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Naik et al. Vessel Plus 2018;2:38 I http://dx.doi.org/10.20517/2574-1209.2018.62 Page 3 of 10

determined the sensitivity and specificity of the modified Allen’s test to be 54.5% and 91.7% respectively with
a diagnostic accuracy of 81.7% at the conventional cut off value of 6 second. Doppler ultrasound, on the other
hand had sensitivity and specificity of 100% and 27% respectively with a diagnostic accuracy of 52% [15,16] .
[17]
Starnes et al. raised concerns that the high false negative rate of the modified Allen’s test could lead to
unnecessary exclusion of some patients by placing some patients at an incorrectly high risk of digit ischemia.
They recommended direct digit pressure measurement, which is simpler and more accurate to determine the
adequacy of collateral circulation in the hand prior to CABG.

[18]
In 1998, Buxton et al. were the first to describe the successful use of the ulnar artery as a conduit in a
series of 8 patients. The idea of collateral circulation to the hand allowing the use of either the radial or ulnar
[19]
artery for harvest was reiterated in a larger, more recent study of 25 patients described by Newcomb et al.
in 2006. Although, both studies conclude that routine use of the ulnar artery is not recommended due to its
close proximity to the ulnar nerve with significant potential for resultant motor and sensory deficits in the
hand along with the fact that the ulnar artery tends to be the dominant artery to the hand [18,19] .

Another factor to be considered before choosing the RA for graft is the previous use of the conduit for
invasive diagnostic procedures, which exposes the artery to post trans-radial access (TRA) occlusion.
Interventional cardiologists commonly use the radial artery as access during procedures like percutaneous
[20]
cardiovascular intervention (PCI) and angiography . Our group previously reported significant endothelial
damage in the vessel post-TRA leading to reduced vasodilatory function of the vessel with no clear evidence
of return of baseline function with time. Along with the biological dysfunction, the risk of RA thrombotic
occlusion has been estimated at 7.7% at 1 day and 5.5% at > 7 days after the procedure in a recent large
meta-analysis with specific clinical factors (i.e., age, diabetes, reduced artery size, female gender, peripheral
vascular disease, smoking, low body weight and lack of statin use) and procedural factors (i.e., use of
non-hydrophilic catheters, prolonged postprocedural high pressure compression, etc.) being described as
[21]
mainly responsible for occurrence of RA occlusion . Additionally, an association between TRA and graft
occlusion has been described, leading to the recent recommendations on the use of non-punctured RA as
graft for CABG and on the preservation of the RA during angiographic diagnostic procedures in surgical
candidates [20,22] . In situations with limited graft options, it is recommended that the surgeon should perform
Doppler ultrasound preoperatively to positively determine the patency and the diameter of the vessel. The
[22]
use of the distal end of the artery should also be avoided .

It was found that the incidence of the RA graft not being suitable for use after findings of non-satisfactory
collateral circulation pre-operatively was around 5% [23-25] . This does not take away from the versatility of the
[21]
RA graft which can be used as a single free graft, as a Y graft, or as a sequential graft .
Apart from the previously mentioned reasons for graft failure amongst venous and arterial grafts, another
very important aspect to address is the degree of native artery stenosis when considering the RA for use as
[26]
conduit. Tatoulis et al. explained that arterial graft patency rate is proportional to native artery stenosis
severity so the more severe the stenosis the higher the patency rate of the arterial conduit. Radial arteries are
[26]
known to be more sensitive and show best results when the native artery has at least 80% stenosis . This
phenomenon is termed competitive flow and results in graft failure if the flow through the graft matches
flow through the native artery after bypass. Vein grafts do not experience this phenomenon since they have
[27]
much less resistance with a larger diameter .

INTRAOPERATIVE CONSIDERATIONS
Radial artery graft harvest could be performed open or endoscopically [open radial artery harvest (ORAH)
[28]
or endoscopic radial artery harvest (ERAH)], preferably from the non-dominant arm . The vessel might be
harvested in skeletonized or pedicled fashion. Despite some advocating an advantage in conduit length and