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Page 4 of 18 Browne et al. Vessel Plus 2024;8:19 https://dx.doi.org/10.20517/2574-1209.2023.126

angiography. The primary outcome was graft failure at 1 year diagnosed by computed tomography
angiography. Our findings, which were collected from 83 centers across 22 countries, revealed graft failure
rates of 6.4% (68/1,068) for LIMA, 9.9% (9/91) for radial artery, 10.4% (232/2,239) for the saphenous vein,
and a notably high 26.8% (22/82) for RIMA grafts. The rate of RIMA graft failure was higher than both the
radial artery (odds ratio: 2.69; 95%CI: 1.30-5.57) and saphenous veins (odds ratio: 2.07; 95%CI: 1.33-3.21).
Particularly concerning were the extremely high failure rates of RIMA grafted to the left circumflex territory
(42% [14/33]), which were more than double those to the left anterior descending territory (19% [6/32]) and
right coronary artery territory (11.8% [2/17]). High rates of RIMA failure compared to other conduits are
concerning and underscore the need for a comprehensive evaluation of angiographic and clinical outcomes
of RIMA use in CABG surgery.

Clinical outcomes
Two main goals of CABG surgery are to prevent major non-fatal events such as myocardial infarction or
stroke and to improve long-term survival. Thus, evaluation of the CABG conduits with regard to clinical
outcomes is essential and complementary to direct visualization of the conduits using imaging. A recent
[29]
individual patient meta-analysis (Gaudino et al. ) pooled data from four of the largest CABG trials
(ART , CORONARY , PREVENT IV , RAPCO ) and included 10,256 patients, of whom 1,510
[31]
[18]
[32]
[30]
received RIMA, 1,385 received radial artery, and 7,361 received saphenous veins to supplement LIMA-to-
LAD grafting [Table 2]. After nearly 8 years of follow-up, patients who received secondary radial arteries
compared with saphenous veins had a reduced risk of all-cause mortality (hazard ratio, 0.62; 95%CI: 0.51-
0.76) and the composite of all-cause mortality, any myocardial infarction, or any stroke (hazard ratio, 0.78;
95%CI: 0.67-0.90) after propensity score matching. Use of secondary radial artery compared with RIMA also
reduced the risk of all-cause mortality (hazard ratio, 0.59; 95%CI: 0.48-0.71) and the composite of all-cause
mortality, myocardial infarction, or stroke (hazard ratio, 0.75; 95%CI: 0.65-0.86). Results using RIMA and
saphenous veins were comparable in terms of mortality and composite outcome.

A previous individual patient meta-analysis (Gaudino et al.) of 6 randomized trials (RAPCO , RAPS ,
[21]
[20]
[23]
[22]
[24]
[25]
RSVP , Petrovic , Stand-in-Y , Song ) from the RADIAL database compared long-term clinical
outcomes in 1,036 CABG patients . Use of radial arteries rather than saphenous veins resulted in a reduced
[33]
risk of the composite of all-cause mortality, myocardial infarction, or repeat revascularization (12.5%
[67/534) vs. 18.7% [94/502]; hazard ratio, 0.67; 95%CI: 0.49-0.90) and a lower rate of graft failure (8.1%
[28/345] vs. 19.9% [61/307]) after 5 years of follow-up. The main drivers of the composite outcome were a
reduced risk of myocardial infarction and repeat revascularization with radial artery use.
In a network meta-analysis (Gaudino et al.) of 4 randomized and 31 observational studies that included
149,902 CABG patients who received a secondary conduit (16,201 radial artery; 112,018 saphenous vein;
21,683 RIMA), the use of saphenous veins was associated with higher long-term mortality compared with
the radial artery (incidence rate ratio, 1.23; 95%CI: 1.12-1.34) and RIMA (incidence rate ratio, 1.26; 95%CI:
1.17-1.35) . However, the use of RIMA compared with radial artery resulted in similar rates of short-term
[34]
and long-term mortality as well as perioperative myocardial infarction, stroke, and deep sternal wound
infections (i.e., the arterial conduits were equivalent with respect to clinical outcomes).

In summary, the latest evidence suggests that the radial artery may be the best conduit to supplement
LIMA-to-LAD grafting to reduce the rate of graft failure and risk of major adverse cardiovascular events
compared with the other conduits. Given the biological equivalence of the RIMA and LIMA, higher failure
rates in RIMA compared with saphenous veins in the most recent individual patient meta-analysis with
clinical outcomes comparable to saphenous veins are concerning. Target vessel location, particularly to