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Raja. Vessel Plus 2019;3:23 I http://dx.doi.org/10.20517/2574-1209.2019.05 Page 7 of 11

tension on the conduit, angulation at anastomotic site, and unresolved harvest spasm are recognized
reasons for hypoperfusion syndrome [33,34] . Preoperative angiographic evaluation of the quality of the
IMA conduit and the subclavian artery, careful conduit harvesting and meticulous construction of
anastomoses, insertion of 1.5-mm flexible probe into the IMA and the radial artery after harvesting, and
flow measurement using transit time Doppler flow meter after completion of anastomosis are some of the
strategies which can mitigate the risk of perioperative hypoperfusion [33,35] .

Competitive flow
Another concern is the augmented risk of competitive flow in the composite graft in comparison with the
individual bypass graft. Competitive flow reduces the antegrade flow especially in the diastole, and the
[33]
phasic delay in pressure wave in the IMA causes a retrograde flow in the early systole . This oscillating
flow pattern in the competitive scenario influences the endothelium. The release of nitric oxide and
prostacyclins is affected leading to string sign, which is considered a physiologic vasoconstriction of the
arterial graft. String sign is associated with moderate stenosis in the target coronary artery [29,35] and results
in failure of the arterial graft [35,36] .

In the composite graft, the mechanism of competitive flow is more intricate than that in the individual
graft. In addition to the relation between the graft and its target coronary branch where competitive
flow occurs, the interactions of all anastomosed branches within the composite graft, the phasic delay
between the in situ grafts, and the whole graft arrangement in the patient contribute to this phenomenon.
Therefore, avoidance of competitive flow and graft occlusion relies on both adequate surgical strategy and
maneuver [33,35] . It is perhaps wise to avoid using composite grafts on moderately stenotic coronary arteries
particularly moderately stenotic branch in the RCA territory which is the most important predictor of
competitive flow and graft occlusion [33,35] .

Deep sternal wound infection
Deep sternal wound infection (DSWI) is a dreadful complication of TAR, especially when BIMA is part
of the revascularization strategy. The Arterial Revascularization Trial reported a 1.3% increase in the
[37]
incidence of sternal wound reconstruction associated with the BIMA . Different techniques of harvesting
the IMA may influence these results. DSWI can be reduced to less than 1% by avoiding BIMA usage in
morbidly obese patients (body mass index above 35), insulin-dependent diabetic patients, and those with
severe chronic obstructive airways disease, and by appropriate timing of prophylactic antibiotics, including
redosing after 4 h, tight blood glucose control intraoperatively and for 48 h, alcohol-based antibacterial
preparation, and Vancomycin paste to the sternal edges .
[27]

Skeletonized technique of IMA harvesting has been shown to conserve considerable collateral flow to the
sternum by sparing some of the sternal and intercostal branches that originate from the IMA as a common
trunk [38,39] . This technique is claimed to reduce the risk of sternal wound complications by improving
wound healing, especially when both left and right IMAs are harvested, due to preservation of sternal
[40]
blood supply .

Other concerns
Harvesting additional arterial conduits takes an additional 20 to 30 min. However, the avoidance of a
proximal anastomosis (in situ RIMA), and the use of sequential anastomoses and “Y” grafts, result in
shorter aortic clamp and bypass times, which may benefit myocardial protection and blood element
preservation .
[27]

Another concern is the potential risk of increased bleeding. A trend towards a higher rate of re-exploration
[41]
for bleeding in the TAR patients is reported , suggesting the need for extra attention during hemostasis
when using 3 arterial conduits.