DISCUSSION
In this study, SR of AMI was associated with lower in-hospital mortality
but higher morbidity, longer LOS, and total hospital charges than PR.
These results remained consistent in patients who had multiple vessel
revascularization (in both ST and non-ST elevation AMI), but not single
vessel, and in patients with/without diabetes, systolic heart failure,
cardiogenic shock or mechanical complications of AMI, despite the fact
that SR group had higher baseline comorbidities. These results persist
after adjustment for baseline characteristics using propensity matching.
Most of the previous studies that showed comparable or superior outcomes
of SR in patients with stable CAD, rather than AMI, and over a longer
period of time.[21] A pooled data from multiple
trials that compared SR to PR in patients with NSTEMI showed that SR was
associated with lower composite end points over 5 years which was mainly
driven by lower infarction rather than lower
mortality.[23] However, another study showed a
trend to lower events rate and lower mortality in comparison to
PR.[24]
Advancements in surgical techniques such as off pump surgery, clampless
and no-touch surgery, epiaortic ultrasonography, and minimally
invasive/robotic SR all have contributed to lower both operative and
long-term mortality and complications rates.[25]Moreover, the heart-team approach for SR patient selection using a
multidisciplinary team could increase the operative safety and success
rate.[26]
Conduit selection has also showed to improve outcomes and
mortality.[11] Internal mammary artery (IMA)
grafting to left anterior descending is a major survival determinant
independently from the presence of other graft. This is likely because
of superior patency rates in comparison to vein grafts[27] and high proportion of elastic composition
compared to muscle or adventitia making it more able to tolerate
coronary blood flow. Furthermore, IMA grafts have physiological
functions that result in anti-atherosclerotic effects by producing much
greater levels of nitric oxide and decreased release of
vasoconstrictors. Nitric oxide is a known potent angiogenic agent which
initiates neocapillary and microvascular bed formation in the affected
and adjacent areas.[11,27] These factors could
have resulted in the lower early in-hospital mortality seen in this
study despite the higher complications rates.
Most of AMI results from non-flow-limiting lesions; however, PR treats
flow-limiting lesions only therefore it is not expected to prevent new
infarcts and subsequently lacks mortality benefit. On the other hand, SR
bypasses the whole diseased segments which creates “surgical
collateralizations”; a condition that allows revascularization of the
diseased-vessel which subsequently causes no or nonfatal AMI which could
also decrease mortality. [21]
This study is based on a large nation-wide database and represents
real-world outcomes in the United States. It adds to the current
literature that SR in the AMI setting is still a feasible option,
especially when PR is expected to be suboptimal or results in incomplete
revascularization, and might be associated with lower in-hospital
mortality in patients with multivessel CAD.