Page 260 - Read Online

Gacad et al. Vessel Plus 2019;3:28 I http://dx.doi.org/10.20517/2574-1209.2019.011 Page 3 of 10

LIMA PATENCY AND OUTCOME
The LIMA is the conduit used for bypass of a diseased LAD in 95% of patients who undergo CABG
[42]
surgery . In patients with a LAD obstruction that decreases resting blood flow, the LIMA patency
rate is > 90% at 10 years post implantation [12,43] . Failure of LIMA graft mostly occurs in patients with
competitive flow between the LIMA and the native vessel as the result of low grade LAD lesion. The
long-term patency of a LIMA graft to a diseased LAD guarantees normal perfusion to ≥ 50% of the
total myocardial mass for many years [17,44,45] . In contrast to DES that only remedy a single focal LAD
obstruction, a LIMA graft protects proximal and mid segments of the LAD against the development of
new atherosclerotic lesions [46-48] . Further, by restoring normal LAD blood flow at rest and during exercise
a LIMA graft enhances downstream vascular endothelial function and thereby delays the progression of
[47]
atherosclerosis . The LIMA endothelium is abundant in inducible nitric oxide (NO) synthase and thereby
has a high NO concentration. The LIMA endothelium prevents graft thrombosis, slows the progression of
target vessel atherosclerosis and maintains distal vessel patency [46,48] .

Observational rather than evidence-based data led to the overwhelming use of LIMA in CABG
surgery [49-51] . In the absence of evidence based data, one can only speculate on the role that the LIMA
plays in the superiority of CABG surgery over PCI with 2nd generation DES in patients with complex
mCAD [47,52,53] . The absence of LIMA was found to be associated with redo operation and high mortality in
patients after CABG surgery [14,54] .

In summary, despite a lack of evidence-based data, the LIMA to LAD bypass graft is largely thought to
underlie the long-lasting and favorable outcome of contemporary CABG surgery.

DES
CABG surgery is rarely performed without implantation of a LIMA graft. Thus, the outcome of patients
who undergo surgical revascularization with only SVG cannot be compared to that of patients who
undergo PCI revascularization with current 2nd generation DES. In the absence of evidence-based data
comparing the effects of SVG vs. DES on outcome measures, data must be compared from findings of
[55]
individual therapeutic trials of these different CAR modalities . The incidence of in-stent thrombosis (ST)
and SVG occlusions was similar at 5 years with 1st generation DES like the paclitaxel eluting stent (PES)
in the SYNTAX trial . Advancements of stent technology, with the development of everolimus eluting
[56]
[57]
stent (EES), have provided improvements in immediate 1-year ST rate (0.60% vs. 1.59%) and 5-year ST
[16]
rate (1.30% vs. 1.86%) when compared to first-generation DES. However, as ST exerts a greater effect on
[56]
mortality than SVG occlusion , ischemia-driven target lesion revascularization (ID-TLR) may be a more
apt comparison with SVG graft failure. In a meta-analysis from 2016, 5-year ID-TLR incidence was 7.53%
[42]
[58]
with EES and 11.50% with PES , which is favorable compared to a 75%-86% patency for SVG in 5-7 years [Table 1].
In summary we do not have randomized trials of surgical CAR with exclusive implantation of SVG vs. PCI
endovascular revascularization with implantation of 2nd generation DES. Therapeutic trials of these 2 CAR
modalities point to similar patency rate and outcome with SVG and 2nd generation DES at 5 years.

MULTI-VESSEL REVASCULARIZATION IN ACUTE CORONARY SYNDROME
Acute coronary syndrome, with its spectrum in disease from unstable angina to ST-elevation myocardial
[59]
infarction (STEMI), portends future repeat cardiovascular events . CABG in STEMI is very rare,
[60]
comprising about 5%-8% of STEMI presentations in the ACTION registry per year ; 39% of those CABG
cases were after primary PCI and median angiogram-to-CABG time was 23.3 h. Numerous studies have
shown a correlation between total ischemia time and overall cardiovascular mortality in STEMI [61-63] .