Long Term Patency

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Journal of the American College of Cardiology
© 2004 by the American College of Cardiology Foundation
Published by Elsevier Inc.

Vol. 44, No. 11, 2004
ISSN 0735-1097/04/$30.00
doi:10.1016/j.jacc.2004.08.064

Long-Term Patency of Saphenous
Vein and Left Internal Mammary Artery
Grafts After Coronary Artery Bypass Surgery
Results From a Department of Veterans Affairs Cooperative Study
Steven Goldman, MD, FACC,* Karen Zadina, RN, MA,* Thomas Moritz, MS,† Theron Ovitt, MD,*
Gulshan Sethi, MD,* Jack G. Copeland, MD,* Lizy Thottapurathu, MS,† Barbara Krasnicka, PHD,†
Nancy Ellis, MS,† Robert J. Anderson, PHD,† William Henderson, PHD,† for the VA Cooperative
Study Group #207/297/364
Tucson, Arizona; and Hines, Illinois
This study defined long-term patency of saphenous vein grafts (SVG) and internal mammary
artery (IMA) grafts.
BACKGROUND This VA Cooperative Studies Trial defined 10-year SVG patency in 1,074 patients and left
IMA patency in 457 patients undergoing coronary artery bypass grafting (CABG).
METHODS
Patients underwent cardiac catheterizations at 1 week and 1, 3, 6, and 10 years after CABG.
RESULTS
Patency at 10 years was 61% for SVGs compared with 85% for IMA grafts (p ⬍ 0.001). If
a SVG or IMA graft was patent at 1 week, that graft had a 68% and 88% chance, respectively,
of being patent at 10 years. The SVG patency to the left anterior descending artery (LAD)
(69%) was better (p ⬍ 0.001) than to the right coronary artery (56%), or circumflex (58%).
Recipient vessel size was a significant predictor of graft patency, in vessels ⬎2.0 mm in
diameter SVG patency was 88% versus 55% in vessels ⱕ2.0 mm (p ⬍ 0.001). Other positive
significant predictors of graft patency were use of aspirin after bypass, older age, lower serum
cholesterol, and lowest Canadian Functional Class (p ⬍ 0.001 to 0.058).
CONCLUSIONS The 10-year patency of IMA grafts is better than SVGs. The 10-year patency for SVGs is
better and the 10-year patency for IMA grafts is worse than expected. The 10-year patency
of SVGs to the LAD is better than that to the right or circumflex. The best long-term
predictors of SVG graft patency are grafting into the LAD and grafting into a vessel that is
⬎2.0 mm in diameter. (J Am Coll Cardiol 2004;44:2149 –56) © 2004 by the American
College of Cardiology Foundation
OBJECTIVES

The success of coronary artery bypass grafting (CABG) is
dependent on the long-term patency of the arterial and
venous grafts. Worldwide, more than 800,000 patients
undergo CABG annually, with more than 350,000 patients
operated each year in the U.S. The majority of these
patients receive left internal mammary artery (IMA) grafts
to the left anterior descending (LAD) coronary artery and
saphenous vein grafts (SVGs) or other conduits to the
remaining vessels. Based on small studies of selected groups
of patients, it is generally believed that SVGs have a 40% to
50% 10-year patency and that the IMA has a 90% to 95%
10-year patency (1–7). To address the question of long-term
patency of saphenous vein and IMA grafts, the Department
of Veterans Affairs Cooperative Studies Program supported
a 10-year angiographic follow-up study of patients who
were participants in two VA Cooperative Trials in the
1980s. These trials were originally designed to examine the
effect of antiplatelet agents on graft patency after CABG
From the *Southern Arizona VA Health Care System and the University of
Arizona Sarver Heart Center, Tucson, Arizona; and the †VA Cooperative Studies
Program Coordinating Center, Hines, Illinois. Supported by the Cooperative Studies
Program of the Department of Veterans Affairs Research and Development Service,
Washington, DC.
Manuscript received May 6, 2004; revised manuscript received August 16, 2004,
accepted August 25, 2004.

with postoperative coronary angiography one week, one
year, and in some cases three years after surgery (8 –12).

METHODS
Study population. This trial, organized and funded by the
Cooperative Studies Program of the Department of Veterans
Affairs Research and Development Service, obtained data from
1,254 male patients entered into two studies at 13 participating
hospitals from July 1983 to September 1988. The Institutional
Review Board approved each study, the subjects gave written
informed consent, and procedures were followed in accordance
with institutional guidelines (8 –13).
Surgery. Coronary artery bypass grafting was done in a
standard fashion as previously described (8 –12). The decision to use arterial or venous conduits was made by the
attending surgeon. The patient was eligible for the trial only
if the determination was made preoperatively to utilize at
least one SVG.
Angiographic analysis. The angiographic analysis was
identical to our earlier trials (8 –12). Briefly, the left IMA
and each aortic anastomosis were selectively engaged and
injected. When the status of a vein graft could not be
determined by graft or stump injection, an aortic root
angiogram was performed. Selective angiography of the
native coronary arteries was performed during the one-week

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Goldman et al.
Long-Term SVG and IMA Graft Patency

JACC Vol. 44, No. 11, 2004
December 7, 2004:2149–56

Abbreviations and Acronyms
CABG ⫽ coronary artery bypass graft
CX
⫽ circumflex
IMA ⫽ internal mammary artery
LAD ⫽ left anterior descending
RCA ⫽ right coronary artery
SVG ⫽ saphenous vein graft

and one-year catheterization only when a graft was occluded. Selective angiography of the native coronary arteries
was routinely performed at the 3-year and 10-year catheterization. Graft patency and stenosis were defined in a
central angiographic laboratory with a computer-based system (8 –12). The data are presented as time-based occlusion
rates where occlusion is defined in two ways. The primary
event of interest is 100% stenosis (Figs. 1 to 4). The
secondary event is 50% to 99% stenosis, not including
vessels totally occluded (Fig. 5). Because of long-term
follow-up and the study group being composed of middleaged men with coronary artery disease, some patients died
before the completion of the study. We obtained autopsies
in as many patients as possible and included the autopsy
patency data in our analysis.
Statistical analysis. Traditionally, reports of long-term
graft patency rates have used coronary angiography results
from a single time point after CABG. Patency rates from a
single time period distant from the original operation may
result in biased estimates if there is no accounting for
interceding interventions.
The data from this study posed two major analytic
problems. The first problem was that the exact time of graft
occlusion could not be known. We addressed this by using
interval-censored observations in the survival analysis

Figure 1. Plot of time-related graft patency (or freedom from graft
occlusion) for saphenous vein grafts (SVG) and internal mammary artery
(IMA) grafts. The number of patients at each time point is listed in the
figure. *p ⬍ 0.001 (IMA vs. SVG). CABG ⫽ coronary artery bypass
grafting.

Figure 2. Plot of time-related graft patency (or freedom from graft
occlusion) for saphenous vein grafts (SVG) and internal mammary artery
(IMA) grafts if the graft was patent at one week after coronary bypass
(CABG). The number of patients at each time point is listed in the figure.
*p ⬍ 0.001 (IMA vs. SVG).

(PROC LIFETEST in SAS [SAS Institute Inc. SAS/
STAT Version 8, Cary, North Carolina]). This analysis
requires identification of the time interval in which the
occlusion occurred. If a patient had only one angiogram and
this showed an occluded graft, the time between the date of
the CABG and date of angiography was used as the
occlusion occurrence interval. If a patient had multiple
angiograms, the time between the date of the most recent
angiogram that showed a graft was patent and the date of
the angiogram that showed occlusion was used as the
occlusion occurrence interval. The date of the latest angiogram was used as the right censored time for grafts, which

Figure 3. Plot of time-related graft patency (or freedom from graft
occlusion) for saphenous vein grafts (SVG) to the left anterior descending
(LAD), circumflex (CX), and right coronary (RCA) arteries. The number
of patients at each time point is listed in the figure. *p ⬍ 0.001 (LAD vs.
CX and/or RCA). CABG ⫽ coronary artery bypass grafting.

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Goldman et al.
Long-Term SVG and IMA Graft Patency

JACC Vol. 44, No. 11, 2004
December 7, 2004:2149–56

Figure 4. Plot of time-related graft patency (or freedom from graft
occlusion) for saphenous vein grafts (SVG) to recipient vessel with
diameters ⬎2.0 mm versus ⱕ2.0 mm. The number of patients at each time
point is listed in the figure. *p ⬍ 0.001 (⬎2.0 mm vs. ⱕ2.0 mm). CABG
⫽ coronary artery bypass grafting.

remained patent. For patients who had patency data from an
autopsy, the date of death was used. If there was an
intervention on a stenotic but still patent graft by either
percutaneous coronary intervention or repeat surgical revascularization, the graft was right censored on the date of the
angiogram and no further data were collected for that graft.
Comparisons of Kaplan-Meier product-limit survival curves
were made with the log-rank test.
Although time-related analyses of graft patency data used
the exact date of each postoperative angiogram, for convenience of presentation, some information is presented in
arbitrarily defined time frames. The 1-week data included

Figure 5. Plot of time to development of 50% to 99% stenosis in internal
mammary artery (IMA) and single saphenous vein graft (SVG) to the left
anterior descending coronary artery (LAD). The number of patients at
each time point is listed in the figure. *p ⬍ 0.001 (IMA vs. single SVG to
LAD). CABG ⫽ coronary artery bypass grafting.

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catheterizations performed between 1 and 60 days postoperation, the 1-year included catheterizations performed
between 61 days and 1.5 years post-operation, the 3-year
included catheterizations after 1.5 to 4.5 years postoperation, the 6-year included catheterizations after 4.5 up
to 8 years post-operation, and the 10-year included catheterizations after 8 to 12 years post-operation.
The second analytic problem was that there were multiple
grafts (i.e., clustered observations, within a patient). We
showed previously (14) that graft patency within a patient is
not independent. This does not affect the estimates for
patency rates, but it does cause the standard error terms to
be underestimated. Recently, the SAS macro IWM (16) has
become available for the analysis of clustered, intervalcensored survival data (15,16). This approach produces
robust estimates of the standard error terms by adjusting for
the correlated nature of the clustered observations. Patientrelated risk variables, graft-related risk variables, and CABG
processes of care variables were used as candidate independent variables in the IWM macro to identify the set of
variables that jointly predict 10-year graft patency. Variables
that were significant at the p ⬍ 0.10 level were included in
the final models. The Appendix gives a description on how
to interpret the importance of the variables.
The t test and chi-square test were used to compare
pre-CABG patient risk factors for patients who received a
10-year catheterization versus those who did not.

RESULTS
Patient data. Of the 1,254 patients undergoing CABG
operations during the study period, 1,079 patients (86%)
had at least one postoperative cardiac catheterization. This
included 1,074 patients with one or more SVG and 457
patients with an IMA graft. Two hundred twenty-five
patients had a single postoperative catheterization (18%),
328 patients had two catheterizations (26%), 384 had three
catheterizations (31%), 119 had four catheterizations (9%),
and 23 had five catheterizations (2%). Patient status during
each of the five angiographic periods is given in Table 1. A
total of 919, 799, 367, 170, and 369 patients had cardiac
catheterizations nominally at the 1-week, 1-year, 3-year,
6-year, and 10-year periods, respectively. The median times
to the catheterizations were 8 days and 1.0, 3.0, 6.2, and 9.7
years, respectively. Ninety-six and sixty-seven percent of the
6- and 10-year catheterizations, respectively, were performed for clinical, not study-related, reasons. The 10-year
catheterizations occurred between May 1991 and January
1999. There were 523 deaths before the 10-year catheterization. Of these 523 patients, serial catheterizations or
autopsy data were obtained on 396 patients (76%). One
hundred thirty patients had a single catheterization before
death (25%), 168 had two catheterizations (32%), 87 had
three catheterizations (17%), and 11 had four catheterizations (2%). There were autopsy data with graft patency
defined on 71 patients. The details of the patient data,

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Long-Term SVG and IMA Graft Patency

JACC Vol. 44, No. 11, 2004
December 7, 2004:2149–56

Table 1. Status of Study Patients at Each Angiographic Period
7–10-Day
Angiogram
Patients having coronary angiography
Patients alive but not having angiography
Deaths
Totals

1-Year
Angiogram

3-Year
Angiogram

6-Year
Angiogram

10-Year
Angiogram

919
302
33

799
389
66

367
738
149

170
797
287

369
362
523

1,254

1,254

1,254

1,254

1,254

including clinical outcomes and complications of the previous catheterizations, have been reported (8 –12). The clinical characteristics of patients with SVGs and IMA grafts
(Table 2) are presented. The patients who did not undergo
the 10-year catheterization had a higher incidence of diabetes (p ⫽ 0.022) and a trend toward more hypertension (p
⫽ 0.057) and a higher incidence of left main disease (p ⫽
0.084) (Table 3).
Overall patency. The 10-year patency for SVGs was 61%
(Fig. 1). If a vein graft was patent at the 1-week study, the
6-year patency rate was 76% and the 10-year patency rate
was 68% (Fig. 2). We note that the sudden drop in
percentage patency in the graphs around six months postCABG occurs because a large amount of new information
was obtained at the one-year angiogram and hence should
not be viewed as having physiologic relevance. For IMA
grafts, the 10-year patency was 85% (Fig. 1). If an IMA
graft was patent at 1 week, the 6-year and the 10-year
patency rates were 90% and 88%, respectively (Fig. 2).
Selected distal sites. The data for a specific vessel grafted
at 10 years show that vein graft patency to the LAD (69%)
was better (p ⬍ 0.001) than vein graft patency to the right
coronary artery (RCA) (56%) or circumflex (CX) (58%)

(Fig. 3). There was no difference in the recipient vessel
diameters among SVGs to the LAD (1.67 ⫾ 0.43 mm)
versus the CX (1.68 ⫾ 0.44 mm) versus the RCA (1.71 ⫾
0.50 mm), p ⫽ 0.179. If the vein graft to the LAD was
patent at 1 week, the 10-year patency was 74%. Similar
improvement was seen at 10 years with early patency for the
RCA (64%) and for the CX (66%). Left IMA grafts to the
LAD had a higher patency than single SVGs to the LAD
(85% vs. 69%, p ⬍ 0.001).
Predictors of graft patency. Along with the location of the
distal site, the best predictor of graft patency over the
10-year post-bypass period was the diameter of the recipient
vessel by angiographic measurement (Fig. 4). In vessels
⬎2.0 mm the 10-year patency was 88%, versus 55% in
vessels with diameters ⱕ2.0 mm (p ⬍ 0.001). For SVGs to
the LAD, the 10-year patency was 90% for vessels ⬎2.0
mm versus 52% for vessels ⱕ2.0 mm (p ⬍ 0.001). For the
IMA, the 10-year patency was 100% for vessels ⬎2.0 mm
versus 82% for vessels ⱕ2.0 mm (p ⫽ 0.008). After
controlling for hospital effects, other positive significant
predictors of graft patency over the 10-year post-bypass
period were older age, use of aspirin after CABG surgery,
lower serum cholesterol, and lowest Canadian Functional

Table 2. Characteristics of Patients Undergoing 10-Year Post-CABG Catheterization by SVG
or IMA Grafts
Variable

n

SVG Patients

n

IMA Patients

Age (yrs)
Cholesterol (mg/dl)
Triglycerides (mg/dl)
HDL (mg/dl)
Left main disease
Diseased vessels
1
2
3
CFC
I
II
III
IV
Angina
Hypertension
Prior MI
Diabetes
Smoking history
Never
Previous
Current

368
338
316
220
366

59.2 ⫾ 6.8
224.4 ⫾ 45.3
224.8 ⫾ 118.5
35.7 ⫾ 11.0
12.6

137
124
114
76
137

59.0 ⫾ 6.8
226.8 ⫾ 47.4
230.7 ⫾ 137.6
35.3 ⫾ 9.0
15.3

16
82
270

4.4
22.3
73.4

5
32
100

3.7
23.4
73.0

8
55
132
169
368
367
368
368

2.2
15.1
36.3
46.4
98.1
45.2
56.0
5.7

2
22
40
70
137
137
137
137

1.5
16.4
29.9
52.2
98.5
46.0
56.2
6.6

79
186
101

21.6
50.8
27.6

33
66
38

24.1
48.2
27.7

CABG ⫽ coronary artery bypass graft; CFC ⫽ Canadian Functional Class; HDL ⫽ high-density lipoprotein; IMA ⫽ internal
mammary artery; MI ⫽ myocardial infarction; SVG ⫽ saphenous vein graft.

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Goldman et al.
Long-Term SVG and IMA Graft Patency

JACC Vol. 44, No. 11, 2004
December 7, 2004:2149–56

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Table 3. Characteristics of Patients Undergoing 10-Year Post-CABG Catheterization and
Those Who Did Not Undergo a 10-Year Post-CABG Catheterization
Variable

n

No 10-Year
Catheterization

n

10-Year
Catheterization

Age (yrs)
Cholesterol (mg/dl)
Triglycerides (mg/dl)
HDL (mg/dl)
Grafted sites
Left main disease
Diseased vessels
1
2
3
CFC
I
II
III
IV
Angina
Hypertension
Prior MI
Diabetes
Smoking history
Never
Previous
Current

883
812
753
571
882
878

59.3 ⫾ 7.9
221.7 ⫾ 50.9
217.1 ⫾ 146.5
34.4 ⫾ 10.8
3.5 ⫾ 1.0
16.4

369
339
317
221
369
367

59.2 ⫾ 6.8
224.4 ⫾ 45.2
224.5 ⫾ 118.4
35.7 ⫾ 11.0
3.5 ⫾ 1.1
12.5

23
178
684

2.6
20.1
77.3

17
82
270

4.6
22.2
73.2

39
130
280
421
882
882
882
882

4.5
14.9
32.2
48.4
96.8
51.0
60.5
9.6

8
55
132
170
369
368
369
369

2.2
15.1
36.2
46.6
98.1
45.1
55.8
5.7

173
430
277

19.7
48.9
31.5

79
187
101

21.5
51.0
27.5

p Value
0.835
0.406
0.387
0.144
0.823
0.084
0.109

0.176

0.211
0.057
0.122
0.022
0.366

Abbreviations as in Table 1.

Class (Table 4). If a graft was patent at one week, significant
positive predictors of graft patency rates over the 10-year
post-bypass period included IMA grafts to the LAD, larger
diameters of the recipient vessel, older age, and lower serum
cholesterol (Table 5). Lower platelet count was mildly
predictive (p ⫽ 0.089) of graft patency. Interestingly, the
presence of diabetes requiring insulin and cigarette smoking
did not predict graft patency independent of whether the
vein graft was patent early or not. Other variables that were
tested in the model that were not predictive of vein graft
patency included the following: race, number of diseased
vessels, presence of peripheral edema, systemic emboli,
hypertension, white blood cell count, prior myocardial

infarction, proximal anastomotic site, temperature of cardioplegia solution, whether preservation solution given via
graft or not, heart size, use of positive inotropic, vasodilator,
antiarrhythmic agent perioperatively, use of an intraaortic
balloon, lowest body temperature, and total volume of
cardioplegia.
Presence of disease within grafts. The primary end point
of this study was the graft patency at 10 years, but disease
clearly develops in grafts. In SVGs, which developed 50% to
99% stenosis by 10 years, there was no difference among
grafts to the LAD, CX, and RCA (17% to 18%). There is
a significant difference in IMA grafts with 50% to 99%
stenosis compared with SVGs to the LAD (5% vs. 22%,

Table 4. Predictors of Long-Term Graft Occlusion Using All Grafts
Variable
Graft location
Distal anastomosis diameter
Age
Randomized treatment
Cholesterol
Canadian Functional Class

Response
Level

Acceleration Factor
(95% CI)

SVG
IMA
ⱕ2.0 mm
⬎2.0 mm
Per 10 yrs
Placebo
Aspirin
Per 50 mg/dl
I
II–IV

Reference
22.77 (9.83–52.72)
Reference
47.66 (18.91–120.15)
1.84 (1.35–2.51)
Reference
2.01 (1.15–3.53)
0.76 (0.60–0.96)
Reference
0.64 (0.40–1.02)

p Value
⬍0.001
⬍0.001
⬍0.001
0.015
0.022
0.058

For each variable, the acceleration factor represents the change in time to graft occlusion for the increment noted. An acceleration
factor ⬎1.0 means that an increase in the value of the associated variable leads to an increase in the length of time to graft
occlusion; an acceleration factor ⬍1.0 means that an increase in the value of the associated variable leads to a decrease in the time
to graft occlusion. For example, adjusting for all other variables, for every increase in 10 years of age, there is a 1.84 increase in
the time to graft occlusion. Thus, if a 50-year old man will occlude his graft at 5 years, then a 60-year old man will occlude his
graft at 1.84 ⫻ 5 or 9.2 years, all other variables being equal.
CI ⫽ confidence interval; SVG ⫽ saphenous vein graft.

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Long-Term SVG and IMA Graft Patency

JACC Vol. 44, No. 11, 2004
December 7, 2004:2149–56

Table 5. Predictors of Long-Term Graft Occlusion Given Grafts Were Open Early
Variable
Graft location
Distal anastomosis diameter
Age
Cholesterol
Platelet count

Response
Level

Acceleration Factor
(95% CI)

SVG
IMA
ⱕ2.0 mm
⬎2.0 mm
Per 10 years
Per 50 mg/dl
Per 100,000

Reference
5.11 (2.85–9.18)
Reference
6.78 (3.86–11.89)
1.28 (1.04–1.58)
0.82 (0.69–0.98)
0.82 (0.66–1.01)

p Value
⬍0.001
⬍0.001
0.021
0.031
0.069

For each variable, the acceleration factor represents the change in time to graft occlusion for the increment noted. An acceleration
factor ⬎1.0 means that an increase in the value of the associated variable leads to an increase in the length of time to graft
occlusion; an acceleration factor ⬍1.0 means that an increase in the value of the associated variable leads to a decrease in the time
to graft occlusion. For example, adjusting for all other variables, for every 50-mg/dl increase in cholesterol, there is a decrease
in the time to graft occlusion by a factor of 0.82. Thus, if a man with a serum cholesterol level of 200 mg/dl will occlude his
graft at 5 years, then a man with a serum cholesterol level of 250 mg/dl will occlude his graft at 0.82 ⫻ 5 or 4.1 years, all other
variables being equal.
IMA ⫽ internal mammary artery; other abbreviations as in Table 4.

p ⬍ 0.001) and with IMA grafts compared with all SVGs
(5% vs. 18%, p ⬍ 0.001). The difference appears to start
somewhere after three years postoperatively (Fig. 5).

DISCUSSION
These data report 10-year serial angiographic follow-up of
patients operated on in the 1980s. For SVGs, the 10-year
patency is 61%, and if a SVG is patent at 1 week after
surgery, that graft has a 68% chance of being patent at 10
years. For IMA grafts, the 10-year patency is 85% and if an
IMA graft is patent at 1 week, that graft has a 88% chance
of being patent at 10 years. Combining the data in this
report with our previous work (8 –12), we know that serial
SVG patency is 95% at 1 week, 84% at 1 year, 80% at 3
years, 69% at 6 years, and 61% at 10 years (Fig. 1). The
serial data for IMA grafts are 99%, 95%, 93%, 87%, and
85% at each of the same time points. Although the
long-term patency of IMA grafts is better than that for
SVGs, the 10-year patency of SVGs is better than what has
been previously reported, and the 10-year patency of IMA
grafts is somewhat worse than previously thought.
The most often quoted results in published reports
regarding graft patency after CABG are that at 10 years,
SVGs have about a 40% to 50% patency and that IMA
grafts have a 90% to 95% 10-year patency. The initial
studies that are the basis of this information were not
prospective and reported on selected patients operated upon
in the 1970s (1– 6). In these retrospective studies, graft
patency was not determined on everyone in the initial
cohort, but rather on those patients who received angiography most often because of symptoms. In 1996 there was a
report from a larger database, which included a combination
of first surgery and re-operation surgery (7). Even though
that trial was designed to follow patients prospectively, the
authors state that their plans “were thwarted by lack of
funds” and their graft patency data, in the subset that
underwent catheterization, were similar to the numbers
cited above. When the present study was planned, the
longest angiographic follow-up studies of IMA grafts were

from the Cleveland Clinic (6,17,18), Karolinska Hospital
(19), and the Montreal Heart Institute (3,20). At or past 10
years, each of these centers has reported studying 37, 39,
and 20 patients, respectively. Although these reports are
important and are obviously responsible for the enthusiasm
for using IMA grafts today, they are relatively small retrospective studies. Perhaps the most telling criticism of these
studies is that the type of patients operated on 10 to 15 years
ago is not the same as patients undergoing CABG now. In
the report from the Karolinska Hospital, the 37 patients
studied at 11 years had an 88% IMA patency rate (19). The
baseline characteristics of this patient population included
an average ejection fraction of 64% and 42 of 99 (42%) of
the original patients had only IMA grafts. This obviously
does not represent the current cardiac surgical population.
The patients in our study had average ejection fractions of
61%, but they received 2.9 vein grafts per patient. Another
reason why the earlier data may not be applicable now is
that the patient population operated on today has more
extensive disease than those operated on in the 1970s
because today surgeons must operate on patients who have
been denied percutaneous coronary intervention or are
having second and third revascularization procedures.
All of the studies from the 1970s were done prior to the
widespread use of antiplatelet therapy after CABG, and it is
now well established that aspirin helps to prevent SVG
occlusion (8 –12). In the 1970s, very little attention was paid
to risk factor control and aggressive lowering of low-density
lipoprotein cholesterol, which may alter SVG patency and
improve clinical outcomes after CABG (21–23). Lastly,
surgical techniques have been modified with regard to
preparation of the vein graft before implantation; for instance, we know that cold vein graft preservation solution
improves long-term vein graft patency (13).
Comparisons are often made between veins and arteries
used as conduits, with the general belief that arterial
conduits have a better long-term patency. In fact, the IMA
has been proclaimed the graft of choice to bypass the LAD
because of its presumed excellent long-term patency rate. A

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JACC Vol. 44, No. 11, 2004
December 7, 2004:2149–56

1986 editorial in the New England Journal of Medicine (23)
stated, “at 10 years internal mammary artery grafts remained
in excellent condition; nearly 95% were patent, with no
signs of deterioration.” Although this suggests that the IMA
is an ideal conduit, it is important to emphasize that there
are no randomized prospectively controlled trials comparing
IMA to SVGs. In the past surgeons tended to use IMA
grafts in better candidates (i.e., the patient was clinically
stable, without severe lung disease, diabetes, and so on).
This clinical approach is borne out by our data and that of
others, which show that patients receiving SVGs tend to
have more severe disease initially than the patients receiving
IMA grafts (9,10,13). This argument is probably not
germane today, when the characteristics of patients have
dramatically increased toward more complex disease as a
result of percutaneous coronary intervention, and yet IMA
grafts are still used in the majority of patients. In the present
study, where patients were not randomized to different
conduits, the 10-year patency of left IMA grafts to the
LAD is 85%, as opposed to 69% for SVGs to the LAD.
Another argument that is often used to support the IMA as
the conduit of choice is that retrospective studies have
shown that survival is improved in patients receiving IMA
grafts as opposed to vein grafts (4,6,25,26). Even though
these studies adjust for demographic and clinical differences,
they are still retrospective nonrandomized analyses. Data
from our study group have shown that use of the IMA is
associated with a longer operative time as well as increased
postoperative bleeding (27). Thus, the sicker, more complicated patients 10 to 15 years ago would have received vein
grafts and not IMA grafts.
The data on predictors of graft patency are interesting.
We and other investigators have previously shown that the
size of the recipient vessel is an important predictor of graft
patency (13). The simple explanation has been that the
larger the recipient vessel, the better the flow and distal
runoff. The size of the recipient vessel is also thought to be
the explanation for why SVGs to the LAD do better than
those to the right or CX (Tables 4 and 5, Fig. 3). The other
significant patient specific predictors of graft patency are, for
the most part, a reflection of the disease in the patient (i.e.,
there was worse SVG patency in younger patients, which
probably is a reflection of worse native coronary disease in
younger patients, and patients with elevated serum cholesterols). Interestingly, diabetes and cigarette smoking were
not predictors of poor graft patency. We have previously
reported on the beneficial effects of aspirin on SVG patency
up to one year after surgery (11–13). That observation is
consistent with our present data that show the use of aspirin
is predictive when looking at all grafts (Table 4), but not in
grafts that were patent originally at one week (Table 5). Our
earlier work also showed that the temperature used to
preserve the vein graft was important, with improved
three-year SVG patency when colder temperatures were
used (13). We hypothesized that the colder temperatures
and the type of preservation fluid used in the vein might

Goldman et al.
Long-Term SVG and IMA Graft Patency

2155

have preserved endothelial function and thus improved
long-term graft patency.
We believe that the estimates of 10-year graft patency
presented here are less biased than any results previously
published. First, although it is generally believed that
patients who die may have much higher occlusion rates than
survivors, the patency rate from 71 autopsies in our study
(13.6% of all deaths) was 76% (156 of 205 grafts). Therefore, the effect of lost observations due to death on longterm patency rates may be minimal. Second, although only
33% of the 10-year catheterizations were done strictly for
the purposes of this study, this is a substantial proportion
compared with previous reported 10-year data, which used
retrospective data collection and based their results solely on
symptomatic patients. The use of survival analysis techniques to estimate long-term patency is a third technique in
fine-tuning the estimates of graft patency. Angiography at
any time point can only tell that a graft has become occluded
at that point in time, but it cannot determine when the
occlusion occurred. Thus, to use the time of the angiography to estimate graft patency will overestimate the patency
rate. The use of interval censoring is an attempt to more
accurately estimate the time that the occlusion occurred.
Lastly, as in all our previous reports, we acknowledge that
graft patency within an individual is correlated and we have
adjusted for this association.
It may be reasonable to assume that graft patency influenced survival. The data are only from the survivors who, by
definition, may have had better graft patency than the
nonsurvivors. We acknowledge that not being able to
address whether graft patency influenced survival is a
potential weakness in our study, but this would be true for
any long-term study of graft patency after CABG. Owing to
the long-term nature of the study and the fact that coronary
artery disease is a progressive disease, we used data from
clinically indicated angiograms, in part, for the 6- and
10-year follow-up. In this older patient population it is
difficult to get patients to agree to repeat invasive procedures
when they already have had a clinically indicated catheterization, are asymptomatic, or when the attending cardiologist would not consider any interventional procedure. Two
notes of caution: the patients who did not undergo the
10-year catheterization had more diabetes and hypertension
and, therefore, the current estimates of patency may be
overestimated. Lastly, all patients were men and, therefore,
long-term angiographic follow-up of CABG grafts is not
available for a female cohort.
In conclusion, we report long-term analysis of SVG and
IMA patency for 10 years after operation, showing that
patency for IMA grafts is better than for SVGs, but the
10-year patency for SVGs is better and 10-year patency for
left IMA grafts is worse than previously thought. The most
important predictors of long-term graft patency are initial
patency at one week after CABG and the diameter of the
recipient vessel into which the graft is placed.

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2156

Goldman et al.
Long-Term SVG and IMA Graft Patency

Reprint requests and correspondence: Dr. Steven Goldman,
Cardiology Section (1-111C), Southern Arizona VA Health Care
System, 3601 South 6th Avenue, Tucson, Arizona 85723. E-mail:
[email protected].

REFERENCES
1. Bourassa MG, Campeau L, Lesperance J, Grondin CM. Changes in
grafts and coronary arteries after saphenous vein aortocoronary bypass
surgery: results at repeat angiography. Circulation 1982;65 Suppl
II:II90 –7.
2. Campeau L, Enjalbert M, Lesperance J, Vaislic C, Grondin CM,
Bourassa MG. Atherosclerosis and late closure of aortocoronary
saphenous vein grafts: sequential angiographic studies at 2 weeks, 1
year, 5 to 7 years, and 10 to 12 years after surgery. Circulation 1983;68
Suppl II:II1–7.
3. Grondin CM, Campeau L, Lesperance J, Enjalbert M, Bourassa MG.
Comparison of late changes in internal mammary artery and saphenous
vein grafts in two consecutive series of patients 10 years after operation.
Circulation 1984;70 Suppl I:I208 –12.
4. Cameron A, Kemp HG, Green GE. Bypass surgery with the internal
mammary artery graft: 15-year follow-up. Circulation 1986;74 Suppl
III:III30 – 6.
5. Lytle BW, Loop FD, Cosgrove DM, Ratliff NB, Easley K, Taylor PC.
Long-term (5–12 years) serial studies of internal mammary artery and
saphenous vein coronary artery bypass grafts. J Thorac Cardiovasc Surg
1990;15:15–20.
6. Loop FD, Lytle BW, Cosgrove DM, Stewart RW, Goormstic M,
Williams GW, et al. Influence of the internal-mammary graft on
10-year survival and other cardiac events. N Engl J Med 1986;314:
1– 6.
7. Fitzgibbon GM, Kafka HP, Leach AJ, Keon WJ, Hooper GD, Burton
JR. Coronary bypass graft fate and patient outcome: angiographic
follow-up of 5,056 grafts related to survival and reoperation in 1,388
patients during 25 years. J Am Coll Cardiol 1996;28:616 –26.
8. Goldman S, Copeland J, Moritz T, Henderson W, Zadina K, Ovitt T,
et al. Improvement in early saphenous vein graft patency after coronary
artery bypass surgery with antiplatelet therapy. Circulation 1988;77:
1324 –32.
9. Goldman S, Copeland J, Moritz T, Henderson W, Zadina K, Ovitt T,
et al. Saphenous vein graft patency one year after coronary artery
bypass surgery and effects of antiplatelet therapy. Circulation 1989;80:
1190 –7.
10. Goldman S, Copeland J, Moritz T, Henderson W, Zadina K, et al.
Internal mammary artery and saphenous vein graft patency: effects of
aspirin. Circulation 1990;82 Suppl IV:IV237– 42.
11. Goldman S, Copeland J, Moritz T, et al. Starting aspirin therapy after
operation: effects on early graft patency. Circulation 1991;84:520 – 6.
12. Goldman S, Copeland J, Moritz T, et al. Long term graft patency (3
years) after coronary artery surgery: effects of aspirin. Results of a VA
cooperative study. Circulation 1994;89:1138 – 43.

JACC Vol. 44, No. 11, 2004
December 7, 2004:2149–56
13. Goldman S, Zadina K, Krasnicka B, et al., for VA Cooperative Study
Group #297. Predictors of graft patency 3 years after coronary artery
bypass surgery. J Am Coll Cardiol 1997;29:1563– 8.
14. Henderson W, Moritz T, Goldman S, et al. The statistical analysis of
graft patency data in a clinical trial of anti-platelet agents following
coronary artery bypass grafting. Control Clin Trials 1988;9:189 –205.
15. Bogaerts K, Leroy R, Lesaffre E, Declerck D. Modelling tooth
emergence data based on multivariate interval-censored data. Stat Med
2002;21:3775– 87.
16. Huster WJ, Brookmeyer R, Self, SG. Modelling paired survival data
with covariates. Biometrics 1998;45:145–56.
17. Lytle BW, Loop FD, Cosgrove DM, Ratliff NB, Easley K, Taylor PC.
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.
18. Ivert T, Huttunen K, Landou C, Bjork VO. Angiographic studies of
internal mammary artery grafts 11 years after coronary artery bypass
grafting. J Thorac Cardiovasc Surg 1988;96:1–12.
19. Grondin CM, Campeau L, Thornton JC, Engle JC, Cross FS,
Schreiber H. Coronary artery bypass grafting with saphenous vein.
Circulation 1989;79 Suppl I:I24 –9.
20. Blankenhorn DH, Johnson RL, Mack WJ, El-Zein HA, Vailas LI.
The influence of diet on the appearance of new lesions in human
coronary arteries. JAMA 1990;263:1646 –52.
21. Knatterud GL, Rosenberg Y, Campeau L, et al., and Post CABG
Investigators. Long-term effects on clinical outcomes of aggressive
lowering of low-density lipoprotein cholesterol levels and low-dose
anticoagulation in the Post Coronary Artery Bypass Graft Trial.
Circulation 2000;102:157– 65.
22. Post Coronary Artery Graft Trial Investigators. The effect of aggressive lowering of low-density lipoprotein cholesterol levels and lowdose anticoagulation on obstructive changes in saphenous-vein
coronary-artery bypass grafts. N Engl J Med 1997;336:153– 62.
23. Spencer FC. The internal mammary artery: the ideal coronary bypass
graft? N Engl J Med 1986;314:50 –1.
24. Acinapura AJ, Rose DM, Jacobowitz IJ, et al. Internal mammary
artery bypass grafting: influence on recurrent angina and survival in
2,100 patients. Ann Thorac Surg 1989;48:186 –91.
25. Cameron C, Davis KB, Green GE, Myers WO, Pettinger M. Clinical
implications of internal mammary artery bypass grafts: the Coronary
Artery Surgery Study experience. Circulation 1988;77:815–9.
26. Loop FD, Lytle BW, Cosgrove DM. New arteries for old. Circulation
1989;79:I40 –5.
27. Sethi GK, Copeland JG, Moritz T, Henderson W, Zadina K,
Goldman S. Comparison of postoperative complications between
saphenous vein and IMA grafts to left anterior descending coronary
artery. Ann Thorac Surg 1991;51:733– 8.

APPENDIX
For the Statistical Appendix and a list of the Department of Veterans Affairs Study Group members, please
see the December 7, 2004, issue of JACC at http://
www.onlinejacc.org.

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