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Page 6 of 11 Raja. Vessel Plus 2019;3:23 I http://dx.doi.org/10.20517/2574-1209.2019.05

reoperation, 8.6% (95% CI, 4.7%-12.6%) and 12.9% (95% CI, 7.6%-18.2%) for cardiac death, and 10.8% (95% CI,
6.5%-15.2%) and 15.2% (95% CI, 9.8%-20.6%) for death from other causes.

[27]
Tatoulis and colleagues in a mulitcentre analysis compared outcomes in patients who underwent TAR
(n = 12,271) with outcomes in those who did not (n = 21,910). They determined the impact of TAR on 10-year
all-cause late mortality by propensity score analyses in 6,232 matched pairs. The 30-day mortality was 0.8%
(96/12,271) for TAR patients and 1.8% (398/21,910) for non-TAR patients (P < 0.001). Late mortality was 7.5%
(918/12,271) for TAR patients and 8.9% (1,952/21,910) for non-TAR patients (P < 0.001). The mean follow-up
time was 4.9 years. In the propensity-matched cohort, the perioperative mortality was 0.9% (53/6,232) for
TAR patients versus 1.2% (76/6,232) for non-TAR patients (P < 0.001). Kaplan-Meier survival in the matched
cohort at 1, 5, and 10 years was 97.2%, 91.3%, and 85.4% for TAR patients and 96.5%, 90.1%, and 81.2% for
non-TAR patients (P < 0.001). Late mortality was 8.0% (n = 500) for TAR patients and 10.0% (n = 622) for
non-TAR patients (P < 0.001). Stratified Cox proportional hazards models showed lower risk for all-cause late
mortality in the TAR group (TAR:HR 0.80, 95% confidence interval 0.71 to 0.90, P < 0.001).

A systematic review and meta-analysis of 130,305 patients from 4 smaller shorter follow-up RCTs, plus 15
matched/adjusted and 6 unmatched/unadjusted larger longer follow-up observational studies suggested
that TAR may improve long-term survival compared with conventional CABG by 15%-20% even when
[28]
compared with two arterial grafts .

CONCERNS
Single blood source
The composite grafting technique has the disadvantage of complete reliance of the coronary bypass flow
on the flow of the proximal IMA. Multiple clinical and experimental studies have assessed the adequacy of
[30]
the IMA as the sole blood source in composite arterial grafting [29,30] . Sakaguchi and colleagues , utilizing
positron emission tomography, demonstrated that the composite Y graft was not as efficient as independent
grafts for increasing the coronary flow reserve soon after bypass grafting. However, most investigations
have reported that the flow reserve of the proximal IMA is adequate as a blood source of composite grafts
[31]
in TAR. Affleck et al. , in an effort to determine the constraint posed by a single source inflow recorded
intraoperative flow in each limb of the T graft before and after distal anastomoses in 204 patients. They
also compared flow capacity with completion coronary flow. Free flow for the radial arterial limb was
reported as 161 ± 81 mL/min, the IMA limb as 137 ± 57 mL/min (combined 298 ± 101 mL/min) compared
with simultaneous limb flow of 226 ± 84 mL/min resulting in a flow restriction of 24% ± 14%. Completion
coronary flow was 88 ± 49 mL/min for the radial artery, 60 ± 45 mL/min for the IMA, and 140 ± 70 mL/min
for both limbs simultaneously to give a flow reserve (vs. simultaneous free flow) of 160% or 1.6. This flow
reserve of 1.6 compares favorably with an IMA flow reserve of 1.8 at 1-month postoperatively and 1.8 for
both the IMA T graft and the IMA/radial artery T graft at 1-week postoperatively as reported by Wendler
and associates .
[32]

Graft spasm and hypoperfusion
Hypoperfusion syndrome, associated with a high mortality, is a recognized sequela of vasospasm of
arterial grafts. Spasm of the proximal IMA in case of composite grafting may result in hypoperfusion of
[30]
the whole left coronary system and may lead to calamitous consequences . Similarly, the radial artery and
gastroepiploic artery with an enhanced spasmodic tendency, owing to preponderance of smooth muscle,
[33]
predispose to a risk of hypoperfusion due to spasm of these vessels if used to construct a composite graft .
In practice however, 1% to 2% of the patients undergoing composite arterial grafting experience
perioperative hypoperfusion resulting in myocardial ischemia, infarction, low output states, or even
extreme hypotension [33,34] . Injury to the conduit during harvest, technical errors in the anastomosis, linear