Change in luminal diameter of the left internal thoracic artery anastomosed to the totally occluded left anterior descending coronary artery
Jung et al. Journal of Cardiothoracic Surgery
Change in luminal diameter of the left internal thoracic artery anastomosed to the totally occluded left anterior descending coronary artery
Yochun Jung 0
Byoung Hee Ahn 0
Gwan Sic Kim 0
In Seok Jeong 0
Kyo Seon Lee 0
Sang Yun Song
Kook Joo Na
Sang Gi Oh 0
0 Department of Thoracic and Cardiovascular Surgery, Chonnam National University Hospital, Chonnam National University School of Medicine , 42 Jebong-ro, Dong-gu, Gwangju 501-757 , South Korea
Background: Coronary artery bypass grafting (CABG) with a composite Y-graft made of the left internal thoracic artery (LITA) and another arterial graft has a risk for hypoperfusion. Changes over time in the diameter of the LITA anastomosed to the left anterior descending coronary artery (LAD) are not known. Methods: Data were collected for 71 patients who had undergone coronary angiography (CAG) immediately and at 1 year following off-pump CABG with a composite Y-graft made of the LITA and either the radial artery or the right gastroepiploic artery. These patients were divided into 2 groups depending on the degree of LAD stenosis. Group 1 (n = 28) consisted of patients with complete occlusion of the LAD. Group 2 (n = 43) consisted of patients with <90% stenosis of the LAD. The clinical state and luminal diameter of the LITA on immediate postoperative and postoperative 1-year CAG were compared and analyzed. Results: On the immediate postoperative CAG, mean LITA diameter of Group 1 was larger than that of Group 2 (2.09 ± 0.53 vs. 1.61 ± 0.33 mm, P = 0.01). Mean LITA diameter 1 year following CABG was also larger in Group 1 than in Group 2 (2.49 ± 0.31 vs. 2.10 ± 0.45 mm, P = 0.005). Both groups showed significant increases in the LITA diameters at postoperative 1 year. Conclusions: The LITA used as a composite Y-graft underwent remodeling, resulting in a larger diameter, to supply adequate myocardial blood. The degree of change in luminal diameter varied according to the severity of the LAD stenosis.
Coronary artery bypass grafting; Internal thoracic artery; Composite graft
Since the publication of the study reporting that the left
internal thoracic artery (LITA) anastomosed with the left
anterior descending coronary artery (LAD) in coronary
artery bypass grafting (CABG) showed excellent
longterm patency , such anastomosis has been regarded as
the gold standard in CABG. Furthermore, there is an
increasing tendency to use total arterial revascularization
(TAR), with the expectation that arterial grafts such as
the radial artery (RA) or right gastroepiploic artery
(RGEA) would have better long-term patency than that
of a vein graft.
There are various strategies for TAR. Composite
Ygrafting with the LITA and another arterial graft is one
of the frequently-performed methods. TAR using a
composite Y-graft, however, results in blood inflow from the
LITA alone; thus, this method is controversial because
of the risk for hypoperfusion .
This study included patients who underwent off-pump
CABG by using a composite Y-graft with the LITA and
the RA or the RGEA, and it aimed to investigate the
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adequacy of blood flow from the LITA to the LAD
territory by using serial coronary angiographies (CAGs),
which were performed just before the patients’ discharge
from the hospital and 1 year after surgery for
measurement of the diameter of the LITA right above the LAD
Among 108 CABGs performed at our hospital between
January 2000 and April 2005, 82 patients underwent
offpump TAR with a composite Y-graft. We excluded cases
of; (1) poor distal run-off of the LAD due to diffuse
atherosclerotic changes, (2) aneurysms of the left ventricle,
(3) less than 20% left ventricular ejection fraction, (4)
LAD stenosis of 90-100%, and (5) significant stenotic
lesions on the LITA, and reviewed the medical records of
the remaining 71 patients. The subjects were divided
into 2 groups. Group 1 included cases of total occlusions
of the LAD before surgery (n = 28, 4 women, mean age
of 60.8 ± 8.9 years). Group 2, the control group, consisted
of cases with <90% stenosis (n = 43 cases, 8 women, mean
age of 58.9 ± 8.1 years). All patients underwent serial
CAG, which were performed just before patients’
discharge from the hospital and 1 year after surgery. Changes
in the luminal diameters of the LITA right above the LAD
anastomotic site of both groups were compared. Before
performing CAG, all the patients were informed of the
necessity of the procedure and agreed to undergo it after
fully understanding the possible complications. This study
was approved by Chonnam National University Hospital’s
Institutional Review Board, with patient consent waived.
Electrocautery and hemoclip were used for skeletonized
harvesting of the LITA, with the goal of complete cut-off
up to the first branch. While harvesting the LITA,
simultaneous harvesting of the other arterial grafts was
performed. The RA was harvested from the non-dominant
arm, and all patients underwent Allen’s Test before
surgery. The approach to the RGEA following median
sternotomy was carried out by extending an incision 2
to 4 cm toward the abdomen. After laparotomy, the
RGEA was first verified by palpating it with the fingers.
Then, the anterior serosa was separated by electrocautery,
and the RGEA and vein were also separated. Warm and
diluted papaverine solution (1 mg/mL) was sprayed onto
the arterial graft externally to prevent vasospasm, without
intraluminal injection. Harvested arterial grafts were
wrapped in a gauze soaked with warm papaverine solution
right up to its utilization. All arterial grafts were ligated
after systemic heparinization (100 U/kg). During surgery,
activated clotting time was maintained at 300 s or longer.
Surgeries were performed by a single surgeon (Ahn
BH) and off-pump CABG using composite Y-graft was
performed for all patients. Either 1) >70% of the segmental
stenosis in the LAD or 2) >50% of diffuse stenosis in LAD
originating from the LM was regarded as in indication
of the composite Y-graft to LAD. On performing the
coronary arterial anastomoses, an intracoronary shunt,
a vascular sling, and carbon dioxide blower were used
for securing the visual field at the incision area of the
coronary arteries. The Guidant AcrobatTM SUV Off-Pump
System (Guidant Corporation, Santa Clara, California,
USA) was used in the surgery. With respect to the
composite Y-graft, the RGEA or the RA was anastomosed to
the LITA at the area entering the pericardium. An 8-0
polypropylene suture was used for the anastomosis via the
continuous running technique. After creating a Y-graft,
the LITA was anastomosed to the LAD for all the patients,
regardless of the state of collateral circulation. Subsequent
anastomoses were performed in the following order:
diagonal, obtuse marginal and right coronary branches. An
intracoronary shunt was used for the performance of the
LAD anastomosis, while a proximal vascular sling was
used for the performance of the anastomoses of the
remaining branches. In cases where the length of the RA
was short for the target coronary artery anastomosis,
the harvested RGEA was used as an extended graft.
The RGEA and RA were anastomosed for cases of 70%
or greater stenosis in the diagonal or left circumflex
branches. Sequential anastomoses of the right coronary
branches were performed for cases of 90% or greater
stenosis. Anastomosis was performed for cases of
coronary artery diameter of 1 mm or greater, with the aim
of complete revascularization. An 8-0 polypropylene
suture was used for anastomosis of the arterial graft. A
diastolic dominant flow pattern was verified with a
transit-time flowmeter (Transonic System Inc., NY, USA)
after performing each anastomosis. At the end of each
anastomosis, diluted papaverine solution was sprayed for
the prevention of early vasospasm. Half of the calculated
dosage of protamine injection was used for patients with
tendencies of bleeding. In cases where bleeding through
the thoracic drainage tube was thought to be insignificant
at the intensive care unit after surgery, 100 mg of aspirin
and 75 mg of clopidogrel were administered through a
Quantitative angiographic evaluation
Angiography was performed before hospital discharge and
1 year after surgery, with mean durations of 13.3 ± 3.8 days
and 12.7 ± 0.7 months, respectively. All the patients were
medicated before CAG such that their systolic blood
pressures were maintained at 110–140 mmHg. In order
to reduce errors in angiography, values obtained from 2
different angles in the end diastolic phase were averaged.
Angiographic findings were evaluated by 3 cardiovascular
specialists. In cases of disagreement in opinions, decisions
were made through discussion. Graft failure was defined
as having an occlusion or stenosis rate of 70% or greater
and included cases of a string sign, indicating diffuse
Continuous variables were presented as a mean ± standard
deviation and were compared using the Student’s t-test or
paired t-test as necessary. A P value <0.05 was considered
statistically significant. The analyses were carried out using
SPSS ver. 12.0 (SPSS Inc., Chicago, USA).
Clinical manifestations and preoperative
echocardiography and CAG findings of both groups are as shown in
Table 1. The total numbers of anastomoses for both
Group 1 and Group 2 were 3.1 ± 0.8 and 2.97 ± 0.9,
respectively and did not show any significant difference
(P = 0.67). Numbers of anastomoses using the RGEA
and the RA are tabulated in Table 2.
The postoperative 1-year CAG revealed no case of a
string sign in the LITA graft anastomosed to the LAD;
however, 1 case of string sign was found in the RGEA
graft anastomosed to the OM in Group 1 and 1 case in
PDA-anastomosed RA in Group 2. Patency rates of the
RGEA and RA immediately after surgery were 96.2%
(25/26) and 100% (32/32), respectively, for Group 1,
Table 1 Preoperative patients’ characteristics
Table 2 Operative and postoperative data
No number, GEA gastroepiploic artery, RA radial artery
while patency rates of the RGEA and the RA
immediately after surgery were 100% (30/30) and 100% (63/63),
respectively, for Group 2. Patency rates of the RGEA
and the RA 1 year after surgery were 96.2% (25/26) and
96.9% (31/32), respectively, for Group 1. Patency rates of
the RGEA and the RA 1 year after surgery were 100%
(30/30) and 96.8% (61/63), respectively, for Group 2. On
follow-up CAG, the first branch of the LITA was not
seen in any of the patients.
No in-hospital mortality was observed. One case from
Group 2 developed low cardiac output syndrome in the
immediate postoperative period but recovered. No cases
of neurologic complications or myocardial ischemia or
infarction were noted during the early postoperative and
Significant increases in mean LITA diameters were
found for both groups on the postoperative 1-year
CAG. The diameters showed a 1.19-fold increase, from
2.09 ± 0.53 mm to 2.49 ± 0.31 mm, in Group 1, while
they showed a 1.31-fold increase, from 1.61 ± 0.33 mm
to 2.10 ± 0.45 mm, in Group 2. Mean LITA diameter of
Group 1 was consistently larger than that of Group 2
on both immediate postoperative CAG and postoperative
1-year CAG (Table 3).
Immediate postoperative CAG
postoperative 1-year CAG
Sex (male : female)
Old myocardial infarction
Acute myocardial infarction
LV ejection fraction (%)
Infarct site on electrocardiogram
Coronary angiographic findings
LV left ventricle, LAD left anterior descending coronary artery, LCX left
circumflex coronary artery, RCA right coronary artery
One case in Group 1 was readmitted to the hospital
for wound infection during the follow-up period. One
case in Group 2 underwent percutaneous coronary
intervention because of stenosis of the posterolateral branch
anastomosis site. There was no cardiac-related death in
As recent advances in percutaneous coronary
intervention are associated with high success rates and reduced
complications, CABG has largely become limited to
patients with chronic diseases or severe multi-vessel coronary
diseases . Over time, patients tend to have a higher
possibility of the need for a reoperation because of
atherosclerotic changes in a graft rather than because of the native
coronary disease itself. In order to reduce reoperation rates
because of graft failure, it would be important to select a
graft with good patency for primary CABG.
Owing to excellent long-term patency, arterial grafts
have been increasingly used recently [4, 5]. In particular,
the internal thoracic artery has the advantages of the
low incidence of atherosclerosis, a functional arterial
intima, an ideal vascular size that concurs with the
coronary artery, and capacity for blood flow in accordance
with changes in myocardial blood flow demand [1, 6].
For these reasons, anastomosis of the LITA to the LAD
has been the basic surgical tenet of CABG.
Based on this fundamental procedure, TAR should be
performed using various arterial grafts anastomosed with
the LITA by using a composite Y- or T-graft
configuration in cases requiring multiple grafting. A restrictive
arterial graft could be utilized for TAR by using a
composite graft, which has the advantage of a "no-touch
technique" of the aorta. Nevertheless, it has the
disadvantage of having the LITA as the only blood inflow
source, and there are controversies regarding flow
competition and inadequate myocardial blood flow in the
immediate postoperative period [7, 8]. Thus, it is
necessary to verify whether the composite LITA anastomosed
to the LAD, which is the most important cardiac blood
flow supply, could supply adequate blood volume.
Sakaguchi et al. asserted that a composite arterial
Ygraft has less coronary flow reserve as opposed to that of
independent grafts, and a small LITA size would call for
precautions . In contrast, Wendler et al. found that
internal thoracic artery composite grafts could also
provide adequate blood flow to the LAD . Akasaka et al.
insisted that an independent internal thoracic artery
graft could supply adequate blood flow similar to that
with saphenous vein grafts . Markwirth et al. used a
Doppler-guided wire to measure the flow of the
proximal internal thoracic artery and coronary flow reserve
after TAR through T-grafts, and observed that the
functional and morphological adaptation capabilities of the
internal thoracic artery were sufficient for higher flow
volume requirements . Citing the data measuring
free flow in the operative field after formation of
composite Y-graft with the LITA and the RA, Royces et al.
reported that TAR with a composite conduit can also
compensate for the myocardial blood flow requirement,
as it shows a 2.3-fold reserve blood flow to the coronary
vascular bed .
In patients subjected to TAR using the LITA as a
composite graft, it is rare to find angiographic studies on
whether sufficient blood flow could be supplied in the
immediate postoperative period before achieving complete
remodeling of the LITA anastomosed to the LAD. This
study was based on patients with total occlusion of the
LAD. The reasons were two-fold: (1) LITA flow to the
LAD would not be affected by the degree of stenosis of
the proximal LAD, and (2) LITA flow would be affected
by myocardial blood flow demand alone.
The diameter of the LITA grafted to the LAD is closely
related to the degree of proximal stenosis of the LAD, i.e.
to the LAD flow volume via the LITA. The diameter of
the LITA becomes larger when the coronary flow is
LITAdependent as a result of a severe proximal LAD stenosis.
In contrast, the diameter of the LITA becomes smaller
when the LAD flow is dependent on the native coronary
artery because of a mild proximal LAD stenosis. Among
children whose myocardial blood flow demand increases
because of somatic growth, remodeling takes place along
the length of the internal thoracic artery, as well as on its
diameter . That is, the internal thoracic artery graft is
an active conduit with functional adaptability to
myocardial flow demand, and not a passive conduit.
The remodeling of the internal thoracic artery is an
integrated activity involving the endothelium, smooth
muscle, fibroblasts, and extracellular matrix . The
internal thoracic artery is autoregulated to maintain the
base shear stress of 15–20 dyne/cm2 . Remodeling
takes place on the basis of the Hagen-Poiseuille equation
(τ = 4ησ/πγ3. τ = shear stress, η = blood viscosity, σ = blood
flow, γ = graft diameter). In the early phase, the LITA flow
would depend on flow velocity increase. However, as the
high shear stress continues by means of high flow velocity,
the diameter of the LITA increases, implicating a
remodeling process in which the extent of shear force would
decrease to base levels [16, 17].
Although the time when remodeling is completed has
yet to be determined, Barner reported that the internal
thoracic artery flow measured again 6–8 h after
reoperation because of bleeding, showed a 40% increase, and
that such increase implicated that flow adaptation of the
ITA could occur immediately after surgery . Akasaka
et al. revealed that the flow velocity within 1 month of
surgery was high and the flow velocity 1 year after
surgery was low, while the internal thoracic artery diameter
increased . Such phenomenon could be analyzed by
the Hagen-Poiseuille equation. Tagusari et al. reported
that the LITA diameter significantly increased on
angiography performed 14 days on the average after
CABG using a composite Y-graft of the LITA and the
RA, and reported that the LITA may undergo early
adaptation . However, the study did not report
diameter change following the LAD stenosis or results
of changes in the late period. Nakayama et al.
suggested, from the results of angiography performed
within 1 month after surgery and a mean interval of
4.5 ± 1.5 years after surgery, that the LITA diameter
increased as the LAD stenosis became severe in cases
without total LAD occlusion; however, they also reported
that the LITA diameters measured for cases of total LAD
occlusion were 2.27 ± 0.32 mm and 2.32 ± 0.38 mm,
respectively, showing little change . This suggests
that LITA remodeling could be completed and may be
able to supply sufficient blood flow required for the
LAD territory within 1 month. In contrast, Akasaka et al.
reported, from cases of independent ITA anastomosed
with a totally occluded LAD, that the ITA diameters
changed by flow demands, showing them to be 2.4 ± 0.1 mm,
1 month after surgery, while being 2.9 ± 0.2 mm 1 year
after surgery .
In this study, both groups showed significant increases
in the LITA diameters on postoperative 1-year CAG,
although the mean LITA diameter of Group 1 was
consistently larger than that of Group 2 in both immediate
postoperative CAG and postoperative 1-year CAG. The
increase in mean diameter of LITA in Group 2 seems to
be related, in a certain part, to the increase in flow
demand due to the progression of the LAD. Sanidas EA,
et al. reported about the natural history of untreated
nonculprit lesions in 697 patients with acute coronary
syndrome. On angiographic study, 44 patients
experienced substantial lesion progression (≥20% angiographic
diameter stenosis increase) . Even in a healthy man
with a normal coronary angiogram, new coronary lesions
do develop . Therefore, it seems to be reasonable
to assume that the progression of LAD stenosis has
occurred and it might affect the diameter of LITA,
although we have not checked the progression of LAD
stenosis in the postoperative 1-year CAG in group 2.
Interestingly, the mean LITA diameter of group 1 in
the immediate postoperative CAG was not different to
that of group 2 in the CAG performed 1 year after surgery
(2.09 ± 0.53 vs. 2.10 ± 0.45 mm, P = 0.46). It shows that the
dilatation of LITA, which happened over 1 year according
to the progression of the LAD stenosis in group 2, had
occurred in an immediately postoperative period in group 1,
indicating that maximum possible enlargement of LITA
can be achieved by the LITA-dependent blood flow in the
The increase in mean diameter of the LITA in Group
1 seems to show the remodeling of the LITA reflecting
the increase in myocardial demand for blood flow during
the first year. This might imply that maximum possible
enlargement of the LITA in early postoperative period
may not fully satisfy the myocardial demand in a certain
circumstance. In this regard, the patients who
underwent CABG to totally occluded LAD by using composite
Y-graft had good to avoid excessive exercises that could
increase myocardial demand during the early
postoperative period, even though no myocardial ischemia-related
complication was noticed in this study.
Limitations of this study are as follows: being an
angiographic study, the flow reserve of the LITA, which
is an early compensatory mechanism for high blood flow
demand, could not be measured; possible effects of
collateral flow of the coronary artery were not considered;
the domain of myocardial infarction was not considered
although preoperative echocardiography showed
significant differences in left ventricular ejection fraction; the
degree of change in native coronary artery disease was
not taken into account in Group 2; the location of the
anastomosis of the LITA and LAD was not considered;
and the degree of remodeling immediately after surgery
could not be investigated because the size of the LITA was
not measured preoperatively. Further studies are needed
to address these aspects and involve a larger number of
patients with LAD stenosis of various levels.
Changes in the diameters of the LITA on serial
angiography, not considering functional LITA flow reserve,
suggest that the LITA used as a composite graft during
TAR undergoes remodeling, resulting in larger diameters,
in order to provide adequate myocardial blood flow. The
degree of change in luminal diameter varies according to
the severity of the LAD stenosis.
Availability of data and materials
Data will not be shared. Our hospital is a local tertiary center covering a
small province and our study cohort is relatively small. When the raw data is
publicly opened, therefore, there is concern about the invasion of privacy of
our patients. We didn’t get our patients’ consent to open their clinical data
to a public repository.
BHA carried out the writing of the report, GSK and ISJ performed data
collection, KSL and YJ carried out data analysis and interpretation, SYS and
KJN participated in data collection and interpretation, SGO designed the
study and carried out data interpretation. All authors read and approved the
Consent for publication
Ethics approval and consent to participate
This study was approved by Chonnam National University Hospital’s
Institutional Review Board, with patient consent waived.
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