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.