.8	28.5	5.2	30.1	5.8	29.7	5.6
LVEF	50.0	11.8	50.8	9.8	50.5	11.3	47.5	12.4	48.6	11.3	49.1	10.9
Perfusion time, minutes	65.9	41.7	68.7	33.6	95.4	63.9	85.9	32.0	88.8	30.4	101.2	27.6
CRI	0.8	0.8	0.8	0.9	1.8	0.8	0.6	0.8	0.7	0.8	1.3	0.9
Number of grafts	2.8	0.8	2.8	0.9	3.8	0.8	3.6	0.8	3.7	0.8	4.3	0.9

BMI = body mass index; COPD = chronic obstructive pulmonary disease; CRI = complete revascularization index; LVEF = left ventricular ejection fraction.

Results

Of the 11,931 patients, 2,532 (21.2%) had 2VD and 9,399 (78.8%) had 3VD. In all, 5,149 patients (43.2%) underwent multiarterial bypass grafting (MABG) with two or more arterial grafts, and 6,782 patients (56.8%) underwent single (one artery) arterial grafting in the form of LITA to left anterior descending artery graft and saphenous vein graft. Radial artery and BITA grafts were used in 94% and 6% of MABG patients, respectively. Only 1% of the entire study group received both BITA and RA grafts, and therefore our three-artery cohort was composed almost entirely of patients receiving a LITA and supplemental RA grafts, either bilateral or sequential or both. The MABG cohort included 3,678 patients (30.9%) with two arteries and 1,471 patients (12.3%) with three arteries.

The use of MABG was more frequent in the 3VD sub-cohort than in the 2VD subcohort: 43.3% and 39.1%, respectively (p = 0.21). The grafting strategies used in 2VD patients versus 3VD patients were as follows: 2VD patients, one artery, n = 1,543 (60.9%), two arteries, n = 756 (29.8%), and three arteries, n = 233 (9.2%); 3VD patients, one artery, n = 5,239 (55.7%), two arteries, n = 2,922 (31.1%), and three arteries, n = 1,238 (13.2%). Patients with 2VD and 3VD exhibited significantly different patient and grafting characteristics. Briefly, 3VD patients were more frequently male, with higher rates of obesity and other comorbidities (Table 1). Patient risk factors and operative variables were substantially different across the three grafting strategies overall and within the 2VD and the 3VD subcohorts (Table 1). The use of MABG was more frequent among male, younger, and generally healthier patients with lower rates of diabetes mellitus, hypertension, peripheral vascular disease, cerebrovascular disease, chronic obstructive pulmonary disease, and congestive heart failure, irrespective of coronary artery disease.

Effects of Arterial Grafting on Survival

ALL PATIENTS.

The average follow-up was 8.7 ± 4.4 years (maximum follow-up, 15.5). The unadjusted perioperative mortality of 2VD and 3VD patients was 1.42% and 1.52%, respectively; and generally decreased with increasing number of arterial grafts: one artery, 1.86%; two arteries, 1.14%; and three arteries, 0.75%. These differences were not significant after risk adjustment.

Overall, 3,780 deaths (31.7%) were documented, and these were more frequent among patients with 3VD compared with 2VD: 1,623 of 4,377 (37.1%) versus 2,157 of 7,554 (28.6%, p < 0.001). The overall unadjusted 5-year survival (84.2% versus 88.5%), 10-year survival (62.9% versus 73.8%), and 15-year survival (42.4% versus 57.4%) was significantly worse for 3VD patients than for 2VD patients (p < 0.001; Fig 1A). The unadjusted 15-year survival in the overall study group was systematically better with increasing number of arterial grafts (one artery versus two versus three, all significant; Fig 1B), and was also noted in 3VD patients (Fig 2A). For 2VD patients, survival with two arteries and three arteries was similar (p = 0.629; Fig 2B).

Fig 1.

Comparison of unadjusted 15-year Kaplan-Meier survival estimates in (A) two-vessel disease (2-VesDis) patients (n = 2,532 [black line]) versus three-vessel disease (3-VesDis) patients (n = 9,399 [blue line]); and (B) multivessel coronary artery disease patients undergoing one-artery (1-art [broken line]), two-artery (2-art [solid gray line]), and three-artery (3-art [solid black line]) grafting strategy. (CABG = coronary artery bypass graft surgery; vs = versus.)

Fig 2.

Comparison of unadjusted 15-year Kaplan-Meier survival estimates in patients undergoing one-artery (1-art [broken line]), two-artery (2-art [solid black line]), and three-artery (3-art [solid gray line]) grafting strategy: (A) three-vessel disease patients (one artery, n = 5,239; two arteries, n = 2,922; three arteries, n = 1,238); and (B) two-vessel disease patients (one artery, n = 1,543; two arteries, n = 756; three arteries, n = 233). (CABG = coronary artery bypass graft surgery; vs = versus.)

Cox regression analysis, applied to 15-year mortality in all patients, with comprehensive forced adjustment of patient factors including VD to estimate the risk-adjusted effects of increasing arterial grafting on survival, is summarized in Table 2. A decreased 0- to 15-year mortality risk with increasing number of arterial grafts was noted (one artery, reference category; two-artery adjusted HR 0.87, 95% CI: 0.80 to 0.95, p = 0.002; three-artery adjusted HR 0.83, 95% CI: 0.72 to 0.95, p = 0.005). Notably, with the adjustment to grafting strategy and complete revascularization index, 3VD was not associated with decreased late survival (adjusted HR 1.04, 95% CI: 0.96 to 1.13, p < 0.365).

Table 2.

Mortality Hazard Ratios for Predictors Including Grafting Strategy of 15-Year Survival Derived by Comprehensive Cox Regression Analysis in All Patients (n = 11,931)

Variable	HR (95% CI)	p Value
Grafting strategy
One artery	1.00 (reference)	…
Two arteries	0.87 (0.80–0.95)	0.002
Three arteries	0.83 (0.72–0.95)	0.005
Diabetes mellitus	1.43 (1.34–1.53)	<0.001
Age	1.06 (1.05–1.06)	<0.001
Peripheral vessel disease	1.60 (1.48–1.74)	<0.001
Cerebrovascular disease	1.39 (1.29–1.50)	<0.001
Ejection fraction, %	0.99 (0.98–0.99)	<0.001
COPD	1.34 (1.25–1.44)	<0.001
Congestive heart failure	1.42 (1.30–1.56)	<0.001
Body mass index, kg/m2
<25	1.00 (reference)	…
25–29.99	0.96 (0.88–1.05)	0.337
30–34.99	0.97 (0.88–1.08)	0.592
35–39.99	1.26 (1.10–1.44)	0.001
≥40	1.53 (1.29–1.82)	<0.001
Complete revascularization index
−1	1.00 (reference)	…
0	0.79 (0.69–0.91)	0.001
+1	0.72 (0.62–0.82)	<0.001
+2	0.65 (0.55–0.77)	<0.001
Female	0.89 (0.82–0.96)	0.004
Myocardial infarction	1.11 (1.03–1.19)	0.004
Hypertension	1.10 (1.01–1.20)	0.021
Left main disease	0.96 (0.89–1.04)	0.307
Emergency	0.94 (0.82–1.07)	0.330
Three-vessel disease	1.04 (0.96–1.13)	0.365
Body surface area >1.7 m2	0.96 (0.86–1.07)	0.500
Previous PCI	0.98 (0.89–1.07)	0.592

CI = confidence interval; COPD = chronic obstructive pulmonary disease; HR = hazard ratio; PCI = percutaneous coronary intervention.

VESSEL DISEASE STRATIFIED ANALYSIS.

The potential for VD and arterial grafting interaction confounding the estimates of the effects of grafting strategy on late survival was investigated by a stratified analysis. Figure 3 shows the covariate pairwise grafting technique adjusted hazard ratios in all patients, 2VD patients, and 3VD patients belonging to each of the binary grafting method comparisons. Pairwise covariate adjusted comparison of two arteries versus one artery, three arteries versus one artery, and three arteries versus two arteries in all patients documented consistent findings of decreasing adjusted mortality HR with increasing number of arterial grafts. Compared with two-artery patients, additional arterial conduits (three arteries) resulted in an incremental yet nonsignificant further reduction mortality hazard ratio (HR 0.89, 95% CI: 0.77 to 1.03). Among 2VD patients, increasing number of arterial grafts beyond one artery showed no significant impact on long-term survival. In contrast, in 3VD patients, a decreasing mortality HR with increasing number of arterial grafts was noted. Pairwise comparison among 3VD patients revealed a survival benefit of two arteries versus one artery (HR 0.84, 95% CI: 0.76 to 0.92) and a further incremental benefit for three arteries versus one artery (HR 0.73, 95% CI: 0.63 to 0.84), with a nonsignificant survival advantage for the three arteries versus two arteries comparison (HR 0.88, 95% CI: 0.75 to 1.02).

Fig 3.

Forest plots showing 15-year hazard ratio (HR) with 95% confidence interval (CI) for pairwise artery grafting group comparisons using covariate-adjusted Cox regression: two arteries versus (vs) one artery (1-art); three arteries versus one; and three arteries versus two. Analyses are shown for the overall population and separately for two-vessel disease (2-Ves Dis) and three-vessel disease (3-Ves Dis) patients. (Comp. = comparison; ref = reference.)

Comment

We report improved long-term survival with extended arterial grafting in LITA-based CABG patients with three or more arterial grafts compared with one artery. This survival advantage was driven by improved survival among 3VD patients only, with no survival benefit beyond a single arterial graft in 2VD patients. Given its ease of harvest, superior durability, ease of handling, ability to reach any coronary target, association with improved late survival, and no increased risk of infection or wound healing complications, RA is a versatile conduit and its use should be considered by the heart team in preference to saphenous venous grafts to affect extended arterial grafting.

Two Arterial Grafts Versus One Arterial Graft

The benefits of two-artery grafting have been known since 2004, when Lytle and associates [1] showed superior long-term survival with BITA grafting compared with LITA-based CABG, and has been confirmed by others [2, 5–7, 9]. This two-artery versus one artery survival advantage has also been repeatedly demonstrated with the RA as the second arterial graft in LITA-based CABG [3, 4, 8]. One notable exception to this two-artery versus one-artery survival advantage is the Arterial Revascularization Trial (ART) [25], with no difference in survival between BITA and LITA-based CABG, although methodologic issues limit the generalizability of this finding. None of these studies assessed the differential survival impact of two versus one arterial graft in patients with 2VD and 3VD, although the rates of 3VD in these studies ranged between 68% and 85%. The superior survival among patients with two versus one arterial conduit in the overall study cohort was driven by enhanced survival among 3VD patients. In our 2VD subcohort, survival of patients with two arteries and one artery was comparable (Fig 3). We are unaware of other studies specifically focusing on the impact of MABG in patients with increasing complexity of native vessel disease.

Three Arterial Grafts Versus One Arterial Graft

We are unaware of other studies specifically assessing the impact of using three arteries versus one artery as grafts in CABG. Guru and colleagues [18] found a survival advantage for patients undergoing either three-artery or two-artery grafting compared with one artery (HR 0.80, 95% CI: 0.72 to 0.99) as well as decreased rate of cardiac hospital readmissions and the composite endpoint of death, repeat revascularization, and cardiac readmissions. No attempts were made to separately assess 3VD and 2VD patients. In our analysis, we found three-artery versus one-artery survival advantage in our entire and 3VD cohorts. The equivalent survival between three-artery and one-artery 2VD patients suggests that the hypothesized superior arterial graft patency translates into a survival advantage only for patients with more complex native coronary artery disease. Because our three-artery 2VD cohort was composed only of 233 patients, larger studies will be required to assess the impact of extended arterial grafting with moderate coronary disease on mortality and other endpoints. Therefore, even without a documented survival advantage, our data should not be interpreted to discourage the use of extended arterial grafting in patients with 2VD, especially as there was no increased risk with this approach.

Three Arterial Grafts Versus Two Arterial Grafts

There are contradictory data on the survival benefits of patients with three arteries versus two arteries as coronary grafts [14–24]. The published studies uniformly compared either the gastroepiploic artery [14–17] or the RA [19–24] as the third arterial graft in patients undergoing BITA grafting. None of the studies separately analyzed the impact of the additional third arterial conduit based on the extent of coronary artery disease.

DiMauro and colleagues [16] found improved freedom from cardiac death with BITA-only grafting compared with BITA/gastroepiploic artery, whereas conversely Glineur and associates [14] reported superior survival with BITA/gastroepiploic artery. Pevni and associates [17] and Lev-Ran and colleagues [15] reported no differences in survival. The differences in these outcomes are likely due to relatively small patient numbers, different surgical eras and grafting techniques (on-pump versus off-pump), and variable follow-up periods.

A number of studies compare the effect of the RA as a third arterial graft in BITA-based CABG. Taggart and colleagues [22], in a post-hoc analysis of the Arterial Revascularization Trial, found that RA use decreased risk of composite endpoints of myocardial infarction, death, and repeat revascularization and was driven exclusively by a decreased rate of repeat revascularization. Grau and colleagues [21] found a survival advantage with three-artery versus two-artery grafts for 183 propensity matched, relatively young and healthy, off-pump BITA patient pairs only 10 to 14 years postoperatively without any earlier differences. Mahammadi and associates [20], among similarly low-risk BITA patients, found equivalent 15-year survival with three arteries versus two arteries, although the survival curves began to diverge 10 years postoperatively, thereby not excluding a possible survival advantage with a longer follow-up. Benedetto and colleagues [19], among 275 low-risk propensity score matched three-artery versus two-artery BITA patients, also reported equivalent survival at 15 years. Conversely, Shi and associates [24] found improved survival among 262 matched pairs of BITA patients using the RA as the third arterial graft.

Our finding of equivalent long-term survival for three-artery and two-artery patients agree with the above studies despite the principal use of LITA plus RA rather than BITA plus RA. Given the preference of placing BITA grafts to the most important diseased target vessels and relegating the RA to targets of secondary importance in these other studies may explain, at least in part, the reported lack of an appreciable survival advantage. Yet even with our grafting technique, where the RA was placed to major non–left anterior descending artery targets in both the right and left arterial systems, we were also unable to demonstrate a survival advantage of three arteries over two arteries. The survival advantage of the third arterial graft was, however, more prominent among 3VD patients than 2VD patients: HR 0.88 (95% CI: 0.75 to 1.02) versus HR 1.01 (95% CI: 0.70 to 1.48). Given the observation of Grau and colleagues [21] of survival advantage of three arteries versus two arteries only after the first postoperative decade, our mean follow-up of 8.7 years may be too short to detect a possible survival advantage among these two grafting techniques. In contrast, in a meta-analysis, Gaudino and associates [23] reported a 24% improved survival (p < 0.001) at 6 years postoperatively with three-artery versus two-artery grafting.

The limitations of this study include its retrospective nature, which expose it to confounding by patient selection bias and inability to adjust for covariates that may not be included in our databases. Such unmeasured confounders have been recognized as drawbacks of observational studies and are possible explanations behind the conflicting results between observational versus prospective trials on the impact of multiarterial grafting on survival [26]. We are also unable to assess the degree of stenosis of the target vessels to which the RA grafts were placed, what targets were grafted with arterial conduits, and their quality. Furthermore, we are unable to differentiate whether arterial grafts in MABG patients were placed to the same coronary artery system or different coronary systems. In addition, the last follow-up of our mortality data was from 2011, given the reliance on the Social Security Death Index for our mortality data. Finally, we do not have data on graft patency, reintervention rates, or cause of death. Given the small number of patients undergoing three-artery grafting, particularly for 2VD patients, our analysis maybe underpowered to detect a statistically significant difference between grafting two arteries and three arteries.

In conclusion, our results document an incremental 15-year survival benefit with increasing number of arterial grafts without increased operative risk. This benefit appears to be particularly evident among patients with more complex native coronary artery disease. The benefit of three-artery grafts versus two-artery grafts was incremental but small in magnitude and did not reach statistical significance.

Abbreviations and Acronyms

BITA

bilateral internal thoracic artery

CABG

coronary artery bypass graft surgery

CI

confidence interval

HR

hazard ratio

LITA

left internal thoracic artery

MABG

multiarterial bypass grafting

RA

radial artery

3VD

three-vessel disease

2VD

two-vessel disease